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).
Letter detailing the performance test results of Bosch sparking plugs on a Bentley engine.
| Identifier | ExFiles\Box 162\4\ img235 | |
| Date | 15th January 1937 | |
| 600h. Experimental Department 15th January 1937. Rm{William Robotham - Chief Engineer}/Wst.4/AP. Messrs K.L.G. Sparkings Plugs Ltd., Putney Vale, LONDON S.W.15. For the attention of Major C.M.Carington. Dear Sirs, We are now able to give you some further information regarding the performance of the Bosch Sparking Plugs type W.145.T. and W.175.T. which you recently submitted to us for test. With regard to the W.145.T. plugs, we ran these for 19 hours on a Bentley engine at between 4000 and 4500 R.P.M. which corresponds to an average road speed on top gear of 87 M.P.H. We are returning these plugs to you, and it will be seen the electrode errosion has been disproportionately severe. Furthermore, it will be noted that in two or three cases the insulator has cracked on the tip of the central electrode. With regard to the W.175.T. plugs, we ran these for 3 hours under the above conditions and they were removed with a report that pre-ignition was occurring. It is thought that this pre-ignition occured due to the earth electrodes over heating. It will be seen therefore, that the performance has not been too good, but as these conditions are not likely to be met with continuously on the road for any length of time, we would not suggest immediate alterations until we have actually tried them on the road. The plugs are being returned to you under separate cover for your examination. Yours faithfully, FOR ROLLS-ROYCE LIMITED | ||