Liberty L-12 vs Allison V-1710

Shortround6 · Feb 1, 2010

Colin1 said:
I don't know why Allison settled on a standardised power section, apart from the fact that it would service all marks of the powerplant with a single production line. This made good business sense in one respect but had the unfortunate effect of hamstringing the Allison (and by extension, the P-40) in future development, technology and events rapidly overtook both.

You have it in a nutshell, "good business sense".

At that point with around 20 engines delivered and only another dozen or so on order (depending on the month) Allison was trying to develop a pusher engines with a 5ft shaft for the Bell Aircuda, The tractor engine with 10ft extension shaft for the P-39, the tractor engines (handed) with turbos for the P-38 and a side by side twin engine the V3420 in addtion to the normal tractor engine for the P-40.

At least FIVE different versions of the same basic engine in quantities of less than a couple of dozen for the most popular one (at this time the Aircuda pusher engine) to have tried to build more specialized engines for each application didn't make economic sense.

What is strange is that Allison never fitted a simple two speed drive supercharger to their engine. At least at this time period.

davebender · Feb 1, 2010

development lead times of 4 years for the Merlin vs around 10 years for a V-1710 that was still having problems.

The Manhattan Project began during December 1941. By July 1945 they had a working atomic bomb. Less then 4 years.

I am confident the Allison V-1710 engine could have a decent supercharger installation by 1941. Probably fuel injection also. The U.S. Army Air Corps just need to throw some resources behind the project.

Colin1 · Feb 2, 2010

davebender said:
The Manhattan Project began during December 1941. By July 1945 they had a working atomic bomb. Less then 4 years

It's not much of an analog, I'm pretty certain the atomic bomb wasn't

i. company funded and
ii. a little bit lost among competition for other types of really loud bomb

Shortround6 · Feb 2, 2010

Colin1 said:
It's not much of an analog, I'm pretty certain the atomic bomb wasn't

i. company funded and
ii. a little bit lost among competition for other types of really loud bomb

Might have been a few more nuclear physicists around than supercharger experts.

With only one company in the US designing aircraft superchargers (until the late 30s) there wasn't much of a supply of supercharger engineers and with only one company doing the work, there wasn't much demand, not a good career choice

davebender · Feb 2, 2010

a few more nuclear physicists around than supercharger experts

I doubt that.

Gottlieb Daimler patented the first automotive supercharger in 1885. Louis Renault patented his own supercharger design in 1902. In the USA a supercharged race car reached 100 mph during 1908. By 1930 automotive superchargers were a mature technology. An entire generation of automotive engineers have known about superchargers since the day they graduated from college.

On the other hand....
By 1942 nuclear physics was still purely theoretical. Nothing useful had been produced and nobody knew if anything useful would ever be produced. The Manhattan Project scientists were groping in the dark. Just like German scientists working on jet engines and 24 cylinder piston engines.

There are plenty of excuses why the Allison V-1710 did not have a better supercharger but no good ones. The U.S. Army Air Corps leadership dropped the ball.

Milosh · Feb 2, 2010

davebender said:
The Manhattan Project began during December 1941. By July 1945 they had a working atomic bomb. Less then 4 years.

Manhattan Project
Born out of a small research program in 1939, the Manhattan Project eventually employed more than 130,000 people and cost nearly US$2 billion ($22 billion in current value). It resulted in the creation of multiple production and research sites that operated in secret.[2]

Project research took place at over thirty sites across the United States, Canada, and the United Kingdom.

Colin1 · Feb 2, 2010

Milosh said:
...the Manhattan Project eventually employed more than 130,000 people and cost nearly US$2 billion

Yup
that would get you a seriously supercharged V12...

Markus · Feb 2, 2010

davebender said:
I agree.

The problem is the U.S. Army Air Corps was willing to settle for a sub standard (compared to Britain and Germany) supercharger installation. If the U.S. Army Air Corps had insisted on a better supercharger "or else we will purchase RR Merlins from Britain" then it would have happened.

