Carbon rod rotor idea

[iter]

I have an idea for a simple rotor made from carbon rod. I've never built an autogyro, so please tell me if this idea is not going to work :=)

The idea is based loosely on Jo Jo Chaulet's two-bladed rotor (http://www.autogyro.com/technic/jojo/giro164a.htm) but would be made from a single piece of carbon. a 4' rod would make ~12" diameter rotor. You could vary the (collective) pitch by changing the vertical distance between leading and trailing edges.

The rotor would go on a fuselage similar to my carbon skeeter (http://www.rcgroups.com/forums/showthread.php?t=330405). I estimate AUW around 21-24g for a disk loading of ~1.1 oz/sq.ft.

Any thoughts or suggestions?

Ari.

[David A Ramsey]

Neat idea and sooooo simple. Might work. The angle of attack for the, ah, paddles would have to be the same. I'm also wondering about the drag and the power needed to overcome? I'd like to see your hub method when you get there.

Appreciate the link, I hadn't seen that.

David

[iter]

So here's my rotor head. It's made of two 1/64" ply plates and spins on 1mm music wire.

[iter]

Here's a side view. Moving the plates closer together results in fine pitch, moving them apart makes coarse pitch. My camera isn't very good at macro photography, so I appologise for poor images.

[iter]

I'll try to borrow a better camera over the weekend. Hope you can see something in this photo. This shows the head with the top plate removed. Each plate has three brass tubes (0.5mm ID) glued to it that act as bearings for little bits of carbon that are glued at 90* to the main rod. (In addition, each plate has a 1mm ID brass tube on which the plate itself rotates on the mast)

[David A Ramsey]

Interesting work. Some clearer shots might be nice

Are you working with true mm tubing? Where did ya get it?

Thanks

[iter]

Interesting work. Some clearer shots might be nice

Thank you. I'm still looking for a camera to borrow.

Are you working with true mm tubing? Where did ya get it?

No, this isn't true metric tubing. It's from K&S Engineering (http://www.ksmetals.com/), some of it from an "assortment" bag, and since it is not marked and I don't have any tools to measure the ID precicely, I just rounded th number :=)

I covered the rotor, and tried to glide it with a fuselage attached. It tends to roll into the advancing blade, my guess it that the blades are wide enough and turning slowly enough that the advancing blade stalls. Some right twist of the mast seems to help (it's a CW rotor), but I'm not getting very consistent results. It takes /a lot/ of right twist (25*?) to keep it from keeling over.

On a related topic, has anyone tried using coil actuators for DC? I wonder if they are going to develop enough torque.

Ari.

[David A Ramsey]

Thank you. I'm still looking for a camera to borrow.

No, this isn't true metric tubing. It's from K&S Engineering (http://www.ksmetals.com/), some of it from an "assortment" bag, and since it is not marked and I don't have any tools to measure the ID precicely, I just rounded th number :=)

I covered the rotor, and tried to glide it with a fuselage attached. It tends to roll into the advancing blade, my guess it that the blades are wide enough and turning slowly enough that the advancing blade stalls. Some right twist of the mast seems to help (it's a CW rotor), but I'm not getting very consistent results. It takes /a lot/ of right twist (25*?) to keep it from keeling over.

On a related topic, has anyone tried using coil actuators for DC? I wonder if they are going to develop enough torque.

Ari.

The roll into the advancing blade was my problem. You need to tilt the rotor head 5 degrees to the right at the top of the mast. Bend your rotor axel wire.
Those blades have a lot of mass. The right tilt will depend on how much rotor speed you need for level flight. If the (25*?) is degrees, you might need to reduce you blade size, maybe try just 2.

Are you doing power tests, or just holding the rotor in the wind?

Thanks for answering the tubing question.

Can't help on coil actuators, but on 1 or 2 threads on this forum there are a couple of guys making very small gyros.

[iter]

The roll into the advancing blade was my problem.Yes, I've seen that post. That's why i tried to bend my mast.
Those blades have a lot of mass. The right tilt will depend on how much rotor speed you need for level flight. If the (25*?) is degrees, you might need to reduce you blade size, maybe try just 2. The rotor doesn't wiegh that much, around a gram. Why would the number of blades, as opposed to anything else like their chord, influence how much it wants to roll? (yes, I meant "roughly 25 degrees")Are you doing power tests, or just holding the rotor in the wind?I was trying to glide it. There was weight on the fuselage to simulate motor and Rx, and my idea was that I should get it to do stable dead-stick landings. Then I put a motor on it, but my pylon wasn't strong enough and kept breaking on "landings". I decided to try and build JoJo's original twin rotor first and then rturn to my idea using the experience from that.

Ari.

[iter]

Here's the twin rotor I'm building. AUW with 250mAh LiPo is 21.3gram. 10" rotors, disk loading 0.69 Oz/fq.ft. RFFS100, KP00, U80, ~3/4 thrust to weight.

Haven't had a chance to try a takeoff run yet, it's been raining here for the last couple of days and is forecast to continue for a week. The best I could do was a "fast taxi" in my garage. Not enough room to take off, but there was a surprise.

