No US-built Merlin: plausible developments?

[Shortround6]

It could mean that

Post Hurricane from the Hawker design stand point in practically anything after 1938.
First flight of a Tornado 6 October 1939 with Vulture engine
First flight of a Typhoon 24 Feb. 1940 with Sabre
First flight of a Tornado 23 October 1941 with a Centaurus.
First flight of a Tempest 2 September 1942 with Sabre
First flight of a F6F 30 July 1942 with an R-2800.

Granted the R-2800 two stage shows up somewhat earlier than that but it is a bit late in timing for Hawker to do much with it.

The Sabre engine was good for 1735Hp at 17,000ft which puts it sort of between the R-2800s power peaks. 1800hp at 15,500ft and 1650hp at 22,000ft. Not so good from around 18,000ft on up but it does have lower drag.

As a substitute when the Sabre is having trouble? Maybe, but you have to engineer the 'power egg', get them into production, ship them to England, rework the Hawker design to take them and do it before the Sabre troubles are fixed. And if done in quantities of more than a few hundred, figure out where the R-2800s are going to come from.

 

[tomo pauk]

Thanks for the time-line and power figures.

And if done in quantities of more than a few hundred, figure out where the R-2800s are going to come from.

In this time-line, Packard is not building the Merlins, but something else. R-2800s?

 

[Shortround6]

The R-2800 is a bit too big and heavy to serve as a substitute Merlin. The US kept 1/3 (at most) of Packard production, some sources say as little as 20%. If Packard doesn't make Merlins that means no Merlin powered P-40s ( not much of a loss) and No Merlin Mustangs ( a much bigger loss) but it also means 36,000-44,000 fewer Merlins for British and Canadian production aircraft. and that is the big loss in this scenario. For existing US engines the R-1820 and R-1830 are too small. The R-3350 is too big and too late. The R-2800 is too big for many applications, It rather leaves the the R-2600 (Hercules replacement in some aircraft and since the Hercules and Merlin both worked on a number of aircraft it might be a small change) and the Allison V-1710, as "plug in" replacements for existing aircraft, at least in a physical size sense.

A Halifax or Lancaster with four R-2800s might be a wondrous airplane but either one with four R-2600s might require a whole lot less redesign. Hurri-bombers with V-1710s might work.

In 1940-41 the British NEED another source of engines to power the airframes they are already planning to make in 1942-43. They don't need a source of engines that won't be making large quantities of engines until 1943/44 and need new airframes to make use of the larger engines. They already have 4 engines larger than the Merlin in the pipeline themselves.

 

[davparlr]

Could the turbo-supercharged Allison ala P-38 be a successful replacement for the Merlin XX used in the Lancaster and Mosquito? Maybe a bit heavier but probably a better performance at altitude. This would be a similar concept to the turbo-supercharged B-17 and B-24s.

 

[Shortround6]

Quite possibly. I don't know what the availability of the turbos was however, There may have been a shortage, there may have been no problem supply 40,000 more turbos.

There is a maintenance issue however. The P-38s often had problems keeping all the exhaust and intake air ducting 'tight' and not leaking. I don't think this was well known (anticipated) in 1940-41 when the engine choice has to be made.

I would further note that in the summer of 1940 the Allison in production was the long nosed "C" series engine. Just like many other manufacturers Allison had a number of "projects" they were working on which included the much improved "E" (P-39)and "F" (P-38 and high propped P-40) series engines and the two stage supercharger was on the drawing board at the time. Would increasing dependence on the Allison result in more resources being applied to increase development rate or would demands for increased production (even in a satellite/shadow factory) slow development?

 

[wuzak]

There may also be a space issue for installing the turbo and intercooler - especially for the Mosquito.

I believe there was one experimental 2 speed V-1710. Maybe that is the short term solution, as per Merlin.

 

[wuzak]

Also, the Lancaster's Merlins came in a Rolls-Royce developed power egg (not sure who actually made them). Something similar would have to be done for Allisons.

 

[Shortround6]

There may have been more than one, at least proposed or given a model designation, I am spot reading "Vees for Victory" and one version ("F" series) has cropped up already but not built. The very late war "G" series may well have had a two speed drive on one or more models.

 

[gjs238]

How feasible are Canadian Merlins?
How feasible is a "big block" version of the Allison? Ala DB 603.

 

[Shortround6]

Canadian Merlins? Not very feasible. No offence intended but a Canadian Merlin factory would have to be supplied (mostly) with US built machine tools. And hundreds of smaller parts would have to come from hundreds of US suppliers in any case. I don't think any US factory was totally self supplied. Allison actual made a fair amount of it's money in the late 20s and for most of the 30s supplying other US engine companies with crankshaft and rod bearings for instance.

"Big Block" is a whole new engine and a tougher engineering proposition than the V-3420. Nothing but nuts and bolts in common and a whole new set of vibration problems to deal with.

 

[wuzak]

How feasible are Canadian Merlins?
How feasible is a "big block" version of the Allison? Ala DB 603.

Do you mean an increased capacity version of the same engine, or do you mean a bigger new engine (as the DB 603 was)?

