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Re: Wheel Howl (not squeal)
Author: Edward
Date: 01-01-2014 - 12:41
In short... Yes.
Corrugations cause the howl in concert with low damping ratio wheels, which in turn contribute to creating the corrugations in the first place.
More on this from the same report:
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4.3.2.2 Relation to Rail Corrugation
The howl appears to grow with time after rail grinding at
large radius curves due to emergence of rail corrugation, and
the corrugation formation is believed to be directly related to
the vibration producing the howl. Thus, a regenerative effect
may occur, where lateral oscillation over a broad frequency
band encompassing the wheel’s fundamental modal frequency
produces rail corrugation with the same corrugation
frequency. The corrugation further excites the wheel,
increasing the amplitude of vibration of the wheel and
radiated noise.
The process appears to occur at large as well as small
radius curves. The howling noise also appears at tangent
track, usually associated with corrugation. One might conclude,
therefore, that, at least at BART, the wheel’s dynamic
properties which contribute to howl at curves are also related
to formation of corrugation at tangents and moderately
curved track. That is, the wheel howl at curves is controlled
by resonances in the wheel which are also active at tangent
track in the formation of short-pitch corrugation through
dynamic lateral slip.
Fortunately, most rail transit systems do not employ composite
aluminum centered wheels, and the problem may be
limited to those systems that do. The most attractive mitigation
measure is to use wheels with higher damping ratio, such
as solid steel wheels. Wheels with tapered treads and sufficient
longitudinal compliance in the primary suspension will
tend to self-steer, align the axle with the curve radius, and,
thus, reduce or eliminate lateral slip and howl. Wheel vibration
absorbers, damped wheels, and resilient wheels, also
reduce or eliminate wheel howl.
Corrugations cause the howl in concert with low damping ratio wheels, which in turn contribute to creating the corrugations in the first place.
More on this from the same report:
*******
4.3.2.2 Relation to Rail Corrugation
The howl appears to grow with time after rail grinding at
large radius curves due to emergence of rail corrugation, and
the corrugation formation is believed to be directly related to
the vibration producing the howl. Thus, a regenerative effect
may occur, where lateral oscillation over a broad frequency
band encompassing the wheel’s fundamental modal frequency
produces rail corrugation with the same corrugation
frequency. The corrugation further excites the wheel,
increasing the amplitude of vibration of the wheel and
radiated noise.
The process appears to occur at large as well as small
radius curves. The howling noise also appears at tangent
track, usually associated with corrugation. One might conclude,
therefore, that, at least at BART, the wheel’s dynamic
properties which contribute to howl at curves are also related
to formation of corrugation at tangents and moderately
curved track. That is, the wheel howl at curves is controlled
by resonances in the wheel which are also active at tangent
track in the formation of short-pitch corrugation through
dynamic lateral slip.
Fortunately, most rail transit systems do not employ composite
aluminum centered wheels, and the problem may be
limited to those systems that do. The most attractive mitigation
measure is to use wheels with higher damping ratio, such
as solid steel wheels. Wheels with tapered treads and sufficient
longitudinal compliance in the primary suspension will
tend to self-steer, align the axle with the curve radius, and,
thus, reduce or eliminate lateral slip and howl. Wheel vibration
absorbers, damped wheels, and resilient wheels, also
reduce or eliminate wheel howl.
