Merlin Stuff from Other Forums of Dubious Truth

[GregP]

I read in another forum that the Packard Merlin engines are perported to be inferior to the Rolls Royce Merlins. The People there are self-proclaimed "experts" with one having over 3,500 posts. He needs to get a life maybe ...

Anyway, I have read that the Packard Merlins were expected to be inferior by Rolls Royce but, when they got one and took it apart, it was machined to closer tolerances than was the Rolls Royce version. Machines are good at being repeatable ...

Anyway, I also read that the U.S.A. mated the Merlin with a superior two-speed supercharger and produced a "high altitude" version that was quite sucdessful ...

However, I've NOT been able to locate much in the way of factual production data (other than the total Packard Merlins built) that includes models, quantities, and specifications for power at altitude.

So ... does anyone out in TGPLaneLand have any indications that the Packard units were any better or worse than the Rolls Royce units? Anyone have any Packard production numbers by model? Or engine specs from Packard?

Thanks in advance ...

[Kutscha]

Got a link?

quote:Anyway, I also read that the U.S.A. mated the Merlin with a superior two-speed supercharger and produced a "high altitude" version that was quite sucdessful ...
What model of the V-1650 would that be?

[curmudgeon]

quote:Originally posted by GregP


So ... does anyone out in TGPLaneLand have any indications that the Packard units were any better or worse than the Rolls Royce units? Anyone have any Packard production numbers by model? Or engine specs from Packard?

Thanks in advance ...

I've read reports that ground crews LOVED Packard engines because they came with very generous tool kits.
Packard engines ended up on a lot of aircraft ...

[Montana]

Packard-Merlins were WAY better than Rolls-Royce-units - perhaps not in terms of power, but certainly in terms of craftsmanship and, design.

a. Packard-Merlins benefitted to a large extend from near-peacetime-conditions in the USA during production, as Maytag - former famous manufacturer of washing-machines - took over the casting of engine-housings in their own foundry. Their castings were CLASSES better than the wartime-RR-ones: Smooth, oiltight - you name it. And beautifull to look at, too...

b. Packard did a great job in re-designing the Merlin for interior oil-lines - a feature which was only adopted by RR from the Merlin XXI upwards, AFAIK. The early RR-Merlins were flush with exterior oillines, plumbed to fit - hence their nickname "Plumber's Nightmare". It's one ell-of-a-Job for mechanics, to keep exterior, bolted-on oillines tight and clean. They are more prone to failiure and battle damage, either: An interior oilline simply can't break or get sheared off by vibrations! Also, you have to exactly puncture it, to make it fail. For exterior oillines, a grazing shot or, a Flak-shrapnell will often "do the job", already.

Cheers!

Montana

[ChrisMcD]

Hi folks,

It is a very long time since I read JK Setrights 'Power to fly' but I remember that he made the same comments that the Packard built Merlins were superior. If anyone has a copy perhaps they can check - at £750 second hand I am unlikely to read it again soon!

One point he made was that Rolls were not good at casting and very old fashioned about crack testing. Apparently Rolls still 'brushed with paraffin and dusted with chalk' to find cracks whereas Napier used electronic techniques and sealed castings with 'boiling bakelite'. When Rolls 'borrowed' a consignment of Napier castings from the boilers to check them out they were totally amazed to find that they apparently had no cracks whatsover!

So claims that Packards had superior castings is corroborated by the master.

Setright also said that Packard achieved much better accuracy with their machining tolerances and defied Rolls by using paper gaskets - with the result that Packard Merlins were vastly more oil tight. Rolls apparently thought all mating surface should be hand 'lapped' to a perfect fit, but since that was impossible under wartime conditions they saw sense and came into line

Cannot comment about supercharger development, but with the P-51 as the main user (in terms of priority demands), it makes sense that a high altitude version would be developed by them.

Am I right in thinking that Henry Royce once commented that Packard were the only US manufacturer that he respected enough to buy components from

One other point. The twin Mustang used Alisons because the Packard Merlins were too expensive.

[Red Admiral]

Theres a lot of crap surrounding this subject which has no actual basis. Both sources below go a long way towards stating that Packard and RR built engines were very similar.

The tolerances on the Packard _design_ were tighter because thats how they were built. Their machines spat out the same part again and again whilst the "monkeys" assembled it. If the part didn't fit, it got thrown away and a new one obtained. RR used skilled fitters and the process involves taking a part from the bin, if it doesn't fit, the fitter machines it so that it does fit.

