Debate about Mark Langford's 3rd crank failure

Discussion in 'Corvair' started by Will Aldridge, Jan 23, 2012.

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1. Jan 30, 2015

William Wynne

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Mr, Kuykendall;

It seems likely the KR-1 you saw in CA may have been Richard Shirley's. He is from Seal Beach and flies out of Corona, but the plane is 3300 Jab powered not a Corvair. I am pretty sure there has never been a KR-1 with a Corvair yet, and I know Richard and flies all over the place. You can tell his KR because it only has 50 square feet of wing area, and it has a heavy taper on a 65 series naca airfoil. It does sound like a Corvair (six cylinders), and the engine is hard to see because he has a complete carbon plenum box on the engine. It was widely thought of as the fastest Jabaru powered plane in the world. It is white overall with a two tone blue tail, a fixed gear tailwheel. It is about a dozen photos down here: KRnet Internet List (the photo was taken with a previous engine.)
.
Being a KR guy Richard also Knows Mark Langford, and perhaps that his how his name was in your conversation that day. Might jog your memory if I point out that Richard is hearing impaired and conversation in noisy places is difficult. Not trying to be a pest or a jerk, just sharing the thought -ww,

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2. Jan 30, 2015

RJW

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To understand the vibration of a system like a crankshaft, “harmonic damper”, flywheel, coupling, gearbox, prop, etc., etc. it is necessary to study systems of coupled harmonic oscillators with forcing and damping. One might even say that an understanding of this is the very least that must be had before anything useful can be said about how a system made up of a crankshaft, coupling, gearbox, prop, etc. fail from resonance. On top of this there are many other subjects such as mechanics of materials that must be understood. Then there is the magic of “grasping” the concepts so one “sees” how these idealized systems can accurately represent something as concrete as an engine with a prop or whatever hooked to it. Here is a lecture that talks only about coupled oscillators without forcing or damping. It is quite involved and only shows a small part of the picture.

There are further videos on forcing and resonance for those interested. (And of course there are mountains of books on the topic since vibration has been well understood for a very long time.) As can be seen there is nothing about Corvair engines in these videos. But if one has an understanding of vibration in general it is not difficult to see how it applies to Corvairs or any other vibrating system. And this without ever having seen or flown an actual Corvair. It’s the magic of physics, real engineering, and understanding.

Rob

3. Jan 30, 2015

Monty

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The problem with this idea, is that it is not a simple thing to model. I have actually done an analytical model on an engine to look at balance and crank loads. This is a dynamic system, with variable damping and forces. What is the damping on each piston with respect to time? What is the force on each wrt time? Any analytical solution is at best a guess with a lot of simplifying assumptions. To perform the FEA you need to know worst case conditions of coupled torsion, inertia, motor drag, and gas loads..... good luck- the kinematics, balance, and propeller loads are the "easy" part. Only engine development engineering organizations have the tools to measure this information and feed it back to the FEA. Then that must be validated with strain, and angular displacement measurements. I really do not think a home builder should entertain the idea of doing this. The combined areas of expertise to accomplish this in a reasonable time frame is beyond almost any engineer, and way more expensive than any homebuilders budget. It would take me a long time to put the FEA model together even if I knew all of this, and validation.....I think I could work on this full time for a year or more, and still not be there.

Start with a sound engine and trust the track record of that basic engine. Then design whatever you are attaching to it to keep the engine happy. Do things that make sense:

Use quality components to build the engine
Build to aircraft specifications using aircraft methods
Maintain good records
don't do anything obviously stupid

Then-test. This strategy is achievable by most people capable of building an airplane. I think trying to re-engineer the entire engine is a waste of time and has little to no chance of success.

One flying example is worth a million analyses, and arm chair engineering sessions.

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4. Jan 30, 2015

Himat

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I do at large agree, but when you say that trying to re-engineer the entire engine is a waste of time, do you then say as I would, stay close to stock engine specifications?

5. Jan 30, 2015

Autodidact

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You guys should take a look at the rear mounted alternator that I think was designed by WW; it is driven directly off of the crank by a small quill shaft which is a classic way to avoid TV resonance. For some reason I thought that was pretty slick, it just seems a little beyond what you usually see on an auto conversion.

