Help me make a flying helicopter!

[Zerobricks]

Few days ago I got this idea about overvolting an RC motor and using the rotors from the education set to make an actual fyling model. When i saw boxerlego's dual power topic, it was a signal to me that the motors can really be overvolted. I tried to make the RC motor take off, but the panel built propellors arent efficient enough, even though it was extremely close, the motor held on one side was vibrating.

Here's my idea made in LDD:

Now does anyone have those blades to build this thing or to borrow them, so that we can once make a true flying Lego model, even if its just a motor supported by a beam! Also a less used RC motor might give me more of the needed power!

So who can help me in any way?

[Sariel]

I'd love to see this work, but I doubt it will. If you take a look at how RC helis, there's a vast difference between their performance and that what you can achieve with LEGO. For instance, a small heli can house motors that go 18,000 RPM while its total weight is 20 grams - there's no way to beat this with LEGO. Anyway, did you try overdriving the main rotor? Looks like the RC motor may have some spare torque to convert into speed.

Edited December 29, 2012 by Sariel

[Zerobricks]

I'd love to see this work, but I doubt it will. If you take a look at how RC helis, there's a vast difference between their performance and that what you can achieve with LEGO. For instance, a small heli can house motors that go 18,000 RPM while its total weight is 20 grams - there's no way to beat this with LEGO. Anyway, did you try overdriving the main rotor? Looks like the RC motor may have some spare torque to convert into speed.

Yes, i tried using modifyed blades inspried by Barman and the motor alone ALMOST took off with 2 Lipo battery boxes in serial.

I still have some reserve in the blades and in using 2 classical battery boxes with higher voltage.

Edited December 29, 2012 by Zblj

[dhc6twinotter]

I like the design. I like how the weight of the motor is offset by the weight of the tail boom. I don't know how much that motor weighs, but the center of gravity appears to be pretty close to correct.

I'm not sure the tail rotor would provide enough thrust to counteract the torque of the buggy motor.

I'm still unsure if LEGO will ever achieve controlled flight, but I think your design is the best attempt I've seen to at least achieve powered flight. :thumbup:

[Conchas]

I made several attempts in this direction with near "take-off" results.

Although the RC Buggy drain to much power and very soon they considerably decrease speed.

The thermal protection on PF batteries doesn't allow the motor to run at full speed for much more than a second or so...

Specially because you need a second motor to take control on the rotor speed, otherwise you won't control the copter at all.

[Zerobricks]

I made several attempts in this direction with near "take-off" results.

Although the RC Buggy drain to much power and very soon they considerably decrease speed.

The thermal protection on PF batteries doesn't allow the motor to run at full speed for much more than a second or so...

Specially because you need a second motor to take control on the rotor speed, otherwise you won't control the copter at all.

What about 2 Rc units wired in series? Those have no current limit. For start we can leave the rear rotor and just fix the motor via a lever for concept.

[Conchas]

My main problem was that I tried it also with a six blade setup to overcome the blades low efficiency.

It increased the torque a lot, which in turn caused the RC motors to drain even more current.

[Zerobricks]

Well for start i would try with 2 or 3 blades, they have less drag.

[DLuders]

@ Zblj: Jernej, I have 6 ea. of those big white Lego Education 89509 "Propeller 1 Blade 14L with Two Pin Holes and Four Axles" parts that I could mail to you. Please let me know what your address is by sending me an e-mail to LudersDG@MSN.com . You can keep them if you want -- I'm not using them and they've been sitting around for 1-1/2 years in my basement. I want to prove to Blakbird that Lego REALLY CAN FLY (in expert hands, like yours)!

[Zerobricks]

@ Zblj: Jernej, I have 6 ea. of those big white Lego Education 89509 "Propeller 1 Blade 14L with Two Pin Holes and Four Axles" parts that I could mail to you. Please let me know what your address is by sending me an e-mail to LudersDG@MSN.com . You can keep them if you want -- I'm not using them and they've been sitting around for 1-1/2 years in my basement. I want to prove to Blakbird that Lego REALLY CAN FLY (in expert hands, like yours)!

Thank you David! I will try not to dissapoint!

[Alasdair Ryan]

Well it would be cool if it does fly,I think those blades need to stick out more though.

Are the main blades of the 9396 helicopter the wrong shape?

Edited December 29, 2012 by Alasdair Ryan

[hrontos]

9396 main blades do not have ideal shape, or the have to be mounted in much more complex rotor to get good angle.

However I am also not sure about those propeler blades. If you take a look at the helicopter models, many of them have blades wider at the center and narrow at the outer edge to make sure they do not need too much torque. Or to be more precise - their air resistence decreases as the diameter increases. This guarantees effective usage of motor torque. The propeler blades may require too much torque without producing effective air flow in the centre.