The only US developments around the supercharger was the introduction of water injection on the V-1650-9, which didn't actually work until post-war. Strangely, the RM.15SM which is the same engine but RR made, didn't need water injection to make the same power.

Rolls-Royce liked Packard so much they paid it the highest compliment, they bought the company.


The Merlin in Perspective - the combat years, Alec Harvey-Bailey, :

"Technically the major difference between RR & Packard Merlins was the supercharger drive, the latter using epicyclic gearing instead of the Farman drive. Naturally American magnetos and Bendix carburettors were used. Some 100 series equivalents were built at the end of the war with the Simmonds fuel control units and these wre installed in later Mustangs.
As one would expect, Packard built engines to very high standards of quality. Technical problems were not dissimilar from those experienced on British engines and when comparing like with like modification standards there was nothing to choose between engine sources.
At Squadron level, there were times when there were fortuitous variations in reliability either way but when dealing with large numbers of engines at Group or Command level there was good consistancy in results between British and Packard engines. The 60,000 engines produced by Packard for the RAF and USAAF were of inestimable value".


----------------------------------------------


Briefly, when Packard took on the job of producing Merlins, it re-drew and
re-toleranced all the RR drawings to 'productionise' them, as RR was not a
company geared up for mass production. British thread standards were
retained and hence most of the parts were interchangeable with British-built
engines.

The major difference was in the supercharger drive, the Farman drive of
British engines being replaced by epicyclic gearing on the Packards. The
carburetter and magnetos were also replaced by American equivalents. Merlins
built for the US Government as the V-1650 used a US-spline propshaft.

I am not aware that Packard blocks were thin-wall castings and the weights
of comparable British- and US-built engines are similar, suggesting that the
blocks were also.

The occasional myth still arises about relative capabilities of RR versus
Packard Merlins but they were equally good and there was actually nothing to
choose between them in both performance and reliability.

Regards
Peter Kirk
RRHT Engine Data

[Wuzak]

quote:Originally posted by ChrisMcD

The twin Mustang used Alisons because the Packard Merlins were too expensive.


The Twin Mustang used Allisons because US production of the Merlin ceased at the end of the war. It was preferred to adapt the two stage Allisons than to import RR Merlins.

[Sid447]

...Anyway, I also read that the U.S.A. mated the Merlin with a superior two-speed supercharger and produced a "high altitude" version that was quite sucdessful ...
Thanks in advance ...

This is incorrect. RR supercharger technology was ahead of anybody at the time.
For example the V-1710 Allison engine was a particularly good engine but with poor supercharger performance.
IIRC the USA was more interested in turbo-charger development at the time.

Red Admiral, Hello!
Your quote from "The Book" says it all.

[GregP]

Hi Sid,

You are correct in that the U.S.A. was interested in turbocgargers. It is a little appreciated fact that ALL the high altitude bombers produced by the U.S.A. were turbocharged and thus could GET to the higher altitudes.

I read somewhere, can't recall where at this time, that we we created a superior 2-speed supercharger. Since it is not in evidence during the war, I am assuming that either the statement is wrong or it was created after the war.

Since I am unable to recall the source, I'll forego the argument and retract the claim until I come across it again ... I usually do that sometime down the road, especially if I am LOOKING for it. We'll see ...

Meanwhile, Ford in England made some Merlins, Ford U.S.A. did NOT, but tried to steal the design, and Packard made some GREAT engines of the Merlin variety.

Ah well, it was worth a thread! Cheers!

[Sid447]

I also read that the U.S.A. mated the Merlin with a superior two-speed supercharger and produced a "high altitude" version that was quite sucdessful ...

RR had developed a 3-speed, 2-stage intercooled blower by the end of WW2.
Had they put this together with the RM17SM merlins which had the "normal" 2-speed, 2-stage intercooled superchargers and were rated at the Maximum Flight Clearance Tested Power of 2,340hp.
........and a Maximum Endurance Tested Power (3000rpm +36lbs boost and WM Injection) of 2,640hp.
It would have not only given the Griffon a run for it's money but "out-altituded"
everything at the time bar gas turbines probably.

The Merlin, whether built in the UK or USA was one serious legend of an engine. Not only did it turn RR from a small specialist company into a serious world-wide aero engine manufacturer but it helped in no small measure by powering so many allied aircraft types.
Heck they are still using them to power the Reno Unlimited's.

