First multiply the mean effective pressure on the cylinder, that is 148 × 15-1/2, which equals 2294. Then, 2294 × 266, equals 610,204. This product represents _foot pounds_. WORK OR ENERGY.--A foot pound is the amount of work or energy expended in raising a weight of one pound, through a distance of one foot. If 550 pounds should be raised one foot in one second of time it would represent one horse power of work accomplished. If 550 pounds should be raised one foot in one minute of time it would be equal to 550 × 60 = 33,000 foot pounds, and this would mean one horse power, or the work done in one minute of time. [Illustration: Fig. 69. Two-cycle Expansion Position.] In our above calculation we have determined how many foot pounds we had in a minute of time, so that if we divide the foot pounds 610,204, by 33,000, we shall get as a result, a little over 18-1/2 horse power. THE TWO-CYCLE ENGINE.--The longitudinal shell A, Fig. 69, is separate from the crank case B, the latter being secured to the former by flanges and bolts, as at C. The piston D is of such length that when it reaches the limit of its compression stroke, as shown in this figure, it covers both the supply port E and the discharge port F. In its outward stroke the upper end clears both of these ports as in Fig. 71, the discharge port F being the first to open, as shown in Fig. 70. [Illustration: Fig. 70. Exhausting.] [Illustration: Fig. 71. Compression.] CYCLE OF OPERATIONS.--The cycle of operation is as follows: The inward stroke, which is in the direction of the head of the cylinder, draws in the gaseous fuel through the valve G, and at its outward stroke the gas in the crank case B is compressed, and the moment the end of the piston passes the inlet port E, the gas passes through the duct H into the cylinder above the piston. The burnt gases within the cylinder pass out the discharge port F, facilitated, in a measure, by the compressed inflowing gas. When the piston again returns, and passes the discharge port, the gas is trapped, and is compressed during the inward stroke of the piston. THE CRANK SHAFT.--The most important element in the engine is the crank shaft. It is usually made of a single steel forging, and out of this are turned up the crank wrists, the crank arms, and the bearings which are placed intermediate the different cranks. It is made extremely large to provide for any strain due to the fuel explosions, and it is the most difficult part of the engine to turn out. [Illustration: Fig. 72. Crank Shaft.] SPECIAL METALS.--Special metals are used by various manufacturers, and the sizes and structural shapes are now so well understood that few of them break, although in the early history of the engine this was the weak and troublesome part of the car. Improper alining, in the case, and poor or faulty bearings, were responsible for many accidents, and now means have been found to overcome most of these objections.