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The front suspension of modern motorcycles is a set of telescopic tubes that absorb impact from the road by moving within each other. They are comprised of two parallel hydraulic cylinders that act as shock absorbers; the first appearance of hydraulics to provide a smooth damping action was in 1935, on a BMW machine. The hydraulic cylinders are attached at the top to the steering bars, and to the centre of the wheel at the bottom; so is connected to the frame at two points. The entire assembly is called the front forks. Within the hydraulic cylinders is a coil, which provides much of the suspension action, surrounded by oil. The coil is under constant compression. The compression and lag are set according to pre-load settings when the machine is first sold, which allows the motorcycle to be ridden by almost any rider and in any style. Fine adjustments can be made to the tuning of the forks within the range where the internal coil is still under compression.
Motorcycle front forks come in two set ups, either the conventional type where the bottom portion of the fork assembly slides up over the fork tubes, or “upside down” (USD) forks, where it is the top portion that moves; the fork tubes are fixed at the bottom. There are benefits to both systems, but the USD forks are stiffer and give better handling at speed, so are often used on race bikes. They are more expensive than conventional forks but the benefits of better track handling make them the first choice for competitive riding. Race forks are also often manufactured with a built in coolant reservoir, which helps keep the oil cool under race conditions.
The oil used in the forks is different to the sort of oil used in the engine; the viscosity makes a big difference in the performance of the hydraulic forks and therefore the ride handling. Different riding conditions also affect the oil, as it becomes less viscous as the temperature increases. For this reason, a hydraulic fork oil of 5w may perform well and give responsive handling under normal road riding conditions, but used in the forks of a race bike it will heat up too quickly and perform badly; as it heats the suspension will become less responsive and feel spongy, so cornering will be affected negatively.
Road riding does not generate the same heat in the engine and body of the motorcycle as track racing, so although an oil of 10w to 12.5w may be used in the USD forks of a track bike, this weight would be very hard and unresponsive when used in a motorcycle that is used for commuting. The weight of the rider is a factor to consider when choosing the appropriate weight for a hydraulic oil, as heavier riders generate more downwards force on the forks and therefore require an oil of higher viscosity to give the same resulting performance. The speed at which the motorcycle travels when in a race situation also increases the downward force on the suspension; the higher the speed the more pressure is exerted.
Hydraulic shock absorbers are also found in the rear suspension of the motorcycle, but unlike the front suspension, which has a small range of setting adjustments, the rear hydraulic shock system has many more settings that can be adjusted. The coil is also usually external to the hydraulic component, instead of housed inside the fork assembly. Also unlike the front forks, the rear shocks do not take the brunt of the impact and force of the road, so are less likely to make a big difference to the comfort of the ride. When taking a pillion passenger, however, it is vital to adjust the rear hydraulic suspension to accommodate the extra weight over the back wheel. The front fork settings are not affected as much by the extra weight and can be left alone unless the passenger is exceptionally heavy.
For most hydraulic applications, induction type variants are commonly used comprising of single phase to 3 phase motors.
To answer this question, we need to look at the type of application you are using and its function. So, for example, if you need a motor for a commercial vehicle application such as a tipper, tailift or trailer the DC motor will suit your needs, whereas AC motors are more commonly found in car lifts, security barriers and dock levellers.
It is therefore always necessary to specify your end use application first when enquiring about which motor you require.
One important fact to remember when positioning your electric motor on a power unit is its location away from other components. It is always recommended to leave sufficient space to allow the motor to breathe effectively especially if your system will be running high temperatures.
As well as the motor mountings, the general level of the ground the power unit stands on should be even as any kind of tilt could affect the motor should it suffer any short circuit forces while operational.
Electric motors are typically configured to run to temperatures from -20C up to +40C and the information on the motors running plate should be strictly adhered to.
• Take care to avoid rotating parts on the motor whilst it is in operation
• While the unit is energised it is imperative that the terminal boxes are not touched or opened as this could lead to a safety hazard
In order to maintain the reliability of the motor, manufacturer service schedules should be strictly adhered to and individual motor components such as seals and bearings should be regularly inspected for any wear or damage and replaced as necessary.
Mobile power packs for hydraulics might be considered to be a long way off from the ventilation system that the Royal Navy of Australia has just installed. However, we like to be in the know and to keep you in the know, as much as possible, when it comes to all things hydraulic, in particular, if something catches our eye because it’s a bit different.
We’re not really geeks (or are we?), but there is also the fact that we find all the different uses of hydraulics really quite wondrous.
Let’s get back to the matter at hand; The Company that designed the hydraulic ventilation system are specialists in the marine industry. They work on a variety of different marine machines and hydraulic controls. Last year they worked on four military landing craft, to add ventilation systems to the engine rooms.
Although it may seem to be over the top to use hydraulics for a ventilation system, the company had their reasons. One was that NATO demand it as a requirement; in that it is essential that the fans used, can operate independently of the speed of the engine. The benefit of using hydraulics is that they are durable and deliver high power density.
