What If: Pratt Whitney build/develop the Sabre under licence?

[wuzak]

The chances of P&W licensing the Sabre prewar are about zero. Why pay license fees/ patent royalties to Napair when they had their own patents for many of the features?

The features of which you speak were designed so that they didn't infringe on Napier's patents - and was, IIRC, to do with the sleeve drive.

They also had no existing manufacturing plant for large liquid cooled engines. No casting facilities (or not enough) to handle the large casting needed for crankcases and cylinder blocks. The radial crankcases being much smaller, and individual cast cylinder heads being almost minuscule in size compared to a Sabre crankcase.

Seriously?

Some of the accesory/supercharger housings for the R-2800 were quite large.

They also had little difficulty casting the crankcase and cylinder blocks for teh X-1800 family of engines.

Sabre cylinder heads were small individual castings too.

We still don't know the cost of the engines. If you can build 2 R-2800s for the cost of 1 Sabre the Sabre really looks like a bad deal no matter how technically advanced it may be.
The Sabre didn't offer a big advantage over the R-2800 in 1939-40 and while it may have gained over the R-2800 during the war years it didn't really offer anything over the other big radials by the end of the war.

Cost is a good point - but the number built has a direct impact on the unit cost. They built a lot of R-2800s during the war. Not so many Sabres.

 

[wuzak]

The Sabre VII may only have been installed in two airframes. A long suffering Folland test bed and a single Hawker Fury prototype.

Good documentation on the Sabre is hard to find. Charts can be found for Sabre IIA using 12lbs boost at 3700rpm and 150 fuel. Books can be found showing 3750 rpm. Sabre IIB s are supposed to be good for 3850 rpm. Boost ratings jump up and down a bit. Sabre IIAs were being installed in the first tempests let alone rather late Typhoons. The Sabre V was fitted to the Tempest VI but I don't think they mad the war and I am not sure they got anywhere near 3000hp, could be wrong on that though.

Not sure that is true of the Sabre IIA in teh Tempest - apart from, maybe, some prototypes.

 

[wuzak]

Those 2800 turbo HP were available in 1944, and no matter what supercharger we add, Sabre in 1944 was not capable for that. It was between 2400 HP (from the chart at ww2aircraftperformance) and 2600 HP. To achieve 3055 HP, we need to go to 1945.
When one says 'earlier marks', what year is that? Sabre VA is in 1945, and I'd like to know if the V and VII were ever in service, even in that year. One thing is to have a superb engine for testing, available in single digits, other thing are the engines produced in thousands.

I do maintain that R-2800 have had the edge in power at altitude, reliability, availability, maintainability, while being less susceptible to battle damage.
Sabre (as is) was offering a better performance at lower altitudes, and (in theory) better streamlining. Looking at R-2800 without turbo or two-stage supercharger is like taking into account only 1-stage Merlins.
For Sabre to beat R-2800 as a complete package, many things would've needed to come along, so the license production of R-2800 in UK makes far more sense than Sabre produced in USA.

When in 1944 was 2800hp available?

From my information it would seem that the 2800hp version of the R-2800 was available in small numbers from late 1944, and wasn't reliable until neary the end of the war in Europe.

The normal R-2800s found in P-47s and the like were around 2400-2500hp - something that the Sabre IIB could match, and the V and VII exceed.

When and by who would the R-2800 be licence produced in the UK? Napiers? I doubt you would get any more R-2800s out of them than they produced Sabres - and probably not before 1944.

My contention is that P&W were already looking at a 2200ci liquid cooled sleeve valve H-24 in 1938 - and in fact built prototypes. That was the X-1800. They could have built some Sabres instead, probably more cheaply as they didn't have to design any thing. Maybe the program doesn't go beyond 1940, as for the X-1800, but I would say that the Sabre held far more promise than the X-1800 ever did.

Instead of building X-1800 prototypes, 1938/39 could have been used to productionise the engine instead. Maybbe not a licence deal, possibly a joint venture?

 

[wuzak]

Replacing an R-2800 with a Sabre (an H-2240?) sounds like a whole lot of work for very little result. The Sabre is heavier in dry weight, a two stage R-2800 weighs about what a single stage Sabre does, not including the inter-coolers. The R-2800 doesn't need 5-600lbs worth of radiators and coolant, although it's cowling is a bit bigger and heavier. Even if the Sabre's nuts and bolts had been a bit more accessible the R-2800 is still easier to work on, needs 12 fewer spark plugs at plug change time and so on.

