Wing Rudder using 9g servo for tricopter updated.

by Pillip Flop | October 16, 2012 | (8) Posted in Just Fun


I was making a streamlined Quad arm to try and make it more efficient and stable when I suggested using a rudder for yaw control in a tricopter.  A couple of people told me that it had been done before but with limited success. I wanted to know if it could be done using a 9gram servo instead of a servo mounted motor to save weight. I`d already made an aerofoil shaped faring to slip over a quad arm so I decided to give it a go and see if I had any better look.

I used a cooling fan for the bearings and just two arms for the motors so I could balance out the weight. I was going to use two rudders to start with because I was warned that it might not be very responsive. Well as it turns out I only needed one. Tomorrow morning I`m getting some digital scales so I can measure exactly how much yaw there is and at what throttle and through rates. I extended the servo arm to get more out of it. For a cheap nylon threaded servo I think it did quite well. I think I could get away with even smaller metal geared servo.

Well, the proof of the pudding is in the eating as they say, so all this doesn’t really mean anything until it`s been tested on a tricopter. I`ll edit this posting tomorrow when I get the scales and maybe someone will be able to tell me if it`s useful or not.




Here’s the update. I made a rig similar to a thrust tester only scaled down a bit. I managed to measure the yaw at low, medium, 75% and 100% throttle and the throw from 0 to 100%. I think the rudder shape could do with some refining, the camber`s not quite right and it`s probably too deep as well. I’ve got hold of some thin, lightweight carbon fibre tubing. So there’ll have to be a few changes anyway. Apart from one or two snags I`m pleased with the way it`s going I`ll do an update when I`ve got it sorted. Thanks for your comments.

http://www.youtube.com/watch?v=XQ5S7iRUNiw&feature=g-upl












COMMENTS

rcjoseb on October 16, 2012
Great idea. I actually tried that on my first tricopter and it worked except that my rudder was above the arm and not inline like yours. Just watch out that on a windy day, the rudder will act like s sail.
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Pillip Flop on October 16, 2012
You`ve tried it then I was looking everywhere trying to find an example. Did the rudder help keep orientation when turning.
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rcjoseb on October 16, 2012
Yes, but only because I made it quite large.
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tramsgar on October 16, 2012
Brilliant. A wild guess: If you extend the rudder to run under the whole prop you could make it smaller and thus get even better response?
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Leo82 on October 19, 2012
I'm thinking hovercrafts and their solutions.
How about making a shroud for prop and putting two rudders under it.
I know, i know, it weights too much. Just a something to try out.
This rudder idea is great. I feel bad for my tail servo in my tri. All that gyroscopic force and weight of the motor.
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Pillip Flop on October 21, 2012
Hi leo82, you know you’re the second person to mention using a shroud Shaun_Mileson suggested it about 10 days ago when the idea came up. So there might be something init. When I find the right parts I`ll try it out (wish I had a 3d printer). I was worried that the turns would be nice and sharp but lose too much down wash. There’s nothing wrong with giving it a go, I’ve got some data to compare it with now any way. I could make the shroud an integral part of the frame then the rudder could be full length and even thinner. You mentioned weight and gyroscopic force. I can`t help but think, even if this yaw rudder thing ends up being heavier than the tail servo setup it might be it anyway just to get rid of the gyroscopic precession. Cheers Leo.
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Pillip Flop on October 17, 2012
I wanted to avoid going under the prop if I could help it. But I could get away with making it as thin as possible and I could defiantly take about a third of the depth so it`s more elegant and less “flappy” and still have more rudder surface area to play with. Yeah the tube makes a good strong hinge so fixing on to it won’t be a problem. If anything the servo will have to do less work.
Cheers tramsgar.

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tramsgar on October 17, 2012
I agree, the way you did it is simpler and more robust.
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Pillip Flop on October 17, 2012
I wanted to avoid going under the prop if I could help it. But I could get away with making it as thin as possible and I could defiantly take about a third of the depth so it`s more elegant and less “flappy” and still have more rudder surface area to play with. Yeah the tube makes a good strong hinge so fixing on to it won’t be a problem. If anything the servo will have to do less work.
Cheers tramsgar.

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Pillip Flop on October 17, 2012
Don’t know what happened there I only posted it once
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Wing Rudder using 9g servo for tricopter updated.