This seems pretty much bordering on the impossible, given the current state of (LEGO) engineering capabilities. What you are describing is a Von Neumann Machine and as far as I know nobody succeeded in creating one, not just in LEGO but in general.

The problems you'd have to overcome:

The robot must be capable to exert sufficient force to overcome the clutch power of the LEGO bricks. This could be done with a suitable set of gears. However the gears themselves eat up a lot of the motor's force due to friction. Pneumatics is absolutely out of the question for these parts.
The robot must be capable of positioning the LEGO pieces with sufficient accuracy. I have no hard data available on the precision of the various LEGO actuators (motors, pneumatics, linear actuators, what else?) but in my previous LEGO experience electric motors can be tricky to program to operate with enough precision, but it can be done with enough testing and refining iterations for a given physical design. Again, gearing down would in theory help a lot, but all gears have some inaccuracy. LEGO gears are not among the most precise ones. You could easily test this by linking about a dozen cogwheels together in a chain, holding one end tight and testing how much can the other end of the chain rotate. Pneumatics are also out here, you can't get them to stop reliably anywhere but the end positions.
The robot must be capable of picking up, holding and placing every type of LEGO piece it is constructed from. This means either an universal actuator that itself can handle every element or more than one actuator, each specialized for a subset of all elements. The actuator(s) should also be capable of orienting the pieces in 3D space, this requires at least 6 degrees of freedom
The robot must be capable of finding and distinguishing between different pieces. The hardest version would have the robot sift through a bin full of pieces, but you could "cheat" by letting it use pre-sorted, pre-positioned stacks or queues of individual piece types. Even that would bring many problems, the robot must know which element is where, how high/far is the current part in each stack/queue, etc.
In the strict sense the robot should transmit it's program to the newly built robot. I'm not familiar with the current lineup of programmable bricks to state confidently whether it is possible at all for a LEGO brick to program another, but even if it's possible it would require some serious programming.

In your examples you can see how complicated, huge and slow can these creations can become. But you can also see how highly does the LEGO community think of these creations, each of which does only a small fraction of your proposed project. I'm not saying that it's impossible, but I don't think it would be an understatement to say that this would be the single biggest achievement in the world of LEGO and in general engineering too.


Can you identify this model of a yellow truck?

This model is built from set 8062-1: Universal Set with Storage Case.
Inventory and building instructions are available here.


Can you identify this truck with spikey wheels?

Legends of Chima 70004-1: Wakz' Pack Tracker


LEGO baseplates are made from ABS plastic, like most of the opaque rigid plastic LEGO elements since 1970. ABS is a thermoplastic consisting of a styrene monomer with the addition of an acrylonitrile momomer and a butadiene monomer. There is no PVC or vinyl present.

I suggest reviewing this thread for more on laser-cutting ABS. It is not a trivial matter to get a good result.

Edited to add:
In response to a query from a "safe toy" website, LEGO categorically stated that they do not use PVC in any of their products except in rare instances like electrical wiring insulation.


How can I connect the LEGO Mindstorms NXT with an iPad?

I'm going to guess that USB would most likely required a jailbroken iPad. The NXT uses a custom USB protocol, so you would need raw access to the USB via IOKit.

If neither Bluetooth nor USB works, then there is no alternative other than using another computer to communicate to the NXT.


Can I Conect 2 NXTs so that they work together?

Without 3rd party hardware or software, the only way to do this is to use Bluetooth messages. For example, you could write motor power to a Bluetooth mailbox on one NXT. The other NXT just has a simple program with a loop that reads the Bluetooth mailbox and connects it to a motor block.


You are using the function run_target... which tells the motor to run to a specific angle.
So it turns to an absolute position...
This might be correct for the pen_up and pen_down cases, but I think that for the movement, you want relative movement, i.e. relative from your current position, hence I think the instruction you need is run_angle instead of run_target.


Can anyone identify this dark grey remote control and receiver with yellow and orange buttons?

Bionicle manas set 8539.
Top part from your foto. Bottom one.


What is the power of Lego Powered Up motors (M, L, and XL) and the Move Hub motors?

Philo is one of LEGO enthusiast and he did quite a number of tests with different motors produced by LEGO, which you can find  here. Table below is based on data measured by Philo:

Motor
Torque
Rotation Speed
Mechanical Speed
Electrical Power

PUP M
4.08 N*cm
270 rpm
1.15 W
2.66 W

PUP Control+ L
8.81 N*cm
198 rpm
1.83 W
4.70 W

PUP Control+ XL
8.81 N*cm
198 rpm
1.83 W
4.16 W

PUP Move Hub
4.08 N*cm
264 rpm
1.13 W
3.37 W


2 Unidentified Printed Pieces, 2x3 Dark Grey Slope and Black 2x2 Tile

The slope piece is Slope 33 3 x 2 with Insectoid Scope Pattern from 9 (or 10) Insectoid sets from 1998-99.

The 2 x 2 tile is Tile 2 x 2 with Insectoid Logo in Triangle Pattern from 9 (or 10) mostly-Insectoids sets.

There are a few sets with both pieces.


Is there a freely downloadable LEGO set and part dataset?

I wasn't able to find anything like this, so I contacted the admins of the sites that I mentioned in the question. Rebrickable was kind enough to send me a dump of their set inventories under a Creative Commons 3.0 BY-SA license, which basically means that you can do whatever you want with the data as long as Rebrickable is acknowledged as the source and you share any updates that you make.
I've created an archive which contains a spreadsheet for each set that was in the dump that I received. Hopefully this is useful to someone else.
Lego Set Inventories as of March 2014
Update:
The raw data that I used to create these spreadsheets is now available directly from Rebrickable and is updated monthly there. I also maintain software to build an SQLite database from these dumps.


Is it possible to create a differential if I don't have it as a ready to use element?

This can definitely be accomplished, although it will be difficult to create a differential as small as the dedicated piece that you mentioned.

Some builders create their own differentials for use in larger models because of the inherent torque limits and slippage that the traditional differential and single bevel gears introduce. Here's one example (source) of a differential that can be created using fairly common elements:

The key is to build the frame containing the three gears and then attach a fixed gear to the frame. The tricky part is finding a gear that can pass an axle through the center without being fixed on it. In the example above, half of a turntable was used, but there are a few other parts that could work as well. Here's the turntable (48452):

If you are comfortable with modifying your parts, you could also drill out the center of a gear to allow it to turn freely.


Simple way to build large circular plates?

The largest truely round base plates in the LEGO system fit in a 8x8 square. You can build them from two LegoPlate, Round Half 4 x 8 or from four quarters.

For a bigger (and thicker!) base plate there is a Duplo version of the above mentioned base plate, fitting into a 16x16 studs LEGO system square: LegoDuplo, Plate Round Corner 4 x 8 Double

EDIT: For a thicker base, you can use these bricks: Brick, Round Corner 10 x 10 with Slope 33 Edge. They make a base fitting into a 20x20 square.


LEGO Friends set identification from sealed bag

This bag is from 3315 - Olivia's House.

The instructions for this set can be found here on the LEGO Customer Service Site.


ID for Off-Brand 1x1 Round Plate, Stud on BOTH Sides (1 is Hollow)

I don't know this exact brand, but please note that Mega Bloks (now Mega Construx) has those male/male studs. They appear in many of their sets and come in many different colors. They are exactly one plate tall, just like the one you have on your picture. The Mega version has a hole going through the middle to accommodate any bar shaped piece, which makes them even more useful!


Can a EV3 program run simultaneously with the Running Robot commander app?

No, the Robot Commander app downloads and runs a program on your EV3. If you already have a program running, it will be stopped and the program downloaded by the commander app will run instead.


What LEGO cases are available for phones?

I am not sure such a case exists for the HTC Desire.
All of the LEGO style phone accessories I have seen in the past have been for the iphone.

A bit of searching turned up these items:

What appears to be a case with LEGO compatible studs (for iphone)

Check out this page for other LEGO relates accessories and a picture of the above case in use with actual LEGO built onto it (near the bottom of the page).

There is also a TinkerBrick LEGO iPod/iPhone 3 case which has studs on the front and sockets on the back. There are taking Votes for the next supported phone on their site.

There is a mock LEGO silicone iphone case available here. The two pieces can be attached in different positions.

To wander off topic slightly, there are other 'phone related' LEGO style accessories available that are compatible with most phones:

Dock cover available here.

LEGO brick earphones available here.


Can two Powered Up train motors be plugged into one hub

You can attach second train motor to B output. However it will be controlled independently from motor attached to output A. So you would need to control speed for each motor separately.

Speaking of traction. The key thing here is your train weight. You might consider putting another full battery box (unpowered) into train just to increase weight and get more friction between wheels and the track.


Who built the LEGO structures for the film "Elf"?

According to an interview with Elf director Jon Favreau, the Lego City set was built in-house by the Rusty Smith's art department.

The IMDB page for the movie thanks The LEGO Group for the permission to use the LEGO logo and trademarks but has no mention of any further involvement in set design.


Is it possible to change the battery in a 54604 light brick?

There's a YouTube video which explains how you can replace the battery in that light brick.

You can also find the owner's explanation on the Eurobricks forums.

Quoting from that site:

  What you'll need:

  ExoForce Light brick (obviously)
  A small screwdriver (or other item with a long, thin shaft) (my s'driver was 2mm (0.07 inches) thick)
  A small 3V battery.

  Put the point of the screwdriver into the hole in the brick (where you'd normally put the fiber optics cord).
  Using quite some force, lever the screwdriver until the 'lid' pops up at the front.
  Insert the screwdriver into one of the small gaps at the side where the 'lid' pops up, and lever the lid up again.
  the lid should come right off. From here, you can shake the brick and the battery should fall out. Simply slide the new battery in and
  click the lid back on.


I was able to find a few elements that are able to make this connection possible. I'm guessing the designer used some type of bar-sized element which is made from a different material that is able to compress slightly more than regular ABS. For example, the softer plastic used on some minifig weapons seems to work nicely:

Another option could be flexible Technic tubing. I was able to make this work, but it feels like a very tight fit. This tubing could also be cut to length under some definition of LEGO purism.

Of course, as Kramii pointed out, this could also just use non-standard elements or part modification.


How to build bridge using 4.5/12v train rails from 1969 Lego brochure

Here is an approximation of the bridge that appears on the cover of the catalog pictured above. Unlike the version in the picture, this model uses bracket pieces to attach the arched section to the rail bed. All the pieces in this build were available prior to 1994.

The arches are decorative and do not really contribute to the strength of the bridge. This is completely computer-generated and may not be very sturdy in real life. It would not be difficult to adapt the rail bed to give it more strength, however.

