On 2010-12-22 16:13:04 -0800, Grimly Curmudgeon
said:

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Eric Stevens
saying something like:

Of course that was another problem. Then, the Roots group (Humber,
Hillman) couldn't control cylinder bore diameter to better than .010"
so that when choosing pistons, all engines had to be selectively
assembled. Ford had similar problems when machining blocks for
crankshaft bearings. Those, too, had to be selectively assembled and
bearing shells had a 'fit' code which had to match the housing in the
block and the cap (often different). Rover decided to take advantage
of generous tolerances to use Loctite to secure cylinder liners in
place. But they couldn't machine all blocks/liners sufficiently
accurately and liners used to move in the block. On occasion a liner
would drop to the point where the top ring on the piston would snap
out over the top. Things stopped rather suddenly once that happened.

These days I shudder when the British talk of British Craftsmanship.
I'll take Japanese craftmanship any time.

Hah, it goes back further.
An oft-repeated tale, but I actually knew (worked with) a bloke who was
there, in the era.
RR Merlins were made under licence by Packard. Nobody in RR service/tech
departments could believe that Packard's production line could possibly
produce engines to the tolerances needed.
On stripping a couple down they found them to be better...

Btw, the bloke I knew was employed by RR to visit the various front-line
fighter bases and rebuild worn and battle-damaged Merlins. The RAF
mechanics were perfectly capable of doing it, but if he did it, the
factory warranty applied. Strange thought - a factory warranty on a
fighter engine in the heat of battle and I wonder if the RAF ever
claimed it. Probably self-limiting, in that if enemy action caused the
damage, the warranty was void.

A 20mm cannon round through the block should pretty much void warranty,
but it might just have been another way of implementing Lend Lease.

I have a feeling those RR Merlins were found, for the most part in
P-51s. So I am not sure just what proportion of Packard built Merlins
ended up in RAF aircraft. The Merlin 61 was built in the US & the UK
but used the Packard designed split head and ended up in Spitfire Mk IX
and P-51s. The later Spitfires used the RR Griffon not the Merlin.

English built Merlins came out of 3 RR plants and one English Ford
factory. There were just too many variants of the Merlin made for a
wide array of aircraft, ranging from all of the British bombers, The
Beaufighter, Mosquito, the Hurricane, & Spitfire. All were different.
Once the move to replace the Allison in the P-51 was made, it only made
sense to build those engines in the US rather than have them make a two
way trip across the Atlantic.



--
Regards,

Savageduck