Shimmy


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shimmy

[′shim·ē]
(mechanics)
Excessive vibration of the front wheels of a wheeled vehicle causing a jerking motion of the steering wheel.

Shimmy

 

(1) In motor vehicles, an intense vibrational process that occurs in a vehicle’s steered wheels and front suspension. Steered wheels that are connected to a motor vehicle’s frame or body by an elastic suspension and a steering linkage are components of a complex vibrating system. Such wheels vibrate when a vehicle travels on a bumpy road, when the vehicle’s wheels are improperly aligned, or when the vehicle’s suspension and steering gear are kinematically mismatched.

Shimmy impairs road safety, increases the rolling resistance at the tires, and intensifies the wear of the parts of the steering gear and suspension. It also increases tire wear.

To reduce the harmful effects of shimmy, independent front suspension is widely used in present-day passenger cars. In other motor vehicles, the kinematic design of the steering gear and suspension may be improved by moving the centers of wheel vibration closer to the drag links and the hinge points of the springs. Other measures to reduce the effects of shimmy include dynamic wheel balancing and stabilization of the direction in which the wheels move when they encounter road irregularities.

(2) In airplanes, a free vibration of the nose wheel of a tricycle landing gear that occurs during taxiing, takeoff runs, and landing runs. The free vibration is manifested as a yawing of the nose wheel. It may result in the collapse of the shock strut or in an airplane crash.

Shimmy is eliminated by means of shimmy dampers. They prevent the occurrence of free vibration but do not prevent the nose wheel from being steered.

References in periodicals archive ?
The present report reviews two popular historic shimmy models and introduces a new model created to address the short comings previously highlighted.
I think Shimmy must have been abandoned as she is very friendly, and has obviously been loved at some point," said Rachael.
The heads that I use for the Swimmin' Shimmy are actually pretty easy to shape if you can get four clean cuts using two single-edge razor blades.
Shimmy, born in 1837, means a chemise, or (short for shimmy-shake) a jazz dance characterized by a shaking of the body from the shoulders down; it can also identify an abnormal vibration, especially in the front end of an automobile.
The Boy Who Loved To Shim-Sham Shimmy by author/illustrator M.
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Dancing with Aunt Janey" is one of the many poems where jazz becomes the canvas upon which the poet paints a portrait of his early life, where people are forces of nature: "Aunt Janey, in a tight black dress on New Years Day, / was doing the shimmy and dancing / the black bottom / as her enormous buttocks whipped about / like the black and starless night sky / in late, windblown March.
SHIMMY into summer at Western Leisure Centre in Cardiff with the Pop Stars dance classes, which are being held on Thursday, August 22.
Whereas a vanner in the 1930s might have landed the van upside down in a ditch and sat trapped while battery acid dripped down onto her tattered uniform (as did Miss Hasell), the hairiest it got for Lauren was a slightly worrying shimmy she felt when the van was going downhill.
It took her six months to learn how to shimmy, a fast, vigorous movement of the hips.