Causes and Corrections of Caster Flutter.
Caster flutter is a phenomenon in which a swivel caster is harmonically excited. This causes the caster to swing uncontrollably from side to side as the wheel rolls forward.
Caster flutter is not just annoying: It also results in excessive noise, increased wear on all bearing elements, and loss of tracking and control of the dolly or cart. There have been numerous studies to understand the causes of caster flutter and three, in particular, are most common:
The three most common causes of caster flutter are loose swivel sections, misalignment, and high speeds.
1. Sloppiness in Swivel Section – If the swivel section is too loose, the caster is more likely to flutter. A loose swivel section no matter the diameter of the raceway will establish as resonance leading to flutter.
2. Misalignment of Caster to Ground – If the caster is either mounted incorrectly or the caster legs have been bent, a resulting misalignment will cause the caster to flutter.
3. High Speed – It is important to note that all casters will flutter once it hits a certain velocity and is excited at its natural frequency. In most applications involving industrial casters and wheels the wheel is not balanced and lends itself to fluttering.
Correcting Caster Flutter
There are a number of techniques that can be employed to minimize caster flutter. While all the listed options may not work in your particular application, you may find some that are helpful to correct your caster flutter problem.
- Increasing swivel lead – A longer swivel lead will reduce the forces that push the caster sideways. It will also increase the caster’s natural frequency. As a result, the caster will only flutter at high floor speeds.
- Incorporating a Precise Bearing Swivel Section – Though a more costly option, casters with precision machined ball raceways flutter less than raceways manufactured through a stamping process. The precision bearing, when manufactured properly, will dampen the oscillation and prevent fluttering.
- Reducing the Mass of the Wheel – Just as increasing swivel lead increases the natural frequency of the caster, reducing the mass of the wheel will also increase the caster’s natural frequency. As a result, the caster will not flutter until it reaches a higher speed.
- Operating at a Low Velocity – The speed at which a caster travels is the main cause of caster flutter. At low speeds (2 or 3 MPH), a swivel caster may behave quite well. However, at higher speeds (8-10 MPH), that same caster may flutter uncontrollably.
- Change Poly Composition to Increase Friction with Ground – Increasing the friction with the ground has a small effect on reducing flutter. Like thicker grease, higher friction acts as a means to dampen out the oscillation reduce the chance of building resonance.
Caster flutter can create excessive noise, cause wear and tear on your wheels and put more strain on an operator trying to move a cart with a bad wheel. It can also cause products on your cart to shift or fall off, damaging your cargo.
If regular maintenance isn’t working, we can help.
The good news is that the engineering staff at Caster Concepts, Inc has extensive knowledge of fluttering issues of industrial casters. When regular maintenance isn’t cutting it, Caster Concepts can assist you in determining the best caster for your application. Caster Concepts, Inc. is an ISO 9001-2015 certified designer and manufacturer of a comprehensive line of industrial casters, ranging from a medium-duty series to a heavy-duty series to meet any application. Learn more at: https://www.casterconcepts.com/.