Which country designed the best engines for WWII? (2 Viewers)

Which country designed the best aircraft engines for WWII?

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Nonsensical Packard did not redesign the Merlin, they merely redrew it to American conventions. There have been plenty of discussions in this forum debunking this myth. Show us your comparative data for speed, cost and maintenance
 
The following video of Ford River Rouge pre WWII shows that Ford weighed not just each piston but each piston connection rod assembly. Start at the 18.00 mark
 
swampyankee said:
One other issue is that a minute scratch on that perfect mirror finish is likely to seriously degrade fatigue life, much worse than a similar scratch on a normally finished surface.
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From "The Merlin in Perspective":
"Because Packard were less flexible in embodiment of modification, engines from this source used the Mod 399 rod for much longer and ran into a number of characteristic failures. When examined the Packard rods appeared to be well finished with heavy polishing of the radius and associated areas. British experience was that rods free of finishing scores were far less prone to failure and this apparent contradiction was surprising. however , when rods were etched it was found that the polishing operation had swaged material into deep score marks , masking them from visual inspection, and failures could therefore be expected. it was a lesson in the effect of heavy over-polishing."
 
Reluctant Poster said:
Nonsensical Packard did not redesign the Merlin, they merely redrew it to American conventions. There have been plenty of discussions in this forum debunking this myth. Show us your comparative data for speed, cost and maintenance
Click to expand...
For those are are genuinely interested in how Packard actually built Merlins here is an excerpt from Fedden's mission to America:



While I'm at it here is the Mission's appraisal of Allison:



 

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Here's an excerpt from the Fedden mission to America on Allison conrods:
 
wuzak said:
Weren't there also sealing issues with the sleeves inside the single piece blocks, hence the move to a separate head design?
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You are correct. From The Merlin in Perspective by Alec Harvey-Bailey:

"External coolant leaks at the base of the cylinder block were overcome by Mod 231 which provided a triple seal ring instead of a single bootlace seal.
A picture tends to be painted of single piece block engines with top joints leaking like colanders and being a risk to the pilots . In fact most engines did not have blocks changed for leaks in the course of a normal life and when engines were pulled for leaks, their total was not a major cause of engine removals, although probably in the top 5. The leaks tended to be more prevalent in fighter operations where engines were subjected to constantly changing conditions."
 
swampyankee said:
PT boats did not use Rolls-Royce engines; they used a marine derivative of a Packard engine designed before the Merlin
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Actually, the prototype for the Elco boats was PT-9 which was built in England as British Power Boats PV70. It was powered by three marinized Merlins.

From "The Magic of a Name" by Harold Nockolds.
"The fame of the Merlin was already extending beyond aviation circles, and in the years immediately before the war Rolls-Royce was asked by Power Boats, Ltd., to co-operate in producing a high speed motor torpedo boat in which they planned to fit three Merlins. It proved quite simple to adapt the engine for marine work- the power output was adjusted to suit the different operating conditions, the airscrew reduction gear was removed, a special air intake was fitted, and a salt-water cooled heat exchanger was added to allow the engine to retain the normal fresh water in the cylinder jackets, pipes and circulating pumps. The Merlin was as successful in this new element as it was in the air, and the prototype M.T.B caused immense enthusiasm by averaging almost exactly 60 m.p.h. in a trial run from Southampton to Cherbourg. The Admiralty ordered a large number of theee boats, which were to give splendid service in various theaters of war, but when hostilities finally broke out the Government instructed Rolls-Royce to drop all marine work and concentrate on making engines for aircraft."

The prototype mentioned was British Power Boats PV70 which was the template for the BPB MGBs used by the Royal Navy, but also was sent to the United States where it became PT9.
Quite a few of the early BPB boats were powered by Merlins as this site lists.
Motor Gun Boats – Spitfires of the Sea
As an aside Vosper's pre war boats used Isotta –Fraschini engines which were twice the displacement of a Merlin
 
Reluctant Poster said:
As an aside Vosper's pre war boats used Isotta –Fraschini engines which were twice the displacement of a Merlin
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The displacement doesn't actually matter.

It is interesting but too many of us have been indoctrinated into assessing engines by displacement due to car and motorcycle racing rules.

Things that matter more for practical use are the weight per hp and volume of the engine (space occupied by the engine) per hp.

There were no rules for engine displacement in war planes and there none for MTBs.

The W-18 Isotta-Fraschini engines were within a few hundred pounds of of the Merlin, this depends on supercharger and reduction gears although a marine Merlin needs a new gear box.
In high speed boats the max continuous power (1 hour or 4 hours or 8 hours) was often more important than max peak power or a 5 minute rating.
 
and for good measure, I just found this memo about Parkard-Merlin / RR Merlin spare parts interchangeability.

Whilst certain parts of the letter are illegible, its obvious that there is no engineering difficulty in fitting of either.

Its almost as if, there was no difference at all in the tolerances... well I never. (actually I already knew this perfectly well
but just didnt have a letter proving it).

I suspect the letter reads:

"Mr Sidgreaves mentioned the interchangability of Packard/Merlin spares, and it was agreed that it might be
these should be used in the repair of Rolls Royce engines so certain Dominions should be supplied with Packard
items from America in lieu of Rolls Royce made items. It was pointed out, however, that this would still leave the same quantity
of these items to be delivered by Rolls Royce because even the Packard engines in this country might have to be fitted with
Rolls Royce made spares. In other words, whatever comes from the stock of Packard items would eventually have to be produced
and repaid, so that the repair of Packard engines need not be prejudiced."

Letter is dated 25th May 1943

 
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