GB876265A - Improvements in and relating to vehicle brake testing apparatus - Google Patents

Abstract

876,265. Testing vehicle brakes. KISMET Ltd. Sept. 23, 1959 [June 26, 1958], No. 20496/58. Class 106 (2). Apparatus for testing the brakes of vehicles comprises transmitting means 18, 20 for applying rotary drive to the wheel of the vehicle and means (not shown) for indicating the force required to rotate the wheel against the action of the brake, the transmitting means being of varying mechanical advantage, so that the final indication given is a true indication of the force required to maintain rotation of the wheel. The wheel is supported on rollers connected by an endless chain (not shown) and mounted on shafts 7, 8, these shafts also supporting toothed wheels 9, 10. A third shaft 14 has rigidly attached to it a cam 16; and a cam 18 is free to rotate on the shaft 14. The cam 16 holds a pawl 17 in engagement with the toothed wheel 9, and a chain 20 is connected at one end to the cam 18, and at its other end to the toothed wheel 10. Pins 19 on the cam 16 slide in slots 19a machined in the cam 18. In use, when a wheel is resting on the rollers and the brake is applied, the shaft 14 is turned by means of a torque wrench. The pawl 17 is released by movement of the cam 16, thus freeing the rollers for rotation. Thereafter, the pins 19 engage the ends of the slots 19a and so drive the cam 18. Rotational movement is transmitted from the cam 18 through the chain 20 to the rollers. Initially, the chain acts on the lowest portion of the cam, as shown, and so the torque required to turn the rollers is less than would be required if the chain acted on the circular part of the cam 18. Thus an artificially low value is indicated by the torque wrench before movement of the wheel starts. Once the wheel is moving, the chain wraps around the circular part of the cam 18 and so a correct value of the force exerted by the brake is indicated on the wrench, which is graduated accordingly.