I put together an LDraw file with steps for building this bridge. The file can be downloaded from my MOCpage.


It appears to be part# 64261 from set# 8983, "Vorox".

https://www.bricklink.com/v2/catalog/catalogitem.page?P=64261&name=Bionicle%20Mask%20Vorox&category=%5BBionicle,%20Kanohi%20Mask%5D#T=C&C=2

https://www.bricklink.com/v2/catalog/catalogitem.page?S=8983-1#T=S&O={%22iconly%22:0}

Instructions can be found here:
https://www.lego.com/biassets/bi/4547677.pdf


Is there an easier way of threading Technic pins into other elements?

As someone who also argues with LDD occasionally, have you tried using a placeholder technic beam to get two connectors at the right distance and then adding the axle into both connectors before deleting the placeholders?

If the placeholders are in a different colour from the rest of the model, you could use as many as you need and then delete them with the Colour Select tool, leaving just the parts behind.


How to design ackermann steering with lego wheel bearing front?

Here is a possible implementation using this exact part: Video .

There are also several other solutions with different pieces if you need more inspiration or explanation: Animated GIF, 4 wheel steering, Top-down view.


Going from the Tan Panel 2 x 2 x 1 Corner (# 91501), I've dug into bricklink: https://www.bricklink.com/catalogItemIn.asp?P=91501&in=S

This particular piece has only been in 9 sets, and the one I can see that matches the rest of the pieces is 10692-1: Creative Bricks


Which 3307 Arch 1 x 6 x 2 is correct for 10225 R2D2 Set? "Thick Top with Reinforced Underside" or "Thin Top without Reinforced Underside"

I cannot give you the definite answer, but LEGO changed the design of the "Brick, Arch 1 x 6 x 2" two times over the last 6 years. The original version is 3307 which was in production/circulation until 2014. It then produced 12939 which entered production/circulation in 2010 and is still out there in new sets, however, in 2014 LEGO started producing yet another design numbered 15254.

Since 10225 R2D2 was produced for about 2.5 years from 2012 to 2014, it fell right smack in the middle of the change-over between these 3 molds. So per set it really depended on what mold had been printed and was sitting in the supply for the given production facility - some sets will have gotten 3307, other sets 12939 and even some late sets will have gotten 15254. For LEGO there is no difference in these parts and they will have been substituted.

Bricklink indeed mentions 3307, but has 12939 listed as alternate, so it recognizes both came in this set. Brickset has both 12929 and 15254 as parts for this set, and Rebrickable has 3307. Finally, BrickOwl is missing this piece from its inventory altogether.


What kind of soap can I use to clean LEGO?

The official guidance from The LEGO group suggests using a mild detergent.

Cleaning your LEGO® bricks is really easy! We recommend that you clean
your LEGO® parts by hand using water no hotter than 104°F / 40°C and a
soft cloth or sponge.** Higher temperatures may affect the quality of
the parts. You can add a mild detergent to the water - please
rinse them well with clear water afterwards and you're done!
A word of warning! Please don't put your LEGO® pieces in the washing
machine or dishwasher, and don't try to dry them in the oven, the
microwave or with a hair dryer. When the bricks get really hot they
may change shape, which means they won't work anymore!

Cleaning your LEGO® bricks
In most cases warm water is enough to clean LEGO bricks, some soap can help remove tougher stains, dirt and smells.
Examples of mild detergent include liquid hand or dish washing soap, as opposed to things like bleach and ammonia which are irritating and corrosive to the skin which may damage bricks.
Mild detergent should be enough to both clean and sanitise.


Separate LEGO Technic wheel from 3 pin hub

The main trick is to simultaneously push all three pins of the hub:

If you have another hub, and the wheel allows for this, take it and push carefully from the other side. If both hubs are half-way in, you should be able to pull out both.
Otherwise, take two wedge belt wheels, align them on top of each other, insert a pin into every second hole and repeat the above. There are various obvious variations of this approach using different parts, if you need a longer tool or don’t have the parts available.


1998 World Cup limited edition soccer figure

Is this the figure in question?

He's the limited edition English or Scottish team player. The other limited edition figure was a Dutch (Netherlands) player. Lego released an entire soccer theme in 1998 in conjunction with the World Cup, which you can see here on Brickset.


Pattern for vertical motion using technic lego

You can accomplish this using gear racks (3743):

You just have to create some type of channel that allows the rack to slide vertically, and then set up a gear to mesh with the rack. You can do this however you like, but here's a quick example that I built to show you what I mean:


How can I automate orders from Lego Pick-a-Brick?

I believe that many AFOL user groups had previously been able to buy in bulk from LEGO, but I don't know if that's still an option with the release of pick-a-brick - however as Joubarc points out there are often limits on the number of different elements, as well as a group limit on the number of bricks. Couple that with the fact that the process often takes months to deliver, and it's not an easy option.

Another option would be to take it offline: the LEGO catalogue often lists Pick-a-Brick elements and has a postal order form, so you could format that up in your spreadsheet application of choice and mail it in.

Doing a quick snoop around the network traffic when adding items from Pick-a-Brick shows that currently it uses a fairly simple post to submit the details to the basket:

ba     0
bricks 4239601,1          <- ElementId,quantity
cat    UK
id     4239601,1          <- ElementId,quantity
sid    0.4886243118128015

So something could possibly be created, but as Joubarc points out, there's no guarantee that the site would continue this way.


I've never seen that part until now, and it's certainly not in the antenna or bar bricklink categories. I'm fairly confident it's not LEGO.

However, it would be far more interesting to know what it is, but that's not easy to search. A few Mega Bloks parts have been catalogued, but your part isn't there either (I could only check categories bar, weapon and tool/gear before I got sick, though). Considering that database is far from complete, it doesn't mean it's not Mega Bloks, though.

Actually, I think there's a good chance it IS Mega Blocks: the antennas on the Repzyllian Trekker and the Gyro Fighter look very much like yours.


What LEGO sets include minifigure with both arms and hands molded together?

Torso with the arms and hands molded together sounds to me like the ones released with NBA basketball (so they can throw the balls better?)
A list on Bricklink


How to cross reference a part to all instruction guide pages

I'm using the discontinued program LEGO Digital Designer where what you want to do can be done with the program's Selection Tools.

BIG NOTE:  The only thing you'll have to do is to search for your model in LDD format.  I'll give you a leg up and schmooogle a search string query for you. You'll just have to sift through and find that file.  Good luck!

Okay, Friend, shall we diiiiive in?! RIGHT! LET'S GO!!

I'm gonna step through the motions using a model comparable to the size of your busted up Falcon.

Schmooogle says there are 7,541 pieces in MF, so we have to go big with Super Mario Bros. End Stage Castle which pieces out at 7,994 bricks.

1)  First let's imagine it was knocked off it's perch:(

2)  Painstakingly rebuild what we can, but... huh, we got extras?... F***!!

3)  We got 5 stragglers in hand...err empty blue glove:

a red inverted slope,
a 1x1 white brick with a hole in it,
a yellow 1x1 tile stuck to a yellow 1x1 plate,
and finally a 2x3 brown brick.

4)  Open your model in LDD.

5)  Use the menu and place a digital copy of each extra real-life piece at the bottom of your model all in a nice neat little row.

6)  Okay, zoom out a little.  One at a time using the "Shape and Color" Selection Tool, click on each extra piece to highlight all bricks in your model that has that same shape and color.

7)  To see those pieces visually unhindered by other bricks, click "Invert" selection to highlight everything that wasn't originally highlighted.

8)  Then hide those obstructing bricks by clicking the "Hide" selection tool.

9) For remaining bricks:

Lather,

Rinse,

and Repeat.

Whoa! That's a lot of 2x3 bricks!.  In cases like this you might have to practice up , and do some old school find the difference picture comparisons, and get yourself geared up to find that missing hole in your model.  Good luck!

Here! Enjoy a troll fish...lol!  Peace!


Not an official LEGO set, that's for sure. As far as I can tell, it's an inspirational model for a building contest a few years back, constructed by John Ho.


Does the Mindstorms EV3 software run on OS X El Capitan?

I've recently upgraded to OS X 10.11 El Capitan (as a matter of fact, I have the exact same model of computer). I've done some basic tests with the EV3 software without running into any issues. I've downloaded programs to the brick using both USB and Bluetooth.

Base on past experience with OS upgrades with both the NXT and EV3 software, the problems have usually been with Bluetooth. The fact that this is working is a good sign.

I have not used the EV3 software extensively yet on OS X 10.11, so there could be some minor issues I don't know about, but at least I can say that it is usable.


How to make a RPG (Rocket Propelled Grenade)

Some of the Indiana Jones sets had some simple heavy weapon builds in them.

Set# 7625 had a belt fed/ammo-box mount style machine gun:

Set# 7626 had a RPG:


LEGO does not directly create military sets.

A LEGO representative gave the following reason:

  Are there any chances that Lego will ever start producing modern day warfare Lego, with tanks and helicopters and what not?

  We have a strict policy regarding military models, and therefore, we do not produce tanks, helicopters, etc. While we always support the men and women who serve their country, we prefer to keep the play experiences we provide for children in the realm of fantasy.

  -- Gizmodo - Everything You Always Wanted to Know About Lego

There have been some sets that have been military-based though.

The 7595-1: Army Men on Patrol is based on characters from a movie series which are based a military toy.

A number of Indiana Jones sets have some military people and vehicles that in the movie are considered military vehicles. Notably missing though is the tank from the tank scene in Indiana Jones and The Last Crusade.

The Dino Attack theme (or Dino 2010 internationally) also has a tank and a helicopter modeled after military vehicles.


As a general practise discount can be quite big (I've seen -50% off) for a small set and tend to be much lower (around -25% off) for a large set.

Discounts tend to vary even during the same day. So it is worth keeping an eye. Some sites, like Brickset tend to announce LEGO sales too. They even have a tracker for Amazon and other services. I suggest to look here to have a sense of understanding how much discounted the set can get.


How to build a waterproof roof out of LEGO blocks?

Since you are willing to use a non-LEGO frame to hold the roof and glue to fix all together, I would recommend buying baseplates in bulk and gluing them onto a wooden frame as if they were shingles. If the gradient and the overlap (vertical between rows and horizontal between individual plates) are correctly matched, the rain won't get inside.

For more resources on professional shingle roofing see these links:

https://www.iko.com/na/pro/building-professional-tools/roofing-101/how-to-install-shingles/
https://www.wikihow.com/Lay-Shingles


What is the Airport Shuttle logo meant to symbolize?

