channel machined between the inner and outer fly-wheel members. This is clearly shown at Fig. 102-A. The fly-wheel hub is enlarged and forms one driving member while the fly-wheel rim, which has a smooth and true inner periphery, forms the other driving member. When the friction driving wheels carried by the transmission main shaft are in the neutral position they are in the space between the inner and outer fly-wheel driving members, and as the friction roller is not in contact with either the hub or the rim of the fly-wheel, one member may revolve independently of the other. To obtain the forward drive, the main shaft is rocked so the friction wheels are brought in contact with the inside of the fly-wheel rim. If this is turning in the direction indicated by the arrow, it will turn the friction roller in the same direction, and the main shaft is revolving in the same direction as the motor crank shaft. To obtain a reverse motion of the main shaft the friction rollers are disengaged from the interior of the fly-wheel rim and are pushed against the exterior of the fly-wheel hub, as indicated at C. This will produce a motion of the main shaft opposite in direction to that of the crank shaft. The leverage is proportioned so that very little pressure is necessary at the operating lever to insure positive drive. The shaft on which the friction pulleys are keyed is hung on pivoted or eccentric bearings, which are located in, such a way that when the friction surfaces are brought in contact with each other they will automatically produce pressure enough to move the load, and as the resistance augments the driving pressure becomes stronger and the rolls can transmit the full amount of power generated by the engine. The friction wheels are made of paper or strawboard fiber and may be very easily replaced when worn. FIG. 102.-Outlining Action of Ohio Friction Roller Clutch. B-Roller in Forward Drive Position. C-Roller A-Friction Roller in Neutral Position. Placed to Obtain Reverse Motion. It is claimed that the friction drive methods cannot be compared to the friction clutch because it will give a much smoother and more flexible drive than is possible with any form of friction clutch. It is contended that the clutch is too positive a lock between the driving and driven parts, while the friction rollers are not so positive in their action. It is also advanced that in event of sudden shock the friction roller will slip to some extent, while with the friction clutch, which is positively locked, a sudden strain will result in breaking a gear or stressing of some of the transmission parts. With either of the friction drives described, a one-lever clutch control is obtained and one can start, stop, or reverse the tractor instantly by using but one control lever. The methods of obtaining the changes of speed on the Ohio tractor may be easily understood by referring to illustration, Fig. 101. If the sliding gears are shifted along the main shaft, so that the smallest pinion on the main shaft is in mesh with the largest gear on the transmission cross shaft the slowest rear-wheel speed is obtained. If the largest pinion on the main shaft is slid into engagement with the smallest gear on the transmission cross shaft the highest rear-wheel speed will be obtained. If the sliding-gear member on the main shaft is placed at a neutral position so that it is not in mesh with either gear on the cross shaft, engaging the friction wheels and the fly-wheel will not produce motion of the tractor. The drive from the transmission cross shaft is by a pinion which engages a large gear attached to the differential spider. The differential gear is attached to a cross shaft to which the bull pinions, which drive the bull gears on the rear wheels, are attached. It will be apparent that with the friction roll clutch it will be possible to obtain the same number of speeds on the |