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Why are low-revving, high torque engines preferred?
On Thu, 27 Nov 2008 09:37:54 -0500, "Peter Dohm"
wrote: IIRC, snowmobiles are/were derived from chain saws--which required an engine light enough for a man to carry and use as a hand held tool. That made them an obvious choice for another application were light weight was the most critical factor--even at the cost of reliability and maintenance intervals... I've never heard that, seems unlikely... they are really very different, except for both (along with outboard motors) being 2-strokes. All for the same reason of light weight. -Dana -- If you glue a piece of toast, butter side up, to your cat's back, and drop it from a high place, which way will it land? |
#3
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Why are low-revving, high torque engines preferred?
"Peter Dohm" wrote IIRC, snowmobiles are/were derived from chain saws--which required an engine light enough for a man to carry and use as a hand held tool. That made them an obvious choice for another application were light weight was the most critical factor--even at the cost of reliability and maintenance intervals... Snow machines were survival, for people living WAY up north. Reliability was life and death, or could be. Lightness was also important, so the sled footprint could be smaller, and not sink too deep, and still haul more. Bombardier made snow machines (and engines) by the name of skii-doo. Only one more step to sea-doo, and to ultralight engines. -- Jim in NC |
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Why are low-revving, high torque engines preferred?
Merlin in 51 had a 2-1 gear reduction. 3000 rpm gave 1500 rpm prop
speed as I recall. Big John On Tue, 25 Nov 2008 19:29:06 -0800 (PST), wrote: On Nov 25, 7:47 pm, wrote: Lycoming has made several geared engines over the years and none has been particularly successfull. I believe the Merlin (or one of the big "V" engines) was also geared. Both the Merlin and Allison V-12s were geared. And most of the big radials were geared. It was one of the few ways to get more horsepower out of a given displacement. R-1830 radial cutaway, with gears in the front of the case: http://aviatechno.free.fr/vilgenis/i...830_02_730.jpg Merlin cutaway: http://www.thunderboats.org/history/...tory0324_1.jpg Common geared Lycs: GO-435 and GO-480. Continental had the GO-300 and GTSIO-520. Daimler Benz DB601a: http://www.aviation-history.com/engines/db601a-1.jpg Geared engines are nothing new at all. Dan |
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Why are low-revving, high torque engines preferred?
Tech Support wrote in message ... Merlin in 51 had a 2-1 gear reduction. 3000 rpm gave 1500 rpm prop speed as I recall. Many of the old big "V" and inline engines were 2:1, and were using the front end of a very strong camshaft as the prop drive, weren't they? -- Jim in NC |
#6
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Why are low-revving, high torque engines preferred?
Jim
Gear boxes had bearings designed to handle prop loads. Engine only saw torque and no thrust or side loads, etc. Only engine I can remember was either a Lyc or Con that drove prop off cam shaft. Was not very popular for some reason and only lasted a few years???? Someone with experience with those engines might want to chime in and comment. Big John ************************************************** On Thu, 27 Nov 2008 07:15:24 -0500, "Morgans" wrote: Tech Support wrote in message .. . Merlin in 51 had a 2-1 gear reduction. 3000 rpm gave 1500 rpm prop speed as I recall. Many of the old big "V" and inline engines were 2:1, and were using the front end of a very strong camshaft as the prop drive, weren't they? |
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Why are low-revving, high torque engines preferred?
Morgans a écrit :
Many of the old big "V" and inline engines were 2:1, and were using the front end of a very strong camshaft as the prop drive, weren't they? Rolls Royce and Allison V engines were (are) overhead camshafts. The prop reduction gear was driven from the nose of the crankshaft. According to Rolls Royce, the Merlin XX drive ratio was 0.42. Best regards, -- Gilles http://contrails.free.fr |
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