I have an idea for a 3D quad.

[guest325]

I';m pretty new to these models but not control systems (Mechatronics degree), I have seen that a 3D quad has been done by using variable pitch props.
This seems to me to be expensive and prone to being difficult to set up.
My idea is very simple, however it would need some clever programming; I see the idea of using 8 motors running pusher props off 4 esc';s switched by a combination of inclinometer to the board and solid state relays to switch the power to each motor set.
What I would need is experienced opinions as regards is it likely that it weight would prevent it working, would having a change over from one set of motors to the other be a problem (would it be better to use 8 esc';s and have a proportional chang over).
The final thing is I have no real experience of programming so would need someone who is interested enough to have a go.
If there is any interest in this sort of project I can contribute ideas; 3D CAD design facilities and most of all enthusiasm.
Anyone interested?

[al-xg]

You';d also need to run the motors under the booms in a "pusher" configuration in order to have the stationary prop above the spinning one and reduce the drag.

I wonder if one could run a single dual shaft motor on each arm and then have a ratcheting system in the prop adapters, you could just reverse the motor to use the other prop 



I saw a variable pitch setup using a single central motor driving four cheap tail rotor assemblies, I thought that was quite a neat idea, you could even run an internal combustion engine that way.

[secretman]

personaly i prefer to have 4 collective pitch than 8 motor and shut some off .. or some ratchet bearing, too mutch prone to failure, collective are here from a long time need care lube but good device. once you know fly your not suppose to hit something and 4 tail rotor from a copter like 4 t rex 500 tail( gear drive) 1 main gear 4 tail block and you can drive all tail assembly on 1 gear or 1 motor.

or this is better http://www.hobbyking.com/hobbyking/store/__6220__Variable_pitch_prop_motor_set_10_Type_A.html
or even this...
http://www.hobbyking.com/hobbyking/store/__16618__CR23L_Contra_Rotating_BL_System_1100kv_.html
4 like this, 8 esc and 4 sec run on upright ans 4 other on the invert and a lot of programing arduino llolll
but look ****** nice :P

[Gaza07]

I think we are going to see a lot of development in the variable pitch side of our hobby more so since the release of the Curtis Youngblood video, I think 4 motors with variable pitch control is always going to be the way to do this and is perhaps not as complex as it first sounds, more so for heli flyers who have already had to setup rotors for zero pitch at mid stick and the use of throttle and pitch curves 

[guest325]

I think we are going to see a lot of development in the variable pitch side of our hobby more so since the release of the Curtis Youngblood video, I think 4 motors with variable pitch control is always going to be the way to do this and is perhaps not as complex as it first sounds, more so for heli flyers who have already had to setup rotors for zero pitch at mid stick and the use of throttle and pitch curves 

To a point I agree with what you are saying but having set up a small cp heli swashplate I know it';s not easy plus then you need to get all 4 pretty much spot on for it all to work properly, but that said once you do get it set up it';s plain sailing.

My idea of having two opposed motors both running pusher props isn';t going to be much heavier but has all of the clever parts of control done by programming and a couple of simple reliable electronic bits; hence me asking if  anyone with more experience than me could see anything obviously wrong with having a go.

[Gaza07]

The thing is it will be no were near as complex as setting up a helicopter rotor, because there is no swash plate or fly bar to consider, its as simple as centre the servo and adjust the blades to zero pitch which is a very simple process and if it wasnt set to accurate the flight controller would auto adjust for it as its controlling the pitch rather than the speed of the motors,
If you did it with 2 opposing motors are you expecting the opposite motors to spin up fast enough for quick changes in direction ?
Or if they are all ready spun up if so then would the opposing props be fighting each other ?
I also think using eaxtra motors the transition from positive pitch to negative just wouldnt be smooth or accurate enough, just my thoughts on it   

[guest325]

Having done a bit more finding out I see what you mean, setting up is not as complex as I thought. The only thing that bugs me is the idea of having a hollow motor shaft with the prop actuator shaft running through it - could be a bit delicate!
You';ve answered my thoughts about transition between motors running though, it was my main concern that an abrupt change over could present serious control problems, also identified an error in my thinking about ramping the two motors up/down you quite rightly say they would be fighting each other and possibly be worse than  the other idea.
Oh well back to the drawing board, perhaps not such a good idea - thanks for the advice.

[Gaza07]

Its always worth considering alternative ways to do things if we didnt we would never make any progress 
I have seen a picture some where not sure where now if a copter that was made variable pitch by using heli tail rotor pitch sliders that where operated with out the need for the hollow shaft, all that was needed was an extended shaft, if I can find it again I will post it here, I actually quite fancy making a variable pitch multi using the multi wii firmware that is available 

[Gaza07]

Here';s a few links you might find interesting Darrell 

http://forums.openpilot.org/topic/9490-variable-pitch-quad-copter-using-single-motor/

http://forums.openpilot.org/topic/7883-variable-pitch-build/

http://www.rcgroups.com/forums/showthread.php?t=1189826

This is the one I saw that is probably the best ive seen 

http://youtu.be/Vy5Ky50eGJs

http://youtu.be/VIkqqVr_u9U

[guest325]

I must admit using tail torque tube drives is a nice mechanical solution and seams to work nicely, me having been trained to try to do the same things electronically goes a bit against the grain. Thanks very much for showing me these it';s so interesting!!!

[al-xg]

http://youtu.be/G1FqV36oEYE
http://youtu.be/NFSRZy-y0YQ

This is the single motor version I was on about. It seems to work pretty well (of course it isn';t using external motion capture and processing  like the MIT one).

[Cozp83]

What about esc';s that reverse and flattened props?
mwc quad // ultraesc 3d #3 on Vimeo

[teslahed]

Personally i think the reversible props / speed controller approach is the best one for acro flying - as shown in the above video.

I can see that it would be difficult with larger heavier props and motors to get them reversing direction quickly enough because of the angular momentum, but if you are flying a small stunt copter (of the sort that will benefit from reverse thrust the most) you are likely to be flying with lighter 8 inch props.

I think reversing the direction of the motors is a good approach because it preserves the mechanical simplicity of quadcopters. Helicopters are a lot more fiddly because of the rotor head and variable pitch props - i don';t fancy that x 4 really.

But it will be interesting to see how these various methods develop - early days yet.

[Cozp83]

Variable pitch is gonna need servos, linkages, and setting up is gonna be a pita.