On 2010-12-22 19:16:49 -0800, Eric Stevens said:

On Wed, 22 Dec 2010 17:49:31 -0800, Savageduck
wrote:

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.

Most of the British bombers used them also e.g. Lancaster and
Mosquito. At one stage it was feared that there would be a shortage of
Merlins and Lancasters were fitted with Bristol engines. See
http://www.aviation-history.com/avro/683.html

Yup! However the British built Merlin type XX used in the Lancaster I,
Beaufighter Mk.II, Hurricane Mk.II, & Halifax Mk.II was not used in any
Spitfire variant. Packard's involvement with this engine came later.

The Spitfires starting with the Mk.II, used the Merlin XII, Merlin 45,
Merlin 47, Merlin 50M (negative G carb), Merlin 61/261(Packard modified
2 piece cylinder block), Merlin 66/266.
The 1934 Mk.I Spitfire used the Merlin predecessor the RR PV-XII.

Packard V-1650 built Merlins had a "2" prefix and were use in
Spitfires, P-51s, and replaced Allisons in P-40F & P-40L. Packard first
started their program in late 1940, with the first motors delivered in
August 1941, and intended for the P-40s being delivered to the RAF,
RAAF, SAAF under Lend Lease. The P-51 was just off the North American
drawing board at that time. The first Allison powered prototype P-51
flew in October 1940, with production deliveries to the RAF in 1942. In
April 1942 the unhappy RAF made the change to add a Merlin 61 and a
Spitfire Mk.IX four blade prop to improve high altitude performance
labeling it the "Mustang Mk.X " The rest is history.

The version of Merlin built by Packard for the P-40 & P-51 was based on
the Merlin 28 which was a type XX as used in the Lancaster. Packard
made modifications to the original blue prints changing the main
bearings from RR copper-lead alloy to silver-lead with iridium plating.
They then added the Wright two speed, two stage supercharger. These
were also used in some Lancasters & Mosquito, some developmental AC and
the F-82 "Twin Mustang".



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.

They needed them anyway.

Yup! I guess the got them.

--
Regards,

Savageduck