Product Improvement Test of Sheridan Weapon System, M551 (Traversing Mechanism Slip Clutch).

The engineering test of the traversing mechanism slip clutch was started at Aberdeen Proving Ground on 1 July 1970 and was terminated on 22 April 1971. The purpose of the test was to determine the ability of the traverse mechanism slip clutch to protect turret components during forced turret rotation, and its suitability for army use. Due to design problems in adaption of the slip clutch into the turret traverse gearbox, testing was terminated before the scope of testing could be achieved. The original slip clutch that was submitted for test failed to perform when a functional test was performed. After this failure, the sponsor submitted another traverse gearbox with slip clutch without changes and the test was restarted using an extreme high pressure lubricating gear oil. After the second test item was installed, the results of a turret pull test using a field dynamometer with a strain gaged drawbar indicated that the same characteristics which caused the first test item to fail still existed. A complete teardown and inspection of the traverse gearbox with slip clutch by Aberdeen Proving Ground personnel disclosed that improper operation of the slip clutch was caused by insufficient clearance for the slip clutch assembly stack-up within the turret traverse gearbox housing. Testing was terminated after the appropriate modifications were made which would have made the test item functionally effective. Thus, it was not possible to test a properly functional turret traverse slip clutch mechanism. Author