An Allison V-1710 with a two-speed supercharger in 1942 (9 Viewers)

[Howard Gibson]

The US did not initially focus on multi speed or two stage superchargers for their in-line engines (used by most USAAF fighters), though they did develop these for radial engines used mainly by the Navy.

I have several thoughts on this.

In 1943/44 over the ETO, the Americans and British had a huge advantage against the Germans at high altitude. This was due to the work of Sanford Moss developing turbochargers in the USA, and Stanley Hooker upgrading superchargers at Rolls Royce. There were good reasons to fire the pair of them. Moss started developing turbochargers during WWI. At the end of the war, the USAAC lost interest, and it is surprising GE did not lose interest too. By several accounts, Moss was an extremely charming, likeable guy, and you could not stay mad at him. A domineering and difficult personality like Roy Feddon might not have lasted. In the late thirties, the USAAC got interested in turbochargers again, and GE was ready. The Rolls Royce Merlin's original supercharger was designed by James Ellor (no Wikipedia page!). When Stanley Hooker told him there was a lot of room for improvement, a lot of people would have taken offence. Ellor was a professional, not an asshole.

I think the radial versus inline discussion is a load of crap. The US Navy liked radials. In the USA in 1940/41, if you needed a reliable 2000hp engine, you specified a Pratt & Whitney R2800. The high altitude performance of the turbocharged P47 was excellent. The non-turbo F4U Corsairs and F6F Hellcats was as good as anything they went up against. The Allisons on the P38 Lightnings were turbocharged. Was there a lot of pressure to improve Allison superchargers?

The British wanted "inline" engines. They were committed to the Rolls Royce Merlin, so there was aggressive supercharger development by the unfired Hooker. One of the Napier Sabre's big failings was its high altitude performance. The RAF had another path to high altitude performance, so they demanded that Napier fix the other big problem, the very short lifespan of its sleeve valves. Two-stage Sabres were worked on, but they did not reach production.

Merlin engines were manufactured in the USA because they were needed for Canadian made Hawker Hurricanes, de Havilland Mosquitos and Avro Lancasters. They were available, and they solved problems.

 

[BarnOwlLover]

If a two speed supercharger itself was such a good idea, why (other than manufacturing issues mentioned), why didn't Allison bite the bullet and make a decent two speed drive? Ignorance, hubris, or simple logistics as mentioned.

 

[Howard Gibson]

It also means that the supercharger is not heating the air as much so the air is,,,,
1, denser
2. lower temperature means you can use a bit more boost before detonation sets in.
3. Not temperature related but you can open the throttle more on carbureted engines and not have as much pumping loss.

I don't think that is an issue. If I am running something like 130 octane fuel, I can maintain 67" manifold boost. If my two speed supercharger does this on its low setting, there is more horsepower for the propeller. On my single speed, high revving supercharger, I need to throttle back a bit more.

 

[BarnOwlLover]

I'd argue that the lack of a two speed (and lack of a good two speed, two stage supercharger later on on top of that) cost Allison/GM when certain USAAF brass voted for the Merlin for the P-51B and later, and the USAAF and US Government had enough power and influence to tell Allison/GM to pound sand on this front.

Only thing that sort of saved Allison on the P-82 project was that the USAAF was looking for alternative engines for the P-82 if Packard didn't renew their license to build Merlins when it expired in January of 1946 (RR wanted royalty fees that the RAF and Air Ministry browbeat/begged for them to waive during World War II, and RR could handle any civvie or mil Merlin or Griffon production for that matter without Packard post war. And Packard, the US Gov't nor NAA were able or willing to pay those fees).

Of course, by that stage Allison did have a V-1710 with two stage superchargers that would fit with minimal changes where a two stage Merlin did in the XP-82 and P-82B/C/D. Of course, as with the -119 in the XP-51J, the V-1710-140 series had a horrible reliability record compared to the single stage Allisons or the Merlin, ironically due to details of the supercharger's design, most notably the lack of backfire screens and some other details.

 

[Howard Gibson]

If a two speed supercharger itself was such a good idea, why (other than manufacturing issues mentioned), why didn't Allison bite the bullet and make a decent two speed drive? Ignorance, hubris, or simple logistics as mentioned.