I would like to see the Corvair eventually evolve into a brand new engine. Most if not all of the internal parts needed can be bought new, so the next step would be a new crank case I would think, and then new heads. There are probably still plenty of cores available, but even if everything were new, it would still be much cheaper to buy and rebuild than an o200. I really like the sound of six cylinder engines in aircraft. Imagine a new Covair based engine with new "split" heads...You could probably build it yourself for half the cost of a Jabiru 3300.

Last edited: Jan 31, 2015
6. Jan 31, 2015

rv6ejguy

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It's hard to explain the 3rd failure of Mark's crank in the position where it failed without looking at TV as a possibility. Bending loads here? I think not despite the opinion of someone highly versed in Continental engines. The bending loads here are no different from any other pairs of throws on the engine and the torsional loads from engine firing impulses are the lowest there. Mark was concerned enough about TV after the Sentra ring gear episode to start digging up GM TV studies and looking at getting an actual measurement study done. Indeed, if the crank is being excited at its natural frequency and other changes up or downstream have changed the damping, TV can vastly shorten crankshaft life. I've seen numerous examples in my 35 years of building performance and race engines.

Your current crank rejection rate might be 1 in 14 but that's not what they are finding in other parts of the country where engines might have a lot more hours on them and/or harder use and reached their fatigue limits. The cranks in question are dye penetrant checked if magnafluxing shows cracks to confirm or deny suitability. The shop does not supply new cranks so they have no vested interest is failing good cores and good cores do not grow on trees any more. He has been using the same shop for a couple of decades- one of the most respected in So Cal. The comments from my friend show that the trend towards seeing more cracked cranks was increasing in the last few years. Of note is the position that cracks are being seen (same as where Mark's broke). On your site you said you'd never seen a cracked crank in a Corvair before. It might be a good idea to revise that entry. You seem to frequently discount outside information if it differs from your own or your own opinions or biases. Granted, as you say, often information is not qualified but in this case I believe it is. There are other people in the world who have even more experience than you do with Corvairs. It would seem prudent to listen at least to what some of them are saying. My comments here revolve around Mark's failure which probably has unusual factors compared to the normal layout most builders are assembling under your guidance.

We always replaced the cast pistons with TRW forged ones since we'd seen a number of the factory ones with cracks above the pin bosses and even 2 cases of separated piston crowns. The TRW stuff was bulletproof and relatively inexpensive- a no brainer. I see many people on all sorts of engine builds put in aftermarket forged rods, better bolts etc. This makes great sense on a high revving, higher output race engine maybe not so much on an engine turning at half redline, however if you want the best and have the money, there is no usually negative aspect to wanting stronger parts in there as long as balancing is maintained.

Of course cost is a concern which is why many of us use auto engines instead of Lyconentals in the first place. Reliability is paramount so when some parts show weakness in an application, they need to be changed out. The build budget then has a defined lower figure for acceptable reliability and after that people can spend more if it makes them comfortable. You can say hindsight is great but so is experience from others if you are willing to listen and be logical. 80 hp, gently flown Corvairs might have been pretty reliable and they should be since stresses were probably little different from what was being experienced in the car. Adding 50% more power and doing aerobatics- much different stress levels yet there was resistance back then to nitrided cranks and 5th bearings. I'd always use the best available factory parts on any rebuild- even a stock one. That's always served me well.

Of course there are many armchair experts and pigheaded people out there who refuse to listen to experience. You can only let them make their own mistakes and learn the hard way. I've been there many times myself from forums to racetracks to Reno... You can only do so much for some people who seem insistent to repeat some mistake learned long ago. I can see you've been there before too.

Last edited: Jan 31, 2015
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7. Jan 31, 2015

BBerson

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Quote from the crankshaft chapter of the book THE AIRPLANE ENGINE, discussing Torsional Vibration:
"The free end of the crankshaft is subjected to much more severe conditions than the propeller end."

book author is Lionel S. Marks, Professor of Mechanical Engineering, Harvard University.

