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Helicopter Rotor Assembly (proof of concept)

weavil
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weavil

weavil

Posted
Posted

I got an idea and wanted to share because I don't have the parts to build and test. I got the idea when I was looking at the parts update for LDD and built it.

It would be a helecopter rotor assembly.

Picture A

Picture B

LXF File

The orange connecter is the CV joint connecter (bug in LDD - won't connect) and the red axles are to control the movements.

I really would like it if someone could build it and test the function of it and post some pictures/video. thanks for your time.

DLuders

DLuders

Posted
Posted (edited)

I don't own the 42000 Lego Technic Grand Prix Racer set to be able to replicate your rotor design, because you used the 11949 "Technic, Steering Portal with 2 Pin Holes and 2 Ball Joint Arms" part that comes only with that set. Nevertheless, your concept looks very promising! I reposted your two pictures, and added a few LDD closeups:

11949.jpg9284563426_b0bdabb027_c.jpg9284566378_53964966a8_c.jpg9284585868_ed038d216f_c.jpg9284592888_32f12e8d9a_c.jpg

Edited by DLuders
Hopey

Hopey

Posted
Posted

Unfortunately that's not how helicopter blades work. Your setup tilts the whole rotor. A real helicopter changes the pitch of the blades.

www.rchelicopterfun.com/helicopter-controls-cyclic.html

DLuders

DLuders

Posted
Posted

@ Hopey: Well, the entire rotor head could still allow the helicopter to move forwards, backward, or sideways. According to this Wikipedia article, Weavil's concept employs "Collective Control" --

"Collective [directly controls] angle of attack for the rotor main blades via the swashplate . [The secondary effect is to] Increase/decrease pitch angle of all main rotor blades equally, causing the aircraft to ascend/descend. [it is used in forward flight to] Increase/decrease torque. Note: in some helicopters the throttle control(s) is a part of the collective stick. Rotor speed is kept basically constant throughout the flight. [it is used in forward flight] To adjust power through rotor blade pitch setting/ [it is used in hover flight] To adjust skid height/vertical speed."

Flight_controls-FAA-RFH.png

Nico71's Helicopter did that too:

ZHowitworks.jpg

dhc6twinotter

dhc6twinotter

Posted
Posted

Unfortunately that's not how helicopter blades work. Your setup tilts the whole rotor. A real helicopter changes the pitch of the blades.

Correct.

@ Hopey: Well, the entire rotor head could still allow the helicopter to move forwards, backward, or sideways. According to this Wikipedia article, Weavil's concept employs "Collective Control" --

"Collective [directly controls] angle of attack for the rotor main blades via the swashplate . [The secondary effect is to] Increase/decrease pitch angle of all main rotor blades equally, causing the aircraft to ascend/descend. [it is used in forward flight to] Increase/decrease torque. Note: in some helicopters the throttle control(s) is a part of the collective stick. Rotor speed is kept basically constant throughout the flight. [it is used in forward flight] To adjust power through rotor blade pitch setting/ [it is used in hover flight] To adjust skid height/vertical speed."

The part quoted in blue text is also correct, and it's what Hopey is referring to. Hopey refers to it as "changes the pitch of the blades", and this is the same as controling the angle of attack for the rotor blades. Same thing, different wording. The entire rotor head does not tilt, but rather each blade (called pitch or, sometimes, angle of attack). Nico is an excellent Technic builder, but his heliopter rotor head does not work like the real thing either (and that is fine....there's nothing that says a LEGO model has to work like a real one).

Here's a pretty good animation of how a rotor head works:

The blue piece is the swash plate. When the swash plate moves up/down, this is called collective. This changes the pitch of each blade equally. When the swash plate tilts, this is called cyclic control. The pitch of each blade changes as it rotates around the rotor hub. Camera angle 1 is probably the easiest to understand. Camera angles 2, 3, and 4 are taken as if the camera were mounted on the blade. You can see how much change in pitch each blade has to have to achieve something as simple as flying straight. It's amazing!

Most helicopters operate in this manner. Tandom helicopters are slightly different, but I'll leave that for a different discussion. That being said, there are different rotor head designs, and some helicopters have a hinged rotor assembly that can tilt. However, that tilt does not come directly from the controls, but rather from the aerodynamic forces acting on the blades.

Weavil, you are of course free to built your rotor system however you wish. As I mentioned above, there are no rules that say you have to build something that work like the real thing. This is LEGO and you can design it however you want. It may not be like the real one, but if you like the design, that's all that matters. :thumbup:

Your design looks good, and that's a clever use of the new hub piece. My only suggestion would be to replace the 1x7 yellow liftarts with something thinner. The vertically mounted 1x5 thin liftarms will contact the 1x7 yellow liftarms when the rotor head is tilted. My suggestion would be to use the new 1x5 thin liftarms with axle holes in the end, plus two addition 1x3 thin liftarm for the side that your control linkage will connect to (the red axle). This should give you enough space for some movement of the rotor head.

It's always nice to see a helicopter moc, and I'm looking forward to your project. :thumbup:

weavil

weavil

Posted
  • Author
Posted

Thanks for the input. I was going for cleanness and function, not for acuracy. But seeing how I can change it.

  • 2 months later...
Blakbird

Blakbird

Posted
Posted

So does 9396 work like that? Collective and cyclic?

No, 9396 only has collective. There has never been a Technic helicopter set with cyclic or with a proper swashplate. A couple of models including 8856 tilted the whole rotor but this is not how cyclic works.

JM1971

JM1971

Posted
Posted (edited)

Sometimes LDD will let you work your model and sometimes it goes nuts for no apparent reason, in your case seems fines to me.

Video: http://www.flickr.co...08/10161356903/

If the video does not work then its still processing, will be ready 5-10 mins.

Back when I was at school my friend almost got his lego contraption off the ground by running 12v though the motor.

Edited by JM1971
weavil

weavil

Posted
  • Author
Posted

Does anyone have the LDD?LXF file from the original poster? The link somehow no longer works.

The link works for me, but I'll move it to brickshelf in a little bit and put it up.

CP5670

CP5670

Posted
Posted

I used the old rotor pieces from the 1990s in my helicopter to get the full range of cyclic and collective blade movements. As Blakbird said, none of the official Technic helicopters have really done this properly, but 852 (the very first helicopter) and 9396 come the closest and have the collective part.

CP5670

CP5670

Posted
Posted
Isn't this weavil's setup basically the same as of the 8856 Whirlwind Rescue. Just studless with a different swash plate solution?

I wonder what the 8856/8412 rotor mechanism would actually do in real life. I think it would simply result in the helicopter's body tilting relative to the rotor, instead of making the helicopter move in a certain direction.

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