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How would you design a cyclocopter?

Piotrsko

Master member
#81
Probably a not linear amp meter, common on cheapo Chinese. Hot to touch is generally defined as 125f and above (not that bad, depends on how long it was run at that setting)

Hot motor on high power does say something is flailing the air,, but you already know that
 
#82
Probably a not linear amp meter, common on cheapo Chinese. Hot to touch is generally defined as 125f and above (not that bad, depends on how long it was run at that setting)

Hot motor on high power does say something is flailing the air,, but you already know that
This was 'i could smell the temperature' hot ;). Glad I stopped the test otherwise the motor would've been toasted. Will be swapping out to a lower kv motor next
 

2jujube7

Well-known member
#83
Maybe try 6:1 gear ratio? I was having lots of problems with heat until I lowered the gearing, and the higher ratio didn't significantly reduce thrust because I guess it made it much more efficient.

Wow, you really got the weight down. I have M3 screws holding the bearings in, and I guess that's really costing me because I have the same diameter and mine weights around ~170g with the servo (and a really heavy/overkill 20A and 26g ESC). You're really pulling heavy amps though, even with a cheap/under-reading current meter. I'm not exactly sure what I'm doing now, but it's definitely single digits and I'm guessing under 8 because that's what my motor is rated to.

Also just noticed that your blades have a really short chord compared to the usual 0.66:1 or 0.5:1 chord to radius ratio. It seems to be working for you in terms of T/W though.

I'm glad to see that you got the 3DP pulley working though, it took me quite a while and an idler to get to a point where it wouldn't slip past half throttle.
 

2jujube7

Well-known member
#84
Well. I started some weight optimization. Ya know, smaller bearings, lighter esc, thinner 3D printed parts, wooden dowel rods and M2 screws instead of M3 screws. And now I'm down to 90g without a servo (and it should be ~105g with). That's a 40% reduction in weight from a week ago!

I think I'm going to try and make an airplane powered by dual rotors, (hopefully it will work this time) unless @Rcjetflyer2 has gotten to it already. I really just want the title of "worlds first working cyclorotor powered fixed wing." :ROFLMAO:
 
#85
Well. I started some weight optimization. Ya know, smaller bearings, lighter esc, thinner 3D printed parts, wooden dowel rods and M2 screws instead of M3 screws. And now I'm down to 90g without a servo (and it should be ~105g with). That's a 40% reduction in weight from a week ago!

I think I'm going to try and make an airplane powered by dual rotors, (hopefully it will work this time) unless @Rcjetflyer2 has gotten to it already. I really just want the title of "worlds first working cyclorotor powered fixed wing." :ROFLMAO:
My plan was to finish up my cycloplane this week while off work for the holiday, but unfortunately I got stranded at my parents house with covid haha. So, if its a race to the first cyclorotor powered plane, I'd say you're in a better position to make it happen. Weather also doesn't look good near me this upcoming week to actually get out and fly it...
 

Piotrsko

Master member
#86
Ummm: I have seen YT videos of flying cyclorotors so this must be a FT first unless there's a subtle difference to yours that I miss.
 

2jujube7

Well-known member
#87
Ummm: I have seen YT videos of flying cyclorotors so this must be a FT first unless there's a subtle difference to yours that I miss.
We're talking about a fixed wing aircraft that's powered by cyclorotors. I tried to make one about a month ago, but it didn't fly because it was too heavy.
 
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2jujube7

Well-known member
#88
I decided to really keep the weight down and go with a nutball-like lifting body. Ain't it a beauty? :ROFLMAO::ROFLMAO: I just need to wait for some glue to dry on the rotors, and then I'll put them in tomorrow and it'll be ready. We'll see when the weather cooperates though. :confused:

beauty (1).jpg
 

Scotto

Elite member
#89
I decided to really keep the weight down and go with a nutball-like lifting body. Ain't it a beauty? :ROFLMAO::ROFLMAO: I just need to wait for some glue to dry on the rotors, and then I'll put them in tomorrow and it'll be ready. We'll see when the weather cooperates though. :confused:

View attachment 214763
I was picturing the cyclorotors being a canard/puller kinda thing, but with this at least the complex part is somewhat protected. Good luck!
 

2jujube7

Well-known member
#90
I was picturing the cyclorotors being a canard/puller kinda thing, but with this at least the complex part is somewhat protected. Good luck!
That's what I was going to do, and I actually started to make the airframe, but it just ended up being too heavy so I abandoned the idea and went with reducing weight as much as possible.
 
#91
Here's my idea, yet to be built:

1641164378025.png


Gonna maiden with the regular propeller and no cyclos, then swap out the prop for the cyclos. Advancing blade on the bottom means nose down pitching moment from the rotors, so I'm gonna mix in a little cyclo vectoring to pitch control and have them thrusting down a bit to create a counter nose-up torque. Wing size and landing gear is sized to protect the cyclorotors at all costs haha. I really like @2jujube7's approach of just putting them in the wing to protect them. I might go that route for a quad vtol that transitions, but that's for wayyyyyyy down the road

This would all be done a lot sooner if I wasn't also trying to document/video everything lol
 

2jujube7

Well-known member
#92
I like it; cool rendering/CAD work.

