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 failure in car 98-NK during tests in France.
| Identifier | ExFiles\Box 71\4\ scan0051 | |
| Date | 7th March 1925 | |
| R.R. 493A (50m) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. Expl. No. 18940 REF Hsl/LG7.3.25. To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair} 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. EAC. 'V' SERIES - TESTS IN FRANCE. 18940 28080 We have had the following report from our man Lidsey as regards the piston failure on 98-NK car :- "Towards the end of the afternoon run, engine was found to be missing on one cyl. (No.6.) Plugs were changed but did not cure it. No.11. and 12 tappet clearances suddenly increased, and on inspection, push rods were found to be bent. Car returned to garage. Days average speed 41.8 m.p.h. Cylinder head dismantled - induction and exhaust system found full of broken bits of piston rings. Considerable difficulty was experienced in dismantling exhaust boxes, owing to dowel holes being very tight on pins. No.6 piston head found to have failed. The piston was fractured in two pieces, the fracture being in line with the horizontal anti-piston slap saw cut. The top part of the piston had been pushed up into the cylinder head and had been prevented from returning by the piston rings opening out. The valves on opening had fouled the piston head, so bending the push rods. Cylinder bore not marked in any way. No.11. and 12. valve seats were slightly damaged by pieces of piston rings. Engine lower half dismantled to ascertain if any further damage had been done. All pistons taken out. These are O.K. None of the piston rings were gummed up. All gudgeon pins found to be slightly slack in piston bosses. No.3. big end bearing has been picking up rather badly, apparently owing to some foreign matter getting in. All remaining big ends in very good condition. All the cylinder bores in excellent condition". We expect Mr. Lidsey to arrive in Derby with the broken pieces today. This car was fitted with the latest die-cast pistons, the same as those being used on production engines. So far, practically all the experimental running has been made with sand-cast pistons. We have, of course, been using die-cast pistons as standard on the 40/50 HP. and 20 HP." for a very long time. Hs.{Lord Ernest Hives - Chair} | ||