WW2 without V-1710: options for the Allies?

In terms of "what if", without the Allison there would have been no P-40 as we know it. The British want NA to build P-40s but were talked into an "improved" version, i.e. the P-51. But even for the initial P-51 there was no question –or option- other than the Allison.
Asking what would have transpired without the Allison is a bit like asking what intelligent life would look like if the dinosaurs hadn't been rendered extinct.

My error. According to Wikipedia, the V-1710 was first run in 1930, which is not the same as flown, but:

"The USAAC purchased its first V-1710 in December 1932. The Great Depression slowed development, and it was not until December 14, 1936 that the engine next flew in the Consolidated XA-11A testbed. The V-1710-C6 successfully completed the USAAC 150 hour Type Test on April 23, 1937 at 1,000 hp (750 kW), the first engine of any type to do so." (Wikipedia: Allison V-1710)

This implies that it flew at some point earlier. Not that it really matters from a practical point of view.

Your argument explains a lot. I had assumed that the lack of alternative engines was due to the Army's fixation with hyper-engines, but your explanation clarifies that if the Army wasn't buying aircraft, there wasn't a market for in-line water-cooled engines, so no one was building them.

ohogain said:

The emphasis on the hyper engine by the US Army greatly hampered the development of water-cooled in-line aircraft engines, in my opinion. The Army began working on the development of hyper-engines in 1932, the same year that they cut the funding of the Curtiss V-1570. The Allison V-1710, which flew in 1930, before the Army switched to researching hyper-engines, was the last US design of water-cooled in-line engine prior to WW2.

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Not to sound silly, but perhaps the Army should have/could have better supported Allison and pursued the hyper-supercharger.
I suppose in a way they did - the turbocharger.
Still, with more support, a "better" supercharger could have been developed for the V-1710.

gjs238 said:

Not to sound silly, but perhaps the Army should have/could have better supported Allison and pursued the hyper-supercharger.
I suppose in a way they did - the turbocharger.
Still, with more support, a "better" supercharger could have been developed for the V-1710.

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At the start Allison was using supercharger impellers from General Electric, who also made the turbos. This was also the case for Wright and Pratt Whitney. Each of them eventually took supercharger design in-house and were able to make significant improvements thereafter.

I think we have been over this one a few times too.

During the 30s you had kind of a chicken and egg thing going on. In the early 30s you had 80 octane fuel and it just won't take much supercharging. Even 87 octane is only good for about 4-6lbs boost in most engines. Please remember that it is not only the boost but the rise in temperature due to the boosting that causes detonation ( along with some other things). Until you had better fuel you couldn't use a high pressure supercharger and since the superchargers that were available could provide all the boost required (or allowed) by the fuels being used there wasn't much research being done on improving them.
In the US this was compounded by General Electric having almost a monopoly on supercharger design. Wright, P W and Packard actually had small design staffs in the 1920s and early 30s and rather than spend time working on superchargers they ALL went to GE and bought not only supercharger designs but supercharger parts (like impellers) if not entire superchargers. I am talking about mechanical superchargers not turbos. Even some Auto racers ( Like Henry Miller) went to GE for advice on car superchargers. So basically you had one supercharger design team in the entire United States and they had a few things wrong with their basic design. Nobody knew it because of the lousy fuel.
By 1937-38 87 octane was common, 91 octane was coming on the scene in America and 100 octane was being used in experiential batches and for record setting. With both Wright and P&W competing on the world scene and having larger design staffs than they had in the late 20s and early 30s they both realized that the GE superchargers left something to be desired and started designing their own. Accounts differ about Wright with either the R-2600 or the R-1800 G-200 series engines being the first to use a Wright designed supercharger (Kenneth Campbell). P W might have been a little faster on the draw but not by much. P W then got into the 2 stage supercharger business.
Allison may have designed their supercharger in house but Allison during the 30s did a lot of sub-contract work for GE making supercharger parts (like impellers) as they sure weren't making any money selling engines until 1939.
The US learned a lot about superchargers and centrifugal compressors during WW II but it took awhile. The Supercharger on a Wright R-2600-8 as used in a Grumman Avenger only supplied about 7 to 7.5lbs of manifold pressure at 12,000ft compared to the 6-6.25lbs the Merlin III supercharger (Pre Hooker) would provide at 16,250ft.

You can have the "idea" of a two stage supercharger. Getting it to work is the big problem. Allison tried to go cheap on the first go round and use identical diameter impellers.

GregP said:

Good luck!

When we tried something as simple as getting some prop pitch specs for a WWII 6-bladed club propeller from Hamilton Standard, we were told "These data were produced for and at the request of the US Army Air Force. Since you are not the USAAF, the data will not be transmitted in any fashion to you. They are the property of the USAAF.".

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Sometimes the "logic" used by others just scares the hell out of me.