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Corvair conversion engines
clare at snyder.on.ca wrote in message ... On Sat, 4 Feb 2006 21:00:11 -0500, "Peter Dohm" wrote: The fact that it ran with a governor means that it was not at full HP. It is admirable for it to run that many RPM's for that many hours, but still, there is no indication of how long it would run at true Wide Open Throttle, making all the HP it could. I suspect its life would have not been as long, if it were loaded to it's maximum output. -- Jim in NC I agree with your basic point. And also feel compelled to add that there is probably no way for anyone to know how much power the VW engine produced in the harvesting application--unless they metered torque, which would not be reasonable. My supposition, just from reading the post, is that at least half of the total fuel burned was applicable to pumping losses rather from the work done. However, also have problems with the wide open throttle scenario. I also suspect that if we were to discuss the issue at length, we would find that we are completely in agreement; but that we insist on using different "phraseology." We really don't operate our Lycomings and Continentals at their sea level maximum output very much of the time. My best guess is that, flying with a fixed pitch prop on a standard day, we can achieve nearly 90 percent just off the runway and that drops gradually to less about 75 percent by around 3000 feet msl. (My recollection on exactly were this occurs is less than perfect as I have not flown in a long time) And 75 percent, on the aircraft engines with which I am familiar, ranges from about a low of about 0.355 to 0.357 HP per cubic inch of the low compression Lycoming O-235 engines through 0.375 HP per cubic inch for the Continental O-200 and their new O-240 FADEC engine, as well as Lycomings 160 HP O-326 and 180 HP O-360 engines, up to 0.420 HP per cubic inch on the 200 HP angle valve Lycoming O-360. Those are all engines that really were designed to run that way, for which the cooling intake and baffling requirements are well documented, and even so many had "teething" problems which were solved long ago. If we apply the same specific power output to a pure stock 1600cc VW as to the smallest Lycomings, 75 percent power should equal 34 HP; which would result in a theoretical 45 HP engine with a take-off rating that could be as high as 60 HP, although 55 HP is more likely--based on a 52 inch diameter prop turning about 3600 RPM. The slightly more agressive specific output of the O-200 would give the 1600cc VW a rating of 48 HP which would equate to a 75 percent level of 36 HP. My point in all this is that a relatively slippery aircraft fitted with a climb prop, to conform to the ancient formula of 0.2 G static thrust measured with a fish scale, should fly safely with an auto conversion. I remain a fan of auto conversions, but my advocacy has its limits. Peter On the old Klaus combine the VW was rated at 40 HP. Actually, that is on the later model units. The early ones were 35. (talking 1200cc). The 1600 engine was rated at 60, IIRC. That really does put a little different light on the matter. IIRC, the 40 HP (1200 cc) VW developed it's full power at 3600 rpm, and the VW racers in SCCA placed the red line on their tachs at 4500, although no beetle could hope to maintain 3600 rpm in top gear. OTOH, I believe that Ken Rand claimed that the prototype KR-1 could wind up to around 4000 rpm. I believe that the "dual port" 1600 cc engines were rated at 65 HP at 4000 rpm. IIRC, they were used in the Super Beetles, Type-3s, and some of the transporters. However, my recollection agrees with yours that the 1600 cc engine used in a lot of the normal Beetles had siamesed intake ports (like the 1200, 1300, and 1500 cc engines) and were rated at 60 HP; but I don't know at what rpm. None of this really is any dispute regarding the often quoted thermal limit in aircraft, since the method of cooling is so different. The centrifugal cooling fan used by VW was/is a *very* high pressure type! Peter |
#2
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Corvair conversion engines
On Tue, 7 Feb 2006 19:41:25 -0500, "Peter Dohm"