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8. Jan 31, 2015

Monty

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I would say, maintain stock HP output. Upgrading material quality in things like pistons/pins, rod bolts, bearings, head bolts, etc. is a plus. Use aircraft methods: Magnaflux the crank and rods. If you have the crank ground, insure larger fillet radius. Relieve the bearings to accomodate. Blueprint the engine. Do a good job balancing it. Gap the rings. Measure everything. Forged components are better, nitriding is better. Take advantage of these things. Don't try to double the horsepower and skimp on materials. Fix known issues that the engine might have in high performance applications. Basic stuff, but don't stray too far. How far.......calculated risk. The current engine I am working on already has forged internals so I am just going to NDE those components. I will replace all the rod bolts and cap bolts. I will maintain the existing continious rated power output. Harmonic balancer and flywheel remain the same. I did an analysis of the Prop and gearbox for reflected inertia and TV. It was a simplification, but the system should be far enough above resonance at idle to avoid it during operation. A spring hub element is used to lower the resonant frequency below idle. Lots of cylinders help....a lot. All of the accessories, intake and exhaust will be installation specific. Ground testing will be a major part of my test program. The process is just as important as the installation details. From what I see, the enlightened corvair flyers are doing the same kinds of things, without the gearbox of course.

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9. Jan 31, 2015

Monty

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Merlins and Allisons had dampers between the accessory end and the accessory case.....for a reason. I think there was a fluid coupling on one of them between the crank and accessory drive. It wasn't there for looks that's for sure.

10. Jan 31, 2015

rv6ejguy

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In the Subaru world, numerous people have learned the hard way that's it's best not to tamper with the factory engineering too far otherwise you throw a lot of the design and validation out the window and are basically starting from scratch. Of course with enough trial and error and perhaps some luck, you can achieve a reliable package even with many mods. Someone going that direction will have to step into the breach at some point, fly it and prove it as reliable. Certain mods don't impact reliability negatively, others might. There is some crazy stuff out there that goes way, way past what the factory engineers envisioned.

You have to admire what guys like this have done with the 'ol Corvair, albeit not for aircraft use:

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11. Feb 1, 2015

mcrae0104

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As one who is designing a plane around the Corvair, I'd love to see some drawings. Do you still have any around that you could share?

Maybe this is a little OT from crankshafts, but I'm curious, what were your HP goals, and how was your road racing engine cooled--using the stock fan setup? Did you clear the heads of casting flash? Did you use stock cooling tins? Was it a stock turbocharger setup, or something more extreme? What instrumentation was used to measure the temperature?

What I'm really getting at it is this: by what method did you isolate heat rejection of the heads as the limiting factor? As you probably are aware, most Corvair installations in aircraft do not use the cooling fan and are likely quite different than what your road racer may have been (either stock or modified). The conventional cooling setup recommended by WW has proven to be effective at the 100-120hp range (and perhaps beyond). Your experience may have very little to do with an aircraft application.

I recall that you said in another thread that Corvairs lacked adequate heat rejection. Because of this, whenever I meet a Corvair builder/pilot in person, I make a point to ask about cooling and CHTs. None of them reported cooling problems (10 that I can remember: 2 KR2s, 4 601s, 1 Panther, 3 Piets). I think it's important that potential builders hear that side of the story, and not base decisions on opinions not backed up with Corvair flight experience.

12. Feb 1, 2015

mcrae0104

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The rear alternator was designed by Dan Weseman. It is available from SPA here. It's a pretty clever, simple setup that addresses the concern of a rear alternator belt failing and taking out the ignition wires or HT cable to the distributor.

