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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).
Causes and potential cures for 'booms' and 'jelly-ing' in cars.

Identifier  ExFiles\Box 137\4\  scan0337
Date  4th May 1931
  
To Hd.{Mr Hayward/Mr Huddy} From Hs{Lord Ernest Hives - Chair}/Les.{Ivan A. Leslie}
c. to EP.{G. Eric Platford - Chief Quality Engineer} Mx.{John H Maddocks - Chief Proving Officer}
c. to Wor.{Arthur Wormald - General Works Manager}

BOOMS.

Owing to the possibility of more cars coming to the works with a complaint of booms, we feel it is time that you were ready to handle such cars. At the same time we should like careful records taken of the necessary alterations to each car, the approx. percentage of improvement effected by each iteration and the approx. percentage cure as made to each car whilst at the works.

We will therefore mention a few experiences of booms which are likely to apply to customer's cars -

Rear Engine feet Disconnected. On the average this gives over 50% cure. The points that need watching are jelly-ing, steer-ing and side spare wheels flapping.

Side spare wheels improve jelly-ing considerably, but brackets to the dash D.73306 will be needed to prevent the wheels and brake lever from flapping. Low rating front springs are worse for jelly-ing.

The steering is generally very little affected. Possibly less road shocks and very slightly less selective. This we do not consider is likely to cause trouble, but should be checked.

When removing rear engine feet, suggested plates Hs.{Lord Ernest Hives - Chair}336 or Hs.{Lord Ernest Hives - Chair}345 can be fitted. The D.O. may want to alter these. It is thought advisable to fit some such plate for the following reasons.

(a) 20 lbs. of unnecessary material is removed from the car.

(b) A suitable clearance can be allowed between the bottom of the plate and the frame so as to give a clearance under all road conditions, and yet this clearance must not be excessive as the plate must be ready to take the weight of the rear of the engine, when the gearbox be removed.

(c) It is less work to fit these up owing to the number of distance pieces otherwise necessary for fixing the side spare wheel brackets. K.{Mr Kilner} bolts are used with these plates for the spare wheel brackets.

(d) Looking at the frame from inside the bonnet, these plates present the impression that the removal of rear engine feet being an after thought. In fact it is not easy to see if the feet are connected or not.
  
  


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