NO. 3 LANGLBY MEMOIR ON MECHANICAL PLIGHT 



247 



balance weights to the crank arms which are prolonged beyond the center of 

 the crank shaft and on I he opposite side from the crank pin; the radius of rota- 

 tion of these balance weights being made approximately equal to the radius of 

 the crank pin. But aside from the co istructional difficulties which would be 

 introduced, it was seen that if this plan was followed in this engine if would 

 require a very large additional weight. Since the amount of this weight could 

 be diminished in exact proportion to the increase of the radius of rotation of 

 the balance weights, it was at first decided to attach the weights to the rims 

 of the fly wheels, the relative amount of weight attached to each wheel being 

 inversely proportional to its actual longitudinal distance from the crank pin 

 center. It was very soon found that the attachment of these balance weights 

 to the fly wheel caused excessive strains on the rims of the wheels, thereby 

 causing them to go out of line. In order, therefore, to keep the amount of bal- 

 ance weight small by carrying it at a considerable distance from the center of 

 the shaft, the weights were finally arranged as clearly shown in the drawings, 

 Plates 78 to 80. There it is seen that the main portion of each of the balance 

 weights consists of a flat arm bolted between the flanges which couple the trans- 

 mission shafts to the engine shafts. The flat arm terminates in a lozenge-shaped 

 lug, additional weight being provided by a plate fastened to one end of a tube, 

 the other end of which terminates in a collar fastened around the transmis- 

 sion shaft. The tube is inclined at an angle of about thirty degrees with the 

 Hat balance arm, thus acting as a brace to prevent the balance arm from wob- 

 bling, the plate on the bracing tube being fastened to the lozenge-shaped lug 

 by means of small bolts. 



The tabulated statement of the weight of this large engine is given below. 

 From this it will be readily seen that the net weight of the engine proper is 

 L24.17 pounds. The fly wheels were in no way necessary to the engine itself, 

 but were used solely for the purpose of smoothing out the torque of the engine 

 so that the transmission shafts and propeller shafts might he kept down to the 

 very minimum in weight. Including the two fly wheels, the weight is 140 pounds. 

 Including the 20 pounds of cooling water the total weight of the power 

 plant is 207.47 pounds. Without flywheels the total weight is 191.64 pounds. 



The construction of this large engine was completed in December, 1901, 

 and the first tests of it were made in January, 1902. As already stated, these 

 first tests were made with the engine mounted on a special testing frame and 

 delivering its power to two water-absorption dynamometers, no fly wheels be- 

 ing used, as none were required. Later, when it became necessary either to 

 use fly wheels or to greatly increase the weight of the transmission and pro- 

 peller shafts, in order to overcome the reverse torque, the two light fly wheels 

 were added, and another series of tests was made of the engine on its testing 

 frame. The arrangement of the engine, dynamometers, and accessory appa- 



