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).
Dynamo failure in a 3.5-litre Bentley caused by shorting wires behind the distribution box.
| Identifier | ExFiles\Box 162\1\ img066 | |
| Date | 13th August 1937 | |
| K/W. By.{R.W. Bailey - Chief Engineer} Rm{William Robotham - Chief Engineer}/GWH{George W. Hancock - Head Chateauroux}/DPB/13.8.37. DYNAMO FAILURE. 3½-litre BENTLEY B.41.DK.V.D.Drury. Mileage 21,000. ------------------ The Kingsbury Depot had the above car in yesterday for a complaint of the dynamo failing to charge until the engine reached 2,000 revs, when the charge came in with a rush. The fault was very hard to find and after checking the output regulator, cut out, all fuse connections, battery wires etc. they finally dismounted the distribution box. At the back of the distribution box it was noticed that the junction wire from No.6 terminal to the accessories terminal for cigar lighter and the junction wire from the bottom terminal of No.6 to No.7 terminal was shorting where they cross one another. The braided covering was frayed and the bare wires were actually touching. Upon parting these wires, the dynamo charge was satisfactory. They have had similar symptoms when the Coachbuilders have fitted too large wire terminals on the accessory terminals which caused a short across the two outputs. I have tried to find a reason for this but cannot find a satisfactory solution, as there does not appear to be any direct short that would prevent the dynamo cutting in. The only solution I can come to is that if there was a slight leak to earth from the horns, it would short circuit the ammeter. We should very much appreciate your opinion of how this could happen, at the same time if it could be arranged to avoid the use of the loose wires behind the distribution box, it would lessen the risk of failure. The 4¼-litre has similar wires. Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux} | ||