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Old Dec 30, 2006, 04:06 PM
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Yes, I think it's possible, just difficult. And hard to reproduce.
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Old Dec 30, 2006, 04:08 PM
iPhly R/C with iPhone
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Quote:
Originally Posted by leadfeather
Here is a short video clip of the flat inverted V tail demonstrating good taxiing yaw control.
The yaw is very impressive. I wonder if the effect has to do with lifting one of the pontoons but keeping the other one on the carpet. This creates significant differential in drag and could be more like turning a caterpillar tractor.

Ari.
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Old Dec 30, 2006, 04:16 PM
iPhly R/C with iPhone
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Quote:
Originally Posted by mnowell129
(I mean does any body still have a 3 channel transmitter and 3 channel receiver? I question the reduced cost and low complexity argument of 3 vs 4 channels. There must be some other attraction to 3 channels that I can't get a handle on.)
It's a little known fact that RXs' weights are proportional to the number of channels :=) I've been hanging out in the indoor forum for too long.

Ari.
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Old Dec 30, 2006, 05:29 PM
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Dan,

if you insist on using three channels, you've got to compromise. In my opinion, the decision you have to make is building a gyro that flies well without the capability of ROGs, or building a gyro that may take off from ground and doesn't fly as you want it to. The first choice results in a fully controlled head as used in the DAG-2 or the Micromum/Minimum without any rudder, the second choice results in more experiments with doubtful outcome.

In my opinion, you only need a rudder, if you want to take off from ground. One of my three Micromums has got a rudder, that's the one I use when there's enough snow to make our airfield smooth enough for ROGs. With the other two I'm only doing hand launches, but flying them is fun, nevertheless.

Well, do you want fun or work?

Jochen
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Old Dec 30, 2006, 06:06 PM
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Quote:
Originally Posted by iter
It's a little known fact that RXs' weights are proportional to the number of channels :=) I've been hanging out in the indoor forum for too long.

Ari.
Point taken. I'm sure this what you're using in your slow stick
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Old Dec 30, 2006, 06:07 PM
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Quote:
Originally Posted by JochenK
if you insist on using three channels, you've got to compromise.
Exactly. Aircraft are fundamentally 3 axis control plus motor. Like Einstein said, make everything as simple as possible but no more.
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Old Dec 31, 2006, 06:32 AM
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Quote:
Originally Posted by JochenK
Dan,



Well, do you want fun or work?

Jochen
Jochen,

This may not make sense to some, but the work is at least half the fun for me. I get a tremendous amount of satisfaction from experimenting, overcoming challenges, and learning. For me the work with the autogyros is not a struggle, it is an adventure...I love it!

Dan
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Old Dec 31, 2006, 07:14 AM
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Quote:
Originally Posted by iter
The yaw is very impressive. I wonder if the effect has to do with lifting one of the pontoons but keeping the other one on the carpet. This creates significant differential in drag and could be more like turning a caterpillar tractor.

Ari.
Ari,

Good question. I hadn't questioned why it worked.

I made a temporary axle and wheels and taped it to the HydroSkimmer to eliminate the possibility of the effect you noted.

On wheels, it turned a bit better and at much lower throttle.

I think this arrangement; shallow inverted V tail, may provide good yaw control on the ground for an autogyro and also provide good roll control in the air.

Dan
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Old Dec 31, 2006, 07:36 AM
edi
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I have a question concerning the tilt of a two-rotor autogyro (twirl-style): Could I add roll control by simply tilting the two rotors to a side and wouldn't the forces cancel each other out so the servo load won't be big?
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Old Dec 31, 2006, 03:19 PM
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I think you would be better off differentially tilting the rotors back and forth. You could set them up as flaperons. Tilt a rotor back, and you get more lift and more drag, just like a flaperon.

The drag differential may be an interesting point--there may be quite a lot of adverse yaw with this setup.

Ari.
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Old Dec 31, 2006, 07:07 PM
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Next topic is planned to be steerage of the two rotor gyro.
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Old Dec 31, 2006, 08:10 PM
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Do the two step....

