Fig. 260. Mogul Wheel Spoke, Felloe and Felloe Band Assembly.
Fig. 262. Besco Cast Rear Wheel for Dual Tires.
The double-disc type for heavier vehicles is shown in Fig. 262. The hub and brake drum are cast integral, while the resiliency is obtained through a wide curvature of both discs. The rim is also of box-like section, however, the discs extend to the hub instead of forming a strut at the bottom.
Fig. 263 depicts a spoke type of front wheel with integral hull and rim. There are eight spokes of cross section thoroughly ribbed and fitted to obtain the greatest possible strength with minimum weight.
Fig. 264 shows this type of rear wheel; however, the spokes are of Y-shape, which affords a greater number of supports to the wheel rim without increasing weight, and enables the driving stresses and road shocks to be more equally distributed over the whole wheel.
Fig. 263 illustrates the hollow-spoke type of wheel. These spokes are of tubular section and are connected to the rim by large fillets. The hub is cast integral, while the brake drum may be cast integral or bolted to this type of wheel.
Efforts to decrease the weight of steel wheels for vehicles under two-tons capacity, has led to the building of wheels having the disc and lighter sections of the wheel made of pressed steel, rigidly connected to cast steel hubs.
This construction is shown in Fig. 266. The construction is similar to the cast wheel mentioned above with a box type hollow rim, except that the discs are flanged a little deeper at the rim to form ft wider box section. The cast flange of the hub is carried out further to carry the brake drum and the driving mechanism. Wheel construction seems to be one of the principal problems on which manufacturers do not agree. The wheels on large capacity vehicles to-day are called upon to carry a very heavy burden at higher speed than ever, and they must also stand the strain due to transmission of power. In order to meet these conditions, the proportions of spokes and felloes have been materially increased, and following the precedent of Europe, cast steel wheels are being considered.
Some advantages of the cast wheel have been outlined above, while of course it possesses certain disadvantages. However, the steel wheel can not be altered for different types and sizes of tires as easily as a wood wheel and a spoke in a wooden wheel, if broken can be replaced; but in this event the entire steel wheel would have to be replaced. Castings are always liable to Haws and blow holes and it is difficult to secure homogeneous metal free from hard spots. Unequal sections cause local variations in strength and internal stresses due to shrinkage in moulding. Where numerous cows are used in moulding, it is difficult to anchor these so that a uniform thickness of metal Can be obtained. Strains due to shrinkage can be eliminated to some extent by heat treating. The principal argument against this wheel is that under severe service it crystallizes; however, the design of this type of wheel is of such nature that this so-called difficulty has never existed.
A steel wheel is made in one piece and can be arranged to have an integral brake drum, hub and flange, and there is no opportunity for any working of the various joints. The very nature of this type of wheel adapts it wonderfully to the transmission of power, as the strength lies in the very points where the driving strains are centered.
The absolute concentricity of the hub, sprocket and flange assist greatly in the economical and efficient transmission of power, for with no high and low spots, there is no alternate tightening and loosening of the chain. In shaft-driven vehicles this condition is even more important.
Steel wheels also possess considerable advantage in carrying dual tires. In the case of off-set felloes, the outer tire is entirely unsupported by the spokes; however, in this case the steel wheel is particularly valuable, as the felloe can be so designed that the strains on the outer part can be successively transmitted to the spokes or discs without any danger to the wheel itself. Another feature is the decreased weight at the rim which permits more rapid acceleration.
The advantage of obtaining wheels all assembled and complete for mounting is considerable. No division of responsibility exists as to the mounting of wheels on hubs, brake downs, etc.
Cast steel or pressed steel wheels can be and are made to-day at figures competitive with wood wheels. If the demand increases and they are ordered in large quantities, the cost will decrease. In considering cost it should be remembered that the steel wheel has the hub integral, and the rear wheel may also have the brake drum integral and the cost of these together with all bolts, nuts, felloe band and the labor of fitting them must be added to the wood wheel to get a comparison in price.
From present indications it appears as though the steel wheel will shortly replace the wood wheel on at least the heavy vehicles. The demand is continually increasing, and quite a number of commercial car builders are experimenting with steel wheels.
Fig. 264. Spoke Type Cast-Steel Rear Wheel.
Fig. 265. Hollow-Spoke Type Rear Wheel.
Fig. 266. Pressed Steel Bear Wheel for Internal Gear Drive.