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#2
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Air cooled two stroke as inboard?
Bruce In Bangkok wrote:
On Mon, 24 Aug 2009 12:01:01 -0400, JustWait wrote: In article , says... On Sat, 22 Aug 2009 10:36:47 -0400, wrote: On Sat, 22 Aug 2009 09:32:43 -0400, "mmc" wrote: "Andrew Erickson" wrote in message ... In article , wrote: On Fri, 21 Aug 2009 11:16:09 -0400, Andrew Erickson wrote: In article , wrote: On Thu, 20 Aug 2009 20:21:25 -0700 (PDT), Robin wrote: I had a brainwave the other day about putting a small (300cc) aircooled two stroke as an inboard in a small wooden boat. With adequate air circulation can anyone see any potential issues here? I would build the boat with this purpose in mind so adapting something to fit would not be a problem. Robin How are you going to cool it adequately? I would assume, for an air-cooled engine, that's where the "adequate air circulation" comes in to play. One would probably have to be a bit careful not to push the engine too hard too long, as well, since many applications for these engines are not at steady high output. (There are exceptions--ultralight aircraft engines for one example.) I don't see any inherent insurmountable objections to doing this. A speed reduction of some sort would be nearly essential, of course, or else using a jet drive. Small two stroke engines in general tend to be inefficient and noisy and smelly and a bit temperamental, although the newer ones are vastly improved over older designs. On the other hand, they are lightweight and generally unaffected by being off level (limited mostly by the particular carburetor design), which can be advantages for use in a small boat. It's not as though there aren't a great many jet skis and boats with older outboards zipping around just fine with two stroke engines every day. Granted, most of these are water cooled, but still... There is a world of difference between a water cooled two-stroke, and an aircooled two-stroke, especially in a confined space. When I ask about cooling, it's because there will be a need for BIG fans to make this work. Air cooled motorcycles tend to overheat sitting in traffic. They need to keep moving to maintain reasonable temps. "Police Special" Harleys have a detuned and lower compression engine for this reason. Just being outside in open air is not enough. Put an engine like that as an inboard on a boat and you are in for trouble. It really needs to be addressed. I'm not sure it can be done practically. Snowmobile engines traditionally were air cooled two stroke engines (although more recently four stroke engines and liquid cooling have become common), and generally inside cowlings, and they generally manage to avoid overheating just fine. Likewise, chainsaw engines don't tend to overheat all the time, despite often being run rather hard. It's a question of the specific engine design (presumably based on the intended application), not a problem common to all two strokes. You are quite correct, though, that the original poster (should they attempt the conversion) should give some careful consideration to cooling. I don't think the end result would ever be an ideal boat motor, but I also think it could be perfectly adequate and probably a lot of fun if you're into that sort of thing. -- Andrew Erickson "He is no fool who gives what he cannot keep to gain that which he cannot lose." -- Jim Elliot Some small outboards were/are air cooled as well like the Sears Game Fishers, I think up to 5hp. Not even remotely the same thing as mounting an air cooled engine as an inboard. Err - the Honda 2 H.P. is an air cooled engine. Apparently has no problems with its cooling system. I had, and several friends presently have, air cooled 2-stroke, portable generators. Millions of lawn mowers are air cooled. I could go on but why bother. the O.P. already mentioned that he could foresee the problem of adequate air supply. What in the world is going to be a problem? Cheers, Bruce (bruceinbangkokatgmaildotcom) Man, if I were ever camped next to someone with a 2 smoke genset, they better also have a good supply of ammunition Why? The little 1 KW (actually 900-something watts) 2 stroke units, made in India by the way, run as quite as a 4-stroke. Not all 2-strokes have tunes exhaust. Uhm, Bruce, that turns out not to be the case. Think of the exhaust pipe as part of the intake system. These India units may be quieter than others, but the pipe is still tuned. I promise. Cheers, Bruce (bruceinbangkokatgmaildotcom) |
#3
posted to rec.boats.building
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Air cooled two stroke as inboard?