How about steering the two rotor gyro layout.
Shown is the typical two rotor gyro. How does it steer.
Lets look closely at one of the tips and the mast attached there. The important point is that the mast is canted inward at the "dihedral" angle of the wing or rotor mount. Note that in the level condition the mast has some right cyclic, but the right tip has left cyclic so they balance out.
Lets now yaw the aircraft with rudder. What happens is that the inward canted left tip rotates rearward and the inward cant becomes backward tilt. Note that we reduce the right cyclic some but to a lesser extent than the inward tilt becomes backward tilt. We then recognize the backward tilt for what it is, up cyclic. This makes this rotor tilt up and now being tilted up further has a greater overall angle of attack and speeds up. This produces more lift on the left tip and rolls the model to the right. Note also that the reverse happens on the right tip. It gets nose down cyclic from the inward tilt swinging forward, the rotor tilts down and slows and this tip falls.
The important points are that the turning mechanism involves using cyclic to create differential rotor speed and angle to make the turn. But speeding up and slowing down the rotor speed takes time and involves inertia. So this kind of model is slow to turn and has a tendancy to overshoot because once the yaw is removed the leading rotor still has extra speed that must be bled off. If you watch the videos of these models you see them "wallow" in the turns and the rotors changing speed with respect to each other, and so this makes sense with how it's turning. Note however that the inward tilt of a rotor becomes helpful with the model is upset and starts to slip. Now the inward tilt becomes backward tilt against the slip and automatically corrects for the disturbance. This makes this layout a good beginner setup as it tends to level itself out and fly like a three channel trainer airplane. The only downside is the "wobbly" kind of control that overshoots, but this is easily overcome by piloting. This explains why these models might fly better with lightweight low energy rotors. These will speed up and slow down faster and provide more positive control. The downside is that light rotors tend to stop easily so you need more negative pitch to keep them spinning. Hence the typical two rotor configuration of dihedraled, lightweight 4 bladed rotors, with fairly substantial negative pitch (-10 or more) seems to make perfect sense in hindsight.
Note that this dihedral is not coning, coning being the shape of a single rotor, not the difference between two rotors.
Note that if you flatten the rotors out then you have two flat rotors that when yawed, don't behave any differently that a single rotor yawed. It might roll the right way, it might not. The trick is that the inward canted rotors works differentially when yawed, thus providing the differential lift needed to roll/turn the aircraft.
You can probably think your way through how coning doesn't improve any of this in any way due to the cross coupled behavior.
Anyhow maybe this will help you understand your dual rotor a little better.
P.S. differential spindle tilt by rotating the "wings" or pivots on the ends provides the same differential cyclic as yawing the aircraft but with more differential throw available. Note that you still have to wait for the rotor to start making more lift due to being pitched up so the control response will still be slower than a single rotor with cyclic pitch directly causing the roll. But you get more control than indirect cyclic/speedup of the rudder controlled dual rotor. The differential cyclic model will likely have adverse yaw issues and need some coordinating rudder. The rudder turned dual will not have such issues since the rudder is already yawing the model the correct direction already.

regards to all.
Happy New Year.
mick
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Old Jan 01, 2007, 07:10 AM
edi
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OK, now you are losing me ...
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Old Jan 01, 2007, 07:27 AM
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Correction

Ok, Edi, where did I lose you?
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Old Jan 01, 2007, 07:32 AM
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Quote:
Originally Posted by edi
I have a question concerning the tilt of a two-rotor autogyro (twirl-style): Could I add roll control by simply tilting the two rotors to a side and wouldn't the forces cancel each other out so the servo load won't be big?
Edi,

In this question, do you intend to have both rotors tilt right to turn right or are you thinking one rotor tilted forward and one tilted aft to make a turn?

In either case the rudder may be a better solution, unless you are trying to accomplish something else. For a twin rotor gyro the rudder is simpler, it works well, and it gives you steering control on the ground.

Dan
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