The crank shaft is supported by two end, and one intermediate bearing, the latter bearing being placed between the two throws of the crank shaft. As the two cylinders are placed on the same side of the crank shaft, the two throws are also on the same side of the shaft and to balance these throws cast iron counter weights are bolted on the bottom of the crank arms. The bearings are exceptionally long, the total length of the three bearings amounting to more than half the length between the outer ends of the bearings. The frame of the tractor consists of four twelve inch “I” beams securely riveted together with intermediate channel stiffeners. The cast steel bearings are riveted to the frame so that the whole construction is one unyielding mass. The bearings are in halves which makes the removal of the shafts an easy task. With the exception of the differential and master gears all of the gears are cut out of semi steel blanks. The fly wheel has a face of 11 inches, and a diameter of 36 inches. (146) The “Big Four” Tractor. The Big Four tractor differs from the majority of tractors in having a four cylinder vertical type motor of 30 tractive and 60 brake horse-power capacity. The cylinders have a bore of 6½ inches and a stroke of 8 inches. The engine runs at the comparatively high speed of 450 revolutions per minute. Gasoline is used for fuel, and is vaporized in a conventional type of jet carburetor. Both the inlet and the exhaust valves are placed in a pocket at one side of the cylinder making what is known as an “L” engine. The cylinders and the heads are cast in one piece, doing away with points between the cylinders and heads. The pistons and connecting rods may be removed without disturbing the cylinders or their connections by pulling them out through hand holes in the base of the crank case. The four throw crank shaft is provided with five bearings, these intermediate bearings between the throws and two end bearings in the case. The interior working parts of the motor are lubricated by the splash system with a positive forced feed oiler. The splash pools can be adjusted at a minute’s notice so that any desired oil level can be obtained. Grease cups provide the lubrication for all bearings outside of the motor. Water is circulated by a direct driven centrifugal pump, and as the cooling water is in a closed system the same water is used over and over again without much loss, a bucketful or so a day being an ample supply. The tubular radiator situated in the front of the tractor is provided with a cooling fan that is driven from the engine in a manner similar to automobile practice. A high tension magneto is gear driven from the cam shaft, and is mounted on a rocking bracket so that the armature is advanced and retarded as well as the circuit breaker. [Illustration: Fig. 131. Views of the Four Cylinder Motor of the “Big Four” Tractor. Note the Massive Construction Compared with Automobile Practice. ]