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).
The development of Bentley rubber rear engine mountings for improved smoothness.
| Identifier | ExFiles\Box 86\5\ scan0097 | |
| Date | 13th December 1933 | |
| To Sg.{Arthur F. Sidgreaves - MD} ) WOF.) From E.{Mr Elliott - Chief Engineer} c. Hs.{Lord Ernest Hives - Chair} By.{R.W. Bailey - Chief Engineer} Bn.{W.O. Bentley / Mr Barrington} Er. EV.{Ivan Evernden - coachwork} Hn{F. C. Honeyman - Retail orders}/Mm. Bentley Smoothness Rubber Rear Engine Mounting. Referring to report Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}1/KT.11.12.33. we have for some time been aware that our standard form of engine mounting in rigid bearings fore and aft did not allow any cushioning for longitudinal vibrations such as would be set up by such phenomena as flywheel flutter. This last has always tended to create booms in the bodies which could not be connected with any of the well known crankshaft vibration speeds. We are, therefore, very pleased that the experiment reported now confirms the beneficial effect of such flexibility. We have in the past instructed experimentally rubber mountings for the rear end of the engine which have taken the form of a bush of this material used in place of the Ferodo lined ring carrying the rear nose of the engine but the limited degree of flexibility thereby obtained has never clearly shown any advantage. We are now engaged on the consideration of a design for both ends of the engine in which rubber of generous proportions is used made more in the form of a saddle piece carrying the engine from below, which we think will meet the conditions required. We think this is the right treatment rather than flexibly mounting the crossmember as shown on the blueprint attached to Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}1/KT.11.12.33, but we realise the latter is probably the readiest means for obtaining this flexibility experimentally although it robs the frame of the partial support provided by a rigid crossmember. We are proposing to have our scheme ready for the next experimental Bentley to do a 10,000 mile test, and it will be applicable in principle to our other chassis. Another point we have in mind in connection with this mounting is that this extra cushioning takes care of lateral vibrations arising from the deflection of the crankshaft as a beam and would be valuable in the event of our adopting a four bearing crankshaft on any future design of Bentley engine. | ||