On Mon, 24 Aug 2009 19:44:45 -0500, cavelamb
wrote: snipped... Why? The little 1 KW (actually 900-something watts) 2 stroke units, made in India by the way, run as quite as a 4-stroke. Not all 2-strokes have tunes exhaust. Uhm, Bruce, that turns out not to be the case. Think of the exhaust pipe as part of the intake system. These India units may be quieter than others, but the pipe is still tuned. I promise. Nope, it isn't. I know because mine rusted out the exhaust and I took it off to have a look at making a new one. Someone stole it before I could make the new one but it certainly did not have a tuned exhaust In fact it was the spitting image of a Honda 4-stroke muffler. Two strokes don't NEED a tuned exhaust and they didn't have them for years and years. Have a look at a Famous James motorcycle, or the early Jawa's, or even the Harley Davidson two stroke from the late 1940's. Or model airplane engines, for that matter. Cheers, Bruce (bruceinbangkokatgmaildotcom) |
#4
posted to rec.boats.building
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Air cooled two stroke as inboard?
On Tue, 25 Aug 2009 07:00:46 +0700, Bruce In Bangkok
wrote: On Mon, 24 Aug 2009 12:01:01 -0400, JustWait wrote: In article , says... On Sat, 22 Aug 2009 10:36:47 -0400, wrote: On Sat, 22 Aug 2009 09:32:43 -0400, "mmc" wrote: "Andrew Erickson" wrote in message ... In article , wrote: On Fri, 21 Aug 2009 11:16:09 -0400, Andrew Erickson wrote: In article , wrote: On Thu, 20 Aug 2009 20:21:25 -0700 (PDT), Robin wrote: I had a brainwave the other day about putting a small (300cc) aircooled two stroke as an inboard in a small wooden boat. With adequate air circulation can anyone see any potential issues here? I would build the boat with this purpose in mind so adapting something to fit would not be a problem. Robin How are you going to cool it adequately? I would assume, for an air-cooled engine, that's where the "adequate air circulation" comes in to play. One would probably have to be a bit careful not to push the engine too hard too long, as well, since many applications for these engines are not at steady high output. (There are exceptions--ultralight aircraft engines for one example.) I don't see any inherent insurmountable objections to doing this. A speed reduction of some sort would be nearly essential, of course, or else using a jet drive. Small two stroke engines in general tend to be inefficient and noisy and smelly and a bit temperamental, although the newer ones are vastly improved over older designs. On the other hand, they are lightweight and generally unaffected by being off level (limited mostly by the particular carburetor design), which can be advantages for use in a small boat. It's not as though there aren't a great many jet skis and boats with older outboards zipping around just fine with two stroke engines every day. Granted, most of these are water cooled, but still... There is a world of difference between a water cooled two-stroke, and an aircooled two-stroke, especially in a confined space. When I ask about cooling, it's because there will be a need for BIG fans to make this work. Air cooled motorcycles tend to overheat sitting in traffic. They need to keep moving to maintain reasonable temps. "Police Special" Harleys have a detuned and lower compression engine for this reason. Just being outside in open air is not enough. Put an engine like that as an inboard on a boat and you are in for trouble. It really needs to be addressed. I'm not sure it can be done practically. Snowmobile engines traditionally were air cooled two stroke engines (although more recently four stroke engines and liquid cooling have become common), and generally inside cowlings, and they generally manage to avoid overheating just fine. Likewise, chainsaw engines don't tend to overheat all the time, despite often being run rather hard. It's a question of the specific engine design (presumably based on the intended application), not a problem common to all two strokes. You are quite correct, though, that the original poster (should they attempt the conversion) should give some careful consideration to cooling. I don't think the end result would ever be an ideal boat motor, but I also think it could be perfectly adequate and probably a lot of fun if you're into that sort of thing. -- Andrew Erickson "He is no fool who gives what he cannot keep to gain that which he cannot lose." -- Jim Elliot Some small outboards were/are air cooled as well like the Sears Game Fishers, I think up to 5hp. Not even remotely the same thing as mounting an air cooled engine as an inboard. Err - the Honda 2 H.P. is an air cooled engine. Apparently has no problems with its cooling system. I had, and several friends presently have, air cooled 2-stroke, portable generators. Millions of lawn mowers are air cooled. I could go on but why bother. the O.P. already mentioned that he could foresee the problem of adequate air supply. What in the world is going to be a problem? Cheers, Bruce (bruceinbangkokatgmaildotcom) Man, if I were ever camped next to someone with a 2 smoke genset, they better also have a good supply of ammunition Why? The little 1 KW (actually 900-something watts) 2 stroke units, made in India by the way, run as quite as a 4-stroke. Not all 2-strokes have tunes exhaust. Cheers, Bruce (bruceinbangkokatgmaildotcom) Correction: run as quiet as... Cheers, Bruce (bruceinbangkokatgmaildotcom) |
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