Read my post above. Was the USAAF screaming at Allison that they needed better superchargers? The term in manufacturing is "demand". The Allison engines were functional as they were. Do we shut down production to make the improvements? Are Allison's engineers as talented as Stanley Hooker?

The Merlin Mustangs happened because the two-stage Merlins were available. The original purpose of the Merlin_60 was to power high altitude Vickers Wellingtons. They were quickly installed in Spitfires where the two stages made them faster at altitude, and the two speeds made them faster down low.

 

[Steamed_Banana]

I have several thoughts on this.

In 1943/44 over the ETO, the Americans and British had a huge advantage against the Germans at high altitude. This was due to the work of Sanford Moss developing turbochargers in the USA, and Stanley Hooker upgrading superchargers at Rolls Royce. There were good reasons to fire the pair of them. Moss started developing turbochargers during WWI. At the end of the war, the USAAC lost interest, and it is surprising GE did not lose interest too. By several accounts, Moss was an extremely charming, likeable guy, and you could not stay mad at him. A domineering and difficult personality like Roy Feddon might not have lasted. In the late thirties, the USAAC got interested in turbochargers again, and GE was ready. The Rolls Royce Merlin's original supercharger was designed by James Ellor (no Wikipedia page!). When Stanley Hooker told him there was a lot of room for improvement, a lot of people would have taken offence. Ellor was a professional, not an asshole.

I think the radial versus inline discussion is a load of crap. The US Navy liked radials. In the USA in 1940/41, if you needed a reliable 2000hp engine, you specified a Pratt & Whitney R2800. The high altitude performance of the turbocharged P47 was excellent. The non-turbo F4U Corsairs and F6F Hellcats was as good as anything they went up against. The Allisons on the P38 Lightnings were turbocharged. Was there a lot of pressure to improve Allison superchargers?

The issue is this. Very good turbo charged and R-2800 powered fighters were swiftly dominating the air battles of 1944-45. But in 1943 these types were still 'teething', with a lot of problems, or were not yet available.

A late 1944 P-47-D25 or D27 with a bubbletop canopy, paddle blade props, 2300 hp+ engine with MW boost, plumbed for two external wing tanks etc., is a beast. A 1943 P-47D razorback with the thin props and a variety of minor issues is significantly less formidable. A late 1944 P-38J or L with the dive flap system, boosted ailerons, combat flaps, fully functioning turbo, two electric generators, functional heater etc. is very effective, an early 1943 P-38F or G not nearly as much. The Hellcat wasn't really involved in the war in any significant way until late in 1943.

For the first three quarters of 1943 the US in particular was in need of better fighters with better altitude performance. P-40s and P-38Fs and Gs were still holding the line for the US in the MTO, P-40s and P39s and Wildcats, and early Corsairs (with a lot of problems) and P-38F or G were holding the line in the Pacific. P-40s and Hurricane IIs in the CBI.

In this pivotal year of 1943, or ideally even a bit earlier say from the last quarter of 1942 through 1943, they could have really used something better. Doesn't have to be Spitfire XXI or P-47M, F4U-4 or P-51H better, but just better. A moderate improvement. Like the P-40F and L were. Or the Spitfires IX and VIII. That's what I'm aiming for here.

The British wanted "inline" engines. They were committed to the Rolls Royce Merlin, so there was aggressive supercharger development by the unfired Hooker. One of the Napier Sabre's big failings was its high altitude performance. The RAF had another path to high altitude performance, so they demanded that Napier fix the other big problem, the very short lifespan of its sleeve valves. Two-stage Sabres were worked on, but they did not reach production.

Merlin engines were manufactured in the USA because they were needed for Canadian made Hawker Hurricanes, de Havilland Mosquitos and Avro Lancasters. They were available, and they solved problems.

I think most of the Canadian made Hawker Hurricanes were basically a waste of resources. You would have been a lot better off producing about another 1400 P-40Ls with those Merlin XX. You can even give those to the British and send them to Italy or India. They definitely would have helped.

Many if not most of the Canadian made Mosquitoes seemed to get re-engined if and when they were sent to the UK. Some of the rest never saw combat. Not sure about the Lancasters.

 

[BarnOwlLover]

I have the book, what page is that?

I got home not long ago and I did find the page #'s. Pg. 145 for the V-1710-45 and Griffon plans (small photos, though) and bonus for the "Packard Pursuit" concept illustration that I like, check out pg 139.

