Rex Keene Posted September 17, 2012 Share Posted September 17, 2012 Or what ever they're called.. I've been given a pair of high wing trainers in a semi finished state, and I've been thinking of making one of them a twin rotor autogyro. I've never tinkered with an auto gyro before, so I've some questions: 1) Any good sources for what I imagine must be a thrust bearing for the rotor hub? 2) Is it true that the blades for a twin don't need aerodynamic profile, that's to say, they're flat plates and not aerofoils? 3) Is there a simple way to calculate "swept area (rotor disk?) needed per kilo? 4) Is there a simole way to decide on the number of blades per rotor? Thanks... Quote Link to comment Share on other sites More sharing options...
Alan Cantwell Posted September 17, 2012 Share Posted September 17, 2012 i flew a DB autogyro for ages, with just a pair of brass collars in the middle of 2 x3bladed high angle of attack 3 bladed flat plate rotors, it was a lot of fun, Quote Link to comment Share on other sites More sharing options...
Alan Cantwell Posted September 17, 2012 Share Posted September 17, 2012 oh, and the pitch of the bladed, which was fixed, was opposite on each side, but sorry, i cant remember which side twisted which way Quote Link to comment Share on other sites More sharing options...
Ian Jones Posted September 17, 2012 Share Posted September 17, 2012 Richard Harris is the man - bet he knows all of the answers. You there Richard? Quote Link to comment Share on other sites More sharing options...
Richard Harris Posted September 21, 2012 Share Posted September 21, 2012 Twin rotors is not really my thing but I do have a couple of DB Autogyros.With these if you look from above and from the rear the LH rotor spins anti clockwise and the RH rotor clockwise. They are just sheet blades with a negative incidence built in by over lapping the blades. I think David Boddingtons 'Gyrace' had 2 options regarding the blades, the first was the four bladed 1/8" sheet type. The second is for a 3 bladed aerofoiled section tape blade and I know a few people who have gone down the latter root. In my opinion the 3 bladed option with a profiled section is the way to go, more lift/less drag and more efficient. As for the spindle bearings all the DB set ups are as Alan has already stated just a simple brass tube. You can buy small flange bearings that I am sure would work better. I have read that the wing type Gyros generate 70% of lift through the rotors and 30% the wing with enough airspeed for them both to work. How true this I don't know? If you need any photos etc of my DB's just let me know and I can take some, I also have a calculation to work out the rotor loading but this is for 'rotor only' models. Rich Edited By Richard Harris on 21/09/2012 14:26:43 Quote Link to comment Share on other sites More sharing options...
Rex Keene Posted September 21, 2012 Author Share Posted September 21, 2012 Thanks for the replies. I'd very much like to see the rotor disk calculation and some pictures of rotor heads and bearings. I'd thought of mounting the rotors on pylons to exclude the compexity of wings. Quote Link to comment Share on other sites More sharing options...
Terence Lynock Posted November 10, 2012 Share Posted November 10, 2012 Bit late on this one Rex but I used a couple of 3mm I/D flanged ball races to fit the main shaft bought off Ebay for pennies, measure the outside diam of the bearings and buy some big washers with a hole the same size,solder the bearings into the middle of the washers then solder the wires that carry the blades onto the washers too. Easiest way I found was fit the bearing into the middle of the washer with the flange underneath, arrange the three wires for the blades after coating everything in flux and then flood the complete area with solder around the outer of the bearing and the three wires, clean up with a brass wire brush then wash the bearing out and re-oil. If you want I have three or four PDF plans of free flight autogiro's that are easily modded for three channel r/c, just about 2/3rds the way through a twin rotor build now but other things keep getting in the way but should be finished soon. Edited By Terence Lynock on 10/11/2012 22:43:03 Edited By Terence Lynock on 10/11/2012 22:48:51 Quote Link to comment Share on other sites More sharing options...
Tom Wright 2 Posted November 10, 2012 Share Posted November 10, 2012 Rex I have plenty of the units as shown below and plenty of the blue wonder types. Give me a shout if I can help. Tom. Quote Link to comment Share on other sites More sharing options...
crispin church Posted December 16, 2012 Share Posted December 16, 2012 i have db twin and there is a simple tube for the bearing i made a new set of blades and put bearing each end and these was a lot slower maybe i was not lined up but gone back to tube the blade is layed in a square with end tuck under the next like folding a top of a box i just painted the blades as easier to ca them if they crack safe trying to lift the covering Quote Link to comment Share on other sites More sharing options...
derek critcher 2 Posted February 12, 2013 Share Posted February 12, 2013 Hi Tom, this bearing holder looks as though it might be suitable for the Panther if you still have any left please contact me with a size and price, Cheers Derek. dekcritcher@aol,com Quote Link to comment Share on other sites More sharing options...
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