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).
The analysis of a fractured 'EAC' piston.
| Identifier | ExFiles\Box 66\1\ scan0013 | |
| Date | 9th March 1925 | |
| R.R. 493A (50n) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. Expl. No. Y8040 REF. Hs{Lord Ernest Hives - Chair}/ACL1/LG9.3.25. To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/ACL. c. to CJ. BJ. c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} S E C R E T. RE. FRACTURED 'EAC' PISTON. We attach a drawing of the piston shewing where the fracture occurred, also the section on the line of fracture. It is seen that the fracture followed the line of change of section, where the skirt thickens out, and followed this up to the oil groove and saw cut. The sectional area at this part is 2.56sq.ins. (taken from the actual piston). The weight of the piston head, complete with rings, above a plane through A.A (see sketch) is 1.09 lbs. At a speed of 3000 r.p.m., and the engine may easily attain this, the inertia due to this mass is, when at top dead centre, equal to 948 lbs. The most severely stressed part appears to be the section formed by the wall and stiffening ribs just above the piston pin bosses and due to the section not being symmetrical about the axis B.B - which gives the equivalent effect to eccentric loading - the stress should be of greatest intensity near the saw cut ( C. in sketch ). The broken piston is in two pieces. There are not the least signs of seizing on the fitting portion. The head portion has been damaged by the valves, but there are no distinct signs of seizure. Hs{Lord Ernest Hives - Chair}/ACL. | ||