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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).
Investigation into a D.W.S. Jack failure and subsequent design modifications and improvements.

Identifier  ExFiles\Box 26\3\  Scan258
Date  20th September 1933
  
S/W.
Hs.{Lord Ernest Hives - Chair}.from PN.{Mr Northey}
Copy to Wor.{Arthur Wormald - General Works Manager} C.
EP.{G. Eric Platford - Chief Quality Engineer} Mx.{John H Maddocks - Chief Proving Officer} Cx.{Major Len W. Cox - Advertising Manager} H.{Arthur M. Hanbury - Head Complaints}

X 3117

PN.{Mr Northey}2/WT20.9.33.

Sir Norman Watson - 38-MY.
D.W.S.Jacks.

With further reference to your Hs{Lord Ernest Hives - Chair}/Eid.2/KT15.9.33 I have now had an opportunity of going thoroughly into this matter, both at N. and subsequently at the Works in Harrow road. of D.{John DeLooze - Company Secretary} W. Session.

It appears that the chance of jacks of this type (especially on the front axle because of the long weighty spindle attached to the jack) starting to unfold in the way which happened in the case of this owner, has always been foreseen by Mr. Session, but it has not apparently occurred in practice, or at any rate to a serious extent.

As you are doubtless aware, the only reason which prevents the jack from becoming extended when it has been once folded up is the amount of friction - and specifically the friction between the nut and the screw which is introduced by the compression of a spring at the end of this screw at the time when the jack is fully closed.

Since the time the set of jacks was supplied to 38-MY, there have been modifications with a view to improving this point in design, the more important one being in respect of the spring-washer at the end of the screw, which is now much stronger, and I am told that a case has never been known for any movement to take place with a folded jack, having the stronger spring - but in spite of this I was shown the improved type of jack for this coming season in which there is provided, in addition, a pair of steel clips which are caused to grip the horizontal screw quite a long time before the final closing of the device can take place, making it therefore less likely for harm to occur, even in the event of the person operating the jack failing to screw it quite home, which of course with the present type it is important shall be done after the jack has been in use.

Mr. Session immediately agreed, on examination of the damaged jack on this car, that the spring-washer was faulty and not strong enough. As the jack was considerably damaged a quite new jack of the later type has been substituted for the old one, and I do not anticipate
  
  


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