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).
Technical discussion in the form of two letters regarding the design of front wheel brakes and pivotal steering.
| Identifier | ExFiles\Box 32\2\ Scan003 | |
| Date | 13th June 1907 | |
| FRONT WHEEL BRAKES AND TRUE PIVOTAL STEERING. [16722.]—In answer to Mr. Pugh's letter [16656], in which he states that he could not understand the second paragraph of my letter [16617] in your issue of the 11th ult., on the matter of the front wheel brakes, I am not at all surprised at this. To be perfectly candid, when I read the paragraph in question in cold print I did not understand it myself! However, the trouble is up to the printer, because on the sixth line of the second paragraph there should have been a full stop after the word pivot. Mr. Pugh's diagram is most interesting, but he is not dealing fairly with the subject in assuming the centre line of the steering pivot to be parallel to the centre line of the wheel. In all cases of front wheel brakes that I have seen other than that fitted to Crossley cars the steering pivots are inclined, and the wheels are consequently splayed, and therefore the centre lines of the pivot and wheels are not parallel, and I do not see how a satisfactory form of stub axle steering-head can be designed on parallel lines, giving such a very small turning moment as is indicated by Mr. Pugh's diagram and figures. I am afraid neither Mr. Pugh nor myself will succeed in convincing each other, and I can only, therefore, hope that I may possibly at some time have an opportunity of demonstrating to Mr. Pugh that what we claim theoretically is carried out in practice. G.{Mr Griffiths - Chief Accountant / Mr Gnapp} HUBERT WOODS. [16723.]—I am afraid not every ordinary reader will care to follow the intricacies of Mr. Pugh's letter [16656]. But, after all, the subject of dispute between Mr. Woods and Mr. Pugh comes down to this: Mr. Woods evidently believes that if a wheel has to meet brake resistance (may I add other resistances such as those caused by deflection in steering, by stones or lumps or holes in a road?), it is better to let the rigid connecting part of the chassis—that is, in case of a steering wheel, the front axle ends—convey their forward push to a part lying within the central plane of this wheel, and, moreover, as near to the centre of that wheel as possible. Mr. Pugh would have the reader believe that all that is required is to deflect laterally the pivotal lines. If that be so, what advantage, may I ask, is there in the special spoking patented by Mr. Pugh and illustrated in his sketch? I fondly imagined it was that Mr. Pugh had recognised the fact that the nearer the pivots were to the centre of the hub, the less would be the adverse turning effects produced by brake or laterally acting resistances, and he therefore sought to narrow his hub on the pivot side. If Mr. Pugh's latest contention in the present case is right, he ought to apply his double spoking to the outer side of the wheel so as to shorten the overall width of the car; the inner sides of the hubs could be extended towards the chassis as far as you like. All you have to do is to bring in the pivots as well, but give them sufficient lateral inclination to point to the point of contact of wheel and ground. The last sentence of Mr. Pugh's letter can surely not be justified. He sets up the amazing proposition that, as front wheel braking brings out and emphasises the faults of imperfect steering designs, every form of front wheel braking must be completely condemned. No, front wheel braking, in spite of the not unnatural opposition of those who can manage to shelve it, is, I firmly believe, bound to become a standard fitment; but long before that happens it will have directed the attention of the motoring public to the inherent defects of the now prevalent system of steering, and call for correction of the same quite apart from the braking question. I repeat what I stated some two years ago in these very columns, that steering can be made, and has been made, so perfect, and that by a design involving not the slightest difficulty in manufacture, that even such irregular stresses as those imposed by braking on one front wheel while the other one is allowed full freedom of rotation has no deflective effect whatever. P.L.R. Handwritten text: X4339 | ||