making a displacement of 60.8 cu. in. which by A. L. A. M. rating would give 7 h.p. The valves are mechanically operated, the inlet valve being above the exhaust valve and operated by a rocker arm. The crank is formed by bolting the two fly-wheels together with a pin which is off center. The two connecting rods, onc straight and one forked, run on a double annular ball bearing on the crank pin. The main bearings are annular ball bearings as are all other rotating bearings. The four valves are operated from one set of cams by jumpers which reach to the valve centers. The carbureter is located between the two cylinders and supplies gas to the cylinder through the manifolds as described elsewhere. Ignition is supplied by a Bosch High Tension Magneto located in front of the engine and driven by a train of gears from the main shaft.

The Blower Fan.

The blower used in these tests was a 40-inch Buffalo Cupola & Forge blower No. 8, built by the Buffalo Forge Co. It has a wheel 20 inches in diameter with 10 vanes, and an outlet opening 84. inches in diameter. On this blower the outlet pipe was fitted with a sliding gatevalve, which was graduated in such a way that each successive opening increased the area exposed by one-tenth the entire area. Starting with the gate entirely closed this would give eleven calibration curves. The fan was driven by an electric motor, through a counter-shaft by means of chains and sprockets in the same way that it would be driven by the motorcycle engine. It was not necessary to consider the efficiency of the chains and sprockets, since it is the same in both cases, and therefore, the power required of the motorcycle engine in the actual test will be the same as that required of the electric motor in the calibration. The electric motor used was of the cradle dynamometer type, in which the reaction between the field coils and armature can be accurately weighed.

The fan was driven by the motor and the weights, at the end of the arm, were taken corresponding to the various speed changes as shown in the following table. The horsepower was then calculated by the formula: 22 R. N. W.

making a displacement of 60.8 cu. in. which by A. L. A. M. rating would give 7 h.p. The valves are mechanically operated, the inlet valve being above the exhaust valve and operated by a rocker arm. The crank is formed by bolting the two fly-wheels together with a pin which is off center. The two connecting rods, one straight and one forked, run on a double annular ball bearing on the crank pin. The main bearings are annular ball bearings as are all other rotating bearings. The four valves are operated from one set of cams by jumpers which reach to the valve centers. The carbureter is located between the two cylinders and supplies gas to the cylinder through the manifolds as described elsewhere. Ignition is supplied by a Bosch High Tension Magneto located in front of the engine and driven by a train of gears from the main shaft.

The Blower Fan.

The blower used in these tests was a 40-inch Buffalo Cupola & Forge blower No. 8, built by the Buffalo Forge Co. It has a wheel 20 inches in diameter with 10 vanes, and an outlet opening 84 inches in diameter. On this blower the outlet pipe was fitted with a sliding gatevalve, which was graduated in such a way that each successive opening increased the area exposed by one-tenth the entire area. Starting with the gate entirely closed this would give eleven calibration curves. The fan was driven by an electric motor, through a counter-shaft by means of chains and sprockets in the same way that it would be driven by the motorcycle engine. It was not necessary to consider the efficiency of the chains and sprockets, since it is the same in both. cases, and therefore, the power required of the motorcycle engine in the actual test will be the same as that required of the electric motor in the calibration. The electric motor used was of the cradle dynamometer type, in which the reaction between the field coils and armature can be accurately weighed.

The fan was driven by the motor and the weights, at the end of the arm, were taken corresponding to the various speed changes as shown in the following table. The horsepower was then calculated by the formula: 22 R. N. W.