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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).
Rate of cylinder wear on small bore engines and comparing various models.

Identifier  ExFiles\Box 132\5\  scan0164
Date  3rd February 1944
  
Wear on 30 GVII
1123

To: Rm.{William Robotham - Chief Engineer} from FJH{Fred J. Hardy - Chief Dev. Engineer}/CTS.{C. Trot Salt - Carburation}
c.c. to Wym.{G. Harold Whyman - Experimental Manager}
c.c. to Jnr.{Charles L. Jenner}

FJH{Fred J. Hardy - Chief Dev. Engineer}/CTS.{C. Trot Salt - Carburation}1/HM.{Capt. W. Hallam - Head Repairs} 3.2.44.

Rate of cylinder wear on small bore engines.

Re. your memo Rm.{William Robotham - Chief Engineer}7/h.{Arthur M. Hanbury - Head Complaints} 31.1.44.

In your memo, you are asking for a suggestion, as to what precautions we could take to combat the rapid rate of wear on our 3¼ bore engines.

At the same time you are suggesting, that this is due to lack of lubrication, or over-effective oil control.

We have only one 3¼ bore engine, running, and that is in 12.B.V. being used by Hs.{Lord Ernest Hives - Chair} To date, this has done over 76000 miles without a rebore. Four of the cylinders have approximately .009" wear, No.5 has .010" wear, and No.6, the worst, has .014" wear. If we take the worst cylinder, the rate of wear is the same as for the average 3½ litre Bentley. Unfortunately we have no reliable records of oil consumption for 12.B.V, but it is worth noting, that when this car came in with the complaint of high oil consumption, as far as I know, this was cured by fitting two "L" section rings to each piston instead of one. It cannot be inferred however that the fitting of two "L" rings has accelerated the wear, since these were fitted only 8600 miles back.

Considering the two smaller bore engines M.40 and B.40 the rate of wear is particularly high. The following comparison is interesting.

Car. Engine. Rate of wear per 1000 miles.
20 H.P. 3.0" .00015.
25/30 3.25" .00015
3½ Bent. 3.25" .00015/.00022
12.B.V. 3.25" .00018
B.40 2.952" .00066
M.40 2.500" .00066

There are however a number of reasons to account for the four cylinder results, and these have to be taken into consideration otherwise we begin to pull our own legs. When we have tabulated these points, we can deal with the lubrication problem more sensibly.

B.40. Total Mileage 20656.

The engine was overhauled at 15000 miles, and the connecting rods were found to be bent. In fitting new bearings (big end), these were "eased", because clearance was inadequate. It is very doubtful whether clearances could be made correct in this way (they are not supposed to be touched), and it is highly

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