First of all, here's a slightly enhanced, upclose image of the logo.

My best guess is that it's meant to represent a railway T-Intersection as seen below.

I believe this is especially possible, considering how the T tapers down to the bottom, similar to a railway T-Intersection.


Are there plans to release new trains for AFOL?

With the exception of evergreen themes like CITY and Duplo, it's not easy to predict when sets are released. Based on trends of the last 11 years, I've included the last 20 train sets that have been released in a table:

At least one train set has been released each year apart from the year 2008. The table marks an average of 1.66 train sets per year. It's fair to assume that a new train set will be released in 2012 or 2013.
Duplo, accessories, motors and track sets not included. I've included the Western Train Chase from the Toy Story theme, The Constitution Train Chase from The Lone Ranger theme and The Ghost Train from the Monster Fighters theme which you may wish to exclude as anomalies. The right-most column marks which sets were sold with track.
Set data gathered from Brickset.
Download .CSV [?]


Unknown stickers with silver lines on black 2x4 tiles

Comes from Set #76047 Black Panther Pursuit.


Can you identify this fiery orange hair?

That seems to be part #24787, Minifigure, Hair Spiked Tall Top. So far it has only been released in orange. It came on the 2016 Syndrome minifig, one of the Disney Collectible Minifigures.


How can I find the original bag listing for 42083 Bugatti Chiron?

As far as I know there is no such resource on the internet.
It's asked from time to time on other fora and groups I frequent, mainly from people who have a collection of bags and want to gather entire sets.
The best that can be done to get the parts per module is disassembling the set in reverse order of the instructions...


Please help me identifying these spaceship parts - big sloping ring

It's from a LEGO UFO set from the late 1990s. You can see all the sets in this theme here: http://www.bricklink.com/catalogList.asp?catType=S&catString=34.311. What you have is most likely the #6975 Alien Avenger:  http://www.bricklink.com/catalogItem.asp?S=6975-1


It's "a campaign to help nurture the creative skills of the next generation", launched by LEGO on September 17, 2019.
From the LEGO website:

Today, the LEGO Group and musician Mark Ronson launch Rebuild The World, a campaign to help nurture the creative skills of the next generation.
Over 100 children will meet Mark and other inspiring figures, such as 19-year-old David Aguilar, who built several prosthetic arms from LEGO® elements, at the LEGO House, Billund, to explore the infinite potential of creativity. Their imaginations will also be fired up in a series of workshops, where they’ll be challenged to rebuild the world they see around them.
“My whole career has been about working with brilliant, creative people and seeing where our imaginations take us. Rebuild The World, is a wonderful opportunity to help inspire the next generation of creators who will come up with their own ideas to shape the future of everything from the way we live to the music we listen to,” explains Mark Ronson.
The LEGO Group believes that every child is born with incredible creative problem-solving capabilities, but we need to act now to nurture that creativity so that it can become a lifelong skill, as the future depends on it.
Inspiring creativity is more critical and urgent than ever. The World Economic Forum Future of Jobs Report places creative problem solving in the top three skills the job market will require from 2020. Imaginative play helps children learn how to innovate, problem solve and think critically throughout their lives.
Mark Ronson will also be joined by representatives from other creative fields to discuss why it’s more important than ever to help nurture creativity as a key skill so that the builders of tomorrow can succeed in an ever-changing world.
Julia Goldin, Chief Marketing Officer, The LEGO Group, said: “Rebuild The World is all about seeing where imagination takes us and celebrating the natural creativity of children. We want to encourage kids around the world to develop and retain these skills as they grow older. With this campaign, we want to inspire people of all ages to play and unleash their creativity to create a world of infinite possibilities.”
Meanwhile, British designer and inventor Dominic Wilcox will lead a series of Rebuilder Workshops on the 17th September. He, along with two other creatives, will challenge kids to reimagine iconic landmarks, invent new gadgets and solve everyday problems – all with LEGO bricks. Other LEGO professionals will lend a hand, helping the kids bring their incredible ideas to life.
“Who knows what will come out of today… a house with a hot air balloon for a roof?  A car with long legs to jump over the traffic ahead? No one sees the world quite like children so we’re excited to see what they come up with,” says Dominic Wilcox.
Kids around the world can also take part by sharing their creations on the LEGO Life app or by visiting www.lego.com/rebuild-the-world-challenge
The LEGO system has long been the ultimate platform for creative expression and creative problem solving. Children don’t just imagine what to build, they can build and rebuild. Experiment. Fail. Break the rules. Fail and Try again… This is the cycle of human creativity and the essence of the LEGO System in Play.
Now, we’re going even further. Through Rebuild The World, we want to inspire children to unleash their creativity, join the Rebuild The World challenge and rebuild a world of endless possibilities for real.  Learn more by visiting www.lego.com/rebuild-the-world
About the campaign
Rebuild The World is a fully integrated global campaign which will be featured across a variety of channels including TV, digital, cinemas and out of home. The LEGO Group will also be hosting a series of high profile public events in cities around the where children and grown-ups will be invited to build and rebuild with LEGO bricks to make the world a little brighter. This includes using LEGO bricks to complete a giant heart on the side of the East Side Gallery in Berlin www.LEGOnewsroom.de
The campaign was created by the LEGO Group’s internal agency with BETC Paris and the film was directed by the multi award-winning Traktor collective. It’s a fun-filled adventure that follows the chase between a clever rabbit and an unlucky hunter and unfolds in the kind of world that only LEGO play could create. Every character, animal and vehicle is based on an existing or past LEGO toy, so heads spin 360 degrees, everyday objects are outsized, and a boat can suddenly fly with a little help from a palm tree.


Suitable arched bricks for building a bridge

This sounds like a fun project! There are lots of options available for arches. It might be helpful to know a bit more about what you are looking for. If you are trying to build an arch bridge such as this:

The 18838 arch or similar might be a good fit. These can be purchased on Bricklink or directly from LEGO fairly inexpensively.

If you don't have an easy way to get that piece or a regular arch piece doesn't meet your needs, you can get pretty good results emulating arches of any shape using inverted slopes (or regular slopes if you get clever). Here's an example brick-built arch by Tom Alphin:


How can I get replacement stickers for a new lego set?

LEGO Customer Service will be probably be happy to help you out. They've been happy to replace missing or broken parts for me in the past. They have an online service for requesting replacement parts here:

https://wwwsecure.lego.com/en-us/service/replacementparts

I don't think sticker sheets are listed in the inventories on that page though, so you'll have to add it manually using the "I can't find what I'm looking for" link at the bottom. Once the sheet is added to your cart, you just need to checkout and provide an address for shipping purposes.

If you have any problems, you can also contact customer service directly from this page:

https://wwwsecure.lego.com/service/contactus/


I believe this to be part of the Insectoid space series,

I think set 6907:

https://www.bricklink.com/v2/catalog/catalogitem.page?S=6907-1

But could also be one of the other 3 sets that contain the stinger.
https://www.bricklink.com/catalogItemIn.asp?P=x239&in=S


Is 'plate between studs' SNOT supported by one of the LEGO building software?

To build your example in MLCad (LDraw), I needed to switch to "Grid Fine" to move the element into the right alignment:

A couple of techniques to note when doing this when you finish with the SNOT modeling:

Set the grid back to coarse so that subsequent pieces are back on the grid.
Select a non-SNOT element (in this case the 2x3 or 2x2 plate) before placing the next element - grid alignment and rotation are inherited from the last selected piece, so this gets you back to "normal".

See also Joubarc's renderings for my Heroica Graveyard question, again from LDraw by the looks of things, with the elements are added within the clips or between grills in the radiators:


Sharks with frickin’ laser beams attached to their heads

The LEGO Agents Speedboat Rescue (8633) set has a set with laser sharks. The set uses a new version of the LEGO shark with two studs on the top behind the head.

Sadly the shark only appeared in two sets, this one and Brickbeard's Bounty (6243) and because of their limited release they are very expensive on Bricklink.

For the original shark you could use a small Technic rubber band (or any small rubber band) to attach a laser.

In the example below, The body of each laser uses a Technic pin joiner, the rubber band runs along the slot in the brick so it's kept in place. The back end of the laser is joined together with a flexible rubber axle connector.


How to load an RCX from a modern system?

Buy a USB to Serial adapter. There are USB IR Towers, but the drivers are only for older version of Windows. A new USB/Serial adapter, on the other hand, should be compatible with Windows 10 (Windows 10 requires signed drivers, so do your homework before buying).
Use 3rd party software. For example, Brickx Command Center and leJOS are compatible with RCX and have a better chance of running on Windows 10 than the official LEGO software for RCX.

I also found this site, which has the same advice, but with pretty pictures and more details: http://www.instructables.com/id/Making-Mindstorms-RCX-Work-Again/

Note: If you use Linux, there is a built-in driver for the USB IR Tower in the kernel, so just about any Linux desktop system will "just work".


What is this LEGO part (kind of wheel or gear) number?

It is a bit tricky to find this piece on Bricklink. Even though I knew the part it took me a little to find it.

The part you are interested in is Hero Factory Weapon Barrel with 2 Pin Holes and 3 Axle Holes. Default item part number is 98585, but 31511, 31520 could also be used for other colors by LEGO.


How should I go about selling a large number of unsorted LEGO sets?

You have three basic choices, depending on how much time you want to spend:

Sell the collection as-is (with as much honest description as you can muster and great photos if you're selling on-line).
Sort the collection into sets and sell them as-is with parts / figs missing.
Sort into sets and replace missing parts / figs.

These three are not mutually exclusive.

Personally, I'd go with the first option unless you have a lot of time on your hands and are a real enthusiast. Otherwise, your time is probably worth more than any additional profits you might make. At the same time, there are plenty of us who would love to take on a collection like this.


How can I get my NXT to turn on - all it does is softly click?

If you are using NXT-G, the software that comes with the NXT set, then here is what you do:

Get into NXT-G, start a new program.
Select the tools option, and from the drop-down menu, select "Update NXT Firmware..."
Plug your USB cable (one comes with the set) into your NXT. Don't try using bluetooth, as it won't work.
Click the download button on the interface which popped up at the end of step 2.
Don't unplug your NXT, wait until it reboots with its firmware loaded.

Congratulations! You have just brought your NXT out of SAMBA mode!


Personal part collection on the web (Bricklink or alternative)

An alternative to using BrickLink for those purposes would be http://rebrickable.com. I personally find the interface to have some warts, but definitely better than BrickLink in a lot of ways. In particular to your requested features it does support importing parts from sets (Look for the "Add to my Parts (Part out set)" link on any set description page) as well as importing from Bricklink Orders in XML format and a few other sources. If your long term plans involve selling some of those parts on BrickLink it also supports a decent set of export options that can help out with that as well.