I don't know much about what it would cost to reproduce cases and heads, but I imagine it would be prohibitive to do, given the relatively small demand. It would certainly appeal to airplane guys and maybe the dune buggy crowd, but my guess it that there isn't a big enough market over which to distribute the startup costs. The new VW cases that are available are another story--much bigger market--but even then, they run $800 or so. I don't know where they are made or how good the quality is. My bet is that a new Corvair case would be a fair bit more, particularly if USA-made. Good cores aren't that hard to find anyway, so new cases may be a solution for a problem that doesn't exist. Why split heads? Granted, it would look more like a J3300 or Continental, but this might be another solution to a nonexistent problem. Someone with more in-depth knowledge of the Corvair might be able to speak to this point better than I can, but if you go to split heads, you'd really need to consider the engineering of the head studs and the cylinder/head assembly holistically. I know it can be done on VWs (I don't know how successfully) but the way cylinders and heads are held onto a Continental or Lycoming is a different animal from a Corvair. Also, I don't think there would be weight savings; you'd need to have at least the same fin area. If you build a Corvair with all the goodies and a new billet crank--and you certainly don't have to go all out like that--the cost can already be close to half of a Jabiru. That's still a really good value as I see it, but to "kit" the engine and manufacture new parts would drive the cost closer to the Jabiru, don't you think? I like the combination of cost, power, simplicity, and reliability offered by the Corvair as it is (especially with the new 4340 crank). 13. Feb 2, 2015 Autodidact Autodidact Well-Known Member Joined: Oct 21, 2009 Messages: 4,513 Likes Received: 799 Location: Oklahoma To me, the split heads would be a good decision because they could then be used without modification on two cylinder, four cylinder, and even a radial. Split heads work fine on a 1/3 Corvair. But a connected head is a good thing, it stiffens up the engine some, apparently. There are connecting plates available to tie the heads on an O-720 together, a similar thing could be done with split Corvair heads if desirable, but unless you're making a hot rod, it wouldn't be needed. And there's no reason for a new crank case to be more prohibitive in cost than a new crank shaft, the Corvair crankcase is relatively simple compared to a Vw (and even a VW case could be greatly simplified for AC use.). With 3d printing (for the casting patterns only...) and CNC machining, it should be possible to make these things - even the heads - at a reasonable cost, but only if there's a market and that would depend on the availability of cores. But if the cores get scarce (off in the future...) and there is no alternative ready to go, then the market will fizzle away. What does it cost an individual to build up a Corvair flight engine? A Jabiru 3300 costs$20,000, I think the that if new case and heads cost as much as $4,000, you could still build up a Corvair flight engine for less than$14,000, possibly as little as $10,000. The crank is about$3,000 (on the high end) and then plus $4,000 is$7,000, then you need pistons, rods, cam and gears, cylinders, oil pump (housing part of the case along with the 5th bearing housing), and other parts to complete, no reason why those things should cost more than 3 or 4 grand. It's not needed now, but I would like to see the engine continue for a long time; air cooling is a handy solution for an aircraft engine.

You could also take the opportunity when designing the new case to make provision for a larger cylinder stud pattern. You could keep going with all kinds of increases, but you have to draw the line any time you design a new engine or engine part, and since there is already a new crank in production, and since the main competition would be the Jab 3300, stopping at providing for a larger bore would be logical IMO. The Corvair hase the same bore spacing as the type 4 VW and could have up to 103 mm bores - 4in bores (101.6) for sure.

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14. Feb 2, 2015

mcrae0104

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Here, here.
Yes, you could. But you might be better off just designing a new engine. The new heads alone would basically be a totally new design. Also if you made a new stud pattern, this would need to be reflected in the new head design and the new cases would require new heads and vice versa (they wouldn't be interchangeable with old cases/heads). Keep in mind that the lower head nuts double as the rocker arm studs on a Corvair head. I'm not saying it couldn't be done, but it may not be as simple as it sounds at first blush.

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15. Feb 2, 2015

Autodidact

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Ahhh yes, but this is what I was thinking; the new case would be designed so that it could be drilled (and the spigots bored) for either stud pattern - you could even put steel inserts in so that the same case could have the small bore pattern, and then be changed over to the large bore pattern. That way, the case could be used before the new heads are even designed, and once the new heads are available, no need to buy a new case.

A 4" bore is stretching it a little, that'd be a little over 3.6L/221ci, but I think you could shoot for 3.4L without excluding the stock heads usage while still being able to change over to the larger heads.

Last edited: Feb 2, 2015
16. Feb 2, 2015

William Wynne

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If you study what is being built today, a Corvair builder has the option of getting very close to a "new" engine already.

If you get a look at the engine in the SPA Panther prototype, it has very few parts that ever drove around the block in a car. Read Why Not the Panther engine? | flycorvair

It is actually easier to list the things that came from a core car engine:

The two case halves
The basic rear oil case
The pushrod guide plates.
The basic stampings of the valve covers.
The 4 ounce distributor housing

That is just 14 parts in the whole motor, plus a few odds and ends like the distributor clamp.

