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).
Analysis of Bentley III petrol tank strap failures during chassis bump testing, comparing them to the Wraith model and suggesting solutions.
| Identifier | ExFiles\Box 100\2\ scan0131 | |
| Date | 18th March 1938 | |
| 451- also 1024. To By.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to Da{Bernard Day - Chassis Design}/Ev.{Ivan Evernden - coachwork} Rm{William Robotham - Chief Engineer}/JBD.{John B. Dixon - Fuel Systems}1/JH.18.3.38. BENTLEY III PETROL TANK BUMP CHASSIS. With the tank 3/4 full of water one of the top straps broke after 22 hours front bumping. The chassis then ran 10 hours with no water in the tank. It was filled right up with water when a top strap broke after 2 hours running and both top straps after another 2 hours. When dismantled both bottom straps were cracked through the supporting eyes. The body buffers and end plates on the tank were still intact though the end plates were slightly dished and very flexible. The straps used are identical to those used on the Wraith which have not given trouble though the tank is larger and heavier. We suspect that the cause of these fractures is due to the tank acting as a tubular cross member on the bed of the frame and the failure takes place on the top strap because it is of more circular section and fits closely to the tank. The bottom strap though carrying the weight does not grip the tank on the flat portion on the bottom but tends to stand clear and so allow a certain amount of spring. On the Wraith chassis both the cross members carrying the tank and side frames are stiffer than those on Bentley III, and should releive the tank from acting as a cross member. We suggest that to overcome this trouble either we allow more spring in the top straps or preferably carry the rear end of the straps on a separate support bar pinned to the middle of the rear cross member. As in attached sketch. The flat section tanks as used on most American cars are more flexible torsionally. We intend to try some simple and cheap methods for overcoming this trouble before resorting to 3 point mounting. | ||