enginehistory.org

[drogell]

On page 272 of "Vees for Victory", Dan Whitney in his authoritative book on the Allison engine states, "this engine (F24R) would have used a newly designed integral two stage supercharger". That choice of words makes the F24 supercharger sound like a Merlin 60 series 'blower'.

Does any further information on the unbuilt Allison V-1710 F24 design survive???

I would be interesting to know how this supercharger would have been arranged. Were the two stages on a single shaft? Or were the stages on different shafts with different step-up gears? Fixed gear ratios or continuously variable hydraulic coupling?? What carburetor would have been used??

[dwhitney]

Unfortunately I have no additional source data on the V-1710-F24R.
What we have is that this was a 1942 era project, concurrent with development of the V-1710-45(F7R), a two-stage engine using an Auxiliary Stage Supercharger.
Allison listed it in an index of engine specifications, yet there is no associated specification in the files.
We can assume that it was configured as a Merlin 60, single shaft, two-speed. Allison did develop a gear driven two-speed supercharger, without a hydraulic drive. This was featured in the V-1710-G2, G3 and G4 models for commercial airliners.
The comprehensive Bendix index to carburetor models does not mention the F24. This says that the project did not get very far along. In 1942 Allison was dealing with production issues as they increased the rate of delivery, as well as engineering and developing the hydraulically driven two-stage. It is likely that they simply did not have the resources to divert to the development of the integral 2-stage supercharger.
Dan Whitney

[drogell]

Thanks Dan.
It is unfortunate that nothing else related to this project has survived.

I assume that the primary driver to build the F24 variant was to provide a two stage engine for an existing airframe into which the auxiliary stage arrangement would not fit, such as the P-51 / P-51A / Mustang I.

Am I correct in that, if balance was to be maintained, that trying to fit an Allison with the auxiliary stage supercharger into the 'original' Mustang would run into some major structure??? Moving the engine with the aux. blower forward far enough to clear that obstruction was out of the question due to center of gravity / balance issues. Or was ther another reason there wasn't a P-51 with a two stage Allison before the totally redesigned XP-51J.

[dwhitney]

Given the date of the -F24, Late 1942, I would concur that it was likely an effort to keep the V-1710 in the high altitude P-51 models. Not everyone appreciates that the 2-Stage Merlin was really a 1943 project.
The reason for not putting the V-1710 with Aux Stage Allison in the wartime P-51s was its length, 9 inches longer than the 2-Stage Merlin alternative. The airframe would have had to be modified, the firewall moved back. When NAA completely redesigned the Mustang into the "Light Weight" Mustang they were able to accommodate the Aux Stage V-1710, see the XP-51J.
Dan

[rfinnerty]

Dan,

I have your excellent V-12 book. I am slowly compiling lists of U.S. Army and Navy aircraft engine serial numbers. Do you have more serials that you would be willing to share? Thank you.

Roger