Over-revved, over-boosted and strengthened just about everywhere to stay in one piece while developing 3,500-3,800hp.
Read the description for Dago Reds race engine specs here:

http://www.supercoolprops.com/articles/gwhitegearheads.php

..From the same basic merlin that was designed back in the 30's!
What an engine! ........Oil leaks or not!

[Ricky]

'Our Merlin is better than your Merlin' is a topic that comes up now and again on pretty much any vaguely-related forum, and is raised equally often by obnoxious Brits as by obnoxious Yanks. I must confess I usually refer to the discussions here to set the record straight.;)

[Wuzak]

Hi Sid,

You are correct in that the U.S.A. was interested in turbocgargers. It is a little appreciated fact that ALL the high altitude bombers produced by the U.S.A. were turbocharged and thus could GET to the higher altitudes.

I read somewhere, can't recall where at this time, that we we created a superior 2-speed supercharger. Since it is not in evidence during the war, I am assuming that either the statement is wrong or it was created after the war.

Since I am unable to recall the source, I'll forego the argument and retract the claim until I come across it again ... I usually do that sometime down the road, especially if I am LOOKING for it. We'll see ...

Meanwhile, Ford in England made some Merlins, Ford U.S.A. did NOT, but tried to steal the design, and Packard made some GREAT engines of the Merlin variety.

Ah well, it was worth a thread! Cheers!


Off the top of my head, both Pratt & Whitney and Allison developed 2 stage superchargers. I think P&W had both a directly geared system (with 2 speeds also) and one with a variable speed first stage. Allison's had a variable speed first stage and single speed second stage. After the first couple made like this Allison moved the carburettor from the intake of first stage to the intake of the second stage. This enabled Allison to make a basic engine which could be used either in turbocharged or two stage supercharged systems. The disadvantage was length.

Rolls Royce did apply the three speed supercharger to the Griffon, but after the war.

Also, much of the supercharger impeller development in the US was done by GE - makers of the turbos. This was to some degree a detriment to the US manufacturers. GE did make a 2 stage turbosupercharger, with one turbine driving two compressor stages. They didn't make the war, but were used post war, IIRC.

[Wuzak]

Had they put this together with the RM17SM merlins which had the "normal" 2-speed, 2-stage intercooled superchargers and were rated at the Maximum Flight Clearance Tested Power of 2,340hp.
........and a Maximum Endurance Tested Power (3000rpm +36lbs boost and WM Injection) of 2,640hp.


Hi Sid. We had some discussion of the RM17SM Merlin on this thread:

http://warbirdsforum.com/showthread.php?t=1536

Truly an incredible performer.

[Wuzak]

'Our Merlin is better than your Merlin' is a topic that comes up now and again on pretty much any vaguely-related forum, and is raised equally often by obnoxious Brits as by obnoxious Yanks. I must confess I usually refer to the discussions here to set the record straight.;)

The reality was that both built the Merlin as best they know how - RR with artisanship, and Packard with precision manufacturing. No doubt it would have been easier to take bits of one Packard Merlin to another than to do that with ones built by RR.

In terms of performance I think they were very much the same - when you compared the equivalent versions.

[GregP]

Wuzak, no doubt you are correct. :-)

[Wuzak]

For the R-1830 & R-2800 Pratt & Whitney had either a single stage two speed supercharger or a two stage two speed supercharger.

The method P&W used for their two stage supercharger was different to RR practice. RR had both stages on a common shaft, and therefore at the same rpm. P&W had the second stage directly geared to the engine with only one speed. The first, or auxiliary, stage supercharger was fitted with two speed gearsets, but they could also be put into neutral - which could be argued is effectively a 3 speed supercharger.

P&W also used fluid couplings to enable the change from neutral to low gear be as smooth as possible, allowing the impeller to ramp up to speed.

Not sure if P&W did anything different with the R-4360, but I suspect that the two stage supercharger systems were essentially the same, though the auxiliary stage could be remotely mounted (as in XP-72).

In the F4U-5 the R2800 was fitted with two first/auxiliary stage superchargers mounted on a cross shaft. The gearing system was very much the same concept as earlier systems. This layout was called the sidewinder.

Interestingly P&W engineers were apparently alarmed at the lack of efficiency of one of the impellers during prototype testing - then they realised that they needed a mirrored impeller for that side!