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 failure of a Silver Ghost chassis frame on chassis 5-AU and 6-EU.
| Identifier | WestWitteringFiles\P\2July1926-September1926\ Scan045 | |
| Date | 13th August 1926 | |
| To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair} c.c. to BJ. Wor.{Arthur Wormald - General Works Manager} c.c. to E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} c. to EY. ORIGINAL. Hs{Lord Ernest Hives - Chair}2/LG13.8.26. X9380 CHASSIS 5-AU AND 6-EU. FAILURE OF SILVER GHOST FRAME. Below is a report we have received from Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} (ref. Rml/Crnll.8.26.) at Paris in connection with the above :- "I have just had an opportunity of examining chassis 5-AU. This chassis frame has broken across the bottom flange on both sides, directly over the rear tie rod support bracket i.e., about 4" in front of the cantulever spring trunnion. (see sketch). The weight of the rear wheels of this car is 26.4 cwts. and the springs fitted are 2400 and 2500 lbs. There is nothing abnormal about the body mounting, the coachmakers have not drilled the frame anywhere in the neighbourhood of the crack, the battery is carried in the normal position in the frame, there is a luggage grid on behind but this is not very large or heavy. From our examination, we would say that the frame has broken due to fatigue occasioned by the ordinary bending moment produced on the trunnion on the rear spring, plus the exceptional bending moment created when the back axle hits the buffers. It is evident from the condition of the buffers, on this car, that it has had pretty rough treatment. As far as we can see, if the frame is to break at all, under these stresses, it will do so at the point indicated, where the rigid portion, held by the tie rod, joins the unsupported flexible portion. We should like to point out that the frames have broken across the bottom flange; this would indicate an upward bending moment, not a downward bending moment, due to unsatisfactory body support, where one would expect the top flange to go. We cannot see any grounds for the supposition that this fracture is due to the fitting of front wheel brakes, because all the torque due to the rear brakes is carried forward to the sphere, and taken on the heavy cross member, which is a long way away from the fracture. Any stresses on the frame due to the application of front and rear brakes, must give contd :- | ||