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Old Jun 28, 2009, 02:48 PM
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Electric helicopter thoughts

Anyone considered (or actually tried) using a couple of brushless motors and built a helicopter from scratch? Would still need some type of rotor head control, but could use variable speed for the tail rotor.

Was an article in Model Aviation News back in the 70's about building a chopper from scratch (there is one like it in the model Aviation museum at AMA headquarters in Muncy)

I have some of the tools and knowledge on how to machine things, (no money to just buy a chopper at present) so I could probably make anything I need.

Any thoughts?
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Old Jun 28, 2009, 03:42 PM
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There have been a few on this forum.

Try searching both in here and in the micro helis forum for keywords such as "homebuilt" or "homebrew".

Toshi
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Old Jun 28, 2009, 10:54 PM
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Given that you're probably not going to make the electronics yourself, this is probably not a project that would save you any money over a low-cost ARF... but for the sake of interest, it would be a fun project. I would go with a Litemachines/Multiplex style design, with a direct-drive brushless main motor, and a constant-speed tail rotor with a servo and gyro. This would be easier to build, and also fly better than a variable speed, constant-pitch tail.
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Old Jun 28, 2009, 11:32 PM
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Most fixed pitch electric helis use variable speed motors on the tail rotor. Not the best, but it definetely works.
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Old Jun 29, 2009, 03:39 PM
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I think you'd have to assume you couldn't improve on existing designs and just consider which parts would be too difficult to make (obviously electronics but also bearings, belts, gears and probably composite blades and ball links)

You can simplify things enormously buy building a FP head, with (as you suggest) an FP tail but there's a performance penalty (depending what sort of performance you want). Then again, you can cheat a little and buy a few of the critical bits - if you bought a Corona rotor head and blades, the rest of the heli would be quite simple.
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Old Jun 29, 2009, 07:52 PM
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Built my first heli kit in 1970. Can't remember who put it out. The Super Tiger 35 motor was mounted on top of the rotor blades with a conventional prop on it. The torque reaction drove the blades in the opposite direction. The blades were free pivoting on a piano wire shaft. At the end of the blade was a wire hanging down and forward on a 45 degree angle, with a lead weight on the end of it. As the blades moved faster the weights would cause the blades to go to a higher pitch through centrifugal force. No gyros back then. Needless to say, the life expectancy was fairly short. It was tethered on all four sides and would lift off a couple of feet till the tethers tightened. Free flying was another story. Very short.

Gord.
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Old Jun 29, 2009, 08:56 PM
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Flypaper, That sounds like the Cox freeflight helicopters. That was about all there was for heli's off-the-shelf back then. I have a 1955 Popular mechanics encyclopedia of DIY projects and I recall a helicopter in there. Will check it when I get back to the lab in couple weeks. Yup, I keep the old stuff around because I don't waste time reinventing the wheel.
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Old Jun 29, 2009, 09:00 PM
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I also found this DIY 4CH heli:
DIY Heli
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Old Jun 29, 2009, 09:13 PM
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Nope, used my PCS radio in it. Think it was called cricket or grasshopper or something like that.

Gord.
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Old Jun 29, 2009, 09:56 PM
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Quote:
Originally Posted by flypaper 2
Nope, used my PCS radio in it. Think it was called cricket or grasshopper or something like that.

Gord.
Dubro Whirlybird...
Vintage R/C Helicopter - Du-Bro Whirlybird 505 (5 min 28 sec)
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Old Jun 29, 2009, 10:17 PM
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Now that was worth watching Jazz. Thanks. Reminded me what it was like when mufflers hadn't been invented yet. Close but not quite the same. Mine had the wire on the leading edge hanging down about a 45 degree angle and the fuse wasn't as cool as that one. Also it was dark blue. Mine also just had a post hanging down at the back to protect the tail rotor. Funny how details come back after that many years. I believe that guy had a gyro in it as they wern't that stable without one.

Gord.
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Old Jun 29, 2009, 10:34 PM
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He says there is no gyro... possible revo mixing or he just knows the bird really well. Definitely a cool video, and possible the design was used by other companies, but the guy claims this was the only one to use the torque reaction design. Apparently there was another one that was blue, but he crashed it. Read the comments on the video, he gives a lot more information a couple of pages into the video comments. Dave Herbert mentions a Cox helicopter?
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Old Jun 30, 2009, 12:29 AM
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if you do get the urge to try and build your own....slaughter some printers.seriously...you will find belts...pulleys,shafts,motors,pinions(for belts) on the slightly more industrial ones 2 stage pulleys with short and long belts(so motor with very short belt drive to mainshaft then long belt to tail)...all sorts.you could actually get all your drive components from motor to tail shaft from one old office printer including main shaft and a one way bearing pulley for your motor
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