Are there any good Brick Labels out there?

Brick Architect has labels available for printing. These are designed to be used with a label maker, but there are also full page PDFs available that can be cut out. Here's an example of how they look:


You might consider donating them to your local library, or an after-school program. Kids love to flip through them!


Where can I find examples of everyday objects built in Lego?

The Lego Ideas Book

Recently released last month (19th Sep 2011). Written with the help of adult Lego Fans. I've had a look through the book myself. The book has six chapters focussing on transport, buildings, space, kingdoms, adventure and 'useful makes'. The buildings chapter in-particular focusses on every day objects.

The LEGO Ideas Book, hmillington @Flickr


I would tend to recommend some options which you didn't consider yet: using bevel gears, but actually use a combination of two gear on each axle: a 12t one (the thin one, as you say), and behind it, a 20t one (there you can use a fat one, which will probably be better).

Another option is to use a worm screw, which will also allow you to change the direction of the axle, but which makes the axles non coplanar.

But it really depends on a variety of factors. Gear reduction is one (keeping in mind it has implications on torque, but frankly I'm already way over my head here so I won't tackle that aspect); but torque transmission is another, and so is strength/reliability.

For example, the knob wheel that you did mention has some uses, as it practically can't slip, but at the cost of lower torque transmitted (or something). Worm screws again have another particularity which is unique to them in that they can transfer torque only one way, which also has its uses (locking a mechanism in place).

And then don't forget that the gears aren't all there is to say: sticking your gears closer to the beams will help, as will replacing the two separate beams by an actual frame. You can also make sure one of the axles goes all the way to the other side of the frame.

And last thing, if you're going to transfer power to two wheels, don't forget to use a differential between them (not sure the new one is very solid though).


I suspect that you used an acrylic paint with a solvent that softens ABS plastic.

Your bricks may take quite some time to harden.

It's possible they never will.


What was the first Lego tie-in film or television production?

I think you already answered your own question: The The earliest Lego television production is Edward and Friends from 1987 that showcased the Fabuland theme.
From the Wikipedia page:

It was Lego's first foray into animation and television in general.


None of the existing wedges have such angles as they are based on integer numbers for the sides. The closest angle you'll find is probably the 2x4 one:

But even that one is about 3° off (63,43° if I remember enough math), so if you place the 2-length sides of 6 of them on a nice hexagonal shape, there will be noticable gaps at the corners.

In short, if you want to build an hexagon-shaped surface without gap, it probably won't be possible.

However, if you want an hexagonal frame for a particular structure, you can use plates the same way you would use Technic beams and get the same results.

Also, the following modified plates could help, as they feature proper angles:


Product description (cannot embed URL for description, so you have to click on "DESCRIPTION" tab) explains why adults are a target audience. (emphasis is mine)

  It’s a super LEGO Star Wars™ gift idea for adult fans and offers a
  testing challenge for experienced LEGO builders, with the familiar
  shape and authentic details of the helmet beautifully recreated using
  LEGO bricks.

  Pay homage to one of the most fearsome bounty hunters in the Star
  Wars™ universe and challenge your LEGO® building skills to construct
  this awesome Boba Fett Helmet (75277) memorabilia model for display.

  The authentic details of the Boba Fett Helmet are beautifully
  reproduced with LEGO® bricks. Displayed on its base with nameplate,
  this model will spark memories of thrilling Star Wars™ scenes.

  This Boba Fett Helmet is part of a range of collectible LEGO® Star
  Wars™ build-and-display models – also watch out for the Stormtrooper
  Helmet (75276).

  The best birthday gift, Christmas present or special surprise for Star
  Wars™ fans aged 18+ and any experienced LEGO® builder, this 625-piece
  Star Wars Boba Fett Helmet offers a challenging construction project.

  This LEGO® Star Wars™ Boba Fett Helmet measures 8.5” (21cm) high, 4.5”
  (11cm) wide and 4.5” (11cm) deep – it doesn’t take up lot of space,
  but its striking details are sure to delight any Star Wars fan.

  This cool, battery-free construction set for creative adults offers a
  stress-relieving, relaxing build. So, take time out, find your
  building Zen and construct a fantastic Star Wars™ character
  build-and-display model!

  Thinking of buying this Boba Fett memorabilia for a Star Wars™ fan new
  to LEGO® sets? No worries. It comes with clear, step-by-step
  instructions so they can take on this complex building challenge with
  confidence.

  LEGO® Star Wars™ construction sets are great for kids and adult fans
  to build and display the models, recreate classic Star Wars movie
  scenes and create their own exciting stories. There’s something for
  everyone!

  No need to use the Force to connect or pull apart LEGO® bricks! They
  meet the highest industry standards to ensure consistency and a
  perfect, easy connection.

  LEGO® bricks and pieces are dropped, heated, crushed, twisted and
  analyzed to ensure that this LEGO Star Wars™ set meets the highest
  safety standards on Earth (and in galaxies far, far away!).

Basically a little more challenging build and not intended for play are the main reasons, I suppose.

Although I'm not sure why they both mention "+18", "adults" as well kids in the same description, like here:

  LEGO® Star Wars™ construction sets are great for kids and adult fans
  to build and display the models, recreate classic Star Wars movie
  scenes and create their own exciting stories. There’s something for
  everyone!

EDIT. LEGO has released new 10273 Haunted House set with a press release explaining why some new sets have "18+" marking.

  Addressing the new packaging, Senior Marketing Manager Anders Hellegaard Iversen said: “So many of our older builders love the Creator Expert products, as they allow them to show off their passion for the bricks. Whether it’s their favourite film moments, sport icons, travel destinations, buildings, fairgrounds or vehicles, LEGO sets help to bring these to life in brick form. That’s also why we have decided to stop using the Creator Expert branding and, instead, use the new adult-focused packaging design to make it clearer which hobbies or brand products they can relate to. We hope this will make it easier for fans to track down models they would be proud to display once completed. Of course, our product range will continue to include the same advanced-build, collectible products that guarantee hours of building enjoyment for fans.”


According to various sources, LEGO pneumatics is not designed to work above 3 (or maybe 4) bars of pressure, so your setup might have been damaged by the overpressure.

If you can "press on the the pumps in certain ways" then I would recommend starting your investigation there. As to actually locating the cause of the leakage, I have five main methods in mind:

1. Vision

The easiest and fastest way is to check all components for loose connections, punctures or cracks. In my experience, when pneumatic hoses are subjected to overpressure or excess mechanical stress, they usually fail by slipping off their connection points. So go over all your connections and ensure that all stiff tubes are pushed into the flexible hoses as far as they can go (4-5 mm at minimum, or about one "arm" of a pneumatic T-joint).

If that fails to reveal any problems, check the lenghts of the hoses for any punctures or hairline cracks, while the system is under pressure (as the cracks might close and seemingly disappear in the absence of a force that acts to open them from the inside).

2. Hearing

It can be hard to hear the sound of air hissing out of a tiny hole, especially with a compressor running, but if you can find a way to remove the compressor from the setup, you could be able to spot the point of failure.

Ideas to remove the compressor:
 - Let it fill up a pneumatic tank, which is isolated from your system via a valve, then turn off the compressor and throw the pole of the valve open.
 - Add a long enough hose between your system and the compressor so that you can set up the compressor a bit of distance away.
 - Apply pressurized air to your system via some alternate means, like e.g. by blowing into a tube, or via an inflated balloon.

3. Feeling

If the hole is too small to see, the escaping air might still be felt on sensitive areas of skin, like fingertips or your cheeks. The hairs on the back of your hand might be helpful in amplifying the weak air movement into an observable feeling.

4. Bubbles

If all above methods have failed, you could consider submerging your system in water. Only do this, if you can remove ALL electronical components (motors, wires) to a safe distance, and only if your setup does not include pistons with metal shafts. After doing so, you only need to watch for the emerging bubbles to see where does air escape from. Note that your compressor pieces must remain above the waterline, or else they will try to pump water, which can damage your parts from the inside (or just stay there for a long time to come).

As an alternative for localizing holes in certain areas, consider applying soapy water to the suspected parts (Tip by JPhi1618 in comments).

5. Deconstruction and reconstruction

In the improbable case that even the submerging method has failed, you could deconstruct your system, inspect each part individually for their ability to produce/transport/direct/use pressure without loss, and then reassemble it with proven flawless parts.


EV3 Brick: Powers on then off and won't stay powered on

If the batteries are new and not even the update mode stays on, then something is wrong with the hardware. You should reach out to LEGO customer support to see if they can help.


Need help identifying a couple of Lego sets, grey tank with 4 short legs, and ship with long wings with lime green tiles

Top set is number 75013, Umbaran MHC (Mobile Heavy Cannon). I think the previous owner modified the cannon, because the actual set looks vastly different up there. I don't recognize the bottom set, but it looks like some star wars set.


Since you are a C# pro, I would recommend MonoBrick. I know they have a plugin for Xamarin Studio/MonoDevelop that lets you do remote debugging. Not sure if they have one for Visual Studio yet.

There is also EV3Basic, which is an IDE that lets you program the EV3 using the BASIC programming language. Unlike most other 3rd party programming languages this one actually uses the official EV3 firmware.


Can I remotly control the points on PF train tracks?

There is a pure way of changing the points at a track. It requires as few pieces as you like: a motor and two technic beam/bricks. This video demonstrates the principles of point changing with a NXT motor and will work with PF and RCX.

You can use Mindstorms to program the events that trigger the points to change, it will cost you extra but there are benefits.


Is there a guide that has the number and kinds of pieces per set?

As mentioned by @gev, Bricklink is a great place to go. It is, however, not the most intuitive site to use. Here is how you can easily get the item counts:

Start with the Search box at the top of the page. Before typing in the name of the set, make sure the selector is set to search the Catalog.
Enter a term from the name of the set (e.g. "Millenium" or "Falcon").
The Catalog results will pop up. You might find sets or individual pieces listed, or even several (regional) variations on the set.
Go to the entry that best describes the set you (think you) have. The entry will start with a number (e.g. 10179-1 for the Millenium Falcon UCS) and after the number, in parenthesis, you will find a link to the inventory (labeled "(Inv)"). Clicking on this link gets you to a detailed inventory with item counts for the particular set.

Rinse and repeat for other sets you have ... good luck!

