3. Components of the Drive System . 



The apparatus is driven by a 3/4-horsepower Reeves variable -speed 

 motor, by any one of three combinations of sprockets, a worm, and worm 

 gear. The worm gear axis is a 31.8-millimeter (1 1/4 inches) steel rod. 

 The two driving arms at opposite ends of the rod are made of 12.7- by 

 101.6-millimeter (1/2 by 4 inches) steel bar. Each arm has a sleeve 

 which can be positioned by threaded rods at any distance, less than 50 

 centimeters from its axis. Each sleeve holds a ball-bearing pin which 

 fits and slides in a 34.9-millimeter (1 3/8 inches) slot along the bot- 

 tom of the adjacent triangular frame forming a side of the scotch yoke. 

 As the two arms rotate about their axis, the yoke moves vertically in 

 simple harmonic motion. The overall system is shown in Figures 1 and 2; 

 details are shown in Figures 4 and 5. 



The yoke is made of aluminum. The slot along the bottom of each 

 triangular frame is formed by an aluminum bar spacer between aluminum 

 angles lined with steel strips. The triangular frames are rigidly 

 joined together at their upper corners, over the cylinders, by a bar 

 made from two aluminum channels. Pins through these channels hold the 

 upper ends of the connecting rods, made of aluminum tubing, which connect 

 rigidly to the pistons below. The yoke is constrained to move vertically 

 by upper and lower guides made of steel angle with spacers forming slots. 

 The upper and lower corners of the triangular frames hold ball bearings 

 which roll in the slots. The tops of the upper guides are fixed to a 

 steel channel extending from wall to wall above the cylinders. The 

 weight of the yoke and pistons is balanced by two steel (passive) counter- 

 weights supported by chains and overhead sprockets. The counterweights 

 extend across the cylinders between the upper guides which also serve to 

 steady them as they move. 



The active counterweight (Fig. 5) is made of steel and held in posi- 

 tion by threaded rods in a steel rectangular frame. This frame rotates 

 about an axis over the motor, and is driven by chain and sprockets from 

 the worm gear shaft at twice the worm gear shaft speed. A system of 

 small sprockets, a chain, miter gears, and a crank permits the threaded 

 rods to be turned, and the position of the counterweight adjusted, 

 during operation. A scale mounted on the counterweight framework gives 

 y/Xm (eq. 16). 



A flywheel (Fig. 5) which rides on the drive shaft between the worm 

 and the cylinder column is made from a pulley wheel with steel blocks 

 bolted to its circumference. It weighs 20.4 kilograms and has an effec- 

 tive diameter of about 33 centimeters. A clutch permits the flywheel to 

 be engaged or disengaged during operation. 



The timing mechanism (Figs. 1 and 5) has several components. The 

 end of a steel rod mounted traversely on the drive shaft just outside 

 the cylinder column passes near a magnetic sensor during each rotation. 

 An electronic timer, when activated, times and displays the interval 



19 



