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).
Cause of chassis vibrations at specific speeds and proposing tests on crankshaft and frame flexibility.
| Identifier | WestWitteringFiles\V\March1931-September1931\ Scan135 | |
| Date | 21th April 1931 | |
| RECEIVED HS.{Lord Ernest Hives - Chair} E.{Mr Elliott - Chief Engineer} ) FROM R.{Sir Henry Royce} ORIGINAL R2/M21.4.31. DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} ) (At Le CanadelHenry Royce's French residence.) [STAMP: RECEIVED 1931 APR 27] [Handwritten: 8634 / 87010] P. 2. VIBRATIONS. There is a strange agreement between these speeds which suggests that all the vibrations complained of in connection with this complete chassis have a common controlling factor because torque reactions add up to - (a) 2200 impulses per min. (b) 37 MPH., 4400 " (c) 57 MPH., 6600 " (a) is gas pressure, (b) may be either impulses or piston inertia or both, (c) it is agreed is piston inertia. Since Mr. Grylls says we get this on sets (when the engine is not running?) it would prove that the periods do not depend on the crankshaft flexibility. This ought to be confirmed many times because one feels that a deflection is necessary to make the pistons give sufficient vibrating energy to the cyl. walls. (I mean that with a really rigid crankshaft the variation in kinetic energy in the two sets of pistons does not exert sufficient force to move the engine enough to be felt, but we do know that the gas pressure would, and also that we get great energy transferred in and out of the flywheel with a crankshaft period: - from memory and impression only, I may be wrong.) I have asked for the deflection torsion of the crankshaft to be examined to see if there is torsional oscillation at these speeds. At 2200. it might be 6 per rev. or 4.5, which would give a master period 4400 or 3300. If we finally decide that the crankshaft deflection is nothing to do with it at 2200. = 53 MPH., and 37 MPH., and torque reactions, then we must find the flexibility elsewhere. I have suggested that the frame determines the torque reaction period and that the engine should be erected on the test plate with steel channels representing the side channels of the chassis frame, then the distance between the supports can be altered to see if the elasticity vertical of the frame is the spring that controls the period. It seems extremely likely. We might also build a chassis with entirely different side members. The same depth heavy might not alter the periodicity, but deeper ones should. Weight and tie-rods might say something, and different rubber in the feet. If we can get the reason of the periods we might quickly do something. R.{Sir Henry Royce} | ||