If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#81
|
|||
|
|||
Corvair conversion engines
J.Kahn wrote:
Myself I am still a big fan of the Corvair but will probably adopt the extra bearing mod he's working on if I ever get to that point. John Kahn Montreal That's one thing I like about the GPASC VW is he has (as an option I think) a heavy duty forged crank with a wider front bearing to take the loads. It would be nice if someone did this for the Corvair with it's higher power capability! John |
#82
|
|||
|
|||
Corvair conversion engines
Richard Lamb wrote: Peter Dohm wrote: Some pretty experienced people (in VW engines) have said that the valves are the weak link, and that much more that 45 HP will melt the valves down, if run at that level for more than a few minutes. -- Jim in NC For what it's worth, I'd have to agree, with the thought that you can operate at higher power - until - the heads are heat soaked. Then it's 45 HP or bust. I think the thinking is that the engine needs to turn up fast to make maximum engine power. Which may be true drag racing dune buggies. Grab a gear and spin that puppy up! Considering the 356/912 Porsche engines have essentially the same upper end as a Type 1 VW and they operate far higher sustained powers than that (think a long 100+ mph Autobahn run or the military gensets they were in designed to make 400 Hz power at continuous power settings, depending on generator efficiency, between 55 and 70 hp), I question this theory provided the cooling blower and baffling are designed for the power in question. But it's easy to prove or disprove-hang a VW on a oversized generator, hook a dummy load up, and monitor RPM, power and CHT! Gen seets make wonderful engine dynos. |
#83
|
|||
|
|||
Corvair conversion engines
J.Kahn wrote: snip Exactly right Clare. The soob has a bulletproof interior but the use of liquid cooling plus a drive system adds two complete failure modes that aren't there at all with the Corvair. With the Corvair if you take care of the systems design aspect, basically by using sound aircraft design practices for carburation and ignition, I question whether LyCon practice, which is actually derived from small flathead gasoline burning farm tractors- a big single barrel updraft carb and two farm tractor magnetos- is intrinsically "Sound design practice". Remember when the Continental, Lycoming and Franklin engines were introduced they were not considered sound aircraft design! Real airplanes used P&W or Wright radials or Allison or Curtiss liquid cooled inlines-the E-2/J-2 Cub and similar planes were considered the ultralights of their day, and before WWII one could fly an airplane without a license if it wasn't registered and flown only within one state (until the states, except Oregon, outlawed it-which is why the early homebuilders often moved there.) Nothing smaller than a Waco was considered a real airplane. |
#84
|
|||
|
|||
Corvair conversion engines
UltraJohn wrote:
J.Kahn wrote: Myself I am still a big fan of the Corvair but will probably adopt the extra bearing mod he's working on if I ever get to that point. John Kahn Montreal That's one thing I like about the GPASC VW is he has (as an option I think) a heavy duty forged crank with a wider front bearing to take the loads. It would be nice if someone did this for the Corvair with it's higher power capability! John Well, I asked about that... Seems it would cost a bazillion bucks for some reason. Aren't the Chinese hot rodders cutting custom cranks yet? |
#85
|
|||
|
|||
Corvair conversion engines
Bret Ludwig wrote:
J.Kahn wrote: snip Exactly right Clare. The soob has a bulletproof interior but the use of liquid cooling plus a drive system adds two complete failure modes that aren't there at all with the Corvair. With the Corvair if you take care of the systems design aspect, basically by using sound aircraft design practices for carburation and ignition, I question whether LyCon practice, which is actually derived from small flathead gasoline burning farm tractors- a big single barrel updraft carb and two farm tractor magnetos- is intrinsically "Sound design practice". Remember when the Continental, Lycoming and Franklin engines were introduced they were not considered sound aircraft design! Real airplanes used P&W or Wright radials or Allison or Curtiss liquid cooled inlines-the E-2/J-2 Cub and similar planes were considered the ultralights of their day, and before WWII one could fly an airplane without a license if it wasn't registered and flown only within one state (until the states, except Oregon, outlawed it-which is why the early homebuilders often moved there.) Nothing smaller than a Waco was considered a real airplane. Simple, light, reliable is the Prime Directive, regardless of how old the technology is. When it comes to airplanes, that is sound design practice, when considering ass pucker levels while in climbout over a builtup area or over a tree line. I don't care if it's made of rocks. If it's simple, light and reliable, the fact that it's derived from tractors is irrelevant. The big radials of the old days, when you look at it, were also very simple, light reliable designs in relative to the alternatives in view of the power requirements. You will note that the "more sophisticated" liquid cooled aircraft engines never survived in a significant way past WWII in commercial service, with one unusual exception, the Canadair North Star airliner, which used Merlins. Everything else was radials because relatively speaking they were the simplest and lightest and most reliable solutions before jet engines, even if their air cooling and pressure carbs were "crude". This is the point. If you want to take advantage of technology like electronic control, you have to design for complete redundancy if your control system has a sudden potential failure mode. Not practical for the homebuilder. The farm tractor technology engine can have its components built with sufficient inherent robustness, or have a very gradual failure mode, to provide the required safety without needing duplicate systems, (like a crude but simple carb) or at least a minimal level of redundancy. I am a fan of auto conversions, but believe that those conversions to be viable must be as close as possible to a traditional aircraft engine from the standpoint of simplicity and overall design, and the Corvair using a Stromberg aircraft carb and a dual primary points ignition comes closest to fitting the bill of any conversion I have seen besides a Great Plains VW. Now that the crankshaft strength issues are known and a way forward is clear, the Corvair engine's potential is even better than before as a conversion IMHO. Cheers John Kahn Montreal |
