CHASSIS KNOCKS
Does your car chatter? Does it talk to you and protest against running
over holes and bumps in the road? If it does, it is a sign to which you
should pay attention, a hint that you should do away with the knocks
and clicks and chattering which annoy you and everybody else within
hearing as you run along. That is, if you can find them, for there are
some noises so obscure as to defy detection even by the expert.
Such was the car which developed a sharp click whenever it was started
forward or backward. It ran quite a long time before it was possible
to discover just what and where it was. It was somewhere in the back,
but so hidden as to defy detection. The rear axle was of the floating
type, the construction in which the driving shaft is connected to the
hub of the wheel by a number of flutings on the shaft, into which
corresponding projections of the flange fitted. These had become worn
and allowed sufficient play to cause a noise.
By walking alongside of the rear wheel while the car was being started
and stopped, it was decided that the sound came from the hub of the
wheel. The hub cap was removed and by placing the finger on the hub
flange and end of shaft at the same time the play was detected by the
sense of feeling, though it was hardly visible to the eye. The trouble
was overcome by having the shaft welded to the flange.
A few days later the owner happened to be at the agency and told what
he had found.
“So glad you came,” was the response, “for we have been looking for
the same kind of a click a long time ourselves and the service-station
mechanics have not been able to locate it. They thought it was in the
brake, but upon examination could see no reason for a click.”
There have been cases where the wheel was keyed on, and where the keys
had acquired sufficient play to cause a continuous knocking, especially
when the machine was being driven at low speed. This sort of knocking
is more likely to occur with the four-cylinder, slow-speed engine than
with the high-speed, many-cylindered type.
A mysterious knock may sometimes be traced to the torque rod, when it
becomes loose at the forward end, or to worn torque-tube bearings, and
in some cases the bolts fastening the torque rods to the rear axle
become loosened, or worn, causing a knock, especially when going over
bumps or dropping into holes.
The brake rods become worn and set up a continuous clattering on rough
roads and this noise is accentuated if the tires are kept inflated at
too high a pressure. As a matter of fact the car owner has the choice
between the greatest life for his tires and accompanying rattles and
discomforts, and riding at a sufficiently low pressure to subdue these
noises and make life in a car worth living; of course there will be an
attendant higher wear of tires. Where the wear cannot be taken up by
adjustments or using new bolts or pins, often the rattle may be ended
by wiring a spiral spring to the frame and rattling part. This keeps it
taut.
Worn spring-shackle bolts will not ordinarily cause knocking or
rattling, but when going over bumps or holes the rebound of the body is
sufficient to make the looseness audible. It can be overcome by having
a new bolt put in, and prevented by keeping the bolts well lubricated.
Worn steering-knuckle pins and tie-rod bolts will sometimes be found
responsible for knocks and rattles in the front end of the car. The
remedy is obvious and the location of the noise is not so hard to find.
In addition to these we have rattles due to tools being thrown loosely
into the tool box, and sometimes from the body bolts having become
loosened. The lamps occasionally jolt loose and the license-plate
bracket is sometimes so loose that it is audible as well as visible.
There are other knocks due to broken gear teeth and other broken parts,
and sometimes these broken teeth, loose nuts, bolts, or pins in gear
or differential case become wedged between the gear teeth and cause a
knocking that is not hard to locate, albeit rather expensive to repair.
And then there are the knocks and rattles from the hundred or more
accessories which are attached to the chassis of many cars and which
sooner or later develop defects and noise.
The up-to-date, well-designed car in perfect shape is practically
noiseless, and if a knock or rattle develops it indicates that
something is worn or out of adjustment, and needs attention. The owner
who takes care to have all parts properly lubricated and kept tight
need fear none of these annoyances, and proper attention means lack
of annoyance when out touring, while slovenly habits will advertise
themselves to everyone along the road.