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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).
Results of engine tests on spark plugs, focusing on fouling, gap erosion, and overall condition.

Identifier  ExFiles\Box 58\2\  Scan028
Date  23th February 1932 guessed
  
-2-

Results.

After the first 3 hours of the 4 power test the plugs were removed from the engine due to fouling. They had then completed the following running.

1 Hour - Power Curves etc.
1 Hour - 2500 R.P.M. 460 B.H.P. (113 lbs/sq.in. MEP)
30 Hours - Endurance Test 2500 R.P.M. 414 BHP (111.5 lbs/sq.in. MEP)
1 Hour - Overspeed Test 2650 R.P.M. 374 BHP.
3 Hours of the 25 Hour 4 Power Test - 2000 R.P.M. 230 GHP.

Before the plugs were stripped the gaps were measured. The average gap was .030", the initial gap was .014" so that the erosion was .016".

When stripped the mica of several of the plugs was pin holed whilst the condition of the plugs as a whole was indifferent.

The external finish of the mica insulation is remarked on here. This is not good, the surface presents a rough appearance which might be taken for pin holing on casual examination.

Summary.

Our chief critian of the plugs is that no adjustment of the spark gap is provided to deal with erosion.

The attached photograph clearly illustrates that the centre point cannot be turned round to present a new part to the earth point and also that no adjustment can be obtained by bending the earth point.

The Lodge A.2. plugs ran through the whole test 97 1/2 hours - with only the routine attention of cleaning and adjusting the spark gap. At the end of the period the insulation of all these plugs was in good condition. On this basis of comparison, we can therefore say that the B.G. 116 is not up to the standard of the Lodge A.2.

HS{Lord Ernest Hives - Chair}/H.R. Young.
  
  


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