Here are some of the parts that are new that most people just glancing at the Corvair or my website don't think about:

SPA Billet Crank
New Cam and Billet gear
Billet connecting rods.
The pistons, pins and cylinders
All the guides, seats, springs, valves, pushrods, rockers, balls, rocker studs, tubes and rotators in the heads
The 5th bearing
All of our gold parts that make the engine conversion, the prop hub, starter, dual ignition, billet pan, pickup etc.There is a list of very part in the flight engine, down to each nut and bolt, at this location: Catalog of Parts Available from The Corvair Authority by Credit Card via PayPal at www.FlyCorvair.com The conversion manual is organized around that numbering system.

There are lots of new parts we make that people glancing at Corvairs miss, like the CNC HV oil pump: High Volume Oil Pump | flycorvair

We also have very detailed information on the smallest aspects of the engine like the dipstick and tube All about Dipsticks, Part #2206 | flycorvair

While it is productive to understanding to speak of engine theory, if you are going to come right down to actually building something to fly, I think most people understand that you can greatly increase your odds of success by following the work of a guy who can write 1,500 words on just the dipstick for the motor off the top of his head. When it comes to Corvairs, I happen to be that guy.

In any discussion about building a whole new motor, Let me point out that Dan Weseman, the SPA /Panther guy spent 19 years working every day as an expert in the installation of industrial CNC tools in machine shops all over the southeastern US. He has countless industy contacts he can call on to efficiently make any CNC part. His personal contact list of subcontractors for almost any process is astounding. If you look at the Panther, study it closely, almost everything in it is a cnc part, made by the most efficient means possible. It has custom extruded longerons, it has machined spars, the steel tubing kits are CNC, all the rivet holes are done, every little bracket it laser or hydro cut, all done in the south east US. Shops that produce many of our parts, like the E/P plates, billet oil pans, starter brackets, cnc starter noses, etc, were referrals from Dan's supplier list, many of whom beat all other quotes by half. In short, if anyone can make the last 14 parts for a whole motor, It is Dan. and yes, he has looked at this in detail, and has a way of producing a new case that isn't a casting, but removes about 80% of the machining that would be required from a block.

The only reason why he has not gone further, is that the core parts for Corvairs remain plentiful. You can buy a complete 1965-69 core engine in rebuildable condition for $300 just about any where in the US on a weeks notice. In many cases a little looking will yield the same motor for$100. Look at the list of new parts and realize that almost nothing on the core engine needs to be salvageable if you are going after a high end build. Even a more modest build needs few parts to be reconditionable. You don't need a running core, or even a mint one. I suggest starting with one that was stored indoors and rotates, but that is not a requirement.

People have been suggesting that cores will run out at some point, but I am yet to see evidence of this. Corvairs are 28" wide. They made 1.8 million, and if you put them valve cover to valve cover it is a line 761 MILES long. Get a calculator and check it if you like, it's correct. Lets say 99% are gone: Then we are just down to 7.6 miles of engines. That is about 35,000 cores. That will put off having new cases and heads made for a while. -ww.

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17. Feb 2, 2015

rv6ejguy

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Not sure if I still have some old 3 views somewhere in the basement... It had a 23 foot span, retractable gear, a bit larger than an F1 plane. Was hoping to see 375mph at 18,000 feet max speed.

Was looking at around 250hp for takeoff and wanting to hold 225 to 18,000 feet. Also note half the air density at 18,000 feet for cooling. This was to be geared, injected and intercooled.

The road racing car was about 350hp, engine all custom built, ported 140 heads, TRWs, the usual mods. Had a custom exhaust mounting an E flow Rajay, blowing through twin Weber 44 IDFs with water injection. One 2 mile lap from cold and the heads were over 450F and climbing rapidly. Intake seats sometimes don't stay tight in 140s above this, even with additional staking. Of course we always cleared casting flash on any rebuilds. I saw the light quickly and developed a 1.7L liquid cooled Toyota which made more hp, stayed cooled, was bulletproof and a fraction of the cost of the Corvair. They went on to win 5 championships and frequently slaying the cars in the class above. The Corvair was fun for one lap and garnered a lot of looks at the track.

One look at the cooling fin area of a Corvair vs. say a 180 Lycoming, shows that it's not going to be able to reject heat at the 225hp level, keeping the CHTs in a desirable range. Pretty well all the Sport Class Reno racers have water spray bars to keep from melting down. Their specific outputs are in the 80-90hp/L range, about the same as my Corvair would have been.

