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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).
Letter from Dennis Bros Ltd reporting on the failure of aluminium centre main bearings (A.C.9 material) during engine testing.

Identifier  ExFiles\Box 116\1\  scan0046
Date  9th July 1938
  
ALL COMMUNICATIONS TO BE ADDRESSED TO THE FIRM AND NOT INDIVIDUALS

BY APPOINTMENT

1020a.

HEAD OFFICE AND WORKS
DENNIS BROS LTD
COMMERCIAL VEHICLE AND FIRE ENGINE MANUFACTURERS
GUILDFORD
SURREY ENGLAND

A B C CODE 5TH EDITION
LIEBERS 5 LETTER
BENTLEYS . MARCONI

TELEGRAMS:
DENNIS GUILDFORD

TELEPHONE:
GUILDFORD 1575 (7 LINES)

OUR REF. JM{Mr Morley}/CS.

YOUR REF. RM{William Robotham - Chief Engineer}/Mths.{Reg Matthews}

DENNIS
ESTABLISHED 1895

9th July, 1938.

Messrs. Rolls Royce Ltd.,
DERBY.

Dear Sirs,

Attention of Mr Matthews ✓

Aluminium Bearings.

We would confirm our telephone conversation of this morning regarding the tests which we have been carrying out on our 100 x 120 4-cylinder engine with centre main bearings made in your A.C.9. material.

Up to the present time we have not had any indications of success such as we have had with the A.C.6. material on our Diesel big ends. The crankshaft on this engine is unbalanced and has a centre journal of 2.375" diameter, [scribbled out text] and an overall length of 2.375". They had a diametral clearance of .004, and an end float of .0065". During the initial running in we found that the engine was not developing its usual power, and we therefore made an inspection rather earlier than we should normally have done. We found that the centre main had definitely tightened up and had scored badly both on the journal and on the thrust faces.

A further bearing was fitted, and this time the diametral clearance was increased to .007, and the end float increased to .010". The initial running in with this bearing proved quite normal, and we commenced a run of six hours at 3000 r.p.m. After running for a short period the speed and power fell momentarily, but as the engine picked up again and resumed its normal performance it was allowed to carry on for about one hour. We then stripped the engine and found that the centre main bearing was in a very bad condition, and the surface metal had been wiped over into the bevel at each end of the bearing, both from the journal and thrust faces.

One half of this bearing has now been sent to Messrs. Wellworthy Piston Rings Ltd., while the other half has been sent to Messrs. High Duty Alloys, for the attention of their Mr. Perry, whom we understand has been dealing with this material.

CUSTOMERS' VEHICLES DRIVEN AT OWNER'S RISK ONLY.
  
  


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