An Inexpensive Hydraulic Dynamometer
Page 43
If you've noticed an error in this article please click here to report it so we can fix it.
TIIE latest Fronde patent 1L1).-type hydraulic dynamometer produced by Heenan and Fronde, Ltd., Worcester, for the running-in and testing of automobile engines has been produced mainly to meet the demands of maintenance shops, being of simple design and comparatively inexpensive.
In addition to the hydraulic apparatus, the new /vI.D. plant incorporates an electric motor which, through reduction gearing, drives the engine. • This motor is mounted on the dynamometer casing in such a way that the torque demanded of the shaft when running-in an engine is accurately indicated on a dial. An accompanying illustration shows a model capable of dealing with any engine up to approximately 10 litres piston-swept volume.
This machine has a hand-barring mechanism to overcome static friction at the instant of starting a stiff engine. The engine is run-in at a constant speed, usually 100 r.p.m. The electric motor drives the dynamometer shaft through the medium of a friction clutch, and a self-disengaging jaw coupling also is interposed. When the engine is ready to commence power tests, the fuel supply is connected and, at the moment the Lengine fires, the coupling is automatically thrown out of engagement and the electric motor shut down.
The hydraulic apparatus is interesting. The engine transmits power to a rotor revolving within the casing, through which water is circulated to provide the hydraulic resistance, at the same time carrying away the heat developed in the destruction of power. Rotation of the hand wheel causes the position of plates, interposed between the casing and the rotor, to be varied, this influencing the amount of hydraulic interaction. The resistance of the wafer to rotation reacts upon the casing, which tends to turn on its anti-friction supports. The casing is anchored to the torque-weighing device, which consists of a spring balance, and the dial is calibrated to show both motoring and absorbing torques.
The brake horse-power absorbed or developed is calculated from the formula b.h.p. equals W x N divided by a constant, W representing the spring-balance load in lb. and N representing the r.p.m. of the main shaft.
A neat universal engine stand is provided with a cardanshaft coupling, which eliminates the need for accurate aligrimeat. The company also makes a flowmeter, which permits immediate reading of any change in the fuel-consumption rate, due to fuel-supply adjustments, etc.