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).
Continuation of a report comparing stress, distortion, and cracking on different connecting rod designs under load.
| Identifier | ExFiles\Box 179b\3\ img329 | |
| Date | 14th March 1931 | |
| -2- He/LBH.{Mr Hall - Aero Design Engineer}2/ML.14.3.31. Cont'd.{John DeLooze - Company Secretary} two, the increase in bolt lug dimension being only .0005" under 11 tons. This increase appears to be a result of the rod bedding on to its bearing block, as it occurred when a load of 8 tons. had been reached, and remained at this dimension on removal of the load. Also it will be noticed that there is no splaying of the foot due to the combined increase in dimensions A.{Mr Adams} and B., as occurred with both the other types of rods. The splaying of the standard type of rod helps to explain the cracks which occur across the bolt lugs of the big end bearing blocks, as the splaying action will cause higher stresses at the inner corners of the lugs, from which points the cracks always develop. The strengthened type of standard rod, having the deepened bolt lugs, shewed more distortion under load than the standard rod. It first it was thought that the degree of tightness of t the bearing block bolts was affecting the rigidity, but on doing a repeat test with the lower half of the big end removed, the rod being located on its top half merely by the spigot portion of the bearing bolts, exactly similar readings were taken. This showed that the bolting up of the lower half of the big end bearing had no effect on the rigidity of the foot of the rod. These tests show that the curved foot type of forked rod is much more suited to take the piston gas loads than the standard types. At the same time it eliminates splaying of the foot which throws heavy stresses on to the lugs of both the rod and bearing block, leading to the development of cracks. to He/L.B.Hall. | ||