Causes And Corrections Of Caster Flutter
Caster flutter is a phenomenon in which a swivel caster is harmonically excited such that it begins to swing uncontrollably from side to side as the wheel rolls forward. Caster flutter results in excessive noise, increased wear on all bearing elements and loss of tracking and control of the dolly or cart in which the caster is installed. There have been numerous studies to understand the causes of caster flutter. The three most common causes of caster flutter in industrial casters and wheels are:
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
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. 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 balance and lends itself to fluttering.
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 problem with fluttering.
Increase swivel lead – A longer swivel lead will reduce the forces that push the caster sideways. It will also increase the caster’s natural frequency and as a result the caster will only flutter at high floor speeds.
Precise Bearing Swivel Section – Though a more costly option, casters with precision machined ball raceways flutter less than those whose raceways are manufacturing through a stamping process. The precision bearing, when manufactured properly will dampen the oscillation and prevent fluttering.
Heavier or Thicker Grease – Heavier grease will damp out the oscillation much like the damping in your shocks in your automobile.
Reduce 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 natural frequency of the caster as well. As a result, the caster will not flutter until it reaches a higher speed.
Reduce 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.
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