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#51
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Corvair conversion engines - cracked crank link
Rich S. wrote:
"Peter Dohm" wrote in message ... Yes. I know that they do, and new design engines are notorious; as are design improvements, changes of supplier, etc. And they include plenty of reasons for loss of power not caused by the crankshaft! However, my concerns include, reliability, maintainability, and eventual replacement; and I think you understand my point. At this point, the Jabiru 3300 is the only engine that really looks to me like a promising replacement; and I really don't know its service record. However, albeit at a higher dollar price, its features seem to preserve: 1) similar or lighter weight, 2) similar or higher power, 3) six cylinder smoothness, 4) reasonably slow idle, and 5) similar dimmensions. Additional benefits are designed in dual ignition and an updraft intake system, similar to Lycoming and Continental, which should be more resistant to ice. Peter.......... Since you answered seriously, I will too. I can agree on the higher price and on #1-3 and #5. I don't understand #4 - do Corvairs idle unreasonably high? The dual ignition is good if the Jabiru 3300 truly has two stand-alone systems. The intake direction is irrelevant if the Corvair is fuel-injected or has a heated intake manifold. Updraft carbs are a lot better at preventing fire as well. The small Continentals will ice up if you look at them cross-eyed even with updraft intake. Rich S. The Lycoming approach, with the intake manifolds passing through the oil sump are less inclined to ice up. I'm sure they can be provoked, though. As for the Corvair's idle? I plain dunno. I have never seen a Corvair on an airplane - in person. ANd that kinda is the point here. The mounted pics I have seen are on a Pietenpol Air Camper, which needs the weight on the nose. On most other planes that's considered a Bad Thing (tm). On small short coupled airplanes, it might qualify as a Very Bad Thing (tm), which is obviously much worse. Now, I've only *seen* the Jabaru on a plane. Haven't flown one myself. But it does look like an engine of fine merit. Light and simple are high on my short list. Cost is there too, of course, but it has to take a place in line with the rest of the conflicting requirements. The Rotax 912 (which I have flown) is a really sweet set-up. There is the extra complication (and weight) of the liquid cooled heads. But it's probably not that big a deal on any two-seater. From what I've heard, the Jabaru/912 power ratings remind me of the old Continental A-65/Lycoming 145 days. Both were rated at 65 hp, but the Continental horses seem a little longer legged. I'd rank most VW power estimates as Shetland ponies... I suspect that most people expect a VW to put out like a Rotax, but it just doesn't work that way. In the end the final choice will depend on the airframe and the mission. On the Corvair question... As I said earlier the Great Plains crank on my 2180 i.e. a way massive hunk of pure confidence. Just the way an A-65 crank compares to other small 4 banger non-flying counterparts. So, why can't someone turn out a new Corvair crank - built to aircraft service requirements? The Corvair engine is a 4 bearing block, isn't it? There is no reason that you _have_ to have a Corvair crank is there? Richard Rich, Whatchit with that BWHAAAAAAaaaaa stuff. Scared the stuffings outta me. O thought Badwater was back and I was going to have to spell check my posts... |
#52
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Corvair conversion engines - cracked crank link
"who cares?" wrote in message
news:54xBf.560$AV.519@trnddc07... Why would an updraft intake system be more resistant to ice? Heat rises, so I would expect a downdraft system, mounted above the engine block, to be more resistant to icing. "Typically" cooling air comes in above the engine, flows down between the cylinders, then out the bottom. This makes it colder up top, and warmer below. There are, of course, exceptions. -- Geoffrey Thorpe The Sea Hawk At WowWay D0t Com |
#53
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Corvair conversion engines - cracked crank link
Peter Dohm wrote:
The Corvairs have a very good idle. But the Rotax, which is one of the possible replacements I would include on my list, seems to have a minimum operating speed restriction. On a KR-2, which has no flaps, I suspect it would result in very flat final approaches. You are right about the small Contintals, time has gone by and I just plain forgot. The KR-2 built to plans do have flaps. The drawings are hanging on the wall behind me;-) John wish I could unload it so I could get/build a SP elegible aircraft! |
