Our Drive for InnovationTuesday, 26 September 2017
Australia’s and New Zealand’s operating conditions for commercial vehicles can be extremely demanding when you factor in long distances, heavy loads and extreme temperatures in certain parts of the continents.
With over 30 years of experience in the commercial vehicle suspension industry, Powerdown design and develop unique suspension solutions specifically for our operational requirements
In the quest to produce products that provide Excellence in Performance, Safety and Value Powerdown have been working on some innovative new developments. Some of these products have been recently released or are on track to do so soon.
Low Pressure Gas Shock Absorbers
Until recently gas shock absorbers have been largely used on cars and small commercial vehicle applications. Powerdown the heavy duty shock absorber experts took up the challenge to create a gas shock absorber for trailers utilising a specialised measured low pressure gas injection process.
The majority of tyre wear on air suspended trucks and trailers is due to poorly performing shock absorbers that have either worn out or due to excessive heat build-up inside the unit. When a shock absorber overheats the oil inside the unit loses viscosity, this affects the ability of the shock absorber to control the trailer. This condition is known as shock absorber fading and causes patchy tyre wear, loss of control and unwanted load movement. The following conditions will result in a significant increase in driver fatigue and operational cost.
The key benefit of the new gas injection process is to provide further cooling properties inside the shock absorber. This will allow the shock to operate cooler for longer and resist a loss of dampening performance. Low pressure nitrogen gas was used over high pressure gas to avoid excessive pressure build up on the main rod seal inside the shock absorber compromising the longevity of the unit.
One thing that really stands out when you pick up the new low pressure gas Powerdown Supershock is the weight of the unit. No compromises were made when designing the shock absorber with a 2.5 mm thick steel pressure tube and 2.0mm thick body. This not only provides better protection from stone damage, but goes a long way to increasing the overall tensile strength of the shock absorber to cope with the higher dampening force requirements in Australia.
Full suspension articulation usually occurs when dropping off the side of a gutter or a steep driveway ascent or descent. This will allow the suspension to reach its full travel, bringing the recoil stop into play. To enhance the performance of the shock absorber a hydraulic stop was incorporated in the design to avoid metal to metal contact within the shock. This acts as a hydraulic cushion of oil which slows the suspension components in a controlled fashion as the suspension reaches the end of its extended travel. This feature is essential when the shock absorbers are used as the primary suspension travel limiter or especially when the truck or trailer is used in conditions where it reaches it maximum travel regularly.
Solving the Ride Height Problem
Changing the ride height on your truck or trailer air suspension, maybe a quick fix for a drive line angle issue or reaching a certain king pin height on a trailer.
One of the most common problems Powerdown encounter when receiving calls about suspension related issues, is the ride height of the rear air suspension or trailer suspension has been adjusted above the OEM (Original Equipment Manufacturers) recommendations. Unfortunately, these quick fix changes will eventually lead to some expensive headaches in the future.
A shock absorber is primarily designed to operate in the midpoint of the extended and compressed length of the unit.
SHOCK ABSORBER AT THE MID- POINT OF THE STROKE:
By increasing the ride height of the suspension, the suspension droop is reduced which limits the downwards travel available in the shock absorber. This dramatically increases the likelihood of the damper topping out when the suspension articulates. The piston will effectively hit the top guide of the shock absorber causing fatigue issues in the design. A re-coil cut off or rebound stop will limit some of the damage in the short term, but this feature is not designed for continual topping out of the unit. This will also lead to premature bush failure and other related end fitting damage.
SHOCK ABSORBER ABOVE RIDE HEIGHT & SHOCK ABSORBER BELOW RIDE HEIGHT
Eventually over time the shock absorber will most likely leak oil due to internal damage from the constant impact. In extreme cases the life of the shock absorber can be reduced by 80% of its normal service life.
Short stroke shock absorbers on trailers and some rear drive air suspensions are more susceptible than others.
ON VEHICLE RIDE HEIGHT GAUGE
In an industry first Powerdown has released a select range of shock absorbers with a recommended ride height sticker. This sticker is designed to indicate where the shock absorber is operating in terms of stroke when the shock absorber is fitted to the vehicle.
The sticker is strategically placed on the body of the shock absorber to indicate shock absorber stroke relative to vehicle ride height.
If the dust shield edge is in the AMBER/YELLOW zone (on either the top or bottom end) the ride height should be checked. In this position the stroke of the shock absorber is starting to stray outside of the optimal performance zone.
If the dust shield edge is in the RED zone (on either the top or bottom end) the ride height is way off. This indicates that the likelihood of the shock absorber topping out or bottoming out is highly increased over time. This may also mean that the wrong shock for the application has been fitted.
If the shock absorber falls into the AMBER/YELLOW or RED zones it is highly recommended that the ride height of the suspension is checked in accordance with the OEM recommendations. This will help avoid premature wear and tear, not only to the shock absorbers, but to the entire suspension of your vehicle.
Introduction of Bigger Bore Sizes
The main benefit of a larger bore size is the internal operating pressure of the shock absorber is spread over a larger piston surface area that has a direct impact on shock absorber longevity and performance.
In our quest to improve the design of our shock absorbers in certain applications, Powerdown have introduced a larger 45 mm disc valve design. The new units further benefit from improved speed sensing disc valving which adapts quicker to different road conditions. This calibration greatly improves wind stability, body roll through cornering and control through dips and potholes.
A key advantage of the new disc valve design is high tunability where we can develop unique valve codes for high dampening forces required for some forward of the axle trailer applications. Upon reaching a certain force / velocity our engineering team can “blow off” the valving to stabilise the dampening. The key advantage of this function is that less strain is placed on shock mounting bolts and bushings in high force applications.
Cross Flow Valve Technology
Air suspensions are specifically designed to be load sharing with air flowing between the air bags to accommodate the transfer of weight on the truck or trailer. The air in the system is regulated by a height control valve which pumps and exhausts air based on the load and the dynamic road conditions.
Due to these load sharing characteristics, trailers with a high centre of gravity or in a dolly configuration can experience a surge of air volume from the front to the rear. On some occasions, this surge can be side to side within the air bag system; this can momentarily render the platform unstable, making continuous driver correction necessary.
Powerdown, in conjunction with Hadley one of America’s largest height control valve manufacturers, have developed a new cross flow air valve. A simple and cost effective design has been used to control the surge from front to rear and side to side that can lead to a trailer or dolly exhibiting a sensation of instability. Air will continue to flow, but this will happen in a more controlled manner whilst maintaining the load sharing ability of the suspension. This can have an effect on tyre wear, but will also greatly reduce driver fatigue in multi combination vehicles.
The new cross flow valve will soon be available in high (blue valve) or medium flow rates (black valve) to suit the operator’s requirements.