The V-1710´s internal supercharger was not sub-standard, at least not in 1939/40. Merlins had a similar critical altitude and the USAAC was thinking they already had the better supercharger, the exhaust powered turbo supercharger. Therefor things like improved mechanical superchargers were considered not necessary and the Air Corps actually advised Allison to stop developing altitude rated engines. Fortunately Allison did not listen.

Colin1 · Feb 2, 2010

Markus said:
Therefore things like improved mechanical superchargers were considered not necessary and the Air Corps actually advised Allison to stop developing altitude rated engines. Fortunately Allison did not listen.

Can you insert some time line in here?
If Allison 'did not listen', where were all of these altitude-rated Allison engines for the majority of WWII?

Shortround6 · Feb 2, 2010

davebender said:
I doubt that.

Gottlieb Daimler patented the first automotive supercharger in 1885. Louis Renault patented his own supercharger design in 1902. In the USA a supercharged race car reached 100 mph during 1908. By 1930 automotive superchargers were a mature technology. An entire generation of automotive engineers have known about superchargers since the day they graduated from college.

Yup, 5 different type types of superchargers used, and, for the most part, none of them operated at the pressure levels needed for aircraft superchargers. The Piston and vane types were pretty much useless for aircraft and the Roots much wasn't much better in spite of a fair amount of testing in the 1920s. Leaves the centrifugal and the axial and the latter didn't find much favor for fitting to piston engines either.

Knowing about (or even working a couple of problems in a college text book) and being able to design one aren't quite the same thing. Let alone make a living at designing them.

By the way, patents for gas turbine engines existed before WW I, as did experimental working (just not very well) hardware. Granted they were for ship propulsion or stationary power plants but hey, most engineering students had heard of them. Wonder why jets and turbo props were so hard to develop?
Just throw a few million on the ground in 1938 and we should have had jets in squadron service in 1942, right?

another example of short sightedness by the AAF

davebender said:
On the other hand....
By 1942 nuclear physics was still purely theoretical. Nothing useful had been produced and nobody knew if anything useful would ever be produced. The Manhattan Project scientists were groping in the dark. Just like German scientists working on jet engines and 24 cylinder piston engines.

German scientists working on jet engines and 24 cylinder piston engines shouldn't have been working in the dark. See above for gas turbine patents and 24 cylinder engines had been built and flown in the 20s.

Another by the way, Grand Prix Mercedes race cars had used two stage superchargers in 1938-39. I wonder why they couldn't use them on airplanes?

Colin1 · Feb 2, 2010

Shortround6 said:
German scientists working on jet engines and 24 cylinder piston engines shouldn't have been working in the dark. See above for gas turbine patents and 24 cylinder engines had been built and flown in the 20s

Oh they weren't
Whittle had a patent for his design in 1930
von Hain followed in either 1935 or 36 although his project got off the ground first

Shortround6 · Feb 2, 2010

Colin1 said:
Can you insert some time line in here?
If Allison 'did not listen', where were all of these altitude-rated Allison engines for the majority of WWII?

Altitude rated often meant a critical altitude of around 10,000ft or better as opposed to a sea level or low level rated engine.

A sea level supercharged engine could use a smaller supercharger giving much less boost than an "altitude" rated engine. This also meant the supercharger was taking much less power to drive it. The difference was that the altitude rated engine had a different net HP to gross HP ratio (poorer) and was economical and may have had a poorer power to weight ratio. At least if comparing sea level or take-off power ratings.

The P&W 1830 and some Wright R-1820 engines might be examples of sea level or low rated engines. Since airliners were not expected to fly at altitudes much over 8,000ft the single speed supercharger versions of these engines were usually set up to have a critical altitude of 4,000-7,000ft.

Markus · Feb 3, 2010

Colin1 said:
Can you insert some time line in here?
If Allison 'did not listen', where were all of these altitude-rated Allison engines for the majority of WWII?

Sure, Allison offered the USAAC altitude rated engines starting with the C-11 in Sept. 1937 but the Air Corps did not buy some until 524 P-40s were ordered in April 39. But a few months earlier the Air Corps showed no interest in the proposed aux. stage supercharger.

I´m guessing they accepted the altitude rated engines just because of the brewing crisis in Europe and expected the turbocharger to be perfected soon.

Liberty L-12 vs Allison V-1710

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