The right rotor spools up very well in the 10 feet or so that it has to run, but the left one hardly does. Running with the model in my hand produces the same result - the left rotor won't come up to speed. As far as I can tell, they are identical (well, symmetric, really) and spin equally freely. Any ideas why they would exhibit such different performance?

Do the specs overall make sense?

Ari.

[David A Ramsey]

Yes, I've seen that post. That's why i tried to bend my mast.
The rotor doesn't wiegh that much, around a gram. Why would the number of blades, as opposed to anything else like their chord, influence how much it wants to roll? (yes, I meant "roughly 25 degrees")
Ari.

I was thinking your rotor blades have so much area, sq. in, that they may be overpowering your ability to trim in corrections. 2 blades would just have less area.

On your twin rotor wind up problem.......... You probably thought of this already, but take off the spining rotor and concentrate on the remaining one, get that going and then try it with both.

[David A Ramsey]

Ari: By the way, I admire your patience.

[iter]

So I figured out the left rotor problem. The washout wasn't symmetric - it actually had positive AoA on one blade's tip. I fixed that. Now both rotors spin up smartly and the model runs convincingly on the ground.

It wasn't raining tonight so I ran it in a parking lot under a streetlight. Like I said, it runs very convincingly and looks like it's going to take off any second, it raises the tail and everything, but won't take off at all. Any ideas about what I should try and tweak?

As for patience... The real test of that will be to see this model though. Until then, there is nothing to admire.

David, you seem to be the only one following this thread. Any ideas on how to make it more appealing to others here and entice them to share their ideas?

Ari.

[clipclop]

Ari,
Try moveing the CG back, ie move the rotors forwards then try it again . Sounds like its nose heavy.
Stewart

[iter]

My CG is less than 1/4" ahead of the masts. Any further back and it will be behind them... I'm lead to blieve that's bad?

Doh! the CG should be relative to the rotor centers, not where the mast and fuselage intersect! With that 10* tilt-back on the masts, these are in two very different places... Of course! I'll try it first thing in the morning.

Ari.

[clipclop]

Ari,
The rubber gyro plan I have says to balance at the rotor centre. 1/4" may be all you need .
Stewart

[Don Sims]

Ari, Don't forget about the folks who are following the thread and learning. Look at the amount of hits the thread has gotten.
Don

[iter]

clipclop: what plan is that? is it available online?

Don: we're all learning :=) I just hope it will be a good learning experience for me and it will fly :=)

Most of the hits is me, I think, looking to see if anyone has replied :=)

Ari

[clipclop]

Ari,
I cant remember were I originally got the plan , its a PDF file too large too post here , but I've copied it to jpeg's here it is .
Stewart

[clipclop]

part 2/

[clipclop]

text 1

[clipclop]

text 2

[David A Ramsey]

Ari; Looks like you've got more attention than you realised and you do, as Mr Sims said, have a lot of views.

Agree with moving the CG back a little at a time till she lifts off. Then you'll probably see what other trim changes might be necessary.

I'm interested in how well those magnetic actuators provide flight contol.

[iter]

It's raining again, so I haven't been able to test my 'gyro with the new CG location. Speaking of which, what would happen if the CG is /aft/ of the rotor? It will want to pitch up, but then what? What is an autogyro equivalent of an ariplane stall when you pull too much aft stick?

David: the fuselage is from a successful airplane and actuators worked very well in that application. I'll let you guys know how they do on the 'gyro (need a name for it... Is 'snakeyes' taken?). So far I only know that the rudder is more than sufficient to turn it around on the ground at full speed (sometimes to the point of tipping it on its side)

clipclop: thanks for the plans. Got to love Australia! 50 years and work goes into the public domain. I won't be able to publish these plans here until some time in the 2030s (70 years after author's death or 90 after publication if corporate copyright). Hate the stupid copyright system. OK. This is going offtopic.

[mnowell129]

[QUOTE=iter] Speaking of which, what would happen if the CG is /aft/ of the rotor? It will want to pitch up, but then what? What is an autogyro equivalent of an ariplane stall when you pull too much aft stick?

QUOTE]
It will pitch up, then because the drag gets very large it will slow down. Then as it slows down the rotor will slow down. Then it will pitch down, then the rotor will speed up, then it will pitch up...etc.
Don't trick yourself into thinking that just because it won't stall that you can't get into trouble. At a high enough pitch angle with lack of power you can get a fairly high descent rate.
mick

[clipclop]

Iter,
Heres an extract from a gyro instruction set Re cg :-
BALANCING AND FLYING:
BEFORE attempting flight, and with the fuel cell empty, hold the model up by the rotor hub/shaft. The model should hang nose down at about 5 to 10 degrees. This is commonly known as the "hang angle". This slightly nose down angle is necessary for flight stability and to enable the model to assume a nose down "glide" if the motor fails, giving you a degree of control over the ground impact. Without it, and if the motor fails, the model may become uncontrollable and where and how it lands will be totally out of your hands. Also, if the CG is on or aft of the rotor, the model may be excessively sensitive in roll control. Instruction sets of Plans can be D/L'ed from here :- http://www.autogyro.com/plankit/plan.htm
Hope this helps
Stewart