#86
|
|||
|
|||
Corvair conversion engines
---------------much snipping------------
This is the point. If you want to take advantage of technology like electronic control, you have to design for complete redundancy if your control system has a sudden potential failure mode. Not practical for the homebuilder. The farm tractor technology engine can have its components built with sufficient inherent robustness, or have a very gradual failure mode, to provide the required safety without needing duplicate systems, (like a crude but simple carb) or at least a minimal level of redundancy. I am a fan of auto conversions, but believe that those conversions to be viable must be as close as possible to a traditional aircraft engine from the standpoint of simplicity and overall design, and the Corvair using a Stromberg aircraft carb and a dual primary points ignition comes closest to fitting the bill of any conversion I have seen besides a Great Plains VW. Now that the crankshaft strength issues are known and a way forward is clear, the Corvair engine's potential is even better than before as a conversion IMHO. Cheers John Kahn Montreal In general, I agree. I wish also to advocate that, in the event that a purpose designed crank and case/front bearing assembly do not become available, a rear drive assembly might also resolve the problem--although it might weigh slightly more. Or may not? Examples of the suggestion include the Greta Planes rear drive for VW and their derivatives as well as Steve Wittmans designs for Formula-V and the Buick/Olds V8s. I took a look and saw that the Wittman plans remain available from Aircraft Spruce. I have a set of the V8 conversion plans that I purchased while he was alive, and presume that the biggest problem in using them on a different engine might be selection of the optimum drive shaft diameter. The obvious advantage is that the original vibration dampening components, which putatively have been thoroughly tested in and for automotive service, remain intact. Just my $0.02 Peter |
#87
|
|||
|
|||
Corvair conversion engines
.... the Greta Planes rear drive for VW ...
Drat! I can't spell either! ):-( Peter |
#88
|
|||
|
|||
Corvair conversion engines
J.Kahn wrote: snip Simple, light, reliable is the Prime Directive, regardless of how old the technology is. When it comes to airplanes, that is sound design practice, when considering ass pucker levels while in climbout over a builtup area or over a tree line. I don't care if it's made of rocks. If it's simple, light and reliable, the fact that it's derived from tractors is irrelevant. The big radials of the old days, when you look at it, were also very simple, light reliable designs in relative to the alternatives in view of the power requirements. You will note that the "more sophisticated" liquid cooled aircraft engines never survived in a significant way past WWII in commercial service, with one unusual exception, the Canadair North Star airliner, which used Merlins. Everything else was radials because relatively speaking they were the simplest and lightest and most reliable solutions before jet engines, even if their air cooling and pressure carbs were "crude". This is the point. If you want to take advantage of technology like electronic control, you have to design for complete redundancy if your control system has a sudden potential failure mode. Not practical for the homebuilder. The farm tractor technology engine can have its components built with sufficient inherent robustness, or have a very gradual failure mode, to provide the required safety without needing duplicate systems, (like a crude but simple carb) or at least a minimal level of redundancy. I am a fan of auto conversions, but believe that those conversions to be viable must be as close as possible to a traditional aircraft engine from the standpoint of simplicity and overall design, and the Corvair using a Stromberg aircraft carb and a dual primary points ignition comes closest to fitting the bill of any conversion I have seen besides a Great Plains VW. Now that the crankshaft strength issues are known and a way forward is clear, the Corvair engine's potential is even better than before as a conversion IMHO. Mechanical fuel injection with electronic trim is within the competence of the homebuilt community and with the existing auto manifolding it's doable. A modified auto carburetor is also useable and just as reliable as an aircraft one. One consideration in auto conversions is that Detroit (or Japan) has sunk billions in reliability engineering and testing and maximizing use of that is critical. The simplicity of the carbureted magneto Lycoming is enviable. Its efficiency and brute force solution of problems are not. If it were cheap enough these could be overlooked, but it isn't and they can't. The simple life, as someone said, isn't so simple. Let's look at the problems with the simple LyCon engine: 1. Free air cooling worked well in the J-3 Cub and the 6:1 cr A-65 Continental engine. The Cub had about a thirty knot airspeed range, maybe forty, and the tops of the cylinders didn't get all that hot and a 1000-hour life was considered fantastic anyway. It was a day VFR airplane, there was no engine management to speak of (many didn't even have a mixture knob, including the Champ I soloed in-in the mid-80s) and you never flew higher than cars drove in