Geoff_H Posted May 8, 2020 Share Posted May 8, 2020 My project has two small engines. I wish that I could go RAA, but I will have to go Experimental GA Link to comment Share on other sites More sharing options...
spacesailor Posted May 8, 2020 Share Posted May 8, 2020 You can,t count, I count Ten. spacesailor Link to comment Share on other sites More sharing options...
APenNameAndThatA Posted May 8, 2020 Share Posted May 8, 2020 Would you class the Bessler as a "Gotta light?" aircraft? Link to comment Share on other sites More sharing options...
facthunter Posted May 8, 2020 Share Posted May 8, 2020 Why not just squirt the steam out the back and forget having the engine? Nev Link to comment Share on other sites More sharing options...
Bruce Tuncks Posted May 8, 2020 Share Posted May 8, 2020 Geoff h, why do you need to go GA just to have more than one engine? Are they stuck in the old days? Link to comment Share on other sites More sharing options...
Geoff_H Posted May 8, 2020 Share Posted May 8, 2020 Yes. A similar design of aircraft doesn't seem to be able to get approval. From what I believe the only thing stopping RAA from approving a multi engine aircraft is that they don't have an approval system and documentation that is approved. Not sure that I have the exact reason. Link to comment Share on other sites More sharing options...
Downunder Posted May 8, 2020 Share Posted May 8, 2020 A variable pitch prop is too heavy and expensive Electric is perfectly suited to IFA props. They can be built far lighter than ICE systems and seriously improve power delivery and efficiency. Especially in folding or full feathering configuration. Remember, an electric motor can be turned completely off and in a reduced drag airframe, a gliding decent can extend range considerably. Today I was asked why you wouldn't do an electric plane as a 2 or 4 or more engines. I wouldn't do it because of the extra wiring,control systems and props increasing weight, unless the smaller motors were considerably more efficient and powerful than a larger single. Link to comment Share on other sites More sharing options...
Mike Borgelt Posted May 9, 2020 Share Posted May 9, 2020 NASA currently has a project where numerous small electric motors/props are mounted on the leading edge of the wing. X-57 Maxwell. https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-109.html Now about using a reverse pitch prop. Most small aircraft can already land in a shorter distance than they can take off in. So you land on the short strip using reverse pitch and get to dis- assemble and truck the aircraft out. The restriction to one engine one prop in RAAus shows up yet again the stupidity of breaking up private aviation into numerous small fiefdoms all with different rules, while we all fly in the same airspace over the same landscape. 6 Link to comment Share on other sites More sharing options...
Blueadventures Posted May 9, 2020 Share Posted May 9, 2020 You can,t count, I count Ten. spacesailor An engine split in two and a four blade prop split in two 1/2 + 1/2 + 1. Link to comment Share on other sites More sharing options...
spacesailor Posted May 9, 2020 Share Posted May 9, 2020 And don,t forget the bureaucratic " wing load rule " . spacesailor Link to comment Share on other sites More sharing options...
Flightrite Posted May 9, 2020 Share Posted May 9, 2020 Multi eng flying machines are all about getting more HP and more blade swept area as well as redundancy without having one large powerplant. Today's modern high bypass jet engines produce well over 100000 lbs thrust, enough for a single powerplant to push a large airliner thru the air on its own, they don't do that cause of redundancy (and a host of other issues) There is a growing amount single engine turbines both prop and jet available these days but the redundancy is mostly removed, all expensive and complex, something we don't need in our basic Sunday flyers? Link to comment Share on other sites More sharing options...
spacesailor Posted May 9, 2020 Share Posted May 9, 2020 WE WILL End up with multiple motors. But it will be electric motors. OR will those bureaucratic knoms kill of that too !. spacesailor 1 Link to comment Share on other sites More sharing options...
Bruce Tuncks Posted May 9, 2020 Share Posted May 9, 2020 I'm sure you are right Mike, but it was the landing on the farm strip which frightened me, not the take-off. I had 550 metres, but came in over the shearing shed and so the effective landing was a bit less. And you could start right back, gun the engine and let off the brake and be off the ground in less than 200m one up. Once I was landing and aiming to miss the shearing shed apex by 1m when the daughter snapped a pic. I was actually more like 30m above the shed roof. Maybe I have been spoiled by the WW2 bomber strips at Gawler. Link to comment Share on other sites More sharing options...
facthunter Posted May 10, 2020 Share Posted May 10, 2020 You MIGHT HAVE to land on a short strip but you NEVER have to take off from a short strip.. When you have only one engine and don't trust it (which is wise) don't fly over what you can't land on.. Having to clear a row of trees on each take off is like russian roulette with one or even two motors. In fact it could be twice as dangerous as with one, in critical circumstances. ie TWO chances of not making it. Either one will do IF it doesn't go well on the one still running (Hard) and requiring YOU to maintain control of it and have the exact speed . All clear around the aerodrome and you could be safe with any engine. Nev 1 Link to comment Share on other sites More sharing options...
