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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).
Analysis of magnet design and the particulars of teeth for a MK.30 gearbox.

Identifier  ExFiles\Box 136\2\  scan0287
Date  2nd August 1940
  
-2-
Ev{Ivan Evernden - coachwork}/Tln.2/JH.2.8.40.

We suggest here that the design of magnets and mating surfaces is worth investigating. Fig. 1 represents the Cotal Magnet; Fig. 2 suggests an airgap of greater area than the magnetic path in the iron and Fig. 3 shows conical mating surfaces.

Fig. 1
Fig. 2
Fig.3.

(3) Particulars of teeth, MK.30 box.

All the gears in this box have the same size teeth.

The following particulars are obtained from examination of a compound planet pinion taken from an MK.30 box.

Millimetre Module = 2.0. This is about 12½ (inch) DP Addendum 2 mm. Dedendum 2.5 mm. Straight teeth. Obliquity appears to be 14½°. Involute form of tooth. Teeth are form ground followed by Maag grinding. The form grinding appears to remove part of the involute flank of the gear near the root and gives a generous root radius.

As an example gear for tooth stresses we have considered the planet pinion of the second train. We think there are 5 planets. We have not a makers figure for input torque, but using B.V. torque of 2400 lb/in. as a basis we find that the root stress and pitch line loading are not excessive under 1st. gear conditions. We have not allowed for maldistribution of load, nor for the exceptionally high loading which can occur if full torque "1st. speed reverse" is ever used.

Cont'd.{John DeLooze - Company Secretary}
  
  


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