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).
Issues with security bolts on cord tyres, referencing trials by the Dunlop Company and customer feedback.
| Identifier | ExFiles\Box 53\1\ Scan119 | |
| Date | 28th August 1922 | |
| X4546 W/B. c. S/Dr. c. Hs. {Lord Ernest Hives - Chair} BY7-P28.8.22. 31-KG AND 38-KG. RE SECURITY BOLTS. X4546 Referring to Bs {A J. Barnes - Assistant Manager} 5/C16822 the position in regard to security bolts is as explained in my memo BY6-P22722 to Sales. Paris, as well as customers, have brought evidence to bear that the original security bolt is useless when fitted to cord tyres. We sent for Mr Bond, Manager of the Service Dept, of the Dunlop Company, to discuss the whole question with him, and he explained to us that the difficulty was caused in the first place by the fitting of a security bolt as such, and that to avoid trouble with tyres it was essential to delete the security bolt altogether. He gave us particulars of very elaborate trials and tests which had been made by the Dunlop Company which conclusively proved that tyres fitted with security bolts had no advantage over tyres without security bolts, whereas when cord tyres were fitted, since a security bolt did not bed down on to the rim, the inner tube stretched out over the edge of the security bolt and frayed itself away until tiny pin holes were formed. When this occurred the pressure dropped slowly in the tyre and when a certain point was reached in depleted pressure the bead of the tyre lifted under the rolling action of the car and the inner tube forced itself in between the bead and the rim with further rolling. The tube gradually worked itself further between the rim and the bead until it finally resulted in a blow-out by the inner tube forcing itself completely out and bursting as a result. In addition to the very careful experiments which I have referred to, the Dunlop Company had also experience from customers of ours who were trying to run cord tyres with security bolts and were having continuous trouble with blowouts caused by the sequence of events related above. They gave us specific details of one customer at Liverpool who complained to them instead of us, and stated that he was unable to run his car due to having continuous trouble along the lines indicated. The Dunlop Company recommended him to leave out security bolts, but he pointed out that the Rolls Royce Company expressly stated they should be fitted, upon which the Dunlop Company told him they did not wish to go against our rulings, but merely in order to prove their point..contd | ||