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#61
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Corvair conversion engines
clare at snyder.on.ca wrote in message ... 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. Perhaps you missed the news flash, from the Corvair Authority, himself. The 'vair cranks are breaking on the new glass planes. -- Jim in NC |
#62
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Corvair conversion engines - cracked crank link
"Richard Lamb" wrote in message
link.net... 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... I believe that you are correct on all of your points. The only thing that I really feel compelled to add is that, in the case of the KR that had a complete crankshaft failure and was "substantially damaged", the owner had been very agressive in his program to keep the weight down. I believe that he told me it was less than 200# firewall forward, which may have even been a record. Even presuming that the weight excluded the cowling, that is very light, and I have no idea how harmonic damping was accomplished on any of these engines. Peter |
#63
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Corvair conversion engines
clare at snyder.on.ca wrote in message
news 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. Interesting. I had assumed they were originally flying with 80HP or less, but had no idea it was that much less. Thanks. 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 |
#64
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Corvair conversion engines - cracked crank link
"UltraJohn" wrote in message
nk.net... 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! Oops! You're right. The plans are rolled in a tube, but I verified it in the book. Peter |
#65
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Corvair conversion engines - cracked crank link
clare at snyder.on.ca wrote in message
... 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. As another poster also pointed out, my memory was faulty and it is easy to form ice in the O-200, even though the carburetor appears to be in the path of heated cooling air from the cylinders. Peter |
#66
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Corvair conversion engines
On Tue, 24 Jan 2006 22:19:55 -0500, "Morgans"
wrote: clare at snyder.on.ca wrote in message .. . 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. Perhaps you missed the news flash, from the Corvair Authority, himself. The 'vair cranks are breaking on the new glass planes. Yup, I'm aware. but the reduction box has more parts to fail. There have been Rinker failures, and not much else in use. Lots of PSRU failures on Soobs. Mine's not fast, and not glass, and my crank is nitrided from the factory. |
#67
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Corvair conversion engines
"Peter Dohm" wrote Interesting. I had assumed they were originally flying with 80HP or less, but had no idea it was that much less. Thanks. You could find many people that would argue that low of a HP figure. I think your 80 is closer, and in might be a few more than that. -- Jim in NC |
#68
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Corvair conversion engines
Here's a formula that is helpful in determining an engine's horsepower.
It is based on an MEP of 150 psi., sort of typical of an 8.5:1 CR. CDI X RPM / 5280. An O-320 at rated 2700 rpm, using this, gives 163.6 hp. Of course, this 5280 constant only works for normally aspirated engines. The 60 hp 800cc/49ci Hexadyne, featured in the just-out Contact! issue #81, calcs to 53 hp at 5750 rpm, but it's 9:1 CR, so the published 60 hp seems reasonable. |
#69
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Corvair conversion engines
On Wed, 25 Jan 2006 19:47:08 -0500, "Morgans"
wrote: "Peter Dohm" wrote Interesting. I had assumed they were originally flying with 80HP or less, but had no idea it was that much less. Thanks. You could find many people that would argue that low of a HP figure. I think your 80 is closer, and in might be a few more than that. Original flying corvairs were the little engine - 145 cu inch, IIRC, producing 128 ft lb gross torque at 2300 RPM. So, at 2300, 56 hp. If run at 2700 rpm, torque approx 125 ft lb, and 64 hp. The 164 inch engines produced up to 160 ft lb torque at 2600 or 2800 rpm depending on the engine, for 80 hp at 2600, or 85 at 2800. Mine produces 90 at 3000. With a fancy cam and a bit of rework they will put out closer to 170 ft lb - and at 3200 RPM with a small prop, that is 103 hp almost 115 at 3500 rpm. The factory 140 hp engine supposedly produced 140hp at 5200 rpm and 160 max torque at 3600. That means the torque dropped off to 140 at 5200. The 110 does not breathe nearly as well at speed, so the 14% torqe drop of the 140 would be more like 20% on a 110 - or 122 ft lbs at 5200 for 120 hp if you ran a 2:1 PSRU for a 2600rpm prop. And that's being optimistic. Assuming 170 peak torque at 3000 RPM (likely pretty close with OT10 cam and properly prepared for aircraft use) it is pretty close to a 100 hp engine .For the extra 10 HP there is a couple hundred dollars worth of Camshaft etc required over and above what I've got -so I'm satisfied, so far, with what I've got. We'll see what 90 HP does in a Pegazair when we get it together. My engine has 180 degree equal length headers and a short smooth equal length intake with a 50mm carb, and it's a 140 based engine, so it breaths a bit better than a "stock" 110 at 3000 RPM |
#70
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Corvair conversion engines
clare at snyder.on.ca wrote:
My engine has 180 degree equal length headers and a short smooth equal length intake with a 50mm carb, and it's a 140 based engine, so it breaths a bit better than a "stock" 110 at 3000 RPM Thanks Clare for the specifics, nice post! John |
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