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Understanding how much a caster deflects under load ensures it will compress accordingly.

Knowing how Shock-absorbing casters work starts with understanding that they are spring-loaded, and these springs deflect when you apply pressure to them. Let’s look at the two different ways they are used.

The most common way they are used is to minimize the impact on a cart and its cargo. A spring cushions the effects of surface unevenness and impacts from the floor. To do this, the caster is designed to support a specific load. This is the caster rating listed in the catalog.

When this load is applied to the caster, it will deflect approximately 50% of its total travel. As the cart moves through its application, the caster can deflect up and down as the floor changes. This dampens the impact on the cargo being carried and helps keep wheels on the ground in cases where the floor is uneven.

The second way that a spring-loaded caster wheel works is to deflect all the way so that the feet on a cart or work stand can touch the floor. The intent here is to have the caster roll freely with lighter loads. With heavier loads, the spring deflects to a hard stop, and the feet on the cart touch the floor and support the load. At that point, the casters no longer support the load.

Ensuring proper deflection.

73 Spring Loaded Casters

73 Series Spring Loaded Casters

In this type of application, it is important to understand how much the caster will deflect and under what loads. That way, we can ensure the caster will work with the cart’s design and compress accordingly. When the cart’s feet are touching the floor, the cart can no longer move. It will remain this way until the load is removed and the springs in the caster uncompress and lift the stand back off the ground.

If you are looking at a spring-loaded caster wheel, never choose one out of the catalog based on height and load alone. This could leave you with a caster that doesn’t perform as intended for the application.

Engineering should always be involved in these types of applications to correctly specify a caster that will do what the customer needs it to do. This also ensures that the caster is sized accordingly so it doesn’t compress so far that it causes damage to the springs.

To learn more about the many spring-loaded casters we offer, click here.

Ideally, the spring within the caster only travels about 80% of its total travel, so we do not cause the spring to compression set. It is critical that we know how much load is on the stand when unloaded and how much more load will be applied. We use this information to ensure the design of the casters will work properly in the application. What we don’t want to happen is the caster not compressing enough or compressing prematurely so the foot potential does not clear the floor when unloaded.

Determining proper load for spring-loaded casters

Putting less load on the caster than it is rated for could mean little to no deflection happening because the springs are stronger than the load being applied. Or, if you put more load on than what the caster is rated for, you could overload the caster. In this case, when the caster hits a bump, there is no travel left in the caster to absorb the impact.

Spring displacement

Spring displacement is linear until the point of full deflection

We must also understand the intent and purpose of the safety factor on spring-loaded casters. If we build the safety factor into the rated load, we potentially get a caster with no spring deflection because it is designed to support loads much heavier than it is seeing.

In cases where a safety factor is required, we design all parts of the caster other than the spring to support the requested safety factor.

The springs used will support the actual load, and a hard stop will ensure that the springs are not taken beyond their rated loads. This allows the caster to function correctly under the intended load and avoids the chance of catastrophic failure in the case of overloading.

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