Arizona republican., 1922-04-09
TIMING GEARS
RESPONSIBLE
FOR RACKE 7
ev RAY o. FIGHTER


one of the greatest causes of en-
dine noise and inefficiency results
when the timing gear drive becomes
worn. Every engine has at its front
end a set of gears, or SprocketS and
chains. by means of which the turn
ing crankshaft is able to turn the
other parts such as the camshaft,
water pump, ignition unit generator.
and etc. In some engines set OF
ordinary straight tooth gears are
used in others the gears have helical
teeth in other a form of bevel gear,
drive and a vertical shaft is en-
ployed. while another class employs
a silent chain. All methods have their
advantages and disadvantages. so
for g. given set of results any one is
a compromise.
The timing gears, commonly caileo
the front end, il of correct design Will
produce little noise, but let the gear
ing be chea ply made. let misalign-
rnent or wear take place and there
is. produced. a. gear noise of very dis
agreeable pitch. The ordinary
straight tooth gear, little used now
except on the very cheapest cars. is
difficult to keep quiet. Even the best
straight tooth gears will howl or
CrovI or knock. On one make OF
ear the nan1o can be given without
looking at the car. but simply by list
ening the front end, 1t has charac-
8eristic noise. In order to effect
uuieter running the helical form OF
tooth was used, but even this un-
less we'll made also Is noisy. 1t IS
however. used on most OF the cars
today. To futher effect quiet running
fl1e gear material has been changed.
some vars ago it was quite common
10 employ only cast iron with
bronze gear between them. Today
Various matrials are used for gears
Including steel. usually for the
erankshaft; cast iron. bronze, alumni
mum alloy. fabric. special non -reso-
hant compounds known by various
trade names. such as condensite, Ia
-broil. In some engines the center
Of the gear is of one material and the
outside rim with the teeth Of another
so that the wear taking part may be
correct for its work and the center
NAV be made so that the sound Will
not he nnagnified. Usually the center
is of compressed cloth, which dead
ems sound.
The gear drives mentioned so far
constitute the common forms III
which the gears are all driven In the
same tram. Ii q uulhDtI OI tSA > StAH
year the overhead camshaft con-
struction is used. and this necessl- :
fates a different form Of drive. In
most engines using this form there is
Aatr of bevel gears which drive a
Vertical shaft. and this drives the
ralashaft In order to drive the ac-
cessories such as pump. generator,
and ETC.. there are talSeoffs on TINS
shaft. This form Of construction
Was used extensively abroad before
the war in special racing and air.
plane engines and was utilized in the
Liberty engines and many others OF
American origin. 1t is expensive TO
saw the least. but it's greatest draw
back comes when repair work is nee
essary. 1t is good engineering, but
IL most Of the designs used 1t can
not be compared in mechanical econ
ornv--xith any of the other forms
The silent chain drive at one time
had quite a vogue. then dropped Out
and now seems to be coming Dach
again. The early troubles with this
form of drive arose because the chair
stretched and needed frequent adjust
ment. The chain life was short
running 5000 to 10000 miles. at the
very maximum. The chainmakers
have learned how to produce