gofastclint Posted February 11, 2009 Posted February 11, 2009 We all love em, their unique noise as they fly by and they eliminate torque roll, so has any one seen them for light aircraft? are there any people thinking of supplying them or making kits?
Deskpilot Posted February 11, 2009 Posted February 11, 2009 Clint, I guess you've seem my signature from time to time and perhaps have concluded that I would like C/R props as well. There is a company in Oz that sells airboats with V8 engines driving caged props. I haven't followed it up but you might be able to but the gear box and prop assemble as a separate item. Other than that, I think it's a case of design and build it yourself. Another thing to look into is the use of 2 props under RA-Aus rules, i.e. one engine, one prop. I've be told that it would be legal under certain conditions, as would retract gear, but you need to look very closely. If it's not allowed, I believe a case could be made, to CASA if neccessary, that it is a single propulsion assembly and no assymetric problems are introduced. Indeed, it would be safer as prop wash torque is eliminated.
Deskpilot Posted February 11, 2009 Posted February 11, 2009 Not sure if this page still works http://www.airboatindustries.com.au/counter_rotating_prop.html
gofastclint Posted February 12, 2009 Author Posted February 12, 2009 After watching a few videos of a mustang fitted with a CRP at reno, It got me thinking of what one would be like in a smaller aircraft.
facthunter Posted February 12, 2009 Posted February 12, 2009 Complexity. All this stuff is great in theory. Rule 1. Never put a piston engine through a gearbox unless you absolutely have to. If it's not there it's not a problem. Simplicity is safer and cheaper. You do not have the resources of the air ministry,and the knowledge of Rotol.. There are plenty of instances of non-certified props shedding blades, where the blade goes one way and the engine goes the other. Even certified ones develop cracks but they are picked up in the required inspections (mostly). The least lethal set-up is a direct drive and a Wooden prop. It's all about harmonics in the drive shaft. It even happens in turbo-props. nev..
gofastclint Posted February 12, 2009 Author Posted February 12, 2009 All this stuff is great in theory. Rule 1. Never put a piston engine through a gearbox unless you absolutely have to. If it's not there it's not a problem. Simplicity is safer and cheaper. You do not have the resources of the air ministry,and the knowledge of Rotol.. There are plenty of instances of non-certified props shedding blades, where the blade goes one way and the engine goes the other. Even certified ones develop cracks but they are picked up in the required inspections (mostly). The least lethal set-up is a direct drive and a Wooden prop. It's all about harmonics in the drive shaft. It even happens in turbo-props. nev.. I saw a few props explode on you tube, not fun. Is that why Jabiru stick to them. The good thing about this forum is if I can't find the answer on the net I get it here. Guess I'm back to the drawing board.
lbarnes Posted February 12, 2009 Posted February 12, 2009 What about this. Sunflightcraft - Paraplanes - Airchopper - Rotax - Coax P - Microlights- Flugzeuge - Ultralight Planes - Ultraleicht Flugzeuge - XTC - XTS
Deskpilot Posted February 12, 2009 Posted February 12, 2009 Clint, you give up too easily. Did the airboat site open for you, I can't get to open
drifter_driver Posted February 12, 2009 Posted February 12, 2009 sunflight coax-prop What about this.Sunflightcraft - Paraplanes - Airchopper - Rotax - Coax P - Microlights- Flugzeuge - Ultralight Planes - Ultraleicht Flugzeuge - XTC - XTS looks like the reduction assembly is derived from one engine to the output of 2 counter-rotating props. unnecessary complexity IMO, probably worth it if designed to be driven from two smaller engines for redundancy
gofastclint Posted February 12, 2009 Author Posted February 12, 2009 Clint, you give up too easily. Did the airboat site open for you, I can't get to open The site didn't open for me but one site I did find was talking about an odd number of blades, for example, 3 on the front and 4 on the back. Something to do with the harmonic pulse of the front prop working better with a different number of trailing rear blades. Sounds interesting.
phvdw Posted February 12, 2009 Posted February 12, 2009 Coax-P ineed for certain engines it's existing as for ROTAX 582;503 CR Gear box system "COAX-P" find more on: www.sunflightcraft.com
Guest ozzie Posted February 13, 2009 Posted February 13, 2009 belt drives are great for taking up the damaging loads that are usually transmitted via a g/box or look at a cluth g/box/ for contra rotating props look for john moody he built them years ago for the easy riser simple and they worked maybe get an idea or two from them ozzie
Deskpilot Posted February 13, 2009 Posted February 13, 2009 John K Moody, father of the Ultralight. Found it, found Easy Riser, but no mention of c/r props. Got any more info?
