kool kitty89
Senior Master Sergeant
Rolls also focused on refining their single-stage developments before seriously moving on to 2-stage and intercooler design was a seriously important innovation for the latter as well. (and would have been relevant for continued development of larger single stage units too -intercooling/aftercooling applied to the impeller used on the high alt Merlin 46 might have been significant, that and using 2-speed gearing) Water injection would be the other alternative for charge cooling and anti-detonation, but that comes with a different set of technical difficulties than intercooler design and may not have been any better/available sooner.
Allison had aux stage supercharger proposals on the drawing board not far from P&W but lacked funding to pursue them. (I suggested seeking navy interest may have been more useful) The hydraulic linkage also would have allowed more options for placement of the aux stage, including keeping engine length down and the accessories drive more open by side-mounting like DB and Jumo did. The eventual rear mounted aux stage ended up problematic due to increased length and I'm unsure why that orientation was chosen. (side mounting should have allowed more immediate conversion onto the P-40, P-39, and P-51 and more heavily marginalize both the XP-76 and P-63, and likely make for better ram performance than the ventral intake on the P-39/76/63)
I'm not sure why the 2-speed supercharger arrangement wasn't adopted for mass production either, it used an improved impeller design for performance better than the later 9.6:1 single speed units. (it came up in another thread too, but it even seemed like that same impeller would also have been superior in a single speed arrangement to the existing production version -more directly competitive with the Merlin 45)
