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).
Piston and crankshaft failures during a high-speed endurance test of a Bentley Unit C.13.
| Identifier | ExFiles\Box 3\6\ 06-page022 | |
| Date | 26th August 1933 | |
| FILES. HIGH SPEED ENDURANCE. BENTLEY UNIT C.13. PISTON FAILURE. Pistons LOP. EB.513. EB.495 Die Cast (Mx.{John H Maddocks - Chief Proving Officer} type of bedding) EB.501 Gudgeon Pin. Cyl. Block. EB.89 (Short type barrels). On the drawing Hs.{Lord Ernest Hives - Chair}1116 is shown the decreased dia. of the lands as on the above pistons, compared with the original type of piston grinding on EB.500. It will be seen that due to side thrust, the smaller piston head will allow increased movement before these lands come into contact with the cylinder walls. The fact that the maximum bedding exists at the bottom of the piston skirt, this increased movement will create a bending force about the section at which failures have occurred. After 6 hours Endurance. 4½ Hours at 4000 R.P.M. 1½ Hours at 4250 R.P.M. No.1 Piston. Crack approx. 1" long. No.2 Piston. First signs of cracks just visible. No.3 Piston. Total running time since overhaul and reassembly to specification RHC{R. H. Coverley - Production Engineer}/WSC{W. S. Cassel}6/AP.8.8.33. = 15 Hours. CRANKSHAFT FAILURE. Crankshaft. 2.250 dia. journals 2.00 dia. crankpins. Chrysler type balance weights. Sch.1557. Shaft modified to suit low inertia spring drive Ex.6869. Bearings. Centrifugally cast white metal. Oil grooves in bearings to Ex.7648-9-50. After 6 Hours Endurance. 4½ Hrs. at 4000 R.P.M. 1½ Hrs. at 4250 R.P.M. | ||