Nobody has any flight experience at 225hp in Corvairs that I'm aware of. IMO, geared turbo engines are best liquid cooled or you need serious, sawed finning like an R3350 has. Air cooled engines have very finite power densities in turbocharged form which is why they've been supplanted in racing by liquid cooled engines. Porsche eventually reached the limit in IMSA GTP racing back in the '80s.

http://3.bp.blogspot.com/-NC9AnOLJTcE/U8la1YyKxWI/AAAAAAAAtas/Z0NtIQy_jck/s1600/17.JPG R3350 67hp/L with WM injection

Last edited: Feb 2, 2015
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18. Feb 2, 2015

mcrae0104

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Sounds like quite a machine. 225hp would indeed be a lot of heat for a Corvair to deal with! I think most that are flying them have a little more modest HP and heat rejection needs.

19. Feb 2, 2015

William Wynne

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Not to be argumentative, but just looking at a more typical example that may be a lot closer to what people are building and flying in some numbers, think this cooling comparison over:

O-320 is a great engine, reliable, and unless you are trying to use it at Reno, has no cooling issues if used with any kind of common sense. Each cylinder is 80 cubic inches..........

A 2700 cc Corvair is a good engine, reliable unless you are trying to make 225 hp at FL18, has no cooling issues if used with any kind of common sense. Each cylinder head is cooling about 80 cubic inches..........

Now think of this: A bare Corvair head weighs 22 to 23.5 pounds. about 75% of this weight is cooling fins or surface area directly exposed to cooing air. Now go pick up an O-320 jug, it does not weigh nearly as much, and a lot of the weight is in the Lycomings steel cylinder. I contend that the pounds of aluminum/fin surface area per cubic inch actually favors the Corvair. Add to this the Corvair has a cross flow head, where the intake does not crowd the cooling fins on the exhaust port, The Corvairs exhaust tube style that doesn't use a flange face, and the Corvair's CHT limit is 100F higher, and we have flat rated the Corvair way down below it's automotive power rating, and it becomes more obvious why it works for the way we use it.

----------------------------------

R-3350s are great engines, and I love to learn things about them, but truthfully I have put a wrench on one exactly once in 25 years, and it was to remove a part from a Turbo-Compound engine that was being scrapped with a L-1649 airframe in Sanford FL in 1989. Dan Weseman's father Jim, also lives at our airport. He had a very long USN career, about half of it was working radial maintenance on the Navy EC-121s. The man is a treasure of detailed operational info on 3350's, Great to talk about, but in the end, you can't put one on your homebuilt, so Jim Weseman's personal plane that he flies is a Corvair powered Fisher Celebrity.

---------------------------------------------------

A flying turbocharged Corvair we built for fun years ago........

From 2002 to 2005 our flying test mule was a Stits SA-7D Skycoupe that my friend Gary Coppen loaned to us. The last thing we did with it was put a Garret TO4B turbo on it, It flew 115 hours that way in a few months before it was damaged in a wind storm, If you were at Sun n Fun 2005, perhaps you remember it, it generated a lot of interest because we had a sign on it that said "The paint job on this aircraft cost \$20 and could easily pass for one twice as expensive."

Before anyone goes hyper critical about the stories below, remember that this wasn't a product, it was just a fun project, you know, the kind we all wanted to do before time in our lives got stolen by trash like...typing long stories on the net. The description isn't meant to substitute for a class in thermodynamics at MIT, it is just an introduction for people who don't know what a turbo looks like. If you know more about engines, get a look at some of the stuff like 321 exhausts and Inconel exhausts we eventually developed, and how the pistons we use came about. Find something you like about it before critiquing it.

The highest power setting we ever tried was 60" on takeoff but the EGT looked like 1600F, so we settled for 45" which the plane could actually deal with and cool. 60" actually added 400 rpm static to the two blade Warp drive prop as it was set for the plane before the turbo. The plane was a draggy box, but that is actually an advantage when HP load testing. You can learn a lot form a really basic flying test like this: Example; when doing ground runs to 36-40", the aluminum intake between the turbo and the head pipes was actually cool to the touch, way below ambient. We were feeding it 8-10 gph to protect it, and this amount of fuel vaporizing consumed more heat than the turbo put in compressing the air. No intercooler needed at this level.