#54
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Corvair conversion engines - cracked crank link
"Capt. Geoffrey Thorpe" The Sea Hawk at wowway d0t com wrote:
Why would an updraft intake system be more resistant to ice? Heat rises, so I would expect a downdraft system, mounted above the engine block, to be more resistant to icing. "Typically" cooling air comes in above the engine, flows down between the cylinders, then out the bottom. This makes it colder up top, and warmer below. There are, of course, exceptions. This has been one of the most friendly informative threads yet on this newsgroup, How refreshing! John |
#55
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Corvair conversion engines
On Wed, 18 Jan 2006 21:26:23 GMT, "Don Lewis n FTW"
wrote: See: http://www.flycorvair.com/crankissues.html "Ron Webb" wrote in message ... Do you have a link for the broken cranks? I cannot find anything about broken cranks on the "Corvair authority" site. http://www.flycorvair.com/ I did find the following statement: "I have never seen a cracked head, cylinder, case, crank or rod in the hundreds of Corvair engines I have inspected. It is a very strong engine." The Corvair engine has been flying since the early 1960's. Seems odd that ANY flaw would only now be being discovered. They are only recently flying at 115HP in 200MPH planes - which is a totally new world. Previous engines were flying at 60HP and 90MPH without any issues. Everything seemed OK until yesterday when I read the most recent updates on their website. Seems that the "untreated" automotive cranks have been cracking in a very short time. Nitriding seems like the only solution. But with standard cranks cracking at under 100 hours, what would be the expected life of a nitrided crank. Twice as long, four times as long, eight times as long? This would still fall short of the 1500 hour TBO stated by the Corvair Authority. Does anyone have any first hand experience with Corvair conversion engines? Any info on their realistic life and reliability? TIA, CV |
#56
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Corvair conversion engines
On Thu, 19 Jan 2006 15:35:13 -0500, "Morgans"
wrote: "Bret Ludwig" wrote in message roups.com... I just think hanging a prop on a crank directly is a non-starter in the first place...especially on a crank and case not specifically designed for this in the first palce. Maybe a good redrive and flywheel would be a better way to go? That is my opinion, also. What isn't there can't break. That's my reson for a direct drive 'vair insted of a geared Soob - same weight - same HP. |
#57
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Corvair conversion engines
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#58
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Corvair conversion engines - cracked crank link
On Tue, 24 Jan 2006 16:22:45 -0500, "Peter Dohm"
wrote: "Rich S." wrote in message ... "Peter Dohm" wrote in message news ---------much snipped----------- These were also 40 year old cranks of unknown provenence, pulled out of old car engines that may have been thrashed to within an inch of their lives in previous "inCARnations" This has been my area of concern as well. I would really find these engines more attractive if I was confident that a complete new engine could be built. New engines don't have crankshaft problems? BWAHAHAHAHAHAHA!!! Rich S. Yes. I know that they do, and new design engines are notorious; as are design improvements, changes of supplier, etc. And they include plenty of reasons for loss of power not caused by the crankshaft! However, my concerns include, reliability, maintainability, and eventual replacement; and I think you understand my point. At this point, the Jabiru 3300 is the only engine that really looks to me like a promising replacement; and I really don't know its service record. However, albeit at a higher dollar price, its features seem to preserve: 1) similar or lighter weight, 2) similar or higher power, 3) six cylinder smoothness, 4) reasonably slow idle, and 5) similar dimmensions. Additional benefits are designed in dual ignition and an updraft intake system, similar to Lycoming and Continental, which should be more resistant to ice. Peter By what reasoning? Virtually all carbureted aero engines are sucseptible to carb ice - doesn't matter where the carb is. |
#59
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Corvair conversion engines - cracked crank link
On Tue, 24 Jan 2006 13:32:22 -0800, "Rich S."