Guest Maj Millard Posted February 19, 2009 Posted February 19, 2009 The designer of the Easy Rider Larry Mauro would not even talk to John Moody after Moody tumbled his modified Easy Riser at Oshkosh. Larry thought it took an idiot to tumble an Easy Riser. The 'Father of ultralights" title was probabily coined by Moody himself. Moodys 'contra rotating props' so to speak, were actually two props mounted on a single shaft but each driven independantly by a separate engine and belt drive. Engines were Partner chainsaw engines I think. He also had a little undercarrage on the plane as opposed to foot launching. All this rearward additional weight is what caused the thing to tumble, in Larry Mauro's opinion. The direct-drive wood prop combination is not the 'perfect combo' as suggested, in fact that combo has also had it's share of problems, with prop/piston harmonics and out of tune pulses leading in some cases to cracked and seperated hubs, and cranks. The belt drive reduction does a good job of smoothing things out, as does the rubber donut in the Rotax 2 stroke gearboxes. The straight cut gearboxes on the 912s seem to be pretty robust and smooth, with good damage resistance qualities. It is unfortunate they choose to use the engine oil to lube the gearbox also, but that is the only weakness. The best belt drive reduction I have come across is the Hirth Poly V multi ribbed belt, fitted to the early F23 and F30s. It is a straight 2 to 1 ratio, and once set up properly, is good for 500 hrs.........
Guest ozzie Posted February 19, 2009 Posted February 19, 2009 I think Moody's set up was the Maximizer twin engine and prop set up. i think your right on Moody's self lable on the father of ultralights.plenty of other american 'quiet achievers' from that time. on a globale scale this title goes to Aussie Ron Wheeler. Ozzie
gofastclint Posted February 20, 2009 Author Posted February 20, 2009 I think Moody's set up was the Maximizer twin engine and prop set up.i think your right on Moody's self lable on the father of ultralights.plenty of other american 'quiet achievers' from that time. on a globale scale this title goes to Aussie Ron Wheeler. Ozzie So many people contributed to the "ultralight" Moody sounds like a wan......
Guest Maj Millard Posted February 20, 2009 Posted February 20, 2009 Yes Ozzie, I think it was the maximizer, your memory is as good as mine !. Gofastclint, I knew Larry Mauro pretty well in California, and yes he did think Moody was, as you say a Wan...............
facthunter Posted February 20, 2009 Posted February 20, 2009 demographics. There does seem to be quite a few wanderers in america sometimes. Some of the snake-oil must have migrated from the fundamentalist, evangelistic capitalist "think" tank. Nev..
Guest ozzie Posted February 21, 2009 Posted February 21, 2009 To avoid any confusion or mis credit the Maximizer and twin maximizer was designed and patented by Don Stewart the original mazimizer is the concept used for virtually all belt driven reduction units that are in use today.It first appeared in his VW powered headwind that appeared at the Rockford EAA convention around 1968. from the EAA sport pilot records july 1998 issue
Guest Maj Millard Posted February 21, 2009 Posted February 21, 2009 I seem to recall it was around 1975 or 76, I had just come back from Wilton after a days jumping. Went by the Parasport shop which was still then under Allan Jays house, to pick something up. Ran into Allan and Andy Johnston, and they told me they had been out somewhere near Cambletown, watching this bloke who had built a little hang glider type areoplane, with a Victa lawn mower motor on it. They said it had flown pretty good. It was Ron Wheeler. It was the first reference to an ultralight I ever heard. Larry Mauro in California had already designed and built the Easy Riser, but it wasn't powered yet. It won the US national hang gliding championships in 1976 as a foot launched hang glider. I have a great photo on my wall of it competing in that meet, but not sure who the pilot was.......................
Guest ozzie Posted February 21, 2009 Posted February 21, 2009 The thing that put Ron Wheeler in front of everyone else is that he had his ANO95:10 in place in 1975. i think that the US FAR part 103 that allowed footlaunch powered ultralights did not sort itself out until 76 or 77 . i remember seeing some footage of a weedhopper being foot launched. someone clicked that the rules did not say how many pairs of feet could be used. a heap of people picked it up and with the engine screaming raced down a hill with about 15 knots wind ,by 79 they sorted out the weight issue and wheel launch became legal.The manufacturer only had to demonstrate the footlaunch once. Ozzie
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