Gonna maiden with the regular propeller and no cyclos, then swap out the prop for the cyclos.
...
This would all be done a lot sooner if I wasn't also trying to document/video everything lol
Haha that's smart. Probably should have test flown it with a prop first, especially because I'm not quite sure where the CG should be. The vectoring is also probably pretty smart and I was going to do it, but while assembling I forgot to put it in. :ROFLMAO:

I'm also trying to document stuff, but your video will probably end up being much more interesting. I'm looking forward to see it :)

Stuck on a few last minute assembling problems, but I think I can get it up in the air tonight.
 

2jujube7

Well-known member
#93
Hm. Took the cycloplane out for the first test flight today, and one of the pins that connect the rotor blades to the bearings (friction fit) slipped out of the bearings and shook itself apart. At least I got a 60fps HD video of it exploding though. :confused: On top of that, It also turns out that one modification I made to try and keep the rotors from flying off added so much friction that it halved the amount of thrust produced. That's a bummer because I had one semi-successful flight before the explosion where it did a rotor assisted glide for ~4 seconds and could've flown but it didn't have the power.

I'm going back to using screws instead of wooden dowels; screws just fasten it down a lot better. I'm downsizing from M3 to M2 screws though which should save ~7g from the last prototype with screws.

Hows your plane going?
 
#94
Sorry about the rapid rotor disassembly, but otherwise congrats on the successful flight! Would love to see that video haha

My airframe is done and waiting for me to get my act together to build a second rotor and add electronics. I've got some other things I want to do like bench top thrust tests and other documenting before I can get to that. Flight maybe next week?

image0 (5).jpeg
 

2jujube7

Well-known member
#95
Sorry about the rapid rotor disassembly, but otherwise congrats on the successful flight! Would love to see that video haha
Haha I'm not quite sure it counts as a flight, I think the title is still up for grabs. I'll get a video up in the next day or two.

Good to hear that you're having luck though, it looks great!
 
#96
Gathered a little data this evening comparing my 3d printed rotor with foam blades to a 5x4x3 prop, same motor:

thrust vs. throttle.png

At low throttle, the cyclo looks promising, but it oddly tapers off and seems to level out at higher throttle/RPM. This doesn't follow any rules of aerodynamic rotor performance and I think I know why. I'll come back to this later...

thrust vs. power.png

Now this plot gives us a better idea of efficiency. It's easy to see that my cyclo is producing less thrust for the same power. Not really surprised, since I spent no time optimizing it haha.

power loading vs. throttle.png

Power loading tells us how much power it takes to generate a given thrust. We want to maximize thrust and minimize power. So larger numbers is better here, and you can see my cyclo falls short compared to the prop. But there's that weird dip at 30% throttle again, similar to the thrust vs. throttle plot that levels off past 30% throttle.

My theory is that my fragile foam blades are bending chord-wise due to the centrifugal force and curvilinear flow (below), leading to that major drop off in performance at higher RPM. I've got super-slo-mo video to prove that's what's happening, and it would make sense that the blades bending to 'adhere' to the flow would lead to less net angle of attack and less thrust. The force that goes into bending the blades translates through the rotor and to the motor and gives nearly the same power draw at the lower angle of attack.

1641690078503.png


Anyways, I'm sick of printing and assembling parts. This rotor gets the 'Good Enough' seal of approval to throw it on the airplane. Maybe I'll find the time one day to optimize this thing...
 

Scotto

Elite member
#97
Ive been wondering about this since the airfoil discussion earlier. If the top side is paddleing air into the center faster than the bottom side can paddle it out, you would have an area of high pressure in the center, right? If anything you would want it to be low pressure for lift, so the airfoil should be more efficient for the bottom side? Idk. I still cant fully wrap my head around the relative AoA and what that should mean as far as airfoil shape.

After staring at that last picture maybe it should be "undercambered" curved in so that at 3 and 9 o'clock its not fighting itself and causing drag. :unsure:o_O

Great work so far though guys! This is very interesting.
 

2jujube7

Well-known member
#98
After staring at that last picture maybe it should be "undercambered" curved in so that at 3 and 9 o'clock its not fighting itself and causing drag. :unsure:o_O
This idea has been in the back of my head for the past few months

I have no idea about anything thing else you just said, but I decided that I agree with this part and I think I'm going to make my next batch of airfoils slightly undercambered.

Somebody let me know if that's proven to be a bad idea (after all, every cyclorotor I know is symmetric), but I feel like having an undercambered airfoil would just negate the virtual camber and make the airfoil more symmetric, which would increase efficiency.
 
#99
What I know and what you guys are demonstrating: you're basically just a squirrel cage fan flinging air directionally. You want to do what the fan people do to optimize thrust and change the thrust to be directional in a somewhat non draggy way. They prefer thin rigid undercambered blades at a slightly positive AOA, BUT flat non profiled work also
 

2jujube7

Well-known member
This idea has been in the back of my head for the past few months
I have no idea about anything thing else you just said, but I decided that I agree with this part and I think I'm going to make my next batch of airfoils slightly undercambered.
I messed around with some other parts, then decided today that I'll follow through on this tonight or tomorrow morning. It should improve efficiency by a good bit.

Any progress on the cycloplane?