Patent GB-1197623-A (GB)
Title: Chassis Dynamometer for Vehicle Testing.
IPC: G01L5/28
Filed: 1967-07-25
Abstract: 1,197,623. Dynamometers. N.L. McCULLOCH (Ostradyne Inc). July 25, 1967, No.34177/67. Heading G1W. [Also in Division G3] A chassis dynamometer for measuring power transmitted through the driving wheels (or driving tracks) of a vehicle comprises for each driving wheel (or track) two (or a group of) support rollers 10, 11 of which the front one is higher than the other (s) and devices for measuring the power transmitted by the driving wheels (or tracks) drivable connected to the associated rollers. Roller 10 is mounted on a shaft 18 which drives a water absorption dynamometer 22 geared to an electric motor generator (24). The shaft 18 extends through bearing posts 19 having bosses 19a rotatably supporting a U-shaped frame 25 which provides journals for the roller 11. The rollers 10, 11 are connected together by a one to one ratio chain and sprocket drive 26 and to equalize the load distribution on the two rollers (by preventing the tendency of the wheel to climb on one) the height of the roller 11 is raised above or below that of the roller 10 by adjusting the free end of the frame 25. Controls for frame angle. The frame 25 may be connected by a swivel coupling 30 to the piston rod 29 of a hydraulic cylinder 27 which is mounted on a swivel mounting 28 and driven by a hydraulic system including a valve 31. The valve may be controlled manually or automatically by servomechanism either (a) by sensing the load on roller 11 pneumatically, Fig. 8 (not shown) and using the pointer of a pressure gauge to close electric contacts controlling a solenoid operated valve (66) to maintain a constant load or (b) in accordance with the braking torque registered by the dynamometer 22, by means of a torque arm bearing on a compressed air load cell driving the rotary tap of a variable resistor in a bridge circuit including another variable resistor whose rotary tap is mechanically connected to the arm 25, the amplified output of the circuit when unbalanced operating the solenoid valve (66) in the hydraulic system controlling the tilt of the frame 25 in accordance with the torque. When the chassis dynamometer is to be used for vehicles of approximately the same size and power at constant test speeds or over a narrow range of test speeds the frame 25 may be supported by a further fixed post and this post may have several holes for coupling pins, Fig. 7 (not shown), to lock the frame in a selected position. The theory of operation is described whereby set points for manual or automatic control may be determined. For testing track-drive vehicles such as tanks, Fig.6, series of rollers 112, 113, 114 and 115 are provided to carry the expected weight, the rollers are inter-connected by one to one ratio chain and sprocket drives 93, 94 and 95 and a roller 122 journalled in a hydraulically controlled frame 121 is driven by a chain and sprocket slightly faster than the other rollers so as to produce a downward force on the vehicle to improve traction and prevent climbing. The drive wheels 131 may overlie the test rollers or the rollers may engage the track 132 between two drive wheels 131. The angle of the frame 121 may be controlled manually or automatically as before. Adaptations and alternative test. Certain adjustments may be made to the track-drive embodiment to adapt it for wheel-drive tests. The co-axial left and right hand drive rollers 10 (12) and (89) 112 in the two embodiments may have their shafts 18 (41) and (106) 128 coupled by disengageable clutches (43) and (129) and measurements may be made with the clutches engaged or disengaged. The first embodiment is for a twowheel drive vehicle but the two pairs of rollers and associated dynamometers and motors may be duplicated in an embodiment for testing a fourwheel drive vehicle. The electric motors may drive the rollers and thence the wheels for brake tests and for measuring power losses in the transmission. Watt meters may be provided for measuring power suppled or absorbed supplementing or inter-changeable with the dynamometer 22. The differential height adjustment of the rollers is primarily of importance when measuring power to minimize slipping and consequential wear on the tyres.