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).
Potential causes and solutions for front road spring breakages.
| Identifier | ExFiles\Box 54\3\ Scan111 | |
| Date | 1st January 1924 | |
| To DA.{Bernard Day - Chassis Design} from R.{Sir Henry Royce} c. to CJ. BJ. HS.{Lord Ernest Hives - Chair} c. to BY.{R.W. Bailey - Chief Engineer} Hl. X2628 R1/Mlo.1.24. RE. FRONT ROAD SPRINGS. X.2628 X.9410 I understand that our breakage on the bump is similar in character and position to that we get on the road, and we consider our test of reasonable severity. Natrually many questions could be asked but can Mr. Hall, Mr. Hives and Mr. Day give any replies to the follows :- (1) Assuming that Lemoine springs are better than the American, Woodheads, and Firths - in this order - after checking the materials of the different makes as regards purity and suitability, one would re-harden pieces of the broken spring to see if any improvement in resistance to fatigue tests could be obtained by improving the heat treatment. My own great point has always been in the fault of the hardening temperature being too high, a fatal fault which is so often made to insure hardening. I leave this for Mr. Hall to investigate all the errors and points of difference in materials and heat treatment. (2) Do we really know which are the chief strains that cause top-leaf fractures. Naturally I should suppose it is combination of all but do we find any difference if we alter the strength of proportions so as to reduce some of the stress and possibly increase others for instance :- (a) Supposing it is chiefly due to deflection from pure road varying, then the 25% stronger and stiffer springs we are proposing should make some improvement, whereas one fears we are getting worse. (b) If the fracture is partly due to radius rod action then the alteration from front to back, and with and without our radius rods should have made some difference. I understand it has not. (c) If the fracture is mainly due to the lateral forces then a wider spring should make a difference, or 1 or 2 of the top blades should be made to help by having an effective clip for lateral pressure near the ends. (I do not remember how far we have gone in investigation of this order, and also if side flexibility has been increased by making the spring narrow and double, or as an experiment of trying other means of taking the lateral forces. (d) It has occured to me that it is worth while to try the rubber fittings for the ends of springs to see if these would make the breakage less. I should say it would, but one would expect to have to fit the radius rods. (e) It will be seen that there are many suggestions above. An important one would be the altered dimensions suggested in the EAC 2. and 3., of 3" longer springs, contd:- | ||