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 from Burman & Sons Ltd. discussing the specifications of a Burman-Douglas steering gear.
| Identifier | ExFiles\Box 28\3\ Scan066 | |
| Date | 14th November 1934 | |
| TELEPHONE: CALTHORPE 2641 (4 LINES). TELEGRAMS: BURMANTH B'HAM. BURMAN ESTABLISHED 1871. CABLES: A.B.C. 5TH EDITION. BURMAN & SONS LTD. BURMAN GEAR BOXES. BURMAN-DOUGLAS STEERING GEARS. CHAIRMAN ALD.{F. Allwood - Experimental Design} J.{Mr Johnson W.M.} B. BURMAN, J.P. MANAGING DIRECTOR THOS. BURMAN. SECRETARY H.{Arthur M. Hanbury - Head Complaints} BURMAN. SG{Arthur F. Sidgreaves - MD}/EL. Ryland Road. BIRMINGHAM 15. 14th November 1934. Messrs.Rolls-Royce, Ltd., DERBY. Dear Sirs, For the attention of Mr.Robotham. We thank you for yours of the 12th, ref. HS{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer} inquiring for further particulars regarding the Burman-Douglas Steering Gear fitted to the 12 H.P. Rover Car. The following details may be of interest to you. The screw is of 1" diameter, .750" lead, 5-start. This is of mild steel and runs in a phosphor bronze nut. The helix angle is 14° 28 mins. and the mean diameter of the screw .988". The rocker shaft radius is 1-11/16" and rotates in two bronze bushes. The power efficiency in the forward direction is 49% and reversed, is 24%. These figures are calculated, but we believe that they are reasonably accurate. In all probability, the figures would improve when the gear was run in, but not to any very considerable extent. We would point out that these efficiencies are such as we have decided are satisfactory, after calculating the characteristics of the front axle on the particular Car in question. Naturally, different axle lay-outs control the efficiencies and helix angles which we can standardise on different types of Car, and in some cases, it is possible to go up to an efficiency of over 60% in the forward direction. It is, of course, one of the features of the design of the Gear, that by varying the rocker shaft radius, the helix angle and diameter of the screw, we can produce a wide variety of characteristics which enables us to choose a design to suit each particular axle lay-out. (Contd) All Orders and Contracts are accepted subject to Strikes, Lockouts and causes beyond our control. [Handwritten Note] Hardy, Cannot understand how he calculates this as we get with TS/KWH/7015 Rm{William Robotham - Chief Engineer} | ||