Some people think that a Thunderbird is some sort of an automobile. Not so. It is a majestic machine shown here. Not our machine but no logging equipment show would be complete without it. This is a swing yarder, so-called because with the cable rigging it can pick up logs and pull them in from thousands of feet away. When they arrive at the machine, it can swing to the side and 'land' the logs off to the side. This area is naturally called the 'landing'. Logs lift easier than they drag so the higher the hill you can get them on the better these machines work. The ideal location is just above the brow (steep breakover) of the hill and the swing feature means that you can position the machine near the edge of a scarf and still land the logs.
The black blob hanging from the leaning tower is the carriage. It is managed in a 'cable car' like fashion downhill to the front (left in the photo). the cables hanging down from it are the chokers which are used to 'hook' the logs. They actually go around the log and fasten in a slipknot fashion. There are numerous ways to actually configure the rigging. The simple configurations use only 2 cables going out in the woods while more complex rigging configurations use 3 or more lines.
The central Tower is located directly above the pivot point. The cables extending to the right are guy lines to keep the whole operation right side up. The central tower allows the unit to swing and for the tail guys to stay tight at the same time. A log loader will be working within reach of the landing area. He will be sorting and piling the logs as they come in by size and grade and loading out the trucks as they arrive.
Cable logging is generally more expensive that ground logging with a skidder, but each has its place. Cables work the best on the steepest ground and skidders work best on the flatest ground and somewhere on moderate slopes you might consider which ever is available.
The methods of cable logging haven't changed much over the last century. The main difference is that in the first half of this century, loggers usually rigged a tree called a 'spar tree', and the machinery required was a drum set and an power source (often a steam engine). They often sat on a sled made of logs. and were moved either by dragging themselves around with their own winches or hauled on a railroad. The machine shown here can drive around on tracks from one location to another and carries its own steel tower eliminating the necessity of a high climber visiting the upper reaches of a tree.
As with the Washington Iron Works machines and the Skagit machines, The Thunderbird product is uniquely a Pacific Northwest designed and built product, and unlike Washington, they are still in business (Well when this was written in 1997 they were, but alas they are gone now too). The TSY-255 is a thee drum machine. In loggers talk this means that it really has 6 or 7 drums on it., as the strawline drum and the guyline drums aren't counted. On this machine, the guyline drums are hydraulic winches with capacities for 120' of 1 1/4' cable which are dedicated for the purpose of guylines. The strawline drum holds what which holds a lot of small cable (usually 3/8ths and called the 'haywire' by loggers). This haywire is strung out often by hand in 250' sections and used to pull out the main cables for the first time. You see a 7/8" cable will weigh around 1.5 lbs to the lineal foot and even Paul Bunyan can't put a 1000 feet of that over his shoulder and run very far with it. Three eights cable on the other hand weighs only 1/4 lb per foot so 250 feet of it with shackles will weigh in at around 75 lbs, -- something that a brush ape can manage after a fashion almost anywhere.
The TSY-255 features a Detroit 8V92 uprated to 525 hp and produces lines speed to 2000 FPM (feet per minute) and line pulls in the 80-100,000 range. The main drums hold 2,000 feet of 7/8's in. line and the haulback handles 4,400 feet of 7/8's line. The interlock on this machine in an inhaul only interlock which is merely a water cooled tensioning clutch mounted on the haulback shaft. Both slackline and running skyline configurations can thus be used.
The tower is of a lattice boom variety which is 55' in height. the track mount carrier is hydrostatic drive with spring set, hydraulic released brakes and gradability up to 50%. Thunderbirds were manufactured here in Oregon by Ross Corporaton. Unfortunately Ross went out of business and sold the residuals to Madill.
Compared to the older generationWashington TL-6 Trakloader the notable differences are:
Most of these are performance /speed issues, but the 3rd drum is more than that. The 3rd drum make possible some types of cable logging rigging configurations that are not easily accomplished with a double drum machine. As reported elsewhere a favorite rigging configuration for a double drum machine is a 'shotgun' configuration with a standing skyline and a power in, gravity out carriage. You can get a power out on a double drum by using a running skyline by doubling the skyline back through a tail block and hooking the end of it to the carriage so the skyline doubles as a haulback line, but the third drum gives you several additional options. Rigging details are beyond the scope of this article, but in short the extra drum allows configurations that more readily support full suspension logging, slack pulling carriages, extended side yarding, downhill logging, and other technically complex operations. The interlock, takes the presence of three drums one step further in that it will allow you to take up one drum and pay cable out of another drum and provide a predictable tension between the two.
See also Logging History for older technology, and the
What isn't available for display here, are the light European Yarders. The thing that is unique about a yarder designed to work in the Swiss alps is that it is of necessity a downhill yarder. They will use a haulback to drag the carriage up the hill and then yard the log on gravity (sort of a reverse shotgun). Instead of using a Witchta water cooled brake their very small yarders (which often maintain suspension via a number of intermediate supports) use an 'air brake' to control the downward movement of the log. The 'air brake' is an airplane propeller inside of a wire cage (for safety) with a flywheel governor on the pitch control. This sort of a 'frictionless' brake never overheats even on a very long run.