wrote: clare at snyder.on.ca wrote in message .. . On Sat, 4 Feb 2006 21:00:11 -0500, "Peter Dohm" wrote: The fact that it ran with a governor means that it was not at full HP. It is admirable for it to run that many RPM's for that many hours, but still, there is no indication of how long it would run at true Wide Open Throttle, making all the HP it could. I suspect its life would have not been as long, if it were loaded to it's maximum output. -- Jim in NC I agree with your basic point. And also feel compelled to add that there is probably no way for anyone to know how much power the VW engine produced in the harvesting application--unless they metered torque, which would not be reasonable. My supposition, just from reading the post, is that at least half of the total fuel burned was applicable to pumping losses rather from the work done. However, also have problems with the wide open throttle scenario. I also suspect that if we were to discuss the issue at length, we would find that we are completely in agreement; but that we insist on using different "phraseology." We really don't operate our Lycomings and Continentals at their sea level maximum output very much of the time. My best guess is that, flying with a fixed pitch prop on a standard day, we can achieve nearly 90 percent just off the runway and that drops gradually to less about 75 percent by around 3000 feet msl. (My recollection on exactly were this occurs is less than perfect as I have not flown in a long time) And 75 percent, on the aircraft engines with which I am familiar, ranges from about a low of about 0.355 to 0.357 HP per cubic inch of the low compression Lycoming O-235 engines through 0.375 HP per cubic inch for the Continental O-200 and their new O-240 FADEC engine, as well as Lycomings 160 HP O-326 and 180 HP O-360 engines, up to 0.420 HP per cubic inch on the 200 HP angle valve Lycoming O-360. Those are all engines that really were designed to run that way, for which the cooling intake and baffling requirements are well documented, and even so many had "teething" problems which were solved long ago. If we apply the same specific power output to a pure stock 1600cc VW as to the smallest Lycomings, 75 percent power should equal 34 HP; which would result in a theoretical 45 HP engine with a take-off rating that could be as high as 60 HP, although 55 HP is more likely--based on a 52 inch diameter prop turning about 3600 RPM. The slightly more agressive specific output of the O-200 would give the 1600cc VW a rating of 48 HP which would equate to a 75 percent level of 36 HP. My point in all this is that a relatively slippery aircraft fitted with a climb prop, to conform to the ancient formula of 0.2 G static thrust measured with a fish scale, should fly safely with an auto conversion. I remain a fan of auto conversions, but my advocacy has its limits. Peter On the old Klaus combine the VW was rated at 40 HP. Actually, that is on the later model units. The early ones were 35. (talking 1200cc). The 1600 engine was rated at 60, IIRC. That really does put a little different light on the matter. IIRC, the 40 HP (1200 cc) VW developed it's full power at 3600 rpm, and the VW racers in SCCA placed the red line on their tachs at 4500, although no beetle could hope to maintain 3600 rpm in top gear. OTOH, I believe that Ken Rand claimed that the prototype KR-1 could wind up to around 4000 rpm. I believe that the "dual port" 1600 cc engines were rated at 65 HP at 4000 rpm. IIRC, they were used in the Super Beetles, Type-3s, and some of the transporters. However, my recollection agrees with yours that the 1600 cc engine used in a lot of the normal Beetles had siamesed intake ports (like the 1200, 1300, and 1500 cc engines) and were rated at 60 HP; but I don't know at what rpm. None of this really is any dispute regarding the often quoted thermal limit in aircraft, since the method of cooling is so different. The centrifugal cooling fan used by VW was/is a *very* high pressure type! Peter In industrial use they were generally rated at 3600 RPM, and if run at that speed required head jobs every 1000 hours or so. Often much sooner than that, particularly if #3 cyl did not have the valve clearance significantly increased (set cold). Air flow to #3 was significantly impaired by the oil cooler. In many apps they were governed to 2800 RPM, which detuned them. On the combines, keeping the chaff out of the head fins was no trivial accomplishment. As for cooling in an aircraft application, with a "pressure cowl" the engine got better cooling than with the "box fan" provided by Wolfsburg on the beetle. The "hang 'em out" style, cub style, was just about as good as the beetle. |
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