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

[wuzak]

In the late 1930s Pratt & Whitney engineer George Mead visited England and saw what was being developed by the aero engine firms.



He was very impressed with the Napier Sabre, and upon his return to the US began the design of a liquid cooled, sleeve valve H-24 - which would be known as the X-1800.

The X-1800 was to produce 1800hp from the same capacity as the Sabre. It was then increased in size to create the H-2600, and again to make the H-3130 and finally again to become the H-3730.

The X-1800 and its successors were physically larger and heavier than the Sabre.

What if Mead returned to the US with a licence to manufacture Sabres in the US? Did P&W have the resources to develop a reliable sleeve manufacturing method. Would it still have been dropped for the R-4360 around 1941?

Another: What if Napiers realised they were in trouble with sleeve manufacture earlier, and had contracted to Bristol to make sleeves for the Sabre?

Bristol were eventually ordered to help Napier with sleeve manufacture, having to hand over information on the process that had been hard won over many years at a not insignificant cost. If Napiers had contracted them to build the sleeves they could have kept their processes secret and earned a small profit from making Sabre sleeves.

And, if P&W had made some Sabres in the US, how long before an airframe designer stuck a turbocharger (or a pair) on the back of one? I think a pair of B-series turbochargers mounted close to back end of the engine could have made a potent and compact package.

[tomo pauk]

The Sabre was a really impressive engine, at least when most of the bugs were ironed out (second half of 1943?). Prior that, I don't see it as a competition vs. P&W's own race horse, the R-2800. And after that, R-2800 leads the race till the end of war.
So, while I hate to rain on your parade, perhaps the Napier building R-2800s would be a better idea?

[davebender]

You appear to be assuming P&W can make a reliable copy of the Sabre engine will little difficulty. I think that's a bad assumption to make. Packard production of the RR Merlin engine was a great success but that program was the exception to the rule. There are many examples where American license production took a long time to perfect and some instances where the effort failed.

Consider the Bofors 40mm/60 AA gun.
U.S. Army interest in the weapon dates to 1937 when we tested sample weapons. During 1940 Chrysler Corporation received a contract to produce weapons using British supplied blueprints. Yet it was 1943 before the 40mm Bofors was in American mass production and mid 1944 before production finally caught up with demand. 6 years to copy the weapon even though we were supplied blueprints already converted from metric to English measurements.

[Shortround6]

A lot of things depend on luck, Bristol "discovered" the final finishing technique for sleeve valves when a workman accidentally used some grinding wheels out of order.

Not to say it might not have been hit on another way but hundreds of alloys and finishing techniques were tried. Bristol might have been able to make sleeve valves for Napier but seeing as how Napier wasn't able to make their own sleeve valves in quantity until 6 Sidestrand centerless grinders were supplied from the US (rushed over on the Queen Mary, and "swiped" from the P&W Kansas City plant, delaying that factory by six weeks or more, I doubt that Bristol was in any shape to supply large quantities of sleeve valves without a similar increase in infrastructure/tooling.

Hobbs gave up on the sleeve valves because he doubted that P&W could bring them to production status in time for the war and believed that P&W should stick with what it knew (air-cooled engines) and that they could get the R-4360 inot service sooner than a sleeve valve engine. Maybe he was wrong but buying a licence for an "UNPROVEN" engine without any idea how to manufacture it in quantity does not sound like a good business decision.

While the Sabre was a technological tour de force it was an economic disaster. Depending on which authors you read the Sabre was 2 to 5 times more expensive PER HORSEPOWER than poppet valve engines. That may or may not include the development costs.

Airline business men can be a hard headed lot and even the British ones, in the post war era when the British tried desperately not to import ANY U.S. goods because of their trade deficit/ trade balance and Bristol and Rolls were coming out with commercial versions of their engines, the Sabre found zero takers.

[Elmas]

“None of the studs, nuts and bolt were accessible- you couldn’t even see them!-You were feeling around corners and you’d got weirdly contorted spanners to get at them, giving it half a turn then chosing another spanner and giving it another bit of turn! oh, that was shocking!

Peter Jago, RAF fitter, about the Napier Sabre engine
in


No doubt that there weren’t Airline managers sufficiently out of mind to want Sabres mounted on their planes.....

[johnbr]

Me I would have Canada build the Farley P-24.Runing on 130 or 150 fuel.

[wuzak]

Me I would have Canada build the Farley P-24.Runing on 130 or 150 fuel.

Why?

By the time that was (would have been) ready for production the Sabre was sorted.