 

[Steamed_Banana]

Read my post above. Was the USAAF screaming at Allison that they needed better superchargers? The term in manufacturing is "demand". The Allison engines were functional as they were. Do we shut down production to make the improvements?

The lack of demand was a problem, but I have yet to see any evidence that improving the Allison moderately in this way would have shut down production. If it took away some resources they could have safely cut back on the number of P-39s they produced after 1942.

I suspect some of the issue with this was because GE owned Allison so it was acting like a subsidiary rather than an independent company.

Are Allison's engineers as talented as Stanley Hooker?

Didn't he design the Merlin XX in 1940? We are asking for a very large engine company to accomplish the same thing two years later, with the benefit of being able to examine Hooker's Merlin XX, or any one of several multi-speed systems used by US firms like Pratt and Whitney etc.

The Merlin Mustangs happened because the two-stage Merlins were available. The original purpose of the Merlin_60 was to power high altitude Vickers Wellingtons. They were quickly installed in Spitfires where the two stages made them faster at altitude, and the two speeds made them faster down low.

Merlin Mustangs were great but came pretty late in the game. Spitfire IX and VIII were also great, they should have made more of both.

 

[Howard Gibson]

Merlin XX powered Spitfire V also sounds pretty good...

You means the Spitfire_III, which was not put into production. The Spitfire_V used the Merlin_45, which was Hooker's fancy new impeller in a one speed drive optimised for high altitude. The Bf109Fs were coming out, and there was not time to do the upgrade properly.

 

[BarnOwlLover]

I suspect some of the issue with this was because GE owned Allison so it was acting like a subsidiary rather than an independent company.

Merlin Mustangs were great but came pretty late in the game. Spitfire IX and VIII were also great, they should have made more of both.

Point #1, GM (as in General Motors, that GM) owned Allison, owning the aircraft engine division until the 1990s (ironically, GM sold that division of Allison to Rolls-Royce) and the automotive/truck/heavy vehicle transmission division until 2003 (?). GE (General Electric, who now makes jet engines among other things such as home appliances and used to own NBC and Universal Pictures) made the turbos used on the P-38 and I believe also the P-47 and B-29, among other aircraft. They were the main aviation turbocharger manufacturer of the period until they got into jet engines.

Point #2, NAA was making P-51B air frames for a good chunk of 1943, but Packard was slow in delivering license built two stage Merlins (IIRC, part of that was down to tooling issues, part of it was a backlog of single stage Merlin contracts for the Canadian and Australian divisions of de Havilland, who were building Mosquitoes for the RCAF and RAAF under license from the parent company in England).

This did expedite deliveries of the P-51B to the USAAF and RAF and testing of the P-51D prototypes in 1943 once the two stage Merlins became available in number, though, having the aircraft stockpiled just waiting for engines. Packard V-1650-7 Merlins (as the Merlin 266) were also used in Spitfire XVIs. The Spitfire XVI being a version of the IX that used the V-1650-7, some later versions also had bubble canopies (unlike the IX).

I should also note that the Spitfire IX was the second most produced Spitfire variant, behind only the V (which the IX was a Mk V air frame modified to use two stage Merlins)

 

[tomo pauk]

If a two speed supercharger itself was such a good idea, why (other than manufacturing issues mentioned), why didn't Allison bite the bullet and make a decent two speed drive? Ignorance, hubris, or simple logistics as mentioned.

A 2-speed supercharger was a very good idea.
Allison was a newcomer in the engine business, and their plate was full with development of several V-1710 versions (the F series differed vs. the C series in far more details than just the reduction gearing; E series with the remote gearbox, the D series for the pusher installations, the X and W projects; changes & improvements of small details numbered probably in hundreds). Buying & incorporating the 2-speed drive would've probably improved the timetable here, like it was the case with RR buying the Farman system, or Packard buying the Wright system for the V-1650 production).

Read my post above. Was the USAAF screaming at Allison that they needed better superchargers? The term in manufacturing is "demand". The Allison engines were functional as they were. Do we shut down production to make the improvements? Are Allison's engineers as talented as Stanley Hooker?