the mountains, so you didn't miss it. Fast forward: the Bonanza with a TSIO-550 Continental. Not a successful concept anymore. With no speed brakes, a very clean airframe, and the expectation of single pilot IFR at FL180 and above by non-full-time (say the word: amateur) aircrew.....engine management and shock cooling (most owners would never execute a power-off approach, not with the price of cylinders what it is!) played a big part in the Bonanza debacle that could have put the keys to the Webb Ave.plant in a plaintiff's pocket many times over. It didn't, but GA has never and may never recover. Single lever power control, is rationally necessary for safe single pilot IFR. Someday the FAA will be forced to make it so. With a piston engine this means, as far as I can tell, either liquid cooling or a regulated, forced fan system. Shock cooling has to be made impossible, even with a cruise power split-S and vertical dive. ( Spare me the no acro airspace rant...unless you think the supposed liability crisis is from people losing their licenses instead of the family into a hillside.) 2. Direct drive means if you land gear up (spare me the you'll get a 30 day suspension anyway rant) it's probably time not only for a new prop but also new crankshaft as well. This in turn makes insurance for RG aircraft much higher. Also makes insurance for taildraggers much higher because you might put it on its nose. A good redrive will fail a belt or quill shaft first. This is called weak link-strong link design. Everything will fail sooner or later. You want a known point of first failure that is accessible, inexpensive, and of predictable consequence. If you use a wood or composite blade on a variable pitch or ground adjustable hub the blades will go and probably protect the hub. And because they won't last "forever' anyway there will be a competitive market for blades. Even if the hub dies, it's a lot cheaper than a complete major OH and new crank. There's also a 3 through about 7 or 8. But that's a good start. |
#89
|
|||
|
|||
Corvair conversion engines
Richard Lamb wrote: Well, I asked about that... Seems it would cost a bazillion bucks for some reason. Aren't the Chinese hot rodders cutting custom cranks yet? Everyone thinks there are these cheap foreign made hot rod parts. I've never seen any, anywhere. They don't hot rod engines in Asia at all-except a few things in Japan, for offroad use, and at very high prices as any 240Z owner can attest! And what pieces are from Europe are HIGH DOLLAR too. Even for VWs most everything is made in Southern California. I've always wanted a Ferrari V12 for a street rod....you think we can get Taiwan to make heads and blocks and cranks? Uh unnh. They will want a million dollars upfront for patterns and core boxes. |
#90
|
|||
|
|||
Cheap Chinese Parts
Bret Ludwig wrote:
Richard Lamb wrote: Well, I asked about that... Seems it would cost a bazillion bucks for some reason. Aren't the Chinese hot rodders cutting custom cranks yet? Everyone thinks there are these cheap foreign made hot rod parts. I've never seen any, anywhere. They don't hot rod engines in Asia at all-except a few things in Japan, for offroad use, and at very high prices as any 240Z owner can attest! And what pieces are from Europe are HIGH DOLLAR too. Even for VWs most everything is made in Southern California. I've always wanted a Ferrari V12 for a street rod....you think we can get Taiwan to make heads and blocks and cranks? Uh unnh. They will want a million dollars upfront for patterns and core boxes. I generally agree with most of what Mr. Ludwig posts but in this instance perhaps my knowledge of the industry could offer some insight. Since the semi-original topic was crankshafts I will confine my observations to these. In fact nearly all forged crankshafts sold in this country by the hot rod industry are forged in China. With the exception of the raw forgings that the OEM auto manufacturers offer, I can't think of anyone who actually forges their own cranks in the USA. Not many aftermarket suppliers will admit to this yet it's always the same story, kind of like the old Midas commercial 'well, we used to, but we don't anymore'. Most of the big names still finish grind the cranks themselves. In a broader sense, it is becoming increasingly difficult, to the point of near impossibility, to find an independent forge shop that will do job work. This is from the point of view of one who has actively looked. Recently, my firm had cause to seek the services of a forge shop for just such a type item, not a crankshaft, but similar in size, weight, and complexity. We were prepared to provide dies. The best price I was able to get quoted in the US, really the only quote that wasn't an obvious brushoff, was for $500 per in quantities of 25. That is forging service only, we were to provide the material. Several firms in China quoted the job at $50 each. If this seems too low, think about hot rod firms selling brand new forged Chevy cranks for $299. Due to a number of issues, not the least of which was my unease at doing this type of business in China, we did not proceed with the forging. Oh yes, for those who would ask how I know about the aftermarket industry, during my researches I approached every aftermarket hot rod firm that I could find. When I asked them if they would certify country of origin for all services, none would agree. In several cases this led to very interesting conversations about the state of the industry. Niall |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Book Review: Converting Auto Engines for Experimental Aircraft , Finch | Paul | Home Built | 0 | October 18th 04 10:14 PM |
P-3C Ditches with Four Engines Out, All Survive! | Scet | Military Aviation | 6 | September 27th 04 01:09 AM |
What if the germans... | Charles Gray | Military Aviation | 119 | January 26th 04 11:20 PM |
Corvair Engine Conversion Breakin Success | Dick | Home Built | 1 | January 11th 04 02:06 PM |
Corvair Conversion | Gig Giacona | Home Built | 17 | October 27th 03 09:43 PM |