From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Issues of road shocks in steering systems, comparing .720 and .940 lead worm and nut designs.
| Identifier | WestWitteringFiles\Q\2-July1927-September1927\ 24 | |
| Date | 19th July 1927 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} c. to BJ. Worx c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} oy copy ORIGINAL Hs.{Lord Ernest Hives - Chair} absent. Hs{Lord Ernest Hives - Chair}/Rn{Mr Robinson}2/LG19.7.27. STEERING. X8430 We have always been disappointed with the immunity from road shocks which results from reducing the helix angle of the worm and nut. Theoretically the .720 should be considerably more irreversible than the .940 lead worm and nut. actually the difference is small, and there are customers who complain about road shocks even with .720 lead steerings. The explanation we have found is that the condition of lubrication of the worm and nut when parking a car and when experiencing joggles are entirely different. When the steering is moving rapidly with frequent alterations in the direction of the load it is highly reversible. When it is moved slowly under a large load it becomes almost self-locking. Thus with a low lead worm and nut the efficiency of the 'parking' conditions fall off rapidly with reduction in the helix angle due to the relatively high co-efficient of friction prevailing, but the tendency to transmit joggles does not alter proportionately when the wheel is moving rapidly with reversing loads. The attached graph illustrates how these two conditions shew up on test. We can reproduce the slow movement of 'parking' but hardly the rapid alternating movement of joggles, therefore the steerings we have tested may be even more reversible for 'joggles' than our results shew. contd :- | ||