Some time ago I made some comments on the pre-war Chevy 6 inline engine.
Scott Fisher came with the interesting retort that the Austin OHV post war
engines were basically derived from it.I had not seen before this idea, and
considered at the time that the Austin had a more likely Nuffield
heritage. Further thoughts on this intriguing point were dormant until I
picked up a most fascinating book on "proper" restoration of Austin Healeys
by a Danish historian who worked for BL, Anders Ditlev Claushager.
It is asserted there that in 1938 the general manager of Austin's, Leonard
Lord directed the designers of the new line of Austin trucks to copy the
successful Bedford truck made in England by the GM subsidiary Vauxhall.The
Bedford engine is , of course closely modeled on the Chevrolet 6 OHV engine
manufactured from 1929.Thus the heritage line Chevrolet-Bedford-Austin
seems a likely conclusion.But further checking,using the indispensable
older copies of the "Automobile Engineer" shows that the likelihood of a
wholesale crib by Austin's is not overwhelming.
In an article on the new line of Austin trucks, the anonymous scribe
mentions that the Austin was designed "entirely on practical experience...
an investigation was made of various other successful vehicles on the
market". No specific mention is made of the Bedford truck. When the engine
characteristics are compared closely, it is seen that there are indeed
remarkable similarities:
-6 cylinder OHV inline block
-bore and stroke nearly identical (85x101.6 mm)
-balanced 4 mains crankshaft
-nearly the same power output: 70 bhp for Austin,72 for Bedford
-general architecture of engine is similar: choice of single DD
carburetor(Zenith 30 VIG-3 in both cases),identical location of
manifolds and distributor.
There are also differences,some of them quite important:
- in the camshaft drive: gear for Bedford,chain for Austin
- the design of the cylinder head: The Bedford has slightly inclined
valves and quite a different combustion chamber shape from the
vertical valved Austin.
Although the similar features of these engines are also common to many
other engines, one cannot but be slightly suspicious that there is a strong
New World lineage on this and subsequent Austin engines.
In fact Claushager mentions the fact that the Austin/Chevrolet
engine was shorn of two cylinders to be the base of the war time Gypsy jeep,
later to be enlarged to 2.6 litres for the Austin-Healey 100 series.
For later engines, the historical problem is complex because of the early
50's merge of Austin with Nuffield,which had their own line of OHV engines.
Thus the MGA or MGB engines might not be too clearly the offspring (however
distant) of the stovebolt 6.
Is there any additional information on this topic?
In my opinion as engineer, all successful designs stem from careful review
(conscious or unconscious) of what works well. The clean sheet design is,
well, a myth in the great majority of cases. Thus to trace the lineage,and
ascertain the successful features of engine design is not an idle quest.
Sergio Montes Department of Civil and Mechanical Engineering
University of Tasmania
Box 252C,Hobart 7000,Tasmania,Australia
Ph. 56-02-202113 (Int) 002-202113 (Australia)
Fax 56-02-234611 e-mail montes@cmech.utas.edu.au
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