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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).
Technical memorandum discussing design improvements for the starting handle and grille trap.

Identifier  ExFiles\Box 113\5\  scan0015
Date  28th April 1937 guessed
  
Our own practice in using a two piece handle has arisen due to difficulties of stowing away the handle in one piece. Now that it is usually carried under the bonnet it is felt that an endeavour must be made to find a place for a one piece handle, as the cost of the two piece handle is excessive. Further, the one piece handle is the better job, as cases have arisen of the handle coming off the shaft while cranking. Trouble has also been experienced in the past with the corners of the dogs chipping which has led to the use of larger diameter dogs than are absolutely necessary. The dogs are case-hardened 5% nickel steel, and in the case of the 25/30 and Bentley, the tips are so small that there is a danger that they will be hard right through, which due to the brittleness of the case will inevitably lead to chipping.

It is proposed to make the dogs in an air hardening nickel chrome steel which will get over the difficulty of chipping, and will provide a sufficiently hard surface for the amount of wear they are likely to receive. The dogs on the crankshaft extension have also been made a detachable piece so that only the dogs themselves will require to be made in nickel chrome steel. With these improvements to the dogs it is intended to try the same dogs on P.III. as on 25/30 and Bentley, and thus do away with the present P.III. construction which involves the provision of a bearing for the starting dogs carried on pressing from the wheelcase and engaged by splines in the end of the starting handle shaft as shown in Fig.5.

The loose sleeve on the handle itself has also been simplified. The deletion of the release spring in the end of the shaft which is no longer considered necessary, has enabled the dogs to be centred by an extension of shaft itself which not only ensures better centralisation, but does away with the need for a rear support bearing for the handle.

The trap in the shutters is much more expensive than the means used by other manufacturers to close the starting handle hole in the grille, but the frontal appearance of our cars, and the use of shutters demands some such fitting. A small part such as this trap can very conveniently and cheaply be made as a zinc base pressure die casting provided sufficient parts are required and provided a durable chromium plated finish can be obtained. An endurance test on the plating is at present in progress. If these tests are successful it is proposed to make the trap in this way and use the same one on all chassis. At present the trap on each chassis is different although the Wraith II. trap has been reduced in price from that on the 25/30 to approximately the same as that on the Bentley and P.III. If a different appearance is required on the Bentley a different lid{A. J. Lidsey} may be used.

Cont'd.{John DeLooze - Company Secretary}
  
  


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