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Old Dec 19, 2014, 07:34 PM
What goes up must come down
Bush Pusher's Avatar
United States, NH, Rochester
Joined May 2014
237 Posts
pirouettes

Quote:
Originally Posted by notaclue View Post
The AS3X doesn't seem to cope well with pirouettes. To combat this I've put a swash mix in and now it rotates predictably. Don't suppose you folks know if this is somehow bad? Got the mix on a switch.
I have only had my nano cpx about 3 wks and pirouettes clockwise are better then counter clockwise might have something to do with air turbulence make by the heli it self I use a dx6i with no special programing.
I am new to helis so I use the nano cpx for inside practice just working on noise in flight and cornering left and right
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Old Dec 20, 2014, 12:57 AM
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CatBird's Avatar
Louisville, Colorado
Joined Oct 2007
379 Posts
Poor Man's Piro Comp

This discussion about piro challenges got me wondering whether transmitter mixes could be used to combat the piro problem. After playing around with it, I'm pretty excited about the results. It's not perfect, but I feel like it's a big improvement in handling. Before I explain the mixes, I'll explain my thinking.

The need for piro comp ultimately stems from the tail rotor. The tail rotor is pushing the heli to the left (upright, tail-in) so to hover motionless the heli has to tip slightly to the right. Because it's tipped slightly to the right, if you add a little right rudder the nose will end up pointed a little bit down. If you add a little left rudder the nose will point up. Therefore when you circle to the right you are always pulling back gently on the elevator stick