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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).
Proposing experimental modifications to the J.2 and Bensport starter motor to increase B.HP and efficiency.

Identifier  ExFiles\Box 62\1\  scan0104
Date  5th December 1932
  
X6134
To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Wst.
c. Ry.
c. Wor.{Arthur Wormald - General Works Manager}
Hs{Lord Ernest Hives - Chair}/Wst.2/AM5.12.32.
X6091

J.2 AND BENSPORT STARTER MOTOR

Our bench tests on this motor show that it is capable of considerable improvement and we have accordingly overhauled the winding quantities and magnetic circuit with a view to ascertaining what experiments would be useful in increasing the B.H.P. and efficiency.

In revising our calculations, we have aimed at a higher starting speed, which has been found very necessary with the latest carburetters, and a higher working load efficiency. We would suggest experimental modifications as follows :-

Field Circuit.

Width of poles to be increased by .100 inches and the field windings modified to accommodate the extra section iron by winding 3¾ turns per pole of copper bar to D.71936 for the main, and 27 turns of 18 S.W.G. D.C.C. for the teazer. We should like the main and teazer windings to be in parallel and not in series as at present. This arrangement, while not interfering with the main magnetisation, lowers the total motor resistance and allows more current through the armature.

Armature.

We suggest we try two armatures, one consisting of 33 slots and wound with armature strip to D.53139, and the other 29 slots wound with armature strip to E.13741 (a supply of each of these sizes of strips is available in the Works).

If you are in agreement we should like these experiments put in hand as soon as possible.

We are also examining the possibilities of further improvement to the Peregrine motor in the direction of :-

(a) Increased power on the teazer circuit.
(b) Higher maximum efficiency and will accordingly suggest modifications for your approval.

Hs{Lord Ernest Hives - Chair}/Wst.
  
  


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