Not sure how much the bore could be taken out. There may be some room to extend the stroke, but I wouldn't think too much.

Or you could just use the bits from the V-1710 and join them together to make a bigger unit - like the V-3420.

 

[Shortround6]

A lot of car engines are designed from the start to have some "stretch" built into them so as to get the maximum use from the tooling and casting patterns. A extra 1/2 of block height or bore spacing isn't that big a deal. So a "small" engine weighs 20-30lbs more than a it should if designed tightly ( no extra capacity hiding anywhere) in a 3500-4000lb car. The car is rolling, not flying and the extra weight matters little to top speed or fuel economy, it does matter for acceleration but the percentage is small.
Aircraft are flying and every pound of extra engine weight is a pound of cargo or fuel NOT carried. There is no real reason NOT to make the largest displacement engine the block/cylinders will support (like marketing in cars). In some countrys the care engines were/are taxed on engine size so being able to offer several engines that fit into different tax categories yet were built with the same tooling made sense. Again, there was no such restriction on aircraft engines.

Airplane engines are very light for their displacement. AS a general statement it took until the 1950s-60s for even Formula I racing engines to reach the horsepower per pound of good aircraft engines of WW II. Their HP per cu in was obviously much higher

 

[davparlr]

There is a maintenance issue however. The P-38s often had problems keeping all the exhaust and intake air ducting 'tight' and not leaking. I don't think this was well known (anticipated) in 1940-41 when the engine choice has to be made.

Was this an issue with the B-17/24? Except for the engine type, the turbo-supercharging section should not be significantly different.

 

[wuzak]

The XB-38 was a V-1710 powered B-17, with turbos. The turbo set up remained as per B-17. One of the V-1710s had an exhaust leak causing a fire, damaging the aircrfat. That was fixed, but another exhaust leak caused another fire, this time severe enough that the aircrfat crashed and was destroyed.

 

[wuzak]

I suppose if Packard weren't busy building Merlins they could have helped with development and production of the V-1710.

It seems to me that Allison had a lot going on with the V-1710 and V-3420 with all their myriad variations. Possibly Packard could have had responsibility for building and developing the V-1710 with Allison's guidance.

Another alternative - what if Rolls-Royce foresaw a need for more Griffons, and requested Packard set up a new line for them, to run alongside the Merlin? I imagine the decision would be mid 1941, after the Griffon had some testing behind it or had flown in the Spitfire (Mk IV - which flew in late 1941).

Can we expect to see a decent number of Griffons rolling off the line by mid 1943?

What can we use them for? Lancaster? B-17? Mosquito? Lightning?

 

[GregP]

Shortround,

This goes back a couple of pages.

I know of two issue with the intake manifolds: 1) The aor-gas mixture was incompletly atomized. Tjhis was cured by plpacing a turbulator in the manifold. 2) The bands were such that two cylin der on one side got correct mixture, tqwo were rich, and two were lean. This was cured by shaping the trubulator like a hollow cone. When we build up an Allison, we use on late-model intake manifolds, and we have enough for our inventory.

I dispute taht fact taht everyone kn ew about Europen fuels becuase opur wearly planes arrived there jetted for American fuel and sufffered operational issues.

Last, taking the P-38 to "warmer eather" would have no effect. Once above 20,000 feet or so, whether youa re in the tropic or over Great Britian or germany, youa re in about teh same temperatures. The reason the P-38's suffered fewer issue in the pacific was they were running American gasoline and, once they were cured of other issues, they operated just fine. All that happened early in Pacific deployment is that the issues with European gasoline use were never there to stat with, ergo no detonation from excessive aromatics versus the jetting.

 

[Shortround6]

Was this an issue with the B-17/24? Except for the engine type, the turbo-supercharging section should not be significantly different.

It may not be different, I don't know how many problems the B-17 and B-24 had with leaky turbo plumbing but it is a sure bet that it was more than Lancasters and Halifax's had with their Merlin XX engines. This is sort of the point, somewhat over 2/3rds of the Packard engines built wound up in British planes. If Packard doesn't build Merlins what engine choice do the British have in the summer of 1940 to power their planes? An Allison "power egg" with turbo might be made to work but it may have more maintenance issues than the Merlin XX series.
The Americans didn't have any great demand or need for the Merlin until the Merlin P-51 came along. While the use of the Merlin XX (V-1650-1) in the P-40 was useful and freed up a couple thousand Allisons for other other aircraft it wasn't a big deal for American planners at this time.

For Wuzak's question:

"Another alternative - what if Rolls-Royce foresaw a need for more Griffons, and requested Packard set up a new line for them, to run alongside the Merlin? I imagine the decision would be mid 1941, after the Griffon had some testing behind it or had flown in the Spitfire (Mk IV - which flew in late 1941).

Can we expect to see a decent number of Griffons rolling off the line by mid 1943?"

I would refer people to this paper. http://www.enginehistory.org/References/WWII Eng Production.pdf

Which has figures for the major engine types by factory and by month. Packard figures are broken down by single stage and two stage engines per month. Building Griffons might require a third production line.
It took until August of 1943 to get decent numbers of two stage engines to come of the line.