A hydraulics gear motor is also considerably lighter than what an electric drive would be. With the vibration and high shock factor of a boat, when there is potentially shelling fire occurring during operations, the electric motor is more prone to failing.
The cooling fans are attached to the engine, to ensure that they start when the engine starts. If the engine isn’t running, then they don’t need to run. The result delivered by these ventilators, is as much as 17,000 square meters of air, being moved per hour from the rotating hydraulically powered blowers, rotating at 2900 revs per minute. To watch this in action must be real eye candy for a true hydraulic engineer.
Which machine would you point to as the best example of the use of hydraulics? Judging on raw power, you might point to a shredder. They can suck things in, chew them up and spit them out within seconds.
Alternatively, you might be under the impression that the bucket wheel excavator is the most outstanding example of hydraulics at work. It’s got serious power as it excavates at a rate of 10,000 yards of earth each hour. Unsurprisingly, your neighbours wouldn’t be happy with the 20ft wide swath at 8 ft deep if you drove one of these down your street though.
Something that many consider to be one of the most awesome machines is the tunnel borer. It can bore through rock at a rate of 22ft in diameter wherever it’s headed – through mountains or under the sea, lakes or rivers: Think Channel Tunnel.
However, I wouldn’t choose any of these; I’d go for the conveyor. Although you may not associate that with a hydraulic, the conveyor can be very powerful. Although the majority of conveyors have an electric motor to power them with either a chain or a belt drive, it’s not the case for all of them.
The hydraulic motor is far smaller and lighter than an electric motor that can deliver the same amount of power. They can also operate at lower speed and aren’t dependent on a belt, chain or gear drives to assist. This is what puts hydraulic motors in front, as this means that they need very little space.
These types of conveyors would be used in a fishing boat. In fact, one that we are aware of can process over 50,000 fish per hour in an environment that has a lot of wash-down. Not a great place for an electric motor to operate.
With hydraulic motors it’s possible to locate them inside the head pulleys of conveyors. There are no external drives, although they are really around the same size as the idler pulleys of the conveyors. If you weren’t aware of the hydraulic hoses that are connected to the pulleys, you’d be puzzled as to how the conveyors are powered. Impressive stuff!
Which hydraulic powered machine most awes you?
If you’ve been following our blog or even if you just happen to know quite a bit about hydraulics, you’ll already be aware that hydraulics are one of the most efficient methods of transferring energy. In today’s post we’re going to be exploring the various hydraulic pumps that enable this amazing form of energy engineering to happen.
Hydraulic energy is very powerful and efficient. It’s something that experienced engineers still marvel at for its ability to literally move mountains. In today’s world, a lot is asked of machinery and it’s the hydraulic pump that enables awe inspiring hydraulic energy to be delivered where it’s needed.
The purpose of the hydraulic pump is to convert from mechanical power to hydraulic energy. This energy can then be used to operate a variety of different devices. The pump works by generating flow with enough power to overcome pressure induced by the load.
First it will create a vacuum at the pump inlet. This will force liquid into the pump’s inlet line from the reservoir. The mechanical action of the pump will then move the liquid or fluid to the pump outlet and then force it into the hydraulic system.
Pumps move or create flow of liquid. They do not generate pressure, although they do facilitate the creation of the pressure by producing the required flow.
There are a variety of different hydraulic pumps on the market. Let’s take a look at the different types:
Hand pumps are manually operated and will usually work in a suction type way.
These are the most commonplace type of pumps, probably because they are recognised as being low cost, simple and durable by engineers and system designers. They are pretty easy to maintain and are considered to be the most economical when it comes to hydraulics. They are also considered to be suitable for pressures below the 3000 psi mark because they work with a constant displacement they may be less efficient in some situations. This makes them best suited to simple hydraulic systems.
Another low cost option that is also of simple design and therefore more reliable. This is particularly true of the gerotor form. They are suitable for low-pressure but higher flow output. They offer higher efficiencies than can be found in gear pumps and are most often used for mid-range pressures up to 180 bars.
These type of pumps are a little more complicated than those we’ve looked at so far. Most of them come with a variable displacement mechanism. This will make it possible for you to vary the flow for automatic control of pressure. Some design types include swash plate (also known as valve plate) and check ball. The latter is sometimes known as a wobble plate pump. These types of pumps can take up to 350 bars. Some types are more sensitive to oil contamination, so do your homework first.
We’ve explored just a handful of pump types that can be used in a hydraulic system. Watch this space for more posts.
When you work with hydraulics every day it is easy to take the technology for granted, especially when you know how it works and for what purposes. However, most hydraulic engineers focus on a specific application of the mechanisms and may not realise that there are other uses for the technology that we use every day. For example, petrol pumps use hydraulics to draw the fuel up from the reservoir and deliver it into your vehicle. When you draw up to the pump you make use of hydraulics to stop the car; most vehicle braking systems use hydraulic action to exert force on the brake discs. Hydraulics then allow you to fill the car up, and drive away, using your brakes several times on the journey home.