Alternatively if the set is from 2002 or later, you can go to http://service.lego.com/en-us/buildinginstructions to download the building instructions, which contain a detailed inventory at the end. Unfortunately, the resolution and color palette of these instructions is not the greatest (at least on the ones I've tried) so it might require some sleuthing to decipher the different pieces (studs are not showing very well, and it is difficult to tell the different color shades apart, like light grey, dark grey and black).


Why does my NXT colour sensor not recognise colour on my iPhone?

The robot in the video has a custom light sensor, a more advanced HiTechnic color sensor V2 which can detect an extended range of 15 colours. The stand colour sensor can detect six (white, black, red, blue, green and yellow).

  The sensors are based on different principles. LEGO sensor uses a RGB
  LED, and successively shines red, green and blue light on the object.
  Reflected light is collected by a light sensor sensitive to all
  wavelength. HiTechnic one has a white LED, and a specialized color
  sensitive chip. This chip has three sensitive areas covered by red,
  green and blue filters. An added advantage of HiTechnic method is that
  it can detect the color of light sent on it (in passive mode, with the
  white LED shut off).

[Source]

A direct LED light against an iPhone's screen will reflect the light back into the sensor, making it difficult for the sensor to detect colour.


How to remember initial position of a robot and return to it

You have two options.

You can use an accelerometer. Lego sells one that can be found here. There are also aftermarket ones at mindsensors.com.  This allows you to independently measure the acceleration of the robot. You have to then integrate this information twice to get positional change. The way to do this is to put it in your control loop and sum up 0.5*dt*dt*a where a is the accelerometer reading (there will be one for each axis of motion) and dt is the time between samples. This nice thing about this is it gives you absolute displacement. That is it accounts for motions that cancel out so you can set a straight line path back.

You can record each displacement into a variable for x and y directions using the servo readings from the motors - remember to reset the encoder value from the servos after each reading. This is harder because you have to account for the geometry of the wheels and keep track of the robot heading - lego also sells a compass sensor if you don't want to deal with finding your heading, but you'll still have to deal with non-spinning turns. It's also prone to accumulation of errors. (the accelerometer is too but not as bad I think.)

Your admonition of 'no other helpers' could be interpreted to mean you don't want the first solution in which case you are left with using the encoders and figuring out the differential motion of your chassis design (which may be non trivial).


I did new research on Rebrickable and found out it is #76086 - Knightcrawler Tunnel Attack


What kind of design is comparable to these programming concepts?

A conditional can perhaps be represented by a door that can be blocked from the other side, or maybe two doors, of which only one is blocked via a sliding brick.

As for loops, I would represent them as conditionals with counters, by blocking a door with a set number of bricks and removing one brick per iteration. If you'd rather count upwards, then a fixed size hole can be filled with bricks gradually.

These analogies were made to the "minifig walking through a set of corridors - the program" analogy, but we could surely find solutions for axles and gears or even pneumatics if you were thinking along those lines.


LEGO doesn't really follow I2C standards, so "close enough" is a good description.

The EV3 hardware developer kit (available for download at http://mindstorms.lego.com) has this to say:

  4.1 I2C communication

  The EV3 platform supports the same level of I2C communication as MINDSTORMS NXT. This means that
  system support a maximum of 9600 bit/s and maximum 32 bytes communication buffers. All I2C
  communication is running within software drivers. External devices are required to include pull-up
  resistors on both pin 5 and 6 on 82K ohm. If multiple sensors are used on the same bus the total
  impedance needs to be adjusted accordingly.

Most off-the-shelf I2C devices use 10k pullup resistors (although it looks like it might be 4.7k in your case). These must be removed and replaced with 82k resistors to be compatible with MINDSTORMS.


You should get in touch with LEGO Customer Support. I'm sure they will be more than happy to ship you missing sticker sheet.
If you are still looking to purchase the stickers instead, you can do so on Bricklink.


Searching Zombies Minifigs on Bricklink I find 22 official Lego zombies, including the Monster Fighters, Minecraft, Scooby Doo, Ghostbusters, Pirates of the Caribbean, and several Mini figures from the collections.

http://www.bricklink.com/v2/search.page?q=zombie#T=M

Most of them are one offs in the set.

The most I found was three zombies in a set.  There were two sets:

Pirates of the Caribbean 4195-1 Queen Annes Revenge: Has three zombie pirates and a skeleton which I'm not counting as a zombie:

Monster Fighters 9465-1 The Zombies Set has Three Zombies, a zombie bride, a zombie groom, and a zombie driver:


What is the name/part number of this 1x1 LEGO brick, used to make "cat eyes"?

Name: Lever Small Base 4592.
Bricklink link HERE.


Here are the two things that I would recommend:

Get yourself a big set if you have the budget for it. These will have a large variety of pieces and once you've built the models from the instructions you'll have a good understanding of a lot of different building techniques.
Watch eBay or similar sites for large lots of Technic parts by the pound. These can be a little hit or miss, but the price per piece is far lower than most other ways of buying parts. Keep in mind that prices tend to be higher around the holidays.

There used to parts packs for Technic like what you are describing, but I believe they were removed now that pretty much everything is available from Pick-A-Brick. You can also get any parts that you want from bricklink.com, and if you don't mind used parts, this can be a pretty affordable option.


These glass panels are

Trans-Green Glass for Window 4 x 4 x 3 Roof

from  6940-1 - Alien Moon Stalker

they fit with

4447 -  Window 4 x 4 x 3 Roof

4741 - Window 4 x 4 x 6 Outward Sloping


Is "public transport" train compatable with Lego City track?

It uses train wheels which means it should work on Lego track.

Sources:

Bricklink set inventory

LEGO Building Instructions lookup


Best way to match minifigs and tell what set they are from?

One way to do this would be to look through the Bricklink categories for minifig torso assemblies and minifig leg assemblies. There are a lot of them, but once you find the part you are looking for, you can then learn what set it came from which should lead you to a couple of complete minifigs (click the part id then click the "View" link under "This Part Appears In" on the right).

You could also search through the Minifig category on Bricklink.

You can go through those categories by year if you know approximately how old the parts that you have are.

If you get stuck on something, feel free to post the picture in a new question here. I'm sure that someone will recognize it. :)


What is this? Is it LEGO? Dark Green, detailed mouldings, roughly trapezoid shaped

That's LEGO piece - 47299 - Bionicle Toa Metru Knee Cover. You can see © sign in LEGO font as well as "47299" part number on the bottom, both of which confirm this is legit item.


One way to do this on Bricklink is to run an advanced search over the "Minifig, Head" category. Here's an example showing all yellow parts in this category with a minimum lot size of 200 sorted by price, lowest first.

This shows you the cheapest stores to order 200 of the same yellow head from. If you want a little variety, I'm sure those sellers have other heads available as well.


The center button does not work on EV3 brick

It is somewhat common for the buttons on the EV3 to stop working. This is usually caused by the failure of the adhesive that holds the metal part of the button in place.

You can always contact LEGO customer support to see if they can help.

For the do-it-yourself person, it can be fixed fairly easily though. This is how I do it...

First, you will need to remove the cover from your EV3. This requires a Phillips screwdriver. Remove the 4 screws in the battery compartment and gently pull the top half of the plastic housing off.

The image below shows a couple buttons that I have already fixed and one button (the right button) where the adhesive has failed. You can see that the plastic covering is coming loose.

Use a sharp knife to cut away the plastic that has come loose. Since the adhesive is no longer sticky, it is not doing any good.

Use clear tape to fix the button back into place.

Then reassemble the EV3.


Sounds like electric, light & sound 4 x 20 x 5 insectoid stinger.

Part# top: x239top

Part# bottom: x239bottom


On what plane is 7292 Propellor Adventures based?

It looks like a pretty generic twin engin-ed WWII bomber.  Maybe like this Mosquito bomber?


Is it safe to remove PC (polycarbonate) arms from minfigures?

The clear PC arms are more brittle, however you should be able to replace them at least once, since the torso you are placing it into is ABS - so there is a bit of a give/flexibility on that side.

One thing to be careful of, is when you take out the PC arms (and when you put them in a new torso), do not hold the arms by the hands! This will put pressure on the wrists and can make the more brittle PC plastic crack. Either hold the arms further up, or even better, take out the hands first, then the arms. Hope this helps.


Get robot to face perpendicular to nearest object, using the ultrasonic sensor in NXC?

I like your username. I'm not exactly good at NXC either, but I'm experienced in C and Java. So here's some pseudocode that should get the job done. This will rotate the scanning motor 180 degrees, while remembering the closest object it's seen, and then rotating that motor back to point towards the closest object. You will need to change the functions to correspond to the actual NXC functions.

int closestObjectDist = 100; //variable records the closest object's distance
int closestObjectAngle = 0;  //variable records the angle pointing to the closest object
int currentAngle = 0;        //variable to hold the scanning motor's current angle.
int currentDistance = 0;     //variable to hold the sensor's current distance reading

resetScanningMotorAngle();   //reset the scanning motor's angle to 0.
turnScanningMotorOn(10);     //start rotating the scanning motor, slowly.

while(currentAngle < 180)    //repeat until the scanning motor has rotated 180 degrees
{
    currentAngle = getScanningMotorDegrees();  //get the motor's current angle
    currentDistance = readUltrasonicSensor();  //get the sensor's current distance

    if( currentDistance < closestObjectDistance )  // Here's the important part:
    {                                              // When the sensor reads a distance that
        closestObjectDistance = currentDistance;   // is the smallest distance yet,
        closestObjectAngle = currentAngle;         // record the angle and distance.
    }
}
                                            //now we have the closest object's angle stored!
rotateScanningMotorTo(closestObjectAngle);  //rotate the motor back to the recorded angle.

This code assumes that the robot scans in a 180-degree arc, but you could easily just change the 180 to 360 to scan in a full circle.

After the loop, you can add or subtract 90 degrees to closestObjectAngle to make the motor point perpendicular to the closest object instead of pointing AT the closest object.

Ask if you have any questions!


What are these grey scoop-shaped parts with a hole for an axle?

This is:

Part# 42042 : Light Gray Bionicle Krana Holder 3 x 4

Keyword: 3 x 4, Color: Light Gray

it appears in 13 sets


What did LEGO bricks look like in the past?

The earliest LEGO bricks were made in 1949, and they had completely empty undersides with vertical notches in two of their sides for attaching windows, doors and decorative cardboard inserts:

Then in 1958 (or 1961, depending on the country) the form known today was adopted, with tubes on the bottom and without notches:


EV3 motor TACHO signal connection. Hardware schematic questions

The EV3 detects when motors are connected and disconnected using the ADC (and gpios). The two 100k resistors are basically a voltage divider, so when the motor is disconnected, the ADC will read 2.5V. If a motor is connected, the motor encoder will either pull the signal high (above 3.7V) or low (between 0.1 and 0.65V). The detection algorithm is actually a bit more involved than this, but this is the general idea.