[wuzak]

The Sabre was a really impressive engine, at least when most of the bugs were ironed out (second half of 1943?). Prior that, I don't see it as a competition vs. P&W's own race horse, the R-2800. And after that, R-2800 leads the race till the end of war.
So, while I hate to rain on your parade, perhaps the Napier building R-2800s would be a better idea?

Doubtful that Napiers couldmake R-2800 any better than they could the Sabre.

[wuzak]

You appear to be assuming P&W can make a reliable copy of the Sabre engine will little difficulty. I think that's a bad assumption to make. Packard production of the RR Merlin engine was a great success but that program was the exception to the rule. There are many examples where American license production took a long time to perfect and some instances where the effort failed.

Not assuming anything. What I would say is that they would have been better fiddling with the Sabre than the X-1800, H-2600, H-3130 and H-3730 that P&W did develop.

For one thing, most of teh design work had been done.

[Shortround6]

P&W stopped fiddling with the X-1800, H-2600, H-3130 and H-3730 in 1940.

in 1940 the Sabre was nowhere near the 2900hp planned for the XH-3730.

Please remember that in 1940 100/130 fuel did NOT exist let alone even higher performance fuels.

[fastmongrel]

Napiers problem wasnt handbuilding prototypes it was building hundreds of reliable copies. Apparently some of there production machinery was Victorian era and more suited to building steam engines. The Sabre might have been reliable a lot earlier if Napiers had been left to do the design work and protoype building and a firm like Fords had been given the job of turning those prototypes into production engines and churning them out like sliced bread.

Unfortunately whilst Napiers wasted time tinkering with the engine problems they should have been building versions with proper superchargers, when the Sabre finally got sorted the power it was churning out per litre was astonishing.

[wuzak]

P&W stopped fiddling with the X-1800, H-2600, H-3130 and H-3730 in 1940.

in 1940 the Sabre was nowhere near the 2900hp planned for the XH-3730.

Please remember that in 1940 100/130 fuel did NOT exist let alone even higher performance fuels.

I don't think teh XH-3130/3730 existed in 1940. My sources say that it was cancelled in 1940 - and only because of the R-4360, which hadn't begun in 1940.

Sabre was 2000hp engine by 1940 using 87 octane fuel - and the R-2800 couldn't match that until the B-series engines and 100 octane fuel.

[wuzak]

P&W stopped fiddling with the X-1800, H-2600, H-3130 and H-3730 in 1940.

in 1940 the Sabre was nowhere near the 2900hp planned for the XH-3730.

Please remember that in 1940 100/130 fuel did NOT exist let alone even higher performance fuels.

I don't think teh XH-3130/3730 existed in 1940. My sources say that it was cancelled in 1943 - and only because of the R-4360, which hadn't begun in 1940.

Sabre was 2000hp engine by 1940 using 87 octane fuel - and the R-2800 couldn't match that until the B-series engines and 100 octane fuel.

[Shortround6]

Here is an interesting but brief article on the Pratt & Whitney engines.

http://www.enginehistory.org/Convent...nK/PWLC3_1.pdf

The XH-3130/3730 project was in existence in 1937 and may have pre-dated the X-1800.

Something to consider when comparing these engines is service rating vs type rating vs power achieved during a short term test. An R-2800 hit 3500hp briefly during a test and survived.

Something else to consider is that fuel was NOT standardized at this time. British fuel contained a much higher level of aeromatics than American fuel. Nobody was actually measuring rich mixture fuel response at this time although they knew it existed. American fuel showed little difference in octane number when running rich while British fuel did. The difference between British 87 and American 100 may be smaller than the numbers suggest. While 100 octane fuel showed up in time for the BoB and was supplied from America it was NOT standard American fuel but fuel supplied by American contractors to BRITISH SPECIFICATIONS.
This makes comparing power outputs of British and American engines in 1939-40-41 a bit difficult unless one knows EXACTLY which fuel was being used.

[tomo pauk]

IMO we should compare usable, powerful, reliable and available types, to arrive at conclusion what would be a better choice (assuming we can build both types). It took to second half of 1943 for Napier to sort out the Sabre, so by that time Sabre is hardly a competition vs. R-2800. Even in 1942, R-2800 has 2000 HP (Sabre is better some 6%), and if we are at 18000 ft and above, Sabre is at disadvantage (all for non-turbo). In 1944, R-2800 lacks some 180 HP (cca 2200 vs. 2380) down low, but again it's better choice at higher altitudes. If there is one clear advantage Sabre has, that should be at streamlining, but the reliability was it's weak point.

My opinion is that if any UK engine was to be made in USA, that would be the Merlin, as it was case historically, Reversely, the R-2800 seem to be the only US engine for production in UK (but not that a necessary undertaking). Typhoon/Tempest with R-2800 just sounds right.