At the end of the war the Sabre offered very little that the big radials could not do.

Leaving peak power aside for a moment and comparing "rated" power or max continuous power we find that the various engines (using single stage superchargers in high gear) were good for:

R-2800 "C" series..... 1500hp/2600rpm/17,500ft.
R-4360-4............... 2200hp/2550rpm/13,000ft.
R-3350BD............... 1800hp/2400rpm/13,000ft.
Centaurus 57.......... 2000hp/2400rpm/16,000ft.
Griffon VI................1340hp/2600rpm/14,800ft.
Sabre VII................1960hp/3700rpm/18,250ft.

a Merlin 130 was good for 1325hp/2850rpm/20,750ft with it's two stage blower.

Take-off power for the engines were:

R-2800 "C" series..... 2400hp/2800rpm/+13.0lbs boost and ADI
R-4360-4............... 3000hp/2700rpm/+10.5lbs boost dry
R-3350BD............... 2800hp/2800rpm/+13.0lbs boost and ADI
Centaurus 57.......... 2800hp/2700rpm/+11.5lbs boost and ADI
Griffon VI................1820hp/2750rpm/+15lbs boost dry
Sabre VII................3000hp/3850rpm/+17.25lbs boost and ADI

Data from the 1946 edition of Wilkinson's "Aircraft Engines of the World"

Those 2800 turbo HP were available in 1944, and no matter what supercharger we add, Sabre in 1944 was not capable for that. It was between 2400 HP (from the chart at ww2aircraftperformance) and 2600 HP. To achieve 3055 HP, we need to go to 1945.
When one says 'earlier marks', what year is that? Sabre VA is in 1945, and I'd like to know if the V and VII were ever in service, even in that year. One thing is to have a superb engine for testing, available in single digits, other thing are the engines produced in thousands.

I do maintain that R-2800 have had the edge in power at altitude, reliability, availability, maintainability, while being less susceptible to battle damage.
Sabre (as is) was offering a better performance at lower altitudes, and (in theory) better streamlining. Looking at R-2800 without turbo or two-stage supercharger is like taking into account only 1-stage Merlins.
For Sabre to beat R-2800 as a complete package, many things would've needed to come along, so the license production of R-2800 in UK makes far more sense than Sabre produced in USA.

I would argue that the R-2800 did not have an edge in power - check SR's max continuous ratings - the Sabre VII is 30% more powerful in continuous rating than a C-series R-2800. In fact it all but matches the R-4360.

The power at altitude is all about the supercharging system. Only turbocharged and 2 stage R-2800s held any power advantage at altitude.

Availability is a measure of the production effort behind the two engines. The R-2800 was built by P&W, Ford and GM in huge new factories. The Sabre was built by Napiers in what was largely a Victorian era factory.

Reliability - sure, it would look on the surface that ths was the case. But that image is somewhat tarnished by the early troubles the Sabre had. Later in the war the Sabre became very reliable.

Maintainability? In what way? Sure there are more spark plugs to clean (48 vs 36) but then they are more accessable, I would think, being there on the side. Instead of being upside down, or on the side or top. Valve clearence adjustment - not needed on the Sabre. Carby? Much the same on each.

The susceptability to battle damage for liquid cooled engines is overplayed by proponents of air cooled engines IMO.

 

[Shortround6]

Not sure that is true of the Sabre IIA in teh Tempest - apart from, maybe, some prototypes.

See: Tempest V Performance

First 100 Tempests produced engine type not given. Produced from 12/43 to 5/44

second batch of 300 with Sabre IIAs starting in 5/44 through 9/44

3rd batch of 199 with Sabre IIBs started in 9/44

4th and last batch with Sabre IIBs started in 1/45

Early Planes may have been re-engined with IIBs in service.

From the page on the Typhoon:

"Sixth batch of 400 aircraft. PD446-PD480, PD492-PD536, PD548-PD577, PD589-PD623, RB192-RB235, RB248-RB289, RB303-RB347, RB361-RB408, RB423-RB459 and RB474-RB512. All aircraft with sliding hood, whip aerial, faired cannon, exhaust shrouds and four blade propeller, most aircraft with Napier Sabre IIa engine but a few among the final 255 were powered by the Napier Sabre IIb. Delivered between June 15th 1944 and January 5th 1945."

