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).
Letter discussing bump-rig testing, shock absorber boiling, and the pre-settling of torsion rods.
| Identifier | ExFiles\Box 170\3\ img003 | |
| Date | 25th January 1936 | |
| H/R.M. COPY. GRY{Shadwell Grylls} Mr B.I.Day., Rolls-Royce Ltd., DERBY. ENGLAND. Jan. 25th 1936. Dear Da{Bernard Day - Chassis Design}, (1) First, thank you and Grylls very much indeed for the picture-light for our rug which we opened and set up on Christmas Day. It improves things very much indeed. (2) Second, again thank you for the information on bump-rig testing. This is most useful, as I have got the go-ahead on this method and hope to prove that we can dispense with a lot of slow and expensive Belgian Block work. First results on my torsion rod suspension were very disappointing. I broke a rod in 15 hours. (3) What do you do about the shock absorbers boiling? Try to cool them with a fan or drill a vent and let them boil? Even our Dubonnet jobs with an enormous oil reservoir boil merrily at 15 m.p.h. with two 2" cams. (4) Here is a problem which I want to put up to you very specially because with most of the guys over here I cannot even get it into their heads that it is a problem, let alone get them really roused and interested. When a coil spring or torsion rod is "pre-settled" to make it carry a given maximum load without further settling - what happens? Is it a case of raising the elastic limit by cold working or is it a case of "slipping" the highly stressed metal until it is no longer highly stressed? or rather, since both effects must exist to some extent what is the proportion of each? As an example - A torsion rod is pre-settled by twisting it through a 12" arm on the Olsen machine until it will take a 30° stroke without further settling. The total "slip" in doing this is .800" at the end of the arm, or 3.8 deg. Then we reverse the twist and settle it in the opposite direction. It now takes longer to settle and the slip before it will carry the 30° twist is 1.200" or 5.7 degrees. If cold working had a great effect one would expect the twisting in one direction to actually improve the rod even for twisting in the opposite direction. | ||