576 TRANSACTIONS OF THE 



pistons at the dead parts of the stroke, was very great. He then 

 placed weights on tlie wheels on one side to balance the force of 

 the crank motion, which at moderate speed had some effect, but 

 did not cure the oscillation at the highest velocity. It will be 

 found when an engine of twenty inch stroke, with six feet driv- 

 ing wheels, goes fifteen strokes per minute, or three miles per 

 hour, it requires one-tenth of the weight moving along the hori- 

 zontal line, that is, the j^iston and gearing moving backwards and 

 forwards within the engine framing, to stop it, and tui-n it again; 

 at thirty-five strokes per minute, or about seven miles per hour, 

 one-half its weight; at seventy -four strokes, fifteen miles per 

 hour, one and a half times its own weight; and at twenty miles 

 an hour, four times its weight. 



Mr. Heaton's improvement consists in connecting to an auxili- 

 ary crank-pin a rod of similar length with the piston rod, on the 

 other end of which is a pulley, working between guide-rods 

 placed on the opposite sides of the axle to the cylinders, thus ob- 

 taining a counteracting fjrce, preventing concussion. The weight 

 must ])e equal to the piston and its gearing, so as to make the 

 weight run to the left hand at the same instant the piston goes 

 to the right; the blow to stop the piston, and make it return at 

 each end of the stroke, will be received in the auxiliary crank, 

 instead of in the wheels, producing a neutral point in the centre, 

 and steadiness of motion; for, when the blow is received in the 

 wheels, the cranks being at right angles, it is communicated 

 through the axle, and gives a twisting motion to the whole 

 framing of the engine. This being repeated with regularity, 

 produces an effect similar to rocking a boat. This oscillation is 

 found to be greatest when the engine is running most regular for 

 speed, and the piston going the same way with the oscillation of 

 the carriage. The effect of this counteracting motion, when 

 in operation, was so great, that not a tremble could be detected 

 in the model. 



There are several objections to oscillating engines. Ernst 

 Alban, of Plan, says, that to set so great a mass in motion as a 

 steam cylinder causes great concussions, and requires a considera- 

 ble expenditure of power; since every time the motion is reversed 

 the inertia of the mass must be arrested, and an impulse given 

 in a contrary direction. It is supposed that by this the cylinder, 

 piston, and piston rod receive injurious shocks and side strains, 

 whereby the cylinder and the stufiing-box of the piston are 

 caused to wear unequally. 