This timing rather coincides with the Tempest production with the Sabre IIB showing up about Sept of 1944.

many companies had the ability to produce small numbers of large casting for experimental work or even sub contracted out some of the casting work. The Matag washing machine company made castings for some US built Merlins. What could be done in tool rooms or in small batches does not mean the company could produce such items at the rate of dozens per day. Especially if the scrap rate was to be held within reasonable limits.

Few, if any, companies licensed prototype engines in peace time. The reasons for licensing engines and having to pay license/royalty fees was to gain knowledge faster. P&W was already a major engine company, one of the 2 largest in the US and a major player on the world market. Their knowledge of air-cooled radials was among the world leaders. Sinking millions of dollars into a sleeve valve engine project could have been a major mistake. Buying a license for an engine that the original company can not get to run right in production form is lousy business. How much do you like paying for crappy software in order to be a "beta" tester even if offered a share of the profits later

 

[Shortround6]

I would argue that the R-2800 did not have an edge in power - check SR's max continuous ratings - the Sabre VII is 30% more powerful in continuous rating than a C-series R-2800. In fact it all but matches the R-4360.

the Sabre VII was never a production engine. The "C" series engine I gave was a commercial airline engine, no war emergency rating. The R-2800 in singe stage 2 speed form is also about 22% lighter than the Sabre and radiator.

The power at altitude is all about the supercharging system. Only turbocharged and 2 stage R-2800s held any power advantage at altitude.

True but then the mechanical 2 stage R-2800 only weighs 2460lbs without intercooler and ducts but including both stages. Please add 200-300lbs for a second stage on the Sabre. (R-R Griffon added 285lbs by adding the second stage.)

And if you really want to compare "Ultimate" versions try the Post war "E" series R-2800s as used in the F4U-5 or F8F-2 aircraft. 2800hp using water injection from either a 2 stage supercharger (-32W) engine or a single stage engine (-30W). at least these engines were made to the tune of hundreds each and not single digits.

Availability is a measure of the production effort behind the two engines. The R-2800 was built by P&W, Ford and GM in huge new factories. The Sabre was built by Napiers in what was largely a Victorian era factory.

Availability is not the same as cost. Sure the P&W R-2800 was built in large numbers, in part because the cost was low to begin with. The "A" series was low powered (1850hp) but didn't stretch the boundaries of manufacturing techniques much, if at all. It allowed for a "getting the feet wet" approach that still gave serviceable engines. later versions required more advanced manufacturing techniques. The R-2800 also wasn't saddled with tens of millions in R&D costs. (strangely the R-4360 was).

Reliability - sure, it would look on the surface that ths was the case. But that image is somewhat tarnished by the early troubles the Sabre had. Later in the war the Sabre became very reliable.

Reliability and durability are not the same thing. Reliability is what are the odds of the engine making it close the suggested overhaul life without crapping out on any given flight. What was the suggested overhaul life of a Sabre even at the end of the war.

Maintainability? In what way? Sure there are more spark plugs to clean (48 vs 36) but then they are more accessable, I would think, being there on the side. Instead of being upside down, or on the side or top. Valve clearence adjustment - not needed on the Sabre. Carby? Much the same on each.

Want to replace the piston rings in only one or two cylinders in the Sabre?? or replace one or two pistons? Often done before a full overhaul.

The Sabre was a nice achievement, it set a few records in engine power per cubic inch for it's type that may never be equaled. The planes it powered were nice looking . It did play a part in the war. The question is if was really worth the cost and that question applies to the entire sleeve valve family. By the time they were perfected did the problems they were intended to solve already disappear due to other developments?

 

[tomo pauk]

When in 1944 was 2800hp available?
From my information it would seem that the 2800hp version of the R-2800 was available in small numbers from late 1944, and wasn't reliable until neary the end of the war in Europe.
The normal R-2800s found in P-47s and the like were around 2400-2500hp - something that the Sabre IIB could match, and the V and VII exceed.

The 2600 HP rating for R-2800 was from summer of 1944 for regular P-47Ds, 2800 HP was flying in XP-47J. The best figure for Sabre in I can extract from a reliable source is 2420 HP ( http://www.wwiiaircraftperformance.org/tempest/tempest-v-ads-sabre-IIb.jpg ).

