Vibration ana its Cure

Poverty Bay Herald, Volume LXI, Issue 18545, 3 November 1934, Page 9

Vibration ana its Cure

JN earlier days it was generally accepted that every car would have some characteristic vibration, for in those times the balancing of the reciprocating parts of the engine and of wheels ami transmission had not been developed to the line art which it >s to-day. The modern car, as a rule, is almost vibrntionlcss, thanks to the excellent counterbalancing of crankshafts, rigid chassis frames, flexible engine mountings, and greater precision of workmanship. Any unevenness of running should investigated without delay.. Such symptoms may be set up by irregular firing of the engine, due to faulty

spark plugs, or Ihe partial clogging of the carburettor, and shortcomings of that sort are easily diagnosed. Ii might happen that although the engine is running sweetly enough, there is the sensation at fast speeds of a general shuddering throughout Hie chassis, which is distinct from any high-pitched rattle produced’ by loose mudguards or other fittings. Such a trouble gives the impression of being deep-seated, and may become more pronounced on bad road surfaces. The easiest course is first of all to check the spring bolts for looseness, and then to coast fast down a hill in neutral, with the engine shut off or merely idling. If the vibration is still present it is obvious that it arises either from the transmission or the wheels, while.if it is then suppressed rhe inference will be that the engine is either loose in its mountings or is running out of balance, probably on account of irregular firing. At high speeds unbalanced road wheels can create a disturbing, effect. Ordinarily that factor is not important *in the case of a car which is driven only at touring speeds, but sometimes, because of irregular tyre wear, accumulation of mud on the spokes or other similar causes, a wheel gets out of balance. The simplest test is to spin the wheel when it is jacked up, if necessary transferring a suspected rear wheel temporarily to the front, where it can be revolved easily, and without the resistance of the back axle gears, and note if it revolves evenly, or invariably comes to rest with a certain “heavy” point nearest, to the ground. In extreme eases a correction might be made by wrapping the opposite spokes with small pieces of lead wire, secured with friction tape, until perfect balance is procured. A more common fault in cars which have open propoller shafts with fabric disc universal joints is that the shaft does not run true, but develops whip, so that the driver is conscious of some heavy part of the mechanism running out of true. The amateur will not find it easy to cure this defect, but lie should look to the universal joints, noting if they seem to have become distorted or flabby, and if the nuts on the driving spiders are tight. Frequently the screwing up of the nuts will banish the trouble, but if it is still thought that the universals are fit fault, or that the shaft might have become distorted, it is best to have a professional survey made.

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