For the full details, see the Device Connection Manager Driver and the actual source code. The documentation is not quite exactly correct, so when in doubt, trust the actual source code and not the comments (documentation is generated from comments).

And even though you didn't ask about it, I should point out that the transistor (Q10A) is also used as part of the detection.
You don't show it, but MA1 is connected to pin 2 on the output port, which is one of the motor driver signals, so MA1 could either be battery voltage, floating or ground depending on the state of the motor driver chip (via 1OUTB2). Additionally, the voltage could be steady or PWM depending on the speed and direction the motor is running. Or, MA1 could also be something else if there is no motor plugged in (or something besides a motor is plugged in).

On NXT sensors, pin 2 is connected to ground (pin 3). In the source code, it looks like this is just used to detect if a NXT sensor is plugged into the output port.


What software should I install for NXT on OSX El 10.11.2 Capitan?

You can try installing the NXT 2.0 software. (See this question)

Here is a working link for the software: http://service.lego.com/en-us/HelpTopics/default.aspx?questionID=2655. Look for "How can I get a replacement for the LEGO® MINDSTORMS® NXT software for set 8547?"

It says that it will not install on OS X 10.10, however, I did successfully install it on 10.10 anyway. I have not tried installing it or running it on OS X 10.11 though.

There are open source alternatives, but the ones I have seen haven't been updated for a long time, so they may have problems running on newer versions of OS X as well.


I once talked with a Lego Builder at the Florida park. He told me they use a glue that actually melts the Lego blocks together. With that in mind, I searched and found this article (on Facebook). It says Lego Park Model Makers

  use a solvent based plastic weld. It heats the bricks up so the edges bind together. Obviously it has to be very strong to withstand weather conditions.

A quick search on that found this from Google shopping.

The article also talks about color fading and model life time (about 5 to 7 years), after which the model can either be rebuilt or cleaned:

  We clean them using a shot blasting technique. They are sprayed with a fine salt spray, which takes a very thin layer off the bricks, and then they are lacquered with a UV coating. This gives them another 3 years or so.

I hope the project goes well.


My guess is that they're LEGO Round Plate 1 x 1 Straight Side (Part ID: 4569058
Design ID: 6141) with paint applied to make them look like food. Details of some of the sets that contain them are available on BrickLink.


What's the maximum pressure one airtank can withstand and how to tell its limit?

You will not destroy the air tank using standard LEGO components. I don't know what it's structural limits are, but I can tell you that the weakest link in the pneumatic system in my experience is the connection between the rubber pneumatic tubes and plastic inlets. Under high pressure, the tubes will simply pop off before any of the components will actually break.

I believe that the most pressure you are going to be able to achieve using standard LEGO components is around 40psi. All of the components can easily handle this pressure.

If you'd like to do some exploration of this on your own, you might want to get your hands on the pneumatic pressure gauge that has been available in the LEGO Education line:

If you really want to know the maximum pressure limit of the tank itself, you'd probably need to somehow attach it to real compressor and wait for it to break. I like my pneumatic components too much to do this myself. :)


EV3 software can be used with the NXT brick. It may require a firmware update. I think firmware 1.31 is the minimum.


How to get VIP vouchers in another currency?

The vouchers available in the VIP rewards centre are linked to one's country - that is, the country linked to one's VIP account.

Note that this is not the same as the country of one's account, even though both are linked, and can't be changed online at the moment but only via the Customer Service. There seem to be some kind of redundancy in the way LEGO handles countries and languages at the moment, hopefully they'll fix it at some point. Summary:

LEGO account (or LEGO.com profile) has a country, which can be changed online (in "Edit Profile" -> "My Information")
VIP account has a language preference which can be changed online, and a country which cannot

In any case, when facing trouble with anything related to the LEGO website, online shop or VIP centre, it is best to contact the Customer Service directly and they'll do their best to help (and even toss in some extra VIP points for your trouble, which is a rather nice gesture).

At the moment, it doesn't seem possible to get vouchers in another currency except through changing the country linked to the VIP account via the customer Service. This means if you want to redeem VIP points for LEGO purchases, you're in effect limited to do it in your own currency (assuming the vouchers aren't country-specific; haven't tried that yet); but that's probably a minor issue for the majority of people.

Also, shopping in LEGO stores in other countries will get you VIP points without problem - the only subtlety might be that due to exchange rate, you might get more or less points for a similar purchase. As an example, I bought 21319 (Central Perk) in The LEGO House for 649DKK and got 649 VIP points; if I compare that to other countries based on the online shop I get:

Denmark: 649DKK (~87€), 649 points, so 1 point per 0,1338 EUR spent
UK: 64,99 GBP (~75€), 520 points, so 1 point per 0,1446 EUR spent
Belgium: 69,99€, 525 points, so 1 point per 0,1333 EUR spent
France: 59,99€, 450 points, so 1 point per 0,1333 EUR spent

So the VIP points given when buying a set are tied to the DKK price of that set, and seem to be aligned on exchange rates, with possible the exception of the UK (the online shop notes explicitly that VIP points are calculated at checkout). The difference in VIP points received is probably not worth taking into account when purchasing; however, the price of the set can vary a lot from country to country, and that's worth taking into account.


Can I use Microsoft Makecode to programme Lego NXT bricks?

Just heard from Microsoft, MakeCode only works with Lego EV3, NOT NXT.


Can the Powered Up app be used to directly control the Boost Move Hub?

As of the Powered Up app version 3.0, this is possible.

Old answer:

As of August 2018, this is not possible. However, TLG has stated that they plan to add more compatibility to the Powered Up system, and this will likely be available as a firmware update in the future:

  Q. Will all different Powered Up components (Boost, WeDo, Train, etc)
  be able to communicate and control each other, e.g. running a Boost
  program sequence using a Powered Up hub or using sensors with Powered
  Up hubs?

  A. It is the aim that the Powered UP platform will work together
  across both with the wired and wireless connection. Some of these
  connections are not implemented yet and will come through firmware and
  app updates.


You have a number of options.

Since you mentioned you know C# the best, have a look at http://monobrick.dk. They have a C# library that lets you remote control the NXT. Then you could use something like http://playground.arduino.cc/Interfacing/Csharp to do the same for the Arduino. UPDATE: MonoBrick project doesn't seem to be around anymore.
For Java, there is a similar NXT remote control library from http://www.lejos.org/. I imagine you could find something similar for Arduino as well.
If you want to connect the Arduino directly to the NXT, you can use USB or Bluetooth. Then you can use the information in the NXT Bluetooth Developer Kit (available from http://www.lego.com/en-us/mindstorms/downloads) to develop a program for the Arduino what will be able to communicate with the NXT.


Ok, I have managed to build a working cam mechanism using LEGO Technic. Only thing missing is a big enough spring or elastic band to pull the entire assembly upwards - Still thinking through that part but sharing in the hopes that others can take my idea further (My current best thought is to have rubber bands on the outside of the mechanism pulling the "clicker" upwards.). Here is a demonstration of the mechanism at work (was difficult to demonstrate with just one hand as I haven't lined the walls of the vertical holder enough and sometimes the up/down motion goes under an angle): video on youtube.

Pictures:

The entire mechanism:

Clicker in the "up" position (i.e. retracted pen):

Clicker in the "down" position (i.e. pen out) - my hand is in the picture as there is no spring to provide pressure upwards:

The insert with the loop (I believe this is what is called a "cam"). There is a resting point on the top (the "down" position) as well as a resting point on the bottom (the "up" position):

The "ball" - in this case a simple Technic axle with 2 1/2-width bushings on it - is supported in this mechanism, which allows the black part to slide freely from left to right. This "ball" moves around the loop defined by the "cam" from the previous picture:


Steering mechanism for City-scale vehicle

It's difficult, but not impossible. A rigid axle turning at the centre would be mechanically simpler. As my crude drawing illustrates;
I would place a 24-tooth gear over the 2x4 wheel axle. A 8-tooth gear is optional but will provide finer control over the steering. The two teeth gears can also be replaced with a pulley gear.

This technique however will not work with current Lego CITY vehicals unless the wheel arch is removed or replaced.


SPUA - Special Part Used Again, a part which is seemingly only for a particular set or theme, but is used again

List of LEGO Abbreviations from Brickipeda


Could not find this LEGO brick, any ideas?

That's Legs without Split, which were used for the very first LEGO minifigures.


Which set do these LEGO bricks belong to?

As already identified in the comments by Uli, the parts Stick 6M W/Flange in bright yellow and Brick 4X6 W/Bow/Angle in bright yellow are only available together in 75092-1: Naboo Starfighter:


Check for 5V on the two middle pins of the motor connectors (plug a cable into the brick, no motor on the other end,  and measure volatege on the contacts of the open other end). NXT/EV3 have separate power to all the sensors, if there's a short (failed capacitor or similar) or the power chip failed then the brick will still work, but the sensors won't get power.


The head is
part # 3626bpx129 : Minifigure, Head Moustache Black Bangs, Striped Sideburns, Cleft Chin Pattern - Blocked Open Stud

Hair

Part# 40251 : Minifigure, Hair Female Mid-Length

The rapier (sword) is from Brickarms


What is the difference between the plastic used in mainstream minifigs and the plastic used to make the popular collectable series of minifigs?

On thebrickblogger.com (February 9, 2017) there was a call to report issues with minifigures. Reading the answers I get the impression that issues with clutch-power, cracks and other problems are occurring with all sorts of minifigures, not only with the collectible series. This would mean that it is not a persistent problem with Chinese factories:

http://thebrickblogger.com/2017/02/lego-collectible-minifigures-quality-issues/

Looking at Ebay I also get the feeling that 90% of all problems will never be noticed because the owners won't open the bags!


Where can I download the English LEGO Catalog for 2005 to 2014?

Brickset.com maintains an archive of all catalogues they can find. Unfortunately it only goes up to 1999 at this time.


It's been a while since I've played, and looking at the strengths and weaknesses of the individual pods does seem to make them look fairly equal.  However, I distinctly remember that some sets had units that gave a slight advantage over other sets, at least for my style of playing.
For instance, the Aqua Pod has several units that can deconstruct and eat, but could not move very far.  (Deconstruct reduces your opponent's unit by 1 level.  Eat deconstructs an opponent's level 1 unit and raises your unit up 1 level.)  While the Aero Pod has several that can move far and deconstruct, but do not have the special ability to eat.