When and by who would the R-2800 be licence produced in the UK? Napiers? I doubt you would get any more R-2800s out of them than they produced Sabres - and probably not before 1944.

That depends on timing? With license obtained in early 1941, we can have them in combat by 1943. But, in light of Fairey/Curiss engine soap opera, I doubt that such a deal would've been made.

My contention is that P&W were already looking at a 2200ci liquid cooled sleeve valve H-24 in 1938 - and in fact built prototypes. That was the X-1800. They could have built some Sabres instead, probably more cheaply as they didn't have to design any thing. Maybe the program doesn't go beyond 1940, as for the X-1800, but I would say that the Sabre held far more promise than the X-1800 ever did.

Instead of building X-1800 prototypes, 1938/39 could have been used to productionise the engine instead. Maybbe not a licence deal, possibly a joint venture?

No quarrels about yours background story, but I like mine better

I would argue that the R-2800 did not have an edge in power - check SR's max continuous ratings - the Sabre VII is 30% more powerful in continuous rating than a C-series R-2800. In fact it all but matches the R-4360.

I'm saying all the time 'better at high altitudes' for R-2800, and that still stands. If we want to take in the account the post-war engines, that defeats the "P&W builds Sabre for ww2" excersise.

The power at altitude is all about the supercharging system. Only turbocharged and 2 stage R-2800s held any power advantage at altitude.

Not quite.
R-2800s in Corsair Hellcat was providing 1600 HP at 23000 ft, Sabre was 1600 Hp at 19000 ft (all values without ram effect).

Availability is a measure of the production effort behind the two engines. The R-2800 was built by P&W, Ford and GM in huge new factories. The Sabre was built by Napiers in what was largely a Victorian era factory.

Acknowleged - maybe the R-2800 was a more conservative design, too - a feature that would allow it to be made easier than a sleve valve engine? Even the Soviets Japanese had no problems to design produce a conventional radial engines of great power levels.

Reliability - sure, it would look on the surface that ths was the case. But that image is somewhat tarnished by the early troubles the Sabre had. Later in the war the Sabre became very reliable.

The quirk is 'late in the war' - what Allies needed was an early war, high performance stuff.

Maintainability? In what way? Sure there are more spark plugs to clean (48 vs 36) but then they are more accessable, I would think, being there on the side. Instead of being upside down, or on the side or top. Valve clearence adjustment - not needed on the Sabre. Carby? Much the same on each.

Elmas has posted en excerpt re. how difficult it was to service the Sabre, in this thread.

The susceptability to battle damage for liquid cooled engines is overplayed by proponents of air cooled engines IMO.

Maybe it is. But even if the difference is 10%, that means more lives planes can return instead to force land or ditch.

 

[johnbr]

I still think the P-24 was a better engine then the Sabre with good Prudential.

 

[wuzak]

I still think the P-24 was a better engine then the Sabre with good Prudential.

On what basis?

Wht do you mean "with good Prudential"?

 

[wuzak]

R-2800s in Corsair Hellcat was providing 1600 HP at 23000 ft, Sabre was 1600 Hp at 19000 ft (all values without ram effect).

The Corsair and Hellcat had 2 stage supercharged R-2800s.

 

[Shortround6]

The Corsair and Hellcat had 2 stage supercharged R-2800s.

True but a 2 stage supercharged R-2800 weighed less than a single stage Sabre if we include the weight of the Sabre's radiator and coolant.

 

[johnbr]

The P-24 showed to have very good reliably 2000hp on 87octane>Just think what it could do with 100 or 130 fuel and a 2 stage supercharger at 20 lb's boost.

 

[wuzak]

True but a 2 stage supercharged R-2800 weighed less than a single stage Sabre if we include the weight of the Sabre's radiator and coolant.

Not the point. Tomo was comparing the altitude performance of a two stage P&W R-2800 with a single stage Sabre. For a fair comparison the R-2800 compared should be the single stage 2 speed types.

 

[wuzak]

The P-24 showed to have very good reliably 2000hp on 87octane>Just think what it could do with 100 or 130 fuel and a 2 stage supercharger at 20 lb's boost.

I doubt it would take 20lbs boost. The thing was very lightly constructed.

The Sabre was type tested at 2000hp on 87 octane, and showed very good reliability. But they were also hand built prototypes.

