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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).
Specifications for bearings and spring shackles, including allowable twist, torsion resistance, and deflection.

Identifier  ExFiles\Box 154a\2\  scan0169
Date  26th July 1939
  
Messrs. Howard Graham Ltd. -2- 26th. July, 1939.

(5) Amount of side twist - small in the present design it may increase in later designs.
(6) Maximum allowable resistance to torsion - this should not be more than 20 lb.ft. on full deflection and should remain substantially constant throughout the life of the bearing.
(7) Maximum allowable deflection in bearing - this should be as small as possible and must not be sufficient to cause the shock absorber pistons to sieze. This means that the axial deflections must be very small. The radial deflections should also be small, but bigger deflections are tolerable.

It is desirable that the pin and eye dimensions should be kept as shown. The diameter can, however, be increased slightly if this is necessary and the length of the eye can be increased if this can be done by bushing. The length of the shaft may be increased and its diameter may be decreased so long as this will not cause failure. These restrictions are imposed only because we wish to use existing pieces for the test and do not wish to go to the trouble and expense of making new forgings or castings.

Spring Shackles.

As already stated, we enclose drawing FCD.1306 which shows the arrangement of the shackle at present in use. We have obtained the following information as far as loads and movements are concerned:-

(1) Type of Motion - Angular oscillations.
(2) Static load - 1000 lbs.
Shock loads - Up to 1600 lbs.
(3) Angle of Motion - Spring eye bearing 65°
Frame bearing 55°
(4) Pin and Eye dimensions. The diameter of the eye can be reduced as desired and the length of eye can be increased so long as this can be done by bushing. The length and diameter of the pin can be increased or reduced subject to the above conditions and so long as the pin is not weakened sufficiently to cause failure.
  
  


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