 

[Shortround6]

I dispute taht fact taht everyone kn ew about Europen fuels becuase opur wearly planes arrived there jetted for American fuel and sufffered operational issues.

We may be getting confused as to which year we are talking about. In 1940 EVERYBODY who mattered knew the fuel was different. One reason the Americans were specifying low aromatic fuel was that the high aromatic fuel tended to dissolve (eat) certain rubber compounds used in American fuel systems. American 100 octane fuel had NO rich mixture response other than what you get going to a rich mixture. American 100 octane fuel was 100 octane running lean and just about 100 octane running rich ONCE the got around to measuring rich response. Now in 1940/early 1941 there were darn few American planes actually being used by the British and certainly no American planes being flown by the Americans in Europe or any other combat theater. British 1940 100 octane fuel with it's 20% (or more) aromatic content, was good for about 115-125 octane ( or performance number) depending on batch. Since in 1939/40 the fuel specification did NOT list a rich mixture number limit as such. As more testing and research went on specifications were written to include the rich mixture response as a measured number and specifications for 100/120, 100/125 (fuel specification AN-F27), and 100/130(fuel specification AN-F28) were quickly written and very quickly superseded each other. the 100/125 may have been an american specification as a number of Allison engines were rated on it. The 100/130 was standardized between the US and the British in fairly short order though. The Americans changing their fuel systems to accommodate the high aromatic fuel.
There are a number of things that go into fuel and fuel specifications. Fuel has to have a certain number of BTUs per gallon, certain gum and/or residue limits, it is held to certain vapor pressure and evaporation limits not to mention lead limits. There are something over 400 compounds that can be used in aviation gasoline. and different compounds or mixtures of common compounds react differently to the addition of certain other compounds, like lead. Some blends give a very significant increase in octane numbers with addition of small amounts of lead, other blends show only a modest increase with the addition of the same amount of lead. Some blends show a bigger change between lean and rich mixture ratings with the same amount of lead than other blends do.
In 1940 The written specifications for American and British fuel spelled out the difference in aromatic compound content. By the middle of the war the Waukesha company had delivered hundreds of single cylinder test engines to oil refineries, research labs and government purchasing agencies to help make sure every body was on the same page as far as testing fuel goes.

Now as more and more high octane fuel was wanted and as supplies of certain compounds changed and as different refining processes were brought online (cat cracked fuel behaves differently than straight run gasoline and straight run can vary depending on the oil field it comes from) the blends or allowable blends were changed to meet the production quotas. It was one of these changes that prompted the development of the Center venturi intake pipe on the Allison. By now it is 1943 and some of the "allowable" blends of 100/130 fuel are not the same as the older 100/125 and 100/130 fuel. Allison knew this and was working on the new manifold before the problem ever cropped up in Europe. It is just that events overlapped. There may have been a few batches of fuel that were less than perfect also.
The "story" that American fuel was "good" and European (British, what other European nation was supplying fuel for American aircraft in 1943/44)fuel was "bad" needs a rethink. There is little point in "standardizing" fuel between allies if major differences are knowingly allowed.

Last, taking the P-38 to "warmer eather" would have no effect. Once above 20,000 feet or so, whether youa re in the tropic or over Great Britian or germany, youa re in about teh same temperatures. The reason the P-38's suffered fewer issue in the pacific was they were running American gasoline and, once they were cured of other issues, they operated just fine. All that happened early in Pacific deployment is that the issues with European gasoline use were never there to stat with, ergo no detonation from excessive aromatics versus the jetting.

You have to go a lot higher than 20,000ft and most air temperature charts do show a difference. There were charts for standard days and "hot days" let alone tropics. Differences could extend well into the 30,000ft range.
P-38s also suffered problems in other theaters, just not as bad or as widely publicized.

There were a number of contributing factors, mis-rigged turbo/throttle controls, poor piloting technique, the temperature ( and the planes operating in the tropics seldom spent as much time (several hours at a time) at high altitudes as the European planes), and the change in KNOWN fuel blend. Throw in a couple of 'poor' batches of fuel with a mixture of the 4 listed "factors" and you get the problem coming up a lot. Take away 2 or 3 of those factors, or even ONE, and the scope of the problem changes.

Late war US fuel use the same high % of aromatics as the British did, especially when you get to things like 100/150 or the post war 115/145 fuel (AN-F-33)

 

[tomo pauk]

Another post as a required reading.

 

[Shortround6]

Thank you Tomo and others.

I can certainly believe American planes had carburetors adjusted after going overseas. In some cases American units trained on 91 or 91/96 fuel in the states to conserve 100/130 fuel for combat theaters and not only had to adjust carburetors but needed timing changes to change over to the 100/130 fuel. Also a plane "adjusted for Southern California or Texas in Aug or Sept may need adjusting for best performance in England in Nov/Dec. Likewise a plane from Buffalo, New York in Feb might need a bit of adjusting in North Africa or in Darwin. Temperature shifts of 50-80 degrees F would not be uncommon and the equivalent air density change would be several thousand feet. Some units might want to adjust carbs for best performance.

The questions we have now are not "if" something was done but "why" it was done. And trying to figure out the "correct why" and not legend or "hanger talk".