M61A1 Posted May 10, 2020 Share Posted May 10, 2020 something we don't need in our basic Sunday flyers As Rec flyers we don't actually need to do anything, so as long as it's for recreation why not open the door for some innovation and experimentation for the fun of it? 1 Link to comment Share on other sites More sharing options...
facthunter Posted May 10, 2020 Share Posted May 10, 2020 Prove it won't up the cost for the others in the show and I'm all for it. But why have two engines when one is enough?. They are expensive, heavy and keeping them in synch will drive you mad. Build a plane that flies nice and costs less. A twin on one motor is a very poor design of flying machine indeed. Yes we should go electric , ducted fan or anything that works OK and isn't basically dangerous and unstable. Gyros fly well in gusts. . Powered gliders have been popular from time to time. with solar panels and electric you might avoid the out landing recovery issues too. Nev 1 Link to comment Share on other sites More sharing options...
ClintonB Posted May 10, 2020 Share Posted May 10, 2020 What about the Lazair. The 2 chainsaw motors, cling wrap covering and plastic props. there is one flying in Tamworth. It’s all up weight is about the equivalent of me. 1 Link to comment Share on other sites More sharing options...
M61A1 Posted May 10, 2020 Share Posted May 10, 2020 Prove it won't up the cost for the others in the show and I'm all for it If you are doing it for the fun of it you don't need to prove anything, just enjoy doing it. Just because someone doesn't think the idea is practical doesn't mean it should stop others from doing it. Link to comment Share on other sites More sharing options...
Marty_d Posted May 10, 2020 Share Posted May 10, 2020 Wouldn't have thought syncing the engines would be a problem with multi-electric... Link to comment Share on other sites More sharing options...
danny_galaga Posted May 10, 2020 Share Posted May 10, 2020 if you run a 3-phase motor faster than it's maximum frequency i.e. 3000rpm or 1500rpm depending on the number of Poles you will generate electricity back into the mains. All you have to do in this case is have a variable speed controller for the power going to the motor and you can recharge a battery and use it as a brake Are they using 3 phase motors in cars and planes? I wouldn't have thought they would be flexible enough? Surely they would be brushless? And DC? Link to comment Share on other sites More sharing options...
Geoff_H Posted May 10, 2020 Share Posted May 10, 2020 They seem to be using multiphase motors with inverters from DC. The CSIRO lightweight solar car powered motors stator has the windings and the rotor is the outside case with high flux permanent magnets. However my post that you have quoted was just to confirm that an AC motor will become a generator when it is running faster than the slip frequency. By the way, Tesla did heaps of work on AC, he discovered ( with straight mathematics) that the greatest power for the least conductor size is when you have 3 phases. It always astounds me when the American 220VAC is done with 2 phases 180 degrees apart. Link to comment Share on other sites More sharing options...
old man emu Posted May 10, 2020 Share Posted May 10, 2020 It always astounds me when the American 220VAC is done with 2 phases 180 degrees apart. Why? If there's a way to be contrary, the Yanks will be. 1 1 Link to comment Share on other sites More sharing options...
Bruce Tuncks Posted May 10, 2020 Share Posted May 10, 2020 Those americans paid quite a price for being pioneers. Their dunnies are not as good as ours either. And yes danny, the motor gets 3 phase from the ESC which draws dc from the battery. Have a look at an ESC and you will see 3 wires to the motor. Electric bikes have a brushless dc motor with hall effect commutation , the halls do the same job the brushes would have done, which is to switch the current to the right motor windings at the right time. Link to comment Share on other sites More sharing options...
Bruce Tuncks Posted May 10, 2020 Share Posted May 10, 2020 I am doing this from a farm which has a single phase supply ( Single Wire Earth Return ). Only one wire... cheap! 1 Link to comment Share on other sites More sharing options...
old man emu Posted May 10, 2020 Share Posted May 10, 2020 Their dunnies are not as good as ours either The first time I went to the USA, I got into my hotel room to find that the toilet bowl was full of water. The Room Service guy must have thought I was some back-country hick when I called to report the broken toilet. Still, a toilet bowl full of water is way better than a squat hole in the floor. It's amazing to see those in the toilets of an international airport. Gives "kangarooing the dike" a whole new meaning. 1 1 Link to comment Share on other sites More sharing options...
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