How would you design a cyclocopter?

[TFerenc]

Adjusted it a little, here's a screenshot with a CG mark. It has an extremely aerodynamically optimized free-handed spline airfoil.

View attachment 195452

Use symmetrical airfoil profile wing as fare as the wing moves on periphery surface, and the angle of attack has a half lap (cyclogyro mechanism 1)

 

[TFerenc]

2jujube7
Just a point but a symmetrical wing section works equally well either way up so it could produce lift on both the top and bottom arcs if the incidence is correct. Or am I missing something?

In cyclogiro case the wing changing its angle (check letter A) against the airflow (blue arrow), so in the upper half part (from position D-to B) of the circle the one side of the wing, but in the down half part (from position B to D) of the circle the other side of the wing should create the lift.

 

[2jujube7]

It's been a while, but its time for a quick update:

I tested the cyclocopter and got 100g thrust at full throttle. The problem is that the motor weighs 80g, and the rest of the rotor weighs ~60g. I *think* that I can put hook up two rotors to one motor, so that's what I'm going to do when I actually try to build a cyclocopter. Along with the other changes that I've made, which should net me around 150g thrust per rotor and an 80-90g rotor weight, it should be able to hover. (Although it would have to be on a tether because the lightest battery I have is an 80g 3s 850mAh)

Along with only using one motor for two rotors, I'm also increasing the "wingspan" of the blades by a good 50%, which should be structurally manageable because I am also going to a symmetrical airfoil (should be much stronger). I don't have a picture from my slicer, but it's basically like this picture that @quorneng posted earlier.

The problem with this is that I have to do 1 wall on the print for it (then 3 on the bottom to serve as the spar) to be light enough, but then there's sometimes rough/patchy spots because my 3D printer isn't good enough to put down a decent 1 wall print. I also tried printing it in 1 piece oriented with a 0 degree AoA on the bed, but that also didn't turn out so well. I also tried another way with airfoils, a spar, and a covering of plastic wrap, but that was kinda complicated and a bit heavy. I'm not quite sure what I'm going to try next, I might order some carbon fiber tubes for spars and 3d print airfoils to try to make a lightweight wing that way.


I also worked a lot with the struts and such that hold the airfoils in place, and I've gotten them lighter and more aerodynamic.
Here's the overall machine so far:

Oh, and here's the airfoil I've been going with. It's the NACA 0020, which was determined in a pretty long and interesting research paper from Texas A&M to be the most efficient.

 

[TFerenc]

The stall angle of the NACA 0020 airfoil is at about 15-16 deg. In cyclogiro the wing angle (check letter A) should be max +13 deg.

 

[NickRehm]

The stall angle of the NACA 0020 airfoil is at about 15-16 deg. In cyclogiro the wing angle (check letter A) should be max +13 deg.

Rotational airflow gives 'virtual camber' effect which reduces stall + increases lift of the symmetrical airfoil. Additionally, high frequency pitching of a rotor blade reduces onset of blade stall due to unsteady aero effects. Performance of the cyclorotor trends upwards until about 40-45 degrees pitching angle

 

[Scotto]

Use symmetrical airfoil profile wing as fare as the wing moves on periphery surface, and the angle of attack has a half lap (cyclogyro mechanism 1)

Welcome to the forum. Are you a part of the Cyclotech team?

 

[Flightspeed]

It's been a while, but its time for a quick update:

I tested the cyclocopter and got 100g thrust at full throttle. The problem is that the motor weighs 80g, and the rest of the rotor weighs ~60g. I *think* that I can put hook up two rotors to one motor, so that's what I'm going to do when I actually try to build a cyclocopter. Along with the other changes that I've made, which should net me around 150g thrust per rotor and an 80-90g rotor weight, it should be able to hover. (Although it would have to be on a tether because the lightest battery I have is an 80g 3s 850mAh)

Along with only using one motor for two rotors, I'm also increasing the "wingspan" of the blades by a good 50%, which should be structurally manageable because I am also going to a symmetrical airfoil (should be much stronger). I don't have a picture from my slicer, but it's basically like this picture that @quorneng posted earlier.
View attachment 204471
The problem with this is that I have to do 1 wall on the print for it (then 3 on the bottom to serve as the spar) to be light enough, but then there's sometimes rough/patchy spots because my 3D printer isn't good enough to put down a decent 1 wall print. I also tried printing it in 1 piece oriented with a 0 degree AoA on the bed, but that also didn't turn out so well. I also tried another way with airfoils, a spar, and a covering of plastic wrap, but that was kinda complicated and a bit heavy. I'm not quite sure what I'm going to try next, I might order some carbon fiber tubes for spars and 3d print airfoils to try to make a lightweight wing that way.
View attachment 204472

I also worked a lot with the struts and such that hold the airfoils in place, and I've gotten them lighter and more aerodynamic.
Here's the overall machine so far:
View attachment 204474 View attachment 204478

Oh, and here's the airfoil I've been going with. It's the NACA 0020, which was determined in a pretty long and interesting research paper from Texas A&M to be the most efficient.
View attachment 204473

I really want to see this thing fly!

 

[PsyBorg]

I think I would get rid of the gear drives, go to a much lower kv motor and replace the motor shaft with the rotor shaft as a thru motor design. Save a TON of weigh between gearing, mounts and basic hardware like heavy screws. Then get rid of the over engineered pitch mechanism and go with simple carbon rods and ball and socket ends like they use in helicopter heads swash plates and such.

 

[Flightspeed]

I think I would get rid of the gear drives, go to a much lower kv motor and replace the motor shaft with the rotor shaft as a thru motor design. Save a TON of weigh between gearing, mounts and basic hardware like heavy screws. Then get rid of the over engineered pitch mechanism and go with simple carbon rods and ball and socket ends like they use in helicopter heads swash plates and such.