The improvements of the S/C of the V-1710 were not originating from the mass production facility within the company, but from the design and testing department. These departments needed a fully year just to debug the 9.60:1 S/C drive. Once it was debugged, it was also used on the mass-produced engines.
USAAF was aware of the weaknesses of the non-turbo V-1710 at altitude even before ww2, hence they specifying turboes for the V-1710, R-1820 and the R-1830, the turboed R-2800 for the P-47B instead of the V-1710-powered P-47A, and hence the V-1650.

 

[Steamed_Banana]

Forgive my error I just learned about Allison being a subsidary today and both GE and GM were part of this story

The Spitfire variant that really think was most in demand and not available in enough numbers was the VIII, which had much better range. It was a real game changer, if you can forgive the overused phrase, in the CBI.

 

[Steamed_Banana]

A 2-speed supercharger was a very good idea.
Allison was a newcomer in the engine business, and their plate was full with development of several V-1710 versions (the F series differed vs. the C series in far more details than just the reduction gearing; E series with the remote gearbox, the D series for the pusher installations, the X and W projects; changes & improvements of small details numbered probably in hundreds). Buying & incorporating the 2-speed drive would've probably improved the timetable here, like it was the case with RR buying the Farman system, or Packard buying the Wright system for the V-1650 production).



The improvements of the S/C of the V-1710 were not originating from the mass production facility within the company, but from the design and testing department. These departments needed a fully year just to debug the 9.60:1 S/C drive. Once it was debugged, it was also used on the mass-produced engines.
USAAF was aware of the weaknesses of the non-turbo V-1710 at altitude even before ww2, hence they specifying turboes for the V-1710, R-1820 and the R-1830, the turboed R-2800 for the P-47B instead of the V-1710-powered P-47A, and hence the V-1650.

They probably figured the turbos would be easier than they actually were, since they were being used in airliners already by 1940 at least.

It was just, as you or somebody else noted, not as easy to put one in a fighter.

 

[Steamed_Banana]

You means the Spitfire_III, which was not put into production.

Not precisely. Spitfire III had a lot of innovations, and while I'm no spitfire expert, I gather it was pretty similar to what eventually became the Spitfire VIII. But sure Spitfire III or a Spit V with a merlin XX, whichever makes the most logistical sense.

The Spitfire_V used the Merlin_45, which was Hooker's fancy new impeller in a one speed drive optimised for high altitude. The Bf109Fs were coming out, and there was not time to do the upgrade properly.

Sadly they weren't that great against Bf-109Fs, at least until they made some changes. I think the metal ailerons helped and in North Africa the Aboukir type filters helped a great deal compared to the older / huge Vokes.

 

[Howard Gibson]

The issue is this. Very good turbo charged and R-2800 powered fighters were swiftly dominating the air battles of 1944-45. But in 1943 these types were still 'teething', with a lot of problems, or were not yet available.

A late 1944 P-47-D25 or D27 with a bubbletop canopy, paddle blade props, 2300 hp+ engine with MW boost, plumbed for two external wing tanks etc., is a beast. A 1943 P-47D razorback with the thin props and a variety of minor issues is significantly less formidable. A late 1944 P-38J or L with the dive flap system, boosted ailerons, combat flaps, fully functioning turbo, two electric generators, functional heater etc. is very effective, an early 1943 P-38F or G not nearly as much. The Hellcat wasn't really involved in the war in any significant way until late in 1943.

The Luftwaffe in the ETO was destroyed by turbocharged P47 Thunderbolts at 30,000ft in 1943. The methanol water injection and paddle blade propellers were improvements, but by that time, the P47s were being replaced by cheaper, longer ranged Mustangs. In 1943, the Hellcats and Corsairs were achieving air superiority in the Pacific. Again, the aircraft, particularly the Corsairs, were improved as the war went on. They were good enough in 1943.

For the first three quarters of 1943 the US in particular was in need of better fighters with better altitude performance. P-40s and P-38Fs and Gs were still holding the line for the US in the MTO, P-40s and P39s and Wildcats, and early Corsairs (with a lot of problems) and P-38F or G were holding the line in the Pacific. P-40s and Hurricane IIs in the CBI.

In this pivotal year of 1943, or ideally even a bit earlier say from the last quarter of 1942 through 1943, they could have really used something better. Doesn't have to be Spitfire XXI or P-47M, F4U-4 or P-51H better, but just better. A moderate improvement. Like the P-40F and L were. Or the Spitfires IX and VIII. That's what I'm aiming for here.

