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).
Chassis periodicity issues and proposals for testing solutions on the 20HP & SS chassis.
| Identifier | WestWitteringFiles\T\March1929-December1929\ Scan032 | |
| Date | 14th March 1929 | |
| HS.{Lord Ernest Hives - Chair} DA.{Bernard Day - Chassis Design} FROM R.{Sir Henry Royce} RY. (At Le CanadelHenry Royce's French residence.) C to SC WOR{Arthur Wormald - General Works Manager} E SECRET ORIGINAL R1/M14.3.29. REC'D AT WW. 18.3.29. 20HP. & SS.{S. Smith} CHASSIS. X7380 Y7420 X5380 I telegraphed "PREPARE TO ABANDON CROSS IN FRAME AND REVERT TO SUBSTANTIAL TUBULAR CROSS MEMBERS." A possible theory for why this wonderfully efficient stiffener is not desirable is that by its use the stiffness against torsion is very much increased, so putting up the periodicity to that of the front axle. Then again such flexibility as remains is not damped in the same way as that the chassis gets from the stiffness of the body. Unless this theory holds good it is quite a mystery to account for the phenomenon. I have suggested that we ought to determine the periodicity. I believe only small blocks on the bumper wheels, or perhaps it would be better to out of balance the road wheels and ascertain the axle period. If the frame follows the axle we should assume that its period in that condition was the same; if not we can alter its period by adding or removing weight which moves with the frame, such as the radiator, wings, etc. or add weights on a cross bar across the frame, and so increase and decrease the periodicity of the frame. Naturally the body or a torsionally stiff box (steel preferred) representing a body could be bolted to the frame so that the side members would have to bend vertically in their length. Such a box could be bolted to the chassis with various degrees of flexibility. Each should produce a certain periodicity. The axle can be made to criss cross at any speed by suitable alternate blocks on the bumper rig when the criss cross speed equals the natural speed of the frame. The frame should go much further than the axle. Perhaps only small blocks would set up the period in the frame and perhaps better without the hydraulic connected up. Whatever results you have got I think we should learn all we can about the above. These diaphragms would need to be cross braced, thus- i.e. 16 sets of crosses This would represent an extremely rigid body, not for road test, but useful on bumper. There is also the influence of weight; much of what we have done may have increased the rigidity and weight at the same time, or decreased both, and so not made little change in the periodicity. The smaller road wheels being inferior suggests to me that they are more flexible and resilient on the road and probably somewhat more liable to bounce, and at a lower speed than their weight would suggest. R.{Sir Henry Royce} | ||