No! Over engineer everything!🤣

 

[TFerenc]

Welcome to the forum. Are you a part of the Cyclotech team?

Hi Scotto! I am a retired airline/mil. pilot, engineer. I just making some study on cyclogyro and CCW by now and just interested to follow 2jujube7 efforts. I am not part of the Cyclotech team.

 

[Scotto]

I think I would get rid of the gear drives, go to a much lower kv motor and replace the motor shaft with the rotor shaft as a thru motor design. Save a TON of weigh between gearing, mounts and basic hardware like heavy screws. Then get rid of the over engineered pitch mechanism and go with simple carbon rods and ball and socket ends like they use in helicopter heads swash plates and such.

I was thinking just the opposite- its built strong enough, increase the span! More power!

@2jujube7 do you know how many watts it was pulling and what its rated for?

 

[2jujube7]

I really want to see this thing fly!

Thanks for your encouragement, I'll do my best. I'll probably even post the STLs when I'm done with it so that anyone can print it off and try to get it to work.

I was thinking just the opposite- its built strong enough, increase the span! More power!
2jujube7 do you know how many watts it was pulling and what its rated for?

For now I'm using a 2212 1400kV generic motor off of Amazon. It's very overpowered for the current rotor I have (100mm span), so I'm in the middle of printing off some longer airfoils (150mm span) and I think I'll try to use belt drives to hook it up to two rotors. I have no idea how many watts its pulling, but I got it up to 98g thrust with the motor turned up to 100% throttle (with an 8:1 gear ratio) and it only got slightly warm.
If I end up needing more thrust, I'll probably start with increasing the radius to get faster speeds.

I think I would get rid of the gear drives, go to a much lower kv motor and replace the motor shaft with the rotor shaft as a thru motor design. Save a TON of weigh between gearing, mounts and basic hardware like heavy screws.

Cyclocopters operate at a much lower rpm than a conventional propeller, so it would need a really low kV motor. Motors are most efficient with a low load and high RPM, so I need to gear it down somehow. I think that I'm eventually going to switch to a belt drive instead of a geared setup, so that'll hopefully be better.

Then get rid of the over engineered pitch mechanism and go with simple carbon rods and ball and socket ends like they use in helicopter heads swash plates and such.

The current pitch mechanism is actually really simple. In my mind, it's less mechanically complex then a swash plate. There's a variety of methods used to change the pitch, and this is one of the more simple ones.

 

[Piotrsko]

No I believe @PsyBorg was calling for just the linkage system instead of the whole swash plate. Stuff is already made and decently robust and it adjusts in a snap.

 

[NickRehm]

A little high-level introduction to the cyclocopter + some interesting facts

 

[TFerenc]

Rotational airflow gives 'virtual camber' effect which reduces stall + increases lift of the symmetrical airfoil. Additionally, high frequency pitching of a rotor blade reduces onset of blade stall due to unsteady aero effects. Performance of the cyclorotor trends upwards until about 40-45 degrees pitching angle

About the "virtual camber" effect;
A symmetric blade at 0 pitch angle in a curvilinear flow can be viewed to behave like a cambered blade at an angle of incidence.
;

Due to curvilinear flow, this effect will be more pronounced with cyclorotors having large chord-to-radius ratio (c/R). so use Asymmetric pitching - where the pitch angle at the top is larger than the angle at the bottom, provided a better power loading than symmetric pitching. 45 pitch angle at the top and 25 at the bottom produced the highest power loading - check the upper and lower position of the blade

Because the airflow in the cyclorotor is curvilinear, an object's (air) mass in motion (momentum), the vector quantity is directly added to the boundary layer, this will increasing the airfoil performance. However to gain a favourable L/D rate we need to increase the speed up to Reynolds number region Re > 100000 !

If the radius of the cyclorotor is r = 0,2m and the chord lenght of the airfoil is c=0,15m, than we need to increase the rotational speed up to 477 rpm to fit a Re>100000 region, as to gain a favourable L/D rate!

 

[TFerenc]

I need to gear it down somehow.

Eccentrically Cycloidal (EC) Gear Model?

 

[Scotto]

Eccentrically Cycloidal (EC) Gear Model?

That's really cool but wouldnt it have a lot of friction?

How do you set up assymetric pitching? And is that mostly to compensate for the accelerated air that the 6 o'clock rotor is in?

 

[Piotrsko]

Well

How do you set up assymetric pitching? And is that mostly to compensate for the accelerated air that the 6 o'clock rotor is in?

they are offsetting the linkage a specific distance from center so that the pitch is more or less depending on it's position. Originally it was for going negative pitch on the inverted airfoil @ 6 o'clock and neutralish pitch at 3 and 9 o clock.

 

[Scotto]

Well


they are offsetting the linkage a specific distance from center so that the pitch is more or less depending on it's position. Originally it was for going negative pitch on the inverted airfoil @ 6 o'clock and neutralish pitch at 3 and 9 o clock.

Thanks. I think thats just symmetric. I was wondering about this-

Asymmetric pitching - where the pitch angle at the top is larger than the angle at the bottom, provided a better power loading than symmetric pitching. 45 pitch angle at the top and 25 at the bottom produced the highest power loading -

Im wondering how you do that without 20 degrees on the sides and still be a relatively simple machine.

 

[TFerenc]

That's really cool but wouldnt it have a lot of friction?

Cycloidal gears experience lower friction and less wear on the tooth flanks due to their rolling contact and lower Hertzian contact stress.