Castor Wheel Flutter and How to Deal With it

December 2, 2013

Ross Castors

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Have you ever been walking through the store with a shopping cart when its casters began to swing rapidly from side to side? This oscillation is known as a flutter, or shimmy, and can be very annoying for individuals who wish nothing more than to push their cart straight ahead and go on about their business.

While they are frustrating while you’re walking down a grocer isle, caster flutters are natural at high speeds, and they are very similar to the speed wobble that wheeled vehicles when pushed to high speeds. With a castor, however, the actual speed that it takes to create a flutter depends on the amount of weight the caster is bearing, as well as the distance between the steering axis and the wheel axis. That distance is also called the trailing distance. In most cases, increasing this distance will be enough to eliminate any flutter that occurs at moderate speeds.

What’s the Danger in Fluttering Castors?

When most people experience fluttering with their casters, they consider to be an annoyance or a frustration. Most don’t realise how truly dangerous this oscillation can be. Consider for a moment this scenario:

You’re walking down the hospital corridor, pushing a patient on a medical gurney. You’re walking at a quick pace, as the patient needs to see the doctor immediately and there’s no time to waste. All of the sudden, the castor wheel on the gurney begins to flutter uncontrollably.

Which way does the gurney go?

Well, that would depend on which way the casters were facing when the fluttering began. If they were facing forward, or in the direction you wanted to go, you won’t have any problems. However, if they were facing left or right, you would lose control over the gurney and the direction that the casters continued to go. The patient could crash into a wall or another cart. You could accidentally run over another patient’s toes, or even knock over a patient standing in the way.

This is the main problem with flutters. Once they occur, it’s hard to control what happens until they stop.

Fixing Fluttering Castor Wheels

There are a few steps you can take if you notice your castor wheels are beginning to flutter.

You can add washer to the swivel joint. This will increase the amount of friction placed on the swivel joint. As more weight is placed on the castors, the friction will continue to grow. This means that when the castors begin to flutter, the weight placed on the castors will increase in the front wheels and slow the cart, chair, or gurney down.

Watch your speeds. Most often, castor flutter only occurs when castors are moving at high speeds. Steer clear of hilly areas if this is a problem and slow down when pushing carts and gurneys fitted with casters.

Increase the trail, or the amount of space between steering axis and the wheel axle. Remember that doing so, however, means you’ll need to take a bit of extra time and space whenever you want to turn.

Are you experiencing a bit of flutter with your castors? Don’t let it get you down. Know why it’s dangerous and take steps to prevent it from happening.