Re: Griffons and Allisons
From everything I've ever read (much of which has been right here and on the other forum), the biggest problem with the Allison is the blower. Race power comes from boost, and Merlins can make far more boost than the Allison. As built, most Allison 1710s had a low-boost single-speed single-stage supercharger since the high-altitude aircraft that used it were intended to be turbocharged, with the turbo force-feeding the blower and doing most of the work at altitude (P-38). The fact that enough turbos weren't available for all the Allison aircraft types was a real problem, and seriously hurt the use of the Aircobra, Kingcobra, and P-40. The Merlin was never turbocharged, instead it had a far more advanced 2-speed 2-stage (in the applications we're all familiar with) mechanical blower. A real work of art capable of rod-bending boost levels. The weak spot for racing in the Merlin is the rods, and grafting Allison rods into it has been an effective solution (WAAAAYYY easier said than done, by the way).
Basically, the whole engine revolves around the blower, and its easier to stick selected Allison innards into a Merlin than it would be to put a Merlin-class blower on an Allison.
Griffon- its BOTH the prop and blower that are a problem for racing. The common Griffon is the Shackleton version which has a low-boost blower and the contra-prop with relatively blade primitive airfoils. Shackletons were made for low-altitude patrolling- no need for high boost or for advanced props. The higher-boost blower and single-prop gearcase for a Griffon are unspeakably rare since so few fighters were built with Griffon power. And even with the single prop, your choices are limited since the dang thing turns the "wrong" way. Is there much choice besides the 5-blade Rotol???
From everything I've ever read (much of which has been right here and on the other forum), the biggest problem with the Allison is the blower. Race power comes from boost, and Merlins can make far more boost than the Allison. As built, most Allison 1710s had a low-boost single-speed single-stage supercharger since the high-altitude aircraft that used it were intended to be turbocharged, with the turbo force-feeding the blower and doing most of the work at altitude (P-38). The fact that enough turbos weren't available for all the Allison aircraft types was a real problem, and seriously hurt the use of the Aircobra, Kingcobra, and P-40. The Merlin was never turbocharged, instead it had a far more advanced 2-speed 2-stage (in the applications we're all familiar with) mechanical blower. A real work of art capable of rod-bending boost levels. The weak spot for racing in the Merlin is the rods, and grafting Allison rods into it has been an effective solution (WAAAAYYY easier said than done, by the way).
Basically, the whole engine revolves around the blower, and its easier to stick selected Allison innards into a Merlin than it would be to put a Merlin-class blower on an Allison.
Griffon- its BOTH the prop and blower that are a problem for racing. The common Griffon is the Shackleton version which has a low-boost blower and the contra-prop with relatively blade primitive airfoils. Shackletons were made for low-altitude patrolling- no need for high boost or for advanced props. The higher-boost blower and single-prop gearcase for a Griffon are unspeakably rare since so few fighters were built with Griffon power. And even with the single prop, your choices are limited since the dang thing turns the "wrong" way. Is there much choice besides the 5-blade Rotol???
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