Brand new for 1997 is Ross Corporations TSY-6140SLR fo which they are mighty proud. They describe it as a half scale TSY-6255SLR which weighs 63,000 lbs and provides a 40'7" boom Swing yarder.
The light weight means it will haul on a 5 axle lowboy, and a new feature (zero tail swing) means that it will swing on a narrow road. This compares to the Old Washington TL-6 featured on this site which has a 12 foot tail swing. by 'zero tail swing' Ross means that the tail swing radius does not extend beyond the end of the tracks.
The SLR configuration is intended to imply that it may be configured to work either as a slackline yarder or a running skyline yarder. With 2 drums of 2,000 feet of line and a 4,000' foot haulback you are in business. In the running skkyline configuration you can use the third wire to control a mechannical slack pulling carriage or grapples, and provide suspension via an interlock between the main drum and the haulback.
As a slacker, the rear drum is converted to the skyline drum with 2,000 feet of 7/8 wire and the front drum is used as the mainline drum. by switch the rear mainline drum to the skyline instad of the haulback drum, as wit other swing yarders this machine retains full use of the 4,000 foot haulback line in the slackline configuration.
In logging talk, a skyline is said to be standing or running. A standing skyline is a cable pulled out from the yarder and tied off at the other end of the job. Other than the fact that you may adjust the amount of sag in the line, it doesn't move. The carriage will hang on the skyline on one or more blocks (pulleys to non loggers). Suspension of the logs is achieved by controlling the sag in the skyline. A running skyline will be extended out to the back side of the job, but then instead of being tied off (dead ended), it will double back through a 'tail block' and extend back toward the yarder and connect with the carriage. In this fashion, the same line serves the dual function of providing a line for the carriage to hang on and also when pulled becomes the haulback to move the carriage outbound from the yarder. The mainline is used to pull the carriage towards the yarder.
With a Standing skyline, either the job has to be steep enough that the carriage will roll out into the woods by gravity (called Shotgun logging) or you must have a third line to rig a haulback to pull the carriage outbound. While the Running skyline approach requires one less wire for the basic operation, it adds a technical problem to the task. As with the standing skyline the degree of suspension of the logs is controlled by the amount of sag in the skyline, but since the line is 'running' you have a degree of dynamics not present in the 'standing' configuration. It isn't a matter of setting the sag and locking the brake, rather, it is a matter of feeding out the skyline/haulback line at a speed which is coordinated with the rate at which the mainline is winding so that the sag is held constant. It is not simply a matter of locking the drums together either, as the feet of wire per wrap on the drum increases as the drum fills and you have one drum filling and the other emptying. The interlock as it's called must be able to regulate the two drums and maintain a 'tension' to dynamically control the sag in the running skyline. The old and somewhat crude way to do this was manually. The running skyline/haulback drum had a Wichita brake on it which was basically, a water cooled friction brake, and the donkey puncher simply rode the outbound brake enough to keep the rigging in the air.
The presence of an 'interlock' implies that a more sophisticated device is being used to tension the outbound drum, such as a mechanical connection with an adjustable viscous slip clutch, etc. If you are using a double drum machine, which usually don't have interlocks, a running skyline with a heavy foot on the brake or a shotgun configuration are pretty much the choices available, but with a 3 drum machine, if it has a proper interlock, the third line can then become available for other uses. A favorite use is for slack pulling. The logs have to be hooked to the carriage so they can be pulled in. Chokers which has a slip noose on one end to go around the log and a way to hook the other end to the carriage make the final link. If the choker is long, the carriage must be much higher above the ground to lift the logs free of the ground and various obstructions. If the choker is short, it won't reach from the carriage to the log. As any choker setter will tell you, the Gods of logging have computed exactly to the inch how much line is needed to reach the log and then NOT provided it.
Since loggers don't make money changing roads (relocating the tailhold), lots of people have looked for ways to make a single setting reach more wood. One trick, with a standing skyline is to set the tail block for the haulback off to the side of the skyline somewhere. This implies that the donkey puncher can jockey the carriage laterally by an interaction of the tension of the skyline and the haulback line.
Another solution often used with a running skyline, is the slack pulling carriage. In this approach you have 2 lines going to the carriage from the yarder, and instead of having the mainline simply hooked to the carriage (and chokers hooked to the carriage also), the main line will pass through the carriage after going in, and around a few turning things, and out the bottom of the carriage where the chokers will be hooked to the end of the main line. The third control line is used to 'pull slack' in that it will cause the turning things in the carriage to wind additional mainline out the bottom of the carriage which the choker setter can drag laterally to reach more logs for side yarding. Once the inhaul sequence is started, the main line feeds back through the carriage pulling the logs up close to the carriage. There are many variations of this theme.
See also Carriages