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#11
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Frank van der Hulst wrote:
Bellsouth News Server wrote: What would be better than a single, would be a smaller two rotary. Whatever happened to the motorcycle rotaries? IIRC Suzuki had a 500cc rotary in a motorcycle about 20 years ago. And Norton too? I'd guess that a rotary of this size would be ideal for a microlight aircraft. They faded into history... Tony |
#12
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How much does the 13b single rotor weigh? And how much does it cost to get
the e-shaft shortened? The basic engine with stock housings is about 120-125 lbs, but you could lose 25 lbs of that in exchange for around $3000 if Racing Beat ever finishes their aluminum side housings. The e-shaft can be cut down from a stock shaft, but it's no small job, so it's better to buy a new one, or find one that someone else has made. Over the years, lots of these have been built, including a number of shafts that were made by NASA. In the near future, there will be a much better availability of these I think, but nothing definite now. There is an outfit here in Canada that is promising to produce some small rotaries for light planes, but I don't know how far along they are. A German outfit makes single-rotor go-kart engines, as well as an UL version. Those are actually the same engine if you're talking about the German place that I'm thinking of. The Canadian outfit bought the rights to the engine, and will eventually start making them in Canada, though the price is pretty high for such an unproven engine. I wish them luck, but haven't seen much interest from the community yet. As for other posts on this subject: There were certainly some smaller rotaries produced, such as the motorcyle, and even some outboard engines. I just don't think any of those were nearly as reliable as the Mazda version has been. They also aren't that available, or I'd love to play with one. As for rotary engines being in cars, yes, they are. The RX-7 was sold until 2001 or 2002, and the RX-8 has a new version of the rotary called the Renesis. Excellent engine! In the US, people still remember the seal problems that Mazda had when they were introduced in the early 70's, which is unfortunate. Other countries have had several cars, trucks, etc with rotary engines, but Mazda doesn't sent them here, because we won't buy them. The RX-7 was discontinued in the US after 95, but sold in other countries until at least 2001. The RX-8 was said to be our last chance, and if the sales in the US were good (and they have been), we would get the next version of the RX-7 as well, and perhaps other rotary powered vehicles. Cheers, Rusty |
#13
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The basic engine with stock housings is about 120-125 lbs,
I meant go make it clear that this is without a redrive, or any other engine accessories. The total installed weight will be somewhere around 220 lbs with stock housings, and the currently available (heavy, overbuilt) redrives. The engine can make 100+ HP pretty easily, and much more with a turbo. Rusty |
#14
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Thanks, for the info, Rusty.
What gearbox are you using? It seems like overkill to put one of Tracy's boxes -- or something similar -- on a single rotor. I would think a belt drive might be engineered that would be considerably lighter -- expecially if you use the poly-v belts. Just to add about why rotaries aren't more popular -- a big reason is that the auto industry is geared around the piston engine. The infrastructure of suppliers and manufacturers is all predicated on that business model, so there is a lot of inertia there and changing course is like trying to do a U-turn in an aircraft carrier. However the wankel engine has some incredible advantages, including smoothness simplicity, ruggedness and power potential that truly puts it a class above the piston engine. There is no question about that, as rotary-powered race cars have proven over and over -- until they are banned because they simply have an unfair advantage. Regards, Gordon. "Bellsouth News Server" wrote in message ... The basic engine with stock housings is about 120-125 lbs, I meant go make it clear that this is without a redrive, or any other engine accessories. The total installed weight will be somewhere around 220 lbs with stock housings, and the currently available (heavy, overbuilt) redrives. The engine can make 100+ HP pretty easily, and much more with a turbo. Rusty |
#15
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On Tue, 26 Jul 2005 23:58:12 -0400, "Gordon Arnaut"
wrote: However the wankel engine has some incredible advantages, including smoothness simplicity, ruggedness and power potential that truly puts it a class above the piston engine. There is no question about that, as rotary-powered race cars have proven over and over -- until they are banned because they simply have an unfair advantage. Regards, Gordon. It's true that the rotory offers some interesting advantages, one of which is the ability to continue to run and produce power after the engine has lost compression due to overheating and warped side seals. It will make power right to point where you shut it down, but you won't get it started again because of low compression. I guessing that it's disadvantages were enough that it never appealed to big auto makers to work on them. Wankel itself was unable to make it a success and it's hard to argue that Mazda has either. It's fuel consumption and inherently dirty emissions which require a lot of technology to clean up plus the investment in machine tools to create it just didn't seem worth it to the bean counters, I suppose. And the public did not seem to care much that it was available. When Mazda first brought it out, it had a number of quirks that the buying public had trouble getting used to. It had a cold temperature starting assist that consisted of an injector that added pure antifreeze from a seperate tank into the intake manifold. This of course created a dense white cloud of smoke, which the owner was told was normal, and it was, but it sure made owners nervous to see it. And the owner had to refill the tank, which they often did not do, which resulted in hard cold weather starting. Add this to the manual choke, which the RX-7's had for many years and which the public had difficulty using and it's easy to see why it was popular only for a limited number of people. Then there was the stench of the exhaust. Nothing smelled worse, not even a diesel, and you could not tune it away. When properly adjusted for emissions, it stank most powerfully, it felt like it was actually burning your nostrils. Mechanics didn't like it because it had two ignitions called a leading and trailing ignition and originally, the distributer held three sets of points in two layers. Not easy to adjust and naturally problematic. That of course went away with the advent of electronic ignition, and eventually the engine was fuel injected and everything was computer controlled. But converting such an engine for use in an airplane is not without it's challenges. Corky Scott |
