El Paso herald. (El Paso, Tex.) 1901-1931, 1917-06-09

run are designed for slow speed a
good average speed for heavy truck
as two and a half miles an hour, ana
at this speed a five-foot wheel makes
about II revolutions per minute. II
IL runs any faster than this under
load il is only for very brler perlous'
horses are not capable Of overspeeo-
ing these bearings.
wheels Must Turn.
Attach the truck to a tractor, how
ever. and the conditions are radlcaIly
altered. With plenty of power ahead.
there is little likelihood of unloading;
the chances are more favorable Ior
load greater than normal. for there
are no horses to worry about. Assume
a normal load, however, and at once
the question of speed intrudes- 1t is
safe to figure that the normal speed
Of the tractor Will be not less than
seven or eight miles an hour. That IS
to say. the speed will be trebled- The
wheels, instead OF turning at Il reVo-
buttons per minute, will turn ABOUT
40 revolutions per minute Now ~
revolutions per minute SOUNDS IKE
very slow speed; but 1t is actually an
increase of 200 percent There are not
many bearings. designed within Ialrly
close limits, that will run satisfac-
torily at such a tremendous increase
Certainly truck axle bearings will
rarely do It Not only is the wear in
creased at least 200 percent, but the
demand for fabrication IS increased
even more because of the tendency to
heating, and the average truck bear
ings simply will not lubrlcate saIls-
factorily at such speeds ANY doubt
ing Thomas can satisfy himself by the
somewhat grimy expedient OF putting
his hand on the axle end OF heavily
loaded horse truck that has been on
the road for some time under Its nor
NAL motive power. -Four chances 10
five there will be a perceptible warm
ing OF the metal. II does not REQUIRE
much imagination to forecast the ef-
feet Of speed 200 percent above nor
NAL
Ricketts, Are Risky.
No small part of The travelling OF
such trucks is done over roads paved
with rough stone blocks and the cl1-
ference in the effects of the vibration
at two and a half miles an hour and
eight miles an hour is enormous. At
the slower speeds the rose truck mere
" climbs the bumps and settles into
the hollows with a comparatively
easy motion. At the higher speeds the
tires actually bounce from peak 10
peak with a series OF hammer like
blows, and the result Is destructive 10
the whole of the construction In two
directions particularly are the effects
apparent. The constant banging
weakens the axles, and breakages oc-
cur at the shoulder where the journal
joins the axle proper.
AXl6 DEGdkdSCS also APT ~ "
cur at this point through failure OF
fabrication, causing the box to freeze
on the journal If the axle is abnor-
mally strong the result may be merely
to slide the wheel, but not many axles
will stand much Of this sort OF treat
ment- An Indication Of the intensity
of the forces involved is found In the
fact that brass boxes have been partly
fused in heavy horse trucks used as
trailers and run under the loads they
were designed for but at speeds OF
about nine miles an hour.
Street Tires Suffer.
steel tires suffer from such service.
The hammering action pounds the
metal down, forcing it out at the side
and breaking It out in splinters. the
ties are peened, so to speak, and en-
Iarged and loosened. Also the ire
mendous energy that must be con-
tended with often crystallizes the
steel tire.
The wheels themselves often feel
the effects of high speeds before any
thing else and the first indication is
a slight cracking creak which, at first
occurring in a single spoke, soon
spreads until the wheel groans and
crackles through its complete revolu-
ton. When a wheel COMPLAINS in this
way there is little or no nope 1or II;
it simply is too weak for the work.
and IL is merely a question of judg-
!
fore il fails. Tightening up or re-
pairing such wheels is a waste Of
time, unless the looseness is caused
by excessive dryness. Usually this
is not the case
Springs seem to suffer less than
other parts of truck used as a trail
er, probably because they are made
/ primarily to stand up under heaVy
work and only secondarily as shock
absorbers. The clips, however. are
rather likely to be points Of weak
ness. not only through breakage but
through loosening up under the fierce
vibration.
That horse trucks will not stand
up under trailer service, as rule.
is not an indication of weakness; II
simply means that they will not do
two or three times the work they
were built to do without wearing out
two or three times faster. This is
perfectly logical. for a truck built
several times stronger than necessary
for its normal work would be need