The Americans used Spitfire_Vs, VIIIs, and IXs in the Mediterranean. They worked hard to increase the range of the P47s, they bitched at the British for not increasing the range of their Spitfires, and then they deployed Mustangs. The Spitfire_XXIs and P51Hs were post-war. This was not happening in 1943.

I think most of the Canadian made Hawker Hurricanes were basically a waste of resources. You would have been a lot better off producing about another 1400 P-40Ls with those Merlin XX. You can even give those to the British and send them to Italy or India. They definitely would have helped.

Many if not most of the Canadian made Mosquitoes seemed to get re-engined if and when they were sent to the UK. Some of the rest never saw combat. Not sure about the Lancasters.

I am astonished the Hurricanes remained in production until June 1944. Maybe they were used as trainers.

Are you sure about the Canadian Mosquitos? There was way more demand for Mosquitos than could be met by existing production. I cannot see somebody pushing a bunch of them onto a parking lot and then leaving them there. The only problem I can see with a Packard Merlin engine would be that you could not maintain it with British tools. Apparently, Packard Merlins came with an American toolkit. The Hispano cannons manufactured in the USA were not good. This may have discouraged the manufacture of fighter-bomber Mosquitos in Canada. Canadian Mosquitos were used as trainers.

 

[Howard Gibson]

Not precisely. Spitfire III had a lot of innovations, and while I'm no spitfire expert, I gather it was pretty similar to what eventually became the Spitfire VIII. But sure Spitfire III or a Spit V with a merlin XX, whichever makes the most logistical sense.

The Spitfire_III was modified to take the Merlin_XX. I assume that its nose was extended a bit, but not as much as it would have been to accommodate the Merlin_61. I would say that the wingtips were rounded, rather than clipped. The tailwheel was retractable. The windscreen was three flat pieces. There were similar modifications to the VII and VIIIs, but they look different.

Sadly they weren't that great against Bf-109Fs, at least until they made some changes. I think the metal ailerons helped and in North Africa the Aboukir type filters helped a great deal compared to the older / huge Vokes.

The Vokes filters were awful. How many Aboukir filters were produced?

 

[MiTasol]

I remember a certain expert on P-39s saying the engine would have been only 2 1/2 inches longer. Various comments were, the rear firewall would have to be moved rearward, necessitating a redesign. My solution, although I did not mention it, would have been the same solution when fitting a 1956 Plymouth V-8 into my 1948 Plymouth replacing the six.
I used a sledge hammer on the firewall to dimple it to allow the right cylinder head to fit. Ran fine until it met a 1957 Ford 2-door hard top.

Actually it is more like 2 1/2 FEET longer. If they had mass produced an integral second stage like Pratt and Rolls etc it would have been shorter.

 

[BarnOwlLover]

The Spitfire_III was modified to take the Merlin_XX. I assume that its nose was extended a bit, but not as much as it would have been to accommodate the Merlin_61. I would say that the wingtips were rounded, rather than clipped. The tailwheel was retractable. The windscreen was three flat pieces. There were similar modifications to the VII and VIIIs, but they look different.

The Spitfire III was built only in prototype form. They were ultimately used by Supermarine and Rolls-Royce as Merlin 60 series engine test beds in 1941/early 1942. This paved the way to the Spitfire VIII and IX.

 

[BarnOwlLover]

Actually it is more like 2 1/2 FEET longer. If they had mass produced an integral second stage like Pratt and Rolls etc it would have been shorter.

View attachment 871148

View attachment 871147

This is a cutaway of a V-1710-119 in a XP-51J. This was similar to the -140 series engines used in the F-82E/F/G/H

And as actually installed:

The later Allisons didn't use the remote supercharger stage that the earlier engines (as used in the P-63) had. The late Allisons were still longer than the Merlin, but the difference was in inches, not the 2.5 feet that it would've been with the remote supercharger stage.

 

[MIflyer]

there is a lot of good things going on for the Merlin XX on a P-38 or a P-51,

A friend of mine, a WW2 P-38 maintenance chief, said that putting a Merlin into a P-38 would not be as easy as it looks, mainly due to the structure not fitting well with the Merlin's updraft carb.