Part one:
Turbocharging Corvair flight engines, Pt #1 | flycorvair

Part two:
Turbocharging Corvair Flight engines Pt. #2 | flycorvair

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Some serious stuff 450HP, 32,500', 385mph, money by the cubic yard:

I like simple machines, but I have also done a lot of work on high end stuff. Fun and education if it is not your wallet. Makes you appreciate a good old direct drive carbureted engine. From 1993 to 1999 I worked on V-8 Lancair IVPs. I led the crew that made the first one, and then we built a handful of others. Our first one was N-420HP. It was on the cover of July 1997 Sport Aviation. In flight testing I was in the plane when we went to 32,500' at the edge of the ADIZ off St Augustine FL. I flew back with Jim Rahm from Oshkosh 2000, and we made it from Wittman field to Spruce Creek FL in 3 hours and 5 minutes. From Chicago to south of Atlanta we held 29,000'. You know you are having a different home built experience when ATC warns you about traffic, and you can clearly see it is a 737 passing below you.

Look at the second photo, it shows Me and Arnold with a 450 HP Engineair V-8 he was working on that day. The story is worth reading also Guest Editorial, Arnold Holmes On Affordable Aircraft… | flycorvair The engines were 377-427 cid Rodac blocks Brodix heads, EPI boxes with one turbo and 2 intercoolers. It had air conditioning (because you can't just open a vent on a pressurized plane)

This story is a very revealing insiders look at how 'hired gun" builders like me damaged homebuilding in the 1990s. It is something of a public apology. The 2nd photo is N420HP in 1995, I am on the left. I look different because it was 20 years ago and I got burned over 45% of my body, including my face, in a crash in 2001.
2,500 words about levels of aircraft finsh…… | flycorvair If you have looked at my website a few times and made a negative judgment, perhaps read the story and learn a bit of who I really am.

Here is a link to the sport aviation cover, with the finished plane flying over Daytona. It eventually logged about 775 hours.Sport Aviation Magazine July 1997 Lancair IV P V8 - Advintage Plus

-ww.

20. Feb 2, 2015

rv6ejguy

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Clearly the flying Corvairs are cooling just fine at the 120hp level. That's not in dispute. I was simply saying that it would be challenging at the 225-250 hp level I needed for my conversion.

I'm not sure if you are aware, but head mass has little to do with heat rejection rates and much more to do with cooling fin area. Also, cubic inches displacement vs. cooling fin area is not an accurate indicator in a comparison either- rather hp per fin area. The Lycoming produces 40hp/ cylinder, the Corvair 20. It would take a while to measure total fin area on both engines but a visual comparison shows that the Lycoming is in the same ballpark as the Corvair for area vs. hp. http://www.enginehistory.org/Museums/FL/Lycoming O-320.jpg

I believe GM set the CHT limit (warning buzzer on at 575F). Lycoming sets their max at 500F and recommend below 435F continuously for maximum service life. Most savvy operators reduce this to 400F, some say 380F. Probably very prudent when you consider that aluminum has lost over half its tensile strength at 400F and only has 1/10th of it at 600F. Aluminum is forged at temperatures between 600 and 900F. Many Corvairs had noticeable HG sinkage into the chamber and Jabiru engines have shown considerable permanent distortion and creep at CHTs of 410F. Their new limit is set at 356F I believe. Detonation limits are also seriously reduced at higher CHTs according to Lycoming detonation studies. High CHTs are obviously not a good idea.

My point about the R3350 was simply to show the cooling fin area necessary to cool an engine producing something over 60hp/L and why the Corvair wasn't going to cut it at 90hp/L for my application. There is no magic free ride in thermodynamics. My father has over 4500 hours behind R3350s in the military- lots of great info on the operation and care of those magnificent engineering marvels.

Again, it's just fact that the Lycomings and Continentals at Reno require water spray bars and ADI to stay alive thermally above the 60hp/L specific output level. We were spraying about 3 gal./min on the 2010 class winning Conti 550 between the ADI and spray bars at full chat- about 83hp/L.

With regards to turbos, anything operating up a bit higher should be intercooled. The compressor discharge temps rise dramatically with pressure ratio and the propensity for pre-ignition also so above IATs of 160F. Fuel cooling is an expensive and inefficient way to drop the charge temperature.

Last edited: Feb 2, 2015