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 effectiveness and dangers of security bolts for tyres, citing arguments from the Dunlop Company.
| Identifier | ExFiles\Box 53\1\ Scan141 | |
| Date | 14th September 1923 | |
| BY5-F14.9.23. contd. - 3 - The Dunlop Co, urged with much force that the word 'security' in connection with the tyre bolt, gives a driver a false sense of reliability and security from covers leaving the rim. They are perfectly definite in their statement that the tyre bolt will not prevent the cover leaving the rim, even when the bolts are of the best type and properly fitted, whilst in many cases due to the unavoidable variations of the bead itself in manufacture, the tyre bolt, even when of correct shape and type, does not bed right down, and in consequence the air tube is frayed where it comes in contact with it, resulting in the slow leakage which causes ultimate failure. When this failure occurs it not only spoils the tube, as admittedly is the case when no tyre bolts are present, but it also destroys the cover and a very small amount of running on a deflated tyre with security bolts is sufficient to accomplish this destruction. A further point is that the security bolt is of such dimensions that if the tyre were deflated and a sudden wrench, due to a skid or the application of a brake were imposed upon the wheel, not only would the security bolt not prevent the tyre coming off, but in a good many cases the security bolt itself has broken due to the abnormal load thrown upon it, a load which the bolt, by its design and dimensions, is entirely unable to cope with. The Dunlop Company pointed out that the line of least resistance for them was to agree to fit security bolts, but they were emphatic that this course was wrong - incidentally it would only lead to a further complaint when a cover wrenched clear, to the effect that the cover itself had been produced in a faulty manner. The Dunlop Co's experience goes to shew that there is far more danger by a tyre being partly flung off the rim when partially held by security bolts and wrapping itself round say the front axle and the wheel, than there is in the tyre itself being flung entirely clear. It must be admitted that a fitting such as a bolt which tends to increase the possibility of a tyre locking the steering in the manner indicated, is a far greater danger than is incurred by the possibility of a tyre being thrown clear on either the inside or outside of the wheel. contd. | ||