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 condition of chassis SS-NK after 21,139 miles, focusing on engine wear and component failures.
| Identifier | WestWitteringFiles\M\2April1925-June1925\ Scan116 | |
| Date | 8th June 1925 | |
| R.R. 493a (50m) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. Expl. No. REF. GWH{George W. Hancock - Head Chateauroux}/Cm.8.6.25. To Hs{Lord Ernest Hives - Chair}! From G.W.Hancock. Report on chassis SS{S. Smith}-NK after 21,139 miles: Engine: Engine power has been good and smooth. Compressions even. Examination of pistons shewed even lubrication, but on heavy side. This had gradually increased towards the end of the run. Heavy carbon deposit on top of pistons, and cyl. head. Valves and fittings to E.{Mr Elliott - Chief Engineer} 2217.B. - these are O.K. The valves have been ground in three times during the 21,139 miles. Inlet valves shewed heavy carbon deposit on the top side, which means that oil has been sucked down through the valve guides. The exhaust valves were free from carbon deposit. Very little wear has taken place in the valve guides, these being in very good condition. Modified cast iron choke valve in down take pipe to Lec. 2035 - this has stuck open once since our last report. We still think that this would be much better if the design was more robust. Carburetter butterfly throttle E.73166/7/8 - we havehad no trouble with this on the last 9,000 miles. The crack in the hot spot induction pipe at the bottom corner close to flange where carburetter is bolted up, has not increased since our last report. Controls to Sch. 625 - a fair amount of slack has developed, chiefly where the compensating device is situated. There is also a fair amount of slack on control going through engine case to carburetter. On dismantling engine we replaced piston rings, we found Nos. 3, 4, 5, and 6 connecting rod bearings on the point of collapsing. The metal had cracked and broken up both in caps and rods. We despatched these to Derby for their examination of same. These rods had run 8,407 miles. We have been very careful during this period not to let the oil in the sump get low, also the pressure has not varied. We have run at approx. 20 lbs. throughout the test. We noticed that on Nos. 1 and 2 conrods, although the metal had not broken up to the extent of the other rods, the metal was loose, i.e. leaving the steel. We assume that the continual hammering after this stage, soon breaks up the metal into pieces. Drain Pipes to hot-spot from induction carburetter pipe were found choked up with carbon, as also was the starting carburetter. Explosions on retard we consider to be equal to the standard 40/50 HP. car. Front engine suspension tube to Lec. 2027 - this is still quite O.K. Modified throttle governor spring to Sch. 632 - using spring E.5925 - this is still operating satisfactorily. Spring Drive to Sch. 628 - from outside examination this is quite O.K. Magneto and dynamo drive to Lec. 2019 and 2028 - as previously reported the fabric coupling XX contd :- | ||