[freakwave]

Good Luck!

That inspires me to put the speedometer onto the RC-motor and go up to 20 - 25Volts

Have also a look at some Helicopter lift equations

fW

[JunkstyleGio]

Proving Blakbird wrong would be an exceptional achievement!

I will cheer your endeavors, but i do think that "Lego will NEVER fly"

[legomuppet9]

Do you think you could change the gear ratio to make the tail rotor spin faster.

Lego has to be able to fly somehow musn't it?

[Carsten Svendsen]

I tried every method of building a chopper and it won't work - It'll be too heavy or the cable will drag it around like a balloon

I have 12 of those white propellers and a couple of those buggy motors. unfortunately I haven't got that small tail rotor, but I can tell you from my experience, that you need A LOT more torque from that small tail rotor to be able to counter the buggies'.

Maybe if you have a 9 volt main rotor, and an 18 volt tail rotor? However, that would probably only last 20 seconds.

You have to be careful not to get too many ideas. This is EXACTLY how I started building my airplane - it costs money - lots of money. I won't be able to make it true LEGO though since those propellers will just bend when too much torque is applied. - You have been warned!

[Hopey]

I'd be concerned that the tail rotor isn't going to do it's job properly (anti-torque, to stop the body rotating the opposite direction to the rotor).

Do you have any idea how much thrust the tail rotor will generate with the given gearing? Or how much is required?

An alternative could be to have a second coaxial set of blades (or a counterweight) rotating in the opposite direction. This would of course increase the weight, but you'd not have the weight of the tail boom.

This could be set underneath, which would be unstable but simpler, or actually coaxial on top, although the only way I can think of to do this would be to use a small turntable. And of course any added mechanism adds weight.

Perhaps a simple proof-of-concept would be to forget about balancing and anti-torque, and simply tether it (with string or whatever) to demonstrate that you can generate enough thrust to lift the motor + batteries, then (assuming success) add weight until it doesn't to see how much you've got left over.

Just a thought.

[hrontos]

I have 12 of those white propellers and a couple of those buggy motors. unfortunately I haven't got that small tail rotor, but I can tell you from my experience, that you need A LOT more torque from that small tail rotor to be able to counter the buggies'.

Maybe if you have a 9 volt main rotor, and an 18 volt tail rotor? However, that would probably only last 20 seconds.

May be a tandem rotor solution will work. If thinking positive and a buggy motor is able to lift itself and few extra grams, two buggy motors in a tandem configuration will be able to lift themselves and extra grams needed to build the structure.

Looking forward to see any results. Positive or negative.

Edited December 29, 2012 by hrontos

[Hopey]

If you take a look at the helicopter models, many of them have blades wider at the center and narrow at the outer edge to make sure they do not need too much torque.

I may be completely out of my depth here, but I was under the impression that real helicopter blades (and aeroplane propellors) were thicker near the centre because the linear speed of the blade is lower near the centre, and a thicker aerofoil generates lift/thrust better at lower speeds.

[hrontos]

I may be completely out of my depth here, but I was under the impression that real helicopter blades (and aeroplane propellors) were thicker near the centre because the linear speed of the blade is lower near the centre, and a thicker aerofoil generates lift/thrust better at lower speeds.

Yes, that's the main reason why even the simpliest coaxial models have blades with triangular shape and they are wider in the center and narrower on the edge. To get equal and effective lift power through the whole length of the blades. On real helicopter this is accompanied by making them thicker and having different shape in the center than at the end. And of course, it is also a structural issue - they cannot be thick and heavy on the ends. But these LEGO propeler blades have opposite construction, so they will not be that effective.

[SheepEater]

Good luck!

One day Lego will come out with a motor that is extremely light weigth & powerful and a battery box that, while short-lasting, will be extremely lightweight. Add in specialized rotor blades and we'll have flying Lego for real.

[Kierna]

I hope you succeed! I know very little about helicopter physics so I have no idea if it is possible.

I'm still working on RC motorcycle designs, and nobody thinks that's possible, so keep at it

[Theo van Vroenhoven]

May be you could try something like this?

https://dl.dropbox.com/u/109037067/PAL-V%20Flying%20Car%20-%20Maiden%20Flight%20-%20YouTube.MP4

[Zerobricks]

About the 9396 rotors. They seem very massive to me, and as said before they need a more complex rotor stem.

@#16 Carsten Svendsen You tried 18 volts too?

[roamingstop]

A quadcopter (not a classic heli) might work better - counter rotating blades etc