In several games between these two Pods, I was able to win by moving next to my opponent's unit, battling till he was down to level 1, and then just eating him, thus raising the level of my unit back up by 1.
It may be that certain combinations of sets are more equally matched than others, or it could be that I was just better than my opponent :)

Edit:
(For a copy of the rules, starter kits, boards, and strategy guide see this question.)
The Advanced Rules and the Advanced Strategy Guide give a few pointers that can help your game.
For building a board, the Advanced Rules suggest:

You should probably have at least 5 obstacles and no more than 9 for a balanced game.

As for strategies, they vary based on the abilities of the Pod you have chosen, and your opponent.  (For complete strategies for each Pod against all other Pods, see the Advanced Strategy Guide)
Aero Pod

Using Obstacles to Your Advantage
The chief advantage of the Aero Pod is that most of its units can fly or jump. This means that yellow units are much less restrained by obstacles than units of any other Pod.  On an arena filled with obstacles, Aero Pod units are, at their best, able to avoid getting boxed in and to score quickly. On less blocked arena, the Aero Pod has less of an advantage, but its jumpers and fliers can move over enemies, while its raiders can move through them.

Aqua Pod

Undersea Dining
Similar to the Wild Pod, the Aqua Pod has a well-balanced set up units and a few different strategies from which to choose.  Pay attention to what team you’re up against to determine your strategy. Fast opponents require deconstructing units that have block them at choke point; slow opponents should be outrun with quick moving and jumping units. And don’t forget about your eat ability. Eating gives you an edge in deconstruction stand-oﬀs, so be sure to have some level-one units of your own on the board to rebuild and preserve your powerhouses.

Arachno Pod

Getting the Opponent in your Web
Arachno units are pretty quick, so you’ll probably want to play an aggressive game where you try to score early and often. The web ability is a great aid to this strategy. Since web has a range of two, you’re able to maneuver your units easily to freeze opponents before they get near you. Use web to incapacitate oncoming units and either zip your faster units by to score, or moving into your deconstructing units to ﬁnish the job. Arachno works particularly well on open boards, where you can web opponents without blocking oﬀ your paths to the opponent’s row.

Auto Pod

Quick Scoring
Auto Pod has the fastest units in the game. It has very few jumpers or ﬂiers, but it makes up for that lack in raw speed. What this means is that an Auto Pod player has a good chance of getting control of the board and scoring points earlier in the game.  This strategy works best on open boards with few obstacles to block your units' movement. On more crowded boards, Auto Pod players have to rely on their pushing, carrying, and limited deconstruction abilities to break the opponent's line and create a path on which to score.

Dragon Pod

Winning with Super-units
The center of a Dragon Pod team is its dragon unit. These four level units are easily the most powerful in the game, so using them eﬀectively is the key to victory. First, the number of units you can use with any individual dragon is limited, so picking a dragon will basically determine your strategy for that board. Your secondary units are fairly weak, so use the dragon aggressively and don’t be afraid to lose a level if it means taking out a key opponent. Still, be sure to have a couple good back-up cards and maybe even some Build and Place X-tras in case the dragon goes down.

Monster Pod

Scaring Your Opponent Stiff
Monster Pod is a slow, steadily moving team with a powerful special ability: scare. What makes scare so powerful is that scaring happens automatically at the end of a turn. This means that every scaring unit freezes all adjacent opponent units every turn, even if you didn’t activate it. As a result, scaring units are terrific to leave near important intersections on the board to stop enemy movement. On the other hand, combining a scare unit with a carrying unit will give you an engine you can march across the board, and deconstructing frozen units is an easy way to clear the board.

Robo Pod

Keeps Going and Going...
Robo Pod units have the most deconstructing units of any Pod so a lot of Robo Pod strategies are about taking apart your opponent's pieces. Use this advantage to guard your home row and hunt down enemy units to keep them from scoring.  Robo Pod units also have an additional advantage that aids them in deconstruction - almost every Robo Pod unit continues to function at its lowest level. This means that your units have to be removed from the board to stop them from moving. Robo Pod works best on boards where there are choke points that its units can guard, and from which it can slowly march its units to victory.

Wild Pod

Eating and the Value of Food
The Wild Pod has the most diversity of all of the Pods, which means that you have a few strategies to choose from. You'll want to tailor your units carefully for the Pod you're facing. The advantage that you have is that your units can eat. This means that any Wild Pod unit on the board can potentially reconstruct itself and that you have a unique edge in deconstructing others. Be sure to make use of the level one "food" units that the Wild Pod has. More powerful units can be accompanied by a couple of level one units that can restore its levels and make it safe from deconstruction.  Using eat well can decimate your opponent's units and allow you to keep your super units for the duration of the game.

Summary
The important thing is to know both your and your opponents strengths and weaknesses, but even the best strategy can be overcome by someone with no strategy.  You must be prepared for anything and have a full knowledge of your own capabilities and how to use them.


What does the 4 digit number embossed on my LEGO set represent?

That number is not a real number, it is a production code (in your case, 27S5) consisting of 2 digits indicating the week of the year the set was made (in this case, the 27th week), a letter indicating the region the box was made in/for (R = US/Canada, S = Europe, I believe) and the last digit is the last digit of the year the set was made in.

So you have a Gingerbread house made in 2015, in the 27th week of the year (June 29, 2015 - July 5, 2015), and it was produced in/for the European market.

These codes typically go on the seals/stickers closing a box, but in case of smaller boxes that are supposed to be pushed open, the code gets embossed into the package.

And just for comparison - all my Gingerbread houses have production code 31R5 (I'm in the US).

UPDATE 5/2/2016: Here is a list of all the plants referred to by the letter code:

H = Nyíregyháza, Hungary
R = Ciénega de Flores, Mexico
S = Kladno, Czech Republic
Q = Purkersdorf, Austria
B = Shenzhen, China (Not Confirmed)
M = Billund, Denmark (Not Confirmed)
O = Billund, Denmark (Not Confirmed)

Note: list attributed to GiliusThunderhead over at the BrickPicker.com forums.


If I understand your question, you are seeking a spacer that can spin freely on a Technic axle. Essentially, you want a 1/2 bush that has a round hole rather than an axle hole. I don't believe that this piece exists in Technic.

The old Technic Hub/Handle (424) may do what you want, but it is thicker than a 1/2 bush:

Failing that, a minifig ring may work for what you need if you have one handy:

Feel free to post pictures of your WIP and we may be able to provide better suggestions if those don't work.

Edit:

Now that you've posted a photo, I wonder if a 1/2 Bush might just work:

Edit2:

I've now had a chance to play around with some alternate designs, and the one that I like best simply replaces the 2x2 plate and 2x2 tile with this wheel hub (3482):

This is solid and has a nice feel in the hand. It gives you the flexibility to have this rotate as tightly or loosely as you'd like.

Some others like to just use an additional 2x2 round plate:


Are Bandai "Figmes" compatible with LEGO?

Yes, they fit!
With a little research I have learned that the hands can hold standard bar pieces, and the legs are compatible with studs.
However, sitting won't work, and pieces can't be swapped for minifigure parts.
The backs look like the front, solid printed plastic.


What files are required to run an ev3 program?

The titles headed with underscores are unneeded. The title is not necessarily required, and the copyright is obviously useless to the machine.

However, none of the other files can be skipped or removed and still allow the program to work.

These others are written in XML, Extensible Markup Language, and are designed for use by both human and machine. The microcontroller needs all the information in these files.


What are these bricks with filled interior and holes/tubes going through?

They were used until 1990 for trains, the holes are there to stick in the wheels.

This is the part: http://www.bricklink.com/catalogItem.asp?P=7049b
And these (for example) were the wheels: http://www.bricklink.com/catalogItem.asp?P=wheel2a


I have a female fig black dress patterned slope only, long hair, intricate face

Hair is Minifigure, Hair Long. In Dark Brown color this was used by just one minifigure, the Highland Battler.

Face seems to be one of two versions of Minifigure, Head Dual Sided Female, Dark Brown Eyebrows, Crow's Feet, Smile / Angry Pattern (HP Narcissa), with Blocked Open Stud OR with Hollow Stud.

Torso is unrecognizable as the picture isn't clear enough.

"Legs" are Slope 65 2 x 2 x 2 with Bottom Tube with Light Bluish Gray Inset Skirt Pattern which, originally, belong to Narcissa Malfoy.

Since half of elements for this minifigure come from Narcissa Malfoy it must have been used as a base for modifying it.


Is my Lego Star Wars "Jabba's Sail Barge" set a one of a kind?

The short answer is no, this does not make your set more valuable.

You have recieved a set that contains what Bricklink calls an "Alternate Item".  These are alternate pieces/stickers/colors/etc. that are packaged into normal sets by LEGO in order to ship out the sets in the event of a part shortage.  They are perfectly normal.  And, usually, they are more common pieces than the pieces they replace, so there is no added value for the part.


Identify these (Technic Steering) parts?

These parts were used for steering in many Technic sets between 1988 and 2001. They are the following parts:

Technic Steering Gear Holder (2790)
Technic Steering Rack (2791)
Technic Steering Top (2792)

Here's an example of how they can be used together for steering from set 8022:


You just can't. This part is fused together with sound-waves so it doesn't separate anymore.

Source and more info: fusing Lego together


Part identification - Red 2x2 tile with fire print

This is part # 3068bp57 : Tile 2 x 2 with Groove with Classic Fire Logo Small Pattern
It was released from 1986 until 1994 and appears in 5 sets


How can I convert an image's pixels to actual LEGO colors?

You can use GIMP for this.
First you need to scale the image to the size you want. (If you want to stack bricks on top of each other instead of a baseplate, use a different y-scaling to correspond the bricks height.)

Now create a palette by going to the Palette tab and click the "New palette" icon.

In this add the bricks colors you want. You can find the colors RGB values to a brick color here: http://www.peeron.com/cgi-bin/invcgis/colorguide.cgi

Now convert into these colors by going to "Image->Mode->Indexed...". (If indexed is already selected, select RGB first and then click Indexed.) A "Convert Image to Indexed Colors" dialog box should appear.

Select "Use custom palette" and select the palette you just created.

Click "Convert" to get your result. If you are not quite satisfied, click undo and try to change/add some colors in your custom palette and convert again.


Are there LEGO sets unique to the UK/Europe?

I completely agree with what Gareth said above. There have been several sets sold exclusively in the Uk and Europe throughout Lego's production history. However, if what you are asking is recent or more unique/exciting ones, then I can think of a couple off the top of my head.