wrote: "Peter Dohm" wrote in message ... Yes. I know that they do, and new design engines are notorious; as are design improvements, changes of supplier, etc. And they include plenty of reasons for loss of power not caused by the crankshaft! However, my concerns include, reliability, maintainability, and eventual replacement; and I think you understand my point. At this point, the Jabiru 3300 is the only engine that really looks to me like a promising replacement; and I really don't know its service record. However, albeit at a higher dollar price, its features seem to preserve: 1) similar or lighter weight, 2) similar or higher power, 3) six cylinder smoothness, 4) reasonably slow idle, and 5) similar dimmensions. Additional benefits are designed in dual ignition and an updraft intake system, similar to Lycoming and Continental, which should be more resistant to ice. Peter.......... Since you answered seriously, I will too. I can agree on the higher price and on #1-3 and #5. I don't understand #4 - do Corvairs idle unreasonably high? The dual ignition is good if the Jabiru 3300 truly has two stand-alone systems. The intake direction is irrelevant if the Corvair is fuel-injected or has a heated intake manifold. Updraft carbs are a lot better at preventing fire as well. The small Continentals will ice up if you look at them cross-eyed even with updraft intake. Rich S. And updraft carbs are NO LESS dangerous firewise. They can't leak on the top of the hot engine (but a properly designed top carb can't either) but they have over a yard of "wet" intake manifold - if or when the (flooded) engine backfires when starting and the battery is low, a bottom carb engine WILL BURN. |
#60
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Corvair conversion engines - cracked crank link
On Tue, 24 Jan 2006 22:10:02 GMT, Richard Lamb
wrote: Rich S. wrote: "Peter Dohm" wrote in message ... Yes. I know that they do, and new design engines are notorious; as are design improvements, changes of supplier, etc. And they include plenty of reasons for loss of power not caused by the crankshaft! However, my concerns include, reliability, maintainability, and eventual replacement; and I think you understand my point. At this point, the Jabiru 3300 is the only engine that really looks to me like a promising replacement; and I really don't know its service record. However, albeit at a higher dollar price, its features seem to preserve: 1) similar or lighter weight, 2) similar or higher power, 3) six cylinder smoothness, 4) reasonably slow idle, and 5) similar dimmensions. Additional benefits are designed in dual ignition and an updraft intake system, similar to Lycoming and Continental, which should be more resistant to ice. Peter.......... Since you answered seriously, I will too. I can agree on the higher price and on #1-3 and #5. I don't understand #4 - do Corvairs idle unreasonably high? The dual ignition is good if the Jabiru 3300 truly has two stand-alone systems. The intake direction is irrelevant if the Corvair is fuel-injected or has a heated intake manifold. Updraft carbs are a lot better at preventing fire as well. The small Continentals will ice up if you look at them cross-eyed even with updraft intake. Rich S. The Lycoming approach, with the intake manifolds passing through the oil sump are less inclined to ice up. I'm sure they can be provoked, though. As for the Corvair's idle? I plain dunno. I have never seen a Corvair on an airplane - in person. ANd that kinda is the point here. The mounted pics I have seen are on a Pietenpol Air Camper, which needs the weight on the nose. On most other planes that's considered a Bad Thing (tm). On small short coupled airplanes, it might qualify as a Very Bad Thing (tm), which is obviously much worse. Now, I've only *seen* the Jabaru on a plane. Haven't flown one myself. But it does look like an engine of fine merit. Light and simple are high on my short list. Cost is there too, of course, but it has to take a place in line with the rest of the conflicting requirements. The Rotax 912 (which I have flown) is a really sweet set-up. There is the extra complication (and weight) of the liquid cooled heads. But it's probably not that big a deal on any two-seater. From what I've heard, the Jabaru/912 power ratings remind me of the old Continental A-65/Lycoming 145 days. Both were rated at 65 hp, but the Continental horses seem a little longer legged. I'd rank most VW power estimates as Shetland ponies... I suspect that most people expect a VW to put out like a Rotax, but it just doesn't work that way. In the end the final choice will depend on the airframe and the mission. On the Corvair question... As I said earlier the Great Plains crank on my 2180 i.e. a way massive hunk of pure confidence. Just the way an A-65 crank compares to other small 4 banger non-flying counterparts. So, why can't someone turn out a new Corvair crank - built to aircraft service requirements? The Corvair engine is a 4 bearing block, isn't it? There is no reason that you _have_ to have a Corvair crank is there? Richard Rich, Whatchit with that BWHAAAAAAaaaaa stuff. Scared the stuffings outta me. O thought Badwater was back and I was going to have to spell check my posts... Got ten grand? You can have a "proper" crank made - or for 300 grand you can have a hundred of them. As for the idle, mine ticked over very nicely at 700 RPM with a 72 inch IVO Magnum - but the Magnum was too much prop and was only able to spin about 2450 or so. It idles fine at 750 with a 3 bladr 68" Ivo ultralight - which is not enough prop and can be spun over 3000 at full pitch. |
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