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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).
Engine friction, rolling resistance, and factors affecting fuel consumption.

Identifier  ExFiles\Box 178\1\  img058
Date  21th November 1925
  
- 11 -

EXPERIMENTAL REPORT. EXPL. NO. REF. Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}1/LG21.11.25.

at very small throttle openings some 20° extra advance can be
given with beneficial results, the car could never be run under
these conditions successfully at full load however.

ENGINE FRICTION AND ROLLING RESISTANCE.

As will have been gathered from previous remarks, engine
friction is of considerable importance in low speed petrol cons.
The two main items in engine friction are the pistons and type of
lubricant used. Both these are fixed by consideration of wear,
piston slap and bearing durability so that, except for freak re-
sults, little can be done. The engine temp. has of course an
effect on the oil viscosity, for this reason steam cooling may
be expected to have beneficial results on cons:

Tyres again will make an appreciable effect, if the car is
driven purely from an economy point of view. Cord tyres may improve
the cons. 10% over canvas tyres. Hard cord tyres will be about 12%
better than the same tyres badly under-inflated. To imagine however,
that the cons. of an owner who averages 40 m.p.h. can be improved
appreciably by attention to tyres or lubricant, is quite futile.

FREAK PETROL CONSUMPTIONS. We hope the foregoing remarks have
indicated how freak petrol cons. are obtained.

With max. economy carb. setting, advanced ignition, high
rad. temp., hard tyres, thin oil in engine, axle, gearbox high
geared axle, and a constant road speed of 20 m.p.h. we anticipate
that the Phantom would do 25 m.p.g. even with its present
compression ratio.

Hs{Lord Ernest Hives - Chair}/W. A.{Mr Adams} Robotham.
  
  


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