In this particular case, we are talking about a jet engine stand used in ground support applications within the aerospace industry. It’s a big stand that costs big money. To choose the proper heavy duty caster for this type of application, you need to consider a number of factors, and this article will highlight the most common ones.
When moving a jet engine on a stand that can cost upwards of $40M, it is important to understand what loads the stand is experiencing and to make sure your casters have an appropriate safety factor. Caster Concepts designs and tests to ICWM standards, which means there is a 4x static safety factory and a 2x dynamic safety factor.
When moving $40M, that may not be enough. In most engine stand cases, manufacturers are looking for a catalog load rating of four times the anticipated load. This means the actual safety factor is 8x dynamic and 16x static. This is where our heavy duty casters come in. Failure is not an option, and the extra cost is worth the assurance that the casters will not fail and damage the jet engine.
Most engine stand casters end up with some type of suspension system due to the nature of the terrain they are used on. With uneven asphalt or concrete, potholes, expansion joints, etc., and the sensitive nature of what the stands are carrying, it makes sense to invest in a spring-loaded or shock-absorbing caster. This helps to maintain even loading of the stand and to reduce any shocks or vibrations felt by the jet engine or other cargo. In jack stand operations, shock absorption is necessary for the jack to operate correctly. When the jack is disengaged, the casters can move the jack around. As the jack is operated and load is applied, the casters deflect and the jack legs take over supporting the total load.
Since most engine stands spend the bulk of their time outside in the elements, corrosion protection is more important than with standard caster applications. Depending on the degree that the end user requires, steps can be taken to zinc plate then powder coat the caster rigs, using stainless steel hardware and other special paints and finishes. For extreme applications, aluminum caster rig construction can be used. The aluminum rig can then have an Alodine or Anodize finish for even more corrosion protection. For more information, check out our blog on Best Casters for Salt Water Applications.
How fast you are towing the engine stand makes a difference in what type of caster wheel needs to be used. For applications under 10 mph, typically a urethane treaded wheel can be used. Since most catalog ratings given are for walking speeds, please consult an engineer to properly design a urethane wheel for the application. For tow speeds that are over 10 mph, a pneumatic or solid-pneumatic wheel will have to be used. These wheels can be used at higher speeds, although they do increase in size quickly to support equivalent loads of a urethane wheel.
Sometimes the engine stand needs some precise movements to get into its final position. These stands can weigh quite a bit which can make them difficult to move. When this is the case, sometimes features like swivel locks are used to help with forward/back movements. Steering tubes can also be added to the swivel casters so that the operator can use a lever to help steer the caster into its final position.
The most common questions we get asked when specifying casters for engine stand/ground support applications are typically focused on safety factors, shock absorption, corrosion resistance, wheel material, and positioning options. Hopefully, this article helped answer your question and explained what features are typically important for these applications.