Lego BR toy minifigure sold(if I remember correctly) in BR stores in the UK:
Brickset BR toy

Team GB series sold in UK and maybe Europe:
Brickset GB team

DFB German football team sold exclusively throughout Europe(possibly only in Germany):
Brickset DFB series

London bus given at store opening in London:
Brickset London Bus

Royal Guard buildable figure exclusive at Leicester Square store:
Brickset Royal Guard

I know the 2 Lego CLub Max minifigures is exclusive, but I dunno if it was only sold in UK/Europe:
Lime Green Max and Regular Max

The lego House minifigure/ set was sold in Billund stores:
Lego House set

The Legoland train is exlusive to Florida and Denmark:
Legoland train

The 2 Nesquik bunny sets were available in Germany, New Zealand, and Australia(who doesn't like chocolate milk?):
Nesquik

British exclusive minifigure Lester(not Chester, if you saw my edits):
Lester minifigure However, it's been a while, so I don't think you can still get this from the scratch ticket.

Oh, alright, you caught me. I used Brickset. Sorry for the long post. This is about all that I could find/think of. Some of the entries that I found, I wasn't sure of, so I didn't post them.
Please note that the places where they are sold are based only on my memory.


Is it possible to use DUPLO bricks in LDD?

LDD is a closed world where people can't add its own parts. If you want to create Duplo building instructions you should use LDraw that has many Duplo parts in its library, and allows you to create the missing ones if needed.


Lego EV3 - sending direct commands over RFCOMM Channel (Objective-C, Xcode)

I have found solution. I create category NSString+NSStringHexToByte:

NSString+NSStringHexToBytes.h

#import <Foundation/Foundation.h>

@interface NSString (NSStringHexToBytes)
+ (NSData *)dataWithString:(NSString *)string;
@end

NSString+NSStringHexToBytes.m

#import "NSString+NSStringHexToBytes.h"

@implementation NSString (NSStringHexToBytes)

+ (NSData *)dataWithString:(NSString *)string
{
    string = [string stringByReplacingOccurrencesOfString:@"0x" withString:@""];

    NSCharacterSet *notAllowedCharacters = [[NSCharacterSet characterSetWithCharactersInString:@"abcdefABCDEF1234567890"] invertedSet];
    string = [[string componentsSeparatedByCharactersInSet:notAllowedCharacters] componentsJoinedByString:@""];

    const char *cString = [string cStringUsingEncoding:NSASCIIStringEncoding];
    const char *idx = cString;
    unsigned char result[[string length] / 2];
    size_t count = 0;

    for(count = 0; count < sizeof(result)/sizeof(result[0]); count++)
    {
        sscanf(idx, "%2hhx", &result[count]);
        idx += 2 * sizeof(char);
    }

    return [[NSData alloc] initWithBytes:result length:sizeof(result)];
}

and now:

NSString* playTone= @"0f0000008000009401810282e80382e803";
NSData* data = [NSString dataWithString:playTone];
[self sendMessage:data toChannel:rfcommChannel];

where sendMessage is:

-(void)sendMessage:(NSData*)data toChannel:(IOBluetoothRFCOMMChannel*)rfcommChannel
{
    [rfcommChannel writeSync:(void*)data.bytes length:data.length];
}


I think you have bag #2 from this set: 60022 Cargo Terminal, based on the tan 4x6 base plates, the black 2x2 round plate with 4 arms and the red City minifig cap. I've also cross-checked the rim piece, the 2x3 Red plate and the 2x4 yellow brick.


Is LEGO element damaged at the molecular level when rubbed with rubbing alcohol?

The LEGO Group has been extremely careful about the formulation of all of the plastic parts they manufacture.
I do not believe they ever used lead in any of their parts. Decades ago they removed cadmium from the yellow pigments.
I have never found that isopropyl alcohol will soften the plastic used for Lego bricks.
What will soften Lego bricks is hot water. Do not use a dishwasher to clean Lego bricks. The water is too hot and the detergent is too aggressive.
To clean most Lego brick mild soap and warm water is the best choice. Air dry only, do not use hot air from hair dryers.


Why are there no faces drawn on the black heads?

They made them solid black so there are no alignment issues when veiwing the masked minifigures. By leaving them blank LEGO ensured the eye slots always appear black. Side note: The only Stormtroopers seen without helmets in the StarWars Movies were Han and Luke in disguise, therefore Stormtroopers are faceless.


What advanced railroad features are possible with the Lego PF train sets?

Track Features

You can do most things that you can do with traditional model railroads using LEGO trains. This includes cross track, bridges, switches, and inclines.

Cross track

As far as I know, this was never released for either RC or PF trains. As you noted, there was a cross track part for the 9V trains. If you aren't aware, 9V, RC, and PF track is mechanically compatible, the only difference is that 9V track has metal rails. If you don't mind the look of metal rails on your cross track when the rest of your track is plastic, the 9V crossing should work fine.

Bridges

You are correct that there aren't dedicated train bridges. You are left to build whatever you like.

You can make anything from a simple bridge that just holds up the track like this one based on the Unofficial LEGO Technic Builder's Guide (source):

Or you can create something elaborate like this bridge from the 2006 NMRA show:

Sloping Track

LEGO does not produce sloping track for the common train gauge. There is sloping track for the 4-stud gauge, but I doubt you will have much use for it. Aside from the tiny gauge, it is also too steep to climb for normal trains. Here's what it looks like:

Monorails did use sloped track, so if you don't mind mixing those into your layout, they could be an easy option. Here's an example of elevated track from 6399:

You can also build your own inclines, but keep in mind that it takes quite a bit of space. You can't do much more than 2 plates of incline per track section for most trains.

Switches

Each era of trains has had switches, so this is not an issue.

Double switches

Other than the one you mentioned, I don't think this has ever been released before. It seems like it would be pretty difficult to build custom track from parts, and this would very challenging to build.

Example layouts

Sets often come with example layouts including which track pieces that you need. Here's one example from an old 12V set:

Here's a similar example from a 9V set:

I'll just leave you with this cool 12V layout video.


SNOT stands for Studs Not On Top and it means building structures where you use hinges or other techniques to change the direction of the bricks, so they are not one on top of the other as it's done traditionally.

This is a very simple example of SNOT:

The technique is particularly useful for spaceships and even some LEGO sets rely on it, for example, look at the wings of the Imperial Shuttle (10212):

as well as any of the star destroyers, like the latest one, the Super Star Destroyer (10221) (the surfaces near the borders are placed at an angle):

There are many ways of performing this technique. Swooshable's SNOT reference tool has many more practical examples.


LEGO twin-engine airplane (black/yellow/grey) set identification please

This is set 8425 (quite a nice set imho) and the instructions are downloadable from lego themselves:
https://www.lego.com/biassets/bi/4101173.pdf
The set is from 1996


How much does the Luke's Landspeeder (8092) weigh?

I just put the box on my balance, and the weight is 275.26 gr.
Yes, I have this in my shop.


How to remove scratches from LEGO windshield parts?

Haven't tried this with Lego, but here are the first two things that come to mind.

Novus plastic cleaners (they make 3 solutions for various scratch depths, with Lego I would probably buy the one for the finest scratches) work well on my pinball machine plastics.

About the transparency, I would try the standard headlight cleaning solutions for a car.


First, you need to learn how to make a TCP connection to your EV3. There is a good guide on this here.

Then you need to learn about EV3 VM bytecodes and how to send direct commands.

Since you are using Unity, you may be able to use a pre-existing library such as the MonoBrick Communication Library or the Brian Peek library.

To send a variable, you need to use mailbox commands along with "Messaging" blocks in the EV3-G software.


I need help identifying the set for 37 bags

I believe you have a mix of at least two sets: 11005 Creative Fun and one of either 10717 Bricks Bricks Bricks or 11717 Bricks Bricks Plates.

Bag 36 contains a Door 1 x 4 x 6 with 4 Panes and Stud Handle (Medium Blue) which was featured in 5 sets.
11003 Bricks and Eyes
10264 Corner Garage
10703 Creative Builder Box
10702 Creative Building Set
11005 Creative Fun
10260 Downtown Diner
31025 Mountain Hut
31065 Park Street Townhouse

Bag 36 also contains a Plate, Round 4 x 4 with Hole (Dark Tan) which was featured in 22 sets.
41167 Arendelle Castle Village
75958 Beauxbatons' Carriage: Arrival at Hogwarts
11005 Creative Fun
11013 Creative Transparent Bricks
80102 Dragon Dance
71730 Epic Battle Set - Kai vs Skulkin
70674 Fire Fang
41395 Friendship Bus
71043 Hogwarts Castle
76129 Hydro-Man Attack
70668 Jay's Storm Fighter
70667 Kai's Blade Cycle & Zane's Snowmobile
70675 Katana 4x4
70677 Land Bounty
70680 Monastery Training
30534 Ninja Workout polybag
40342 Ninjago 2019 Minifigure Set blister pack
75270 Obi-Wan's Hut
75937 Triceratops Rampage
70840 Welcome to Apocalypseburg!
70419 Wrecked Shrimp Boat
75255 Yoda

These two pieces have only appeared together in 11005 Creative Fun.

However, bag 32 contains a Slope, Curved 3 x 1 x 2 with Stud (Lime) which was featured in 19 sets - none of which were 11005 Creative Fun.
11011 Bricks and Animals
10717 Bricks Bricks Bricks
11717 Bricks Bricks Plates
70803 Cloud Cuckoo Palace
10703 Creative Builder Box
10702 Creative Building Set
8961  Crystal Sweeper
45810 FIRST LEGO League (FLL) Jr Challenge 2019 - Boomtown Build Inspire Set
41345 Heartlake City Pet Center
71367 Mario's House & Yoshi - Expansion Set
41339 Mia's Camper Van
60270 Police Brick Box
7676  Republic Attack Gunship
75021 Republic Gunship
21208 Resort Designer
76134 Spider-Man: Doc Ock Diamond Heist
70922 The Joker Manor
41455 Unikingdom Creative Brick Box
60125 Volcano Heavy-lift Helicopter

Bag 32 also contains a Slope 45 2 x 4 (Lavendar) which was featured in 7 sets.
10717 Bricks Bricks Bricks
11717 Bricks Bricks Plates
10704 Creative Box
41340 Friendship House
41108 Heartlake Food Market
41310 Heartlake Gift Delivery
41253 Lonesome Flats Raft Adventure

These two pieces have only appeared together in 10717 Bricks Bricks Bricks and 11717 Bricks Bricks Plates.