#16
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Hi Gordon,
I'm starting out with one of Tracy's RD1C drives, which is 2.85:1, and good for way more power than I'll make wiht the single rotor. Unfortunately, it's about 45 lbs stock. Speaking with Tracy, there's probably about 5 lbs of weight that can be removed without losing any strength, and perhaps more if you're willing to sacrifice strength in the drive. That wouldn't be a problem for the single rotor, but if you ever wanted to use it on a two rotor, it would be. Richard Sohn has a running 12A single rotor now, and he's using a Hirth G-40 gearbox. At last report, his total engine weight was 170 lbs, which is pretty great. He's custom made many of the parts on his engine to save weight, and might produce them if it all works out well. He's currently on a slow, and careful development and test program, and eventually plans to put the engine in his Avid, which I believe is flying with a Subaru. It will be interesting to see how the Hirth box works out, but I'm not sure how much lighter it really is in the long run. I've asked Richard for the total weight, but since so much of the adaptation is dependent on his custom end housings, he hasn't been able to come up with a number. My guess is something around 30 lbs total for the drive. I asked about belt drives, and found that someone was making one for the single rotor that David Atkins is selling. So far, I haven't heard any reports of how that worked, if it even got finished. One other fellow who makes belt drives told me that he refused to make such a drive for Atkins, because it wouldn't be strong enough. His point was that the single rotor is still full sized, and gives the same strength power pulses as the two rotor does. Because of this, he felt the drive has to be as strong as the two rotor drive. This does make sense to me, but I'm sure there has to be a way to reduce the weight further. FWIW, my plan was to bolt together off the shelf parts, and see what it weighs. The Kolb Slingshot that I'll be using initially will handle the weight, when flown as a single place, and with a BRS chute to balance the CG. Once I get a worst case weight, then I'll start working on reducing it. Cheers, Rusty (hiding rotary info in the light twin thread) What gearbox are you using? It seems like overkill to put one of Tracy's boxes -- or something similar -- on a single rotor. I would think a belt drive might be engineered that would be considerably lighter -- expecially if you use the poly-v belts. |
#17
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Saying that Rotaries have an unfair advantage is only part of the
story. In the appropriate classes, they were raced for years, often successfuly. But they were still hated because they were so LOUD. Unbearably, explosively loud without big heavy mufflers - which got to be mandatory in many venues This might not matter much for a target drone or a tiny cart engine but it does everywhere else. |
#18
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Saying that Rotaries have an unfair advantage is only part of the
story. In the appropriate classes, they were raced for years, often successfuly. But they were still hated because they were so LOUD. Unbearably, explosively loud without big heavy mufflers - which got to be mandatory in many venues This might not matter much for a target drone or a tiny cart engine but it does everywhere else. |
#19
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I guessing that it's disadvantages were enough that it never appealed
to big auto makers to work on them. Wankel itself was unable to make it a success and it's hard to argue that Mazda has either. How can you say that Mazda hasn't made this successful? Sure, the initial introduction had it's share of problems, but since the RX-7 made the re-introduction of the rotary here in the US, the engine has been as troublefree as any engine produced. Emissions was one of the biggest problems, but the newly redesigned Renesis engine cleaned that up, as well as taming a bit of the bark, and overly hot exhaust. Fuel consumption in aircraft use does not seem to be any worse than any other engine of the same power range. The truth is that other manufacturers tried the rotary, but didn't feel like it was worth developing, since they were perfectly happy to churn out piston engines. Only Mazda seems to have had the willingness to stick with it, and make it successful. But converting such an engine for use in an airplane is not without it's challenges. Corky Scott What challenges does it present, that aren't shared by any other auto engine? Heck, it already has dual ignition. These days, two rotor engines are not nearly the challenge that some engines would be, because Tracy Crook sells engine controllers, monitors, and gear drives. Conversion Concepts makes excellent mounts. About the only thing missing is an off the shelf intake, and exhaust, which aren't far behind. Cheers, Rusty 13B powered RV-3 flying (2500+ fpm climb, 200 mph cruise) Kolb Slingshot being converted from 912S to single rotor almost as I type |
#20
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Earlier, Bellsouth News Server wrote:
How can you say that Mazda hasn't made this successful? Sure, the initial introduction had it's share of problems, but since the RX-7 made the re- introduction of the rotary here in the US, the engine has been as troublefree as any engine produced. Well, Corky didn't say that Mazda hasn't made the Wankel rotary a success. He only said that it's hard to argue it: Earlier, Corky Scott wrote: : Wankel itself was unable to make it a : success and it's hard to argue that : Mazda has either. That the vast majority of Mazda cars are powered by conventional piston engines supports Corky, at least when you consider the aspect of commercial success. And it is undeniably commercial success by which car manufacturers measure themselves and each other. Sure, the RX-7 and RX-8 motors seem to be trouble-free, but at what cost? And further, since most of the patents that cover the Wankel innovations are now expired or are about to expire, you'd expect to see other manufacturers adopting the Wankel. That you don't see this tends to support Corky's argument that for the vast majority of engine applications the Wankel's disadvantages outweigh its advantages. Personally, I think that Wankel rotaries continue to be part of Mazda's automobile offerings only because it would be harder sell an RX-series car without them. I believe that Mazda decided to continue the Wankel heritage of the RX only after carefully balancing the greater cost per unit horsepower of their rotary against the whizz-bang (Okay, whizz-hummm in this case) technical appeal in the RX package. An RX without a rotary would be like a Mustang without three-element taillights or a Buick without fake exhaust portholes. Thanks, and best regards to all Bob K. http://www.hpaircraft.com/hp-24 |
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