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).
The efficiency and friction of a thread and nut under load, particularly regarding reverse efficiency.
| Identifier | WestWitteringFiles\N\July1925-September1925\ Scan181 | |
| Date | 12th June 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. -2- Expl. No. REF: Hg/ACL1/L031825 rest with the thread under load and are as follows :- Actual μ starting from rest with the thread under load - .161 Effcy. in starting from rest - 42.5% We attempted to obtain a value for the efficiency of the nut in a reverse direction. By this we mean the efficiency when we are working in a direction from the road wheels to the steering wheel. We were unable to get any reliable results for the following reason. When the nut is in motion the virtual angle of friction is on an average 5° 20' (expl. results), consequently under these conditions the action is reversible, but when starting from rest with the thread under load the virtual angle becomes 9° 25' and this being greater than the angle of the thread, in a perpendicular plane to the axis, the action is irreversible and therefore of zero efficiency. We are therefore modifying our apparatus to test this reverse efficiency by arranging for the applied axial thrust to grow from zero to the value required while the resisting torque can be measured. Hg/ACL. | ||