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 to John Marston Ltd. discussing weight discrepancies and savings on Phantom III and Bentley matrices.
| Identifier | ExFiles\Box 150\3\ scan0074 | |
| Date | 29th October 1936 | |
| 1280 Exptl. Dept. Rm {William Robotham - Chief Engineer} /Std.18/JH. 29th October, 1936. Messrs. John Marston Ltd., Wolverhampton. For the attention of Mr. J. {Mr Johnson W.M.} Coltman. Dear Sirs, Referring to your letter of the 16th instant, for which we thank you, the 51 lb figure which we quoted was the average of four Ph.III matrices which we weighed here. However we note that you give the average of 50 cars as 52 1/4 lbs. On this basis the saving with the lightened construction is 4 lbs. (with copper strip of upper limit of the thickness) i.e. a saving of 7.6%. If the copper strip did not exceed the minimum thickness the saving would be increased to approx. 6 lbs. or 11.4%. Providing that your average core figure of 52 1/4 lbs. is correct we are in agreement with the above figures, but what is puzzling us is the discrepancy between the Ph.III saving of weight and the saving of the Bentley matrix which you have just sent us. This matrix weighs 24 7/8 lbs. (it is 2.025" thick) and the previous 53 m.m. Mark VI matrix (in our standard thickness of strip) which you supplied to us weighed 29.3 lbs. This represents a saving of 4.425 lbs. or 15% and even if the strip used was of maximum thickness, the saving with strip on the upper thickness limit would still be 3.6 lbs. or 12.3 % Hence it seems that your Bentley matrices are better constructed than your Ph.III blocks. We should like you to make us a second Ph.III block and see if any weight reduction can be made. We will send you an official order for these. | ||