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).
Proposal for a simplified crown wheel mounting for the back axle of Bentley, Bentley 50 and Wraith cars.
| Identifier | ExFiles\Box 7\3\ X 602 Axle Rear-page48 | |
| Date | 10th December 1937 | |
| COPY FOR FILES. Da.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} c. Rm.{William Robotham - Chief Engineer} 602 also 202 1044 Da{Bernard Day - Chassis Design}/Hdy.{William Hardy}2/G.10.12.37. BENTLEY, BENTLEY 50 AND WRAITH - BACK AXLE. We send herewith PD.74 showing an application to Bentley II, for test purposes, of a simplified crown wheel mounting which we propose for the above cars. In the final design we should enlarge the deep groove ball bearing to give increased load capacity, and by making it the same dimensions as the A.C. bearing the same series of adjusting washers could be used on both sides. Two nuts are deleted, and the A.C. bearing is approximately 5/- cheaper than the Duplex. The larger ball bearing costs the same as the present roller bearing. A further modification which is suggested for the permanent design is that the aluminium oil seal housing required on the deep groove bearing side is used on the A.C. bearing side also, with the result that access to the adjusting washers (complained of on production) is much improved. The above proposals bring the crown wheel mounting into line with common practice, but there is a difference found also on the Alvis, we believe, in that our aluminium centre casing expands more than the differential unit, and for 100°C rise separates the bearing abutments by 5/1000". We calculate that when under load, either forwards or backwards, the crown wheel is always thrust away from the pinion, and therefore the expansion has no different effect from what occurs at present. When under no load and with 100°C higher temperature than normal the crown wheel can be moved 5/1000" further into mesh. It is difficult to conceive that the no load condition can last longer than is required to take up the slack when changing from drive to overrun or vice versa; however, this experiment is suggested to determine, if possible, whether there is any ill effect from the modification. We think it quite likely that a pre-load of 5/1000" could be applied without much load on the bearings, as the parts concerned are relatively flexible compared for instance with the pinion thrust bearing. Da{Bernard Day - Chassis Design}/Hdy.{William Hardy} | ||