The P24 showed some 200lb savings over the Sabre, but was also a lot bulkier (length, width, height). There was some suspicion about the reliability of the contra prop arrangement - I believe pitch control was an issue with later systems (just ask Howard Hughes). The P24 also required 2 separate coolant and oil cooler circuits - because when one half isn't working there is no point pumping warm fluids through it.

The P24 had some very dodgy features, IMO. Like the way the intake air was fed to the cylinder chambers - something that could not have been rectified easily.

No doubt the P-24 could have been manufactured more easily than the Sabre.

 

[tomo pauk]

The Corsair and Hellcat had 2 stage supercharged R-2800s.

IMO there is no much sense to compare type that is in use with a type that is not. So I was comparing the real engine (two-stage R-2800) with another real one (single stage Sabre). They are of comparable weight and time frame, with comparable application in real airframes. I apply same logic when comparing eg. DB-605, BMW-801 and Merlin 60 series.

At least we agree on something, I like very much the P-24

 

[wuzak]

IMO there is no much sense to compare type that is in use with a type that is not. So I was comparing the real engine (two-stage R-2800) with another real one (single stage Sabre). They are of comparable weight and time frame, with comparable application in real airframes. I apply same logic when comparing eg. DB-605, BMW-801 and Merlin 60 series.

Fair enough.

But still, you are comparing a high altitude version of one engine with a low altitude version of another. They weren't used for the same purpose.

At least we agree on something, I like very much the P-24

Actually I don't rate the P24.

 

[wuzak]

The P-24 showed to have very good reliably 2000hp on 87octane>Just think what it could do with 100 or 130 fuel and a 2 stage supercharger at 20 lb's boost.

Have a look here: http://www.ww2aircraft.net/forum/aviation/fairey-aero-engines-any-good-info-30710.html

 

[tomo pauk]

Fair enough.

But still, you are comparing a high altitude version of one engine with a low altitude version of another. They weren't used for the same purpose.

I'm comparing the fighter version of R-2800 with a fighter (unfortunately, the only) version of the Sabre.

Actually I don't rate the P24.

Doh

 

[Shortround6]

Not the point. Tomo was comparing the altitude performance of a two stage P&W R-2800 with a single stage Sabre. For a fair comparison the R-2800 compared should be the single stage 2 speed types.

It is sort of the point. A single stage R-2800 without intercoolers is going to be around 600lbs lighter than the single stage Sabre. So the aircraft designer has a choice, lighter weight (but bigger diameter) with the R-2800 or the same weight with better altitude performance.
One reason the Bearcat was such a good climber. the "E" series R-2800 it used offered a lot of power (if still a bit less than an ultimate Sabre) for a lot less weight. The F4U-5 used the extra weight and bulk of it's two stage "E" series engine for some rather impressive altitude performance and it's engine, while bulkier, weighed about the same as the Sabre.

 

[Siegfried]

It seems to me that the Bristol Sleave valve engines offered no discernable advantage over poppet valve rradials. I've looked for performance advantages but none over radials of equal weight, power, displacement at all. That includes the centaurus The Sabre at least promised advantages in power.

The Sabres trick was reving at high RPM, I suspect that this was a result of the horisozontall opposed configuration as much as the sleeve valve. Junkers was already running the Jumo 213 at 3250 rpm and were planning to productionise the the 3750 rpm jumo 213J. Part of the trick of the Jumo was the twin overhead cams. Overhead cams might allow higher revening but cams increase the dimensions of the rocker cover, hence a tendancy to use pushrods on radials.

It would seem to me a similar configuration to the Sabre but with DOHC poppet valves might produce the same result, perhaps with somewhat more width and frontal area. A back to back arrangment of two 120 degree V's might overcome even this. Two 90 degree V-12 might also achieve this. The Sabre avoided shaft issues by useing two shafts and gearing them together. The RR Vulture didn't, but retained only one shaft. I rather suspect that had RR had the resources to continue with the Vulture it would have turned into an engine abl,.e to match the Sabre and probably entered service as a reliable unit years earlier. Assuming the same volumetric efficiency as the Merlin then the 42 litre Vulture should produce 1.62 x the power of the Merlin: ie 2750hp at 18psig and maybe 3300 at the higher boost levels.

Sleeve valves may have had little to do with it.