Rolls-Royce Archives
         « Prev  Box Series  Next »        

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).
Knocking issue in 20 HP hydraulic shock absorbers and suggesting a potential solution.

Identifier  ExFiles\Box 55\4\  Scan306
Date  30th January 1929
  
S/W for Hs.{Lord Ernest Hives - Chair}

Copies to:
Da.{Bernard Day - Chassis Design}
C.
PN.{Mr Northey}

X235

CWB7/GCD30.1.29.

KNOCK IN HYDRAULIC 20 H.P. SHOCK ABSORBERS.

As I understand the position with regard to this matter it is as follows:-

We have discovered that certain internal parts of our hydraulic shock absorbers give rise to a slight knock. It is possible to make shock absorbers without this knock, but this is hardly a manufacturing proposition, and even if it is done, in the course of five or six weeks normal work, the same knock becomes apparent.

This knock is hardly apparent on our test rigs, nor is it normally noticeable when the shock absorbers are mounted in the front of the 40 - 50 h.p. and the 20 h.p. chassis, nor in the rear of the 40 - 50 h.p. chassis.

It is, however, very noticeable in the majority of cars when mounted in the rear of the 20 h.p. chassis, and in a large percentage of cases is so apparent that it cannot be tolerated.

It is not noticeable in the rear of a 20 h.p. chassis if a sub frame is fitted.

It would therefore appear that for the majority of cases in which our shock absorber is used, it is quite satisfactory.

Should not therefore the cure for our trouble be sought for in the method of mounting the shock absorber on the 20 h.p. chassis, or in the method of mounting the body which is quite different from the method adopted on the 40 - 50 h.p. chassis?

It is noted that on the 20 h.p. chassis, there is a bracket for body mounting fitted quite close to the position at which the shock absorber is attached to the frame, and it may well be that the exact position of this bracket on the frame is such that any slight noise from the shock absorber is most effectively transmitted to the main framing of the body, and so is most effectively amplified by the body.

I suggest that it would be a useful experiment to isolate a body with which this knock is very apparent, at this bracket, or possibly at one of the other brackets, to determine whether this is the case, and if this is found to be so, it would be perfectly simple either to eliminate the bracket in question, or to so move it's position that it no longer acts in this manner.

(CWB)
CWB.
  
  


Copyright Sustain 2025, All Rights Reserved.    whatever is rightly done, however humble, is noble
An unhandled error has occurred. Reload 🗙