If you go to any large shopping centre or office there are lifts, which can make use of hydraulics to raise and lower the elevator car. Some older lifts still use a pulley system, but many newer systems use hydraulics. The sandwiches you have for lunch also rely on hydraulics to exist; the mechanisms in large bakeries use this technology to move conveyor belts and other large scale mixing machines to keep the dough moving along the production line. If you sit at an office chair while eating lunch you are also making use of hydraulics, as the mechanism that allows you to lower and raise the seat is usually a hydraulic one.
Visiting the dentist also involves hydraulics at least once, more if you drive there and fill the car up on the way! Dentist chairs use hydraulic pumps to lower and raise the body of the chair as well as to adjust the angle of the foot rest and head rest. Hospital beds and barbers chairs work on the same principle. Vehicle mechanics use hydraulic lifts to raise vehicles up for inspection and repair work in much the same way.
Hydraulics also make an appearance in entertainment; theatre stages that can be raised and lowered use hydraulic systems to make this happen, and similarly, theme parks rides use them to create and control motion. On arriving home from a day out at the theatre or a theme park you may drive your car into a garage with a hydraulically operated opening mechanism, or through a gate that employs the same technology to open and close at the touch of a button. Once in the house you may have to load the dishwasher and set it to run; even here there are hydraulics at work to improve water pressure for better cleaning. Hydraulics are found in many aspects of everyday life that it is possible to make use of six or seven different applications in a single day.
Hydraulics makes a flexible and efficient form of energy transfer. With the introduction of modern machinery the need to power them has driven innovations in hydraulic energy; hydraulic pump technology is often chosen for their efficiency and simple designs.
So how does a hydraulic pump work?. It can be described as a device that converts a rotary or linear motion to hydraulic energy. The fluid when exists the pump it will have a higher velocity and pressure than at entry. It must be noted that the pump does not produce pressure, it only produces flow, it has the ability to do this at elevated pressures.
Hydraulic pumps are used in a wide scope of engineering fields and are available in a variety of designs. Each type has a different internal mechanism based on the same fundamental principles. So let us introduce some of the common types.
Probably the simplest and most common used today, they are easily maintained and economic. Two basic types exist, the internal gear and external gear both are of the positive or fixed displacement pump group. External pumps use two external gears that mesh and push oil around the outside of the gear. Pressures up to 250bar are common, but cast iron designs increase this to 320 bar. Straight cut and helical spur gears give lower noise performance.
Internal gear or Gerotor pump designs have one external gear rotor meshing with the inside of an internal idler gear these are commonly found in automotive oil pumps. The off-centre rotor seals to the idler and the volumes are continuously changing, passing fluid from suction inlet to outlet. Gerotor pumps are generally found in low pressure applications where they are moderately efficient yet not too noisy.
Two helical screw form shafts intermesh inside a common housing, one shaft has a drive end. Fluid passes through this pump in a linear direction giving a fixed displacement output. Screw pumps are generally low noise due to the continuous gear contact and very reliable. Efficiencies can be low especially in increased viscosity applications.
These hydraulic pumps can be either fixed or variable displacement types. The pump body houses a rotating cylinder with pistons acting around its periphery. The pistons acts at angle to a thrust plate mounted on the shaft end. When the shaft rotates the pistons are reciprocated in turn relative to the pump body. To vary the pump displacement angle of the thrust plate is varied. This effectively changes the stroke of the piston and hence changing the amount of fluid moved for each revolution. The mechanics of this pump is highly efficient and reliable, and is often found in mobile machinery.
Similar in layout to the Bent Axis pump, yet the variable displacement mechanisms are simplified. The axial arrangement of the shaft and pistons means this design is compact, efficient and economically produced. A wide variety of pressure, flow and power control functions can be fitted to ensure this pump matches the machines needs.
Simple versions are fixed displacement type, but many come is a variable displacement option. An odd number of radial pistons are arranged around a rotating shaft. This is encased within an eccentric ring. As the shaft rotates the distance between the eccentric ring and shaft centre line varies, hence the pistons move through a suction and pressure cycle. The driven shaft is often hollow and allows fluid to enter and exit the pump. The displacement is varied varying the amount of eccentricity; this is done either manually via adjustment screws or hydraulically with a piston. These are excellent for high pressure and are strong and reliable.
A good choice for low noise and reliable service, but pressure capability can be low <140bar. By and large fixed displacement designs are used, but variable designs are possible. Sliding vanes are arranged around the rotating shaft. This is within an eccentric ring, which can be adjusted. The vanes form a seal against the eccentric ring and in the rotating shaft. Easily serviced these are common for in machine tool applications.
This is an overview of the main types of hydraulic pumps used today, along with a simplified description of the mechanisms of each. A further study of each type of pump, their applications and relative merits will soon be published.
Hydraulic Power Pack
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