The Bridgeport times and evening farmer., 1922-04-01
The Kant Slip
(H. W. SIauson, M. E.. Mgr. En-
 gineering Service Dept.)

When you compress anything you
 make it occupy a smaller space than
 it did before. Thus, when you pump
 up pneumatic tire you take a large amount of the surrounding air and
 squeeze it into the restricted space of
 the tube. That air is compressed be- 1 cause the same amount of 1t occupies | less space than it did before.
 | But rubber is not compressible. You can change it's shape because of it's elasticity, but not the amount of 1 space that a given mass occupies. | Therefore, we say that it is not com pressible but that it is replaceable. | Take an ordinary pencil with a soft eraser on the end and squeeze it down on the desk. The eraser ''squasnes' out and bulges all around. It is shorter but it is also correspondingly wider. You have not compressed it by the pressure on the pencil, for you have not changed the total mass or volume-you have merely changed it's shape by displacing part of it into the bulge. The softer and more elastic the eraser, the greater will be the amount of this bulge under a given pressure.
 The Destructive Traction Wave. This displacement of the rubber is l exactly what occurs in a solid tire. If the tire is sufficiently soft and elastii to produce resiliency, it will be con- Siderably flatened at it's point of con 1 tact with the road. The rubber which 1 is pressed out by this hattening must go some place, and it squeezes out in the form of a bulge at the beginning l of the point of contact with the road. ] Now as a wheel revOlves. carrying it's | load, this bulge stays in the same place with relation to the road, but continually changes its position on the rubber of the tire. Thus when the wheel is rolling this bulge forms what | is known as a traction wave" which is the principal cause of wear in solid tire. The fore resilient the rub- Der of which the tire is composed, the greater will be this traction wave, with all of the increased stretching and pulling of the rubber which ac- companies it.
 Breaking Up the Traction Wave. The traction wave is formed in a solid tire, because the rubber has
 space into which it can flow when it
 is displaced by pressure. If we cut
 notcheS in the tire. however, the rub Der will bulge and the wave will
 travel only until the notch is reached
 into which the rubber can flow. These
 notches- form one of the patented
 principles of the Kelly-Springf1eld
 Caterpillar tire and provide a dis
 placement space into which the rub
 ber of each section may be forced
 The action of these displacement
 notches is two-fold. as illustrated by
 the accompanying photograph. When
 a truck is backed into the curb or
 other sharp obstruction. the surface
 of the tire is pressed in at one point
 and is stretched. Instead of extend
 ing this stretch throughout the large surface of the tire it is taken up by the notches which grow wider at the
 outside ends as the surface Of the
 tire is elongated
 On the other hand, a Caterpillar
 tire subjected to load on a flat sur
 face, especially at the moment of ap-
 pication of the engine power. will
 force the section of rubber in con-
 tact with the road out on each side,
 because the resilient rubber has been
 Hattened. But if this rubber has been
 fiattened, it must also occupy a longer space because the mass or volume is the same. This added length of the
 section of rubber under load is aSb
 sorbed by the displacement notches
 cut into the tire, which. under, such
 a condition, tend to close slightly as
 the tire revolves. AS a. succeeding
 section comes under load. the same
 action takes place, the elongation be-
 ing absorbed by each of the displace-
 meth notches in turn. Thus the de-
 stru cfive traction wave is absolutely
 absorbed and the stretch and strain
 of rubber is localized. with the result
 that the kelly-Springfeld Caterpillar
 tires are the longest-wearing and most resilient cushion tires yet pro- duced.
 The displacement notches in the Caterpillar tire also IuUIllSh ct TIT III traction grip to driving and steering wheels when running through mud, sand or snow. The resilient rubber allows the portion of the tire under load to become f1attended, but the displacement notch, as it turns into contact with the road, presents a sharp, firm edge to the road material. | Each section of the tire becomes
 soft. padded foot of large area which | enables the Caterpillar equipped tr-1cl< to negotiate road difficulties 1n-
 surrn ounta'ble to other types of tires | This same notch construction also serves effectively to prevent wheel l spinning and side skidding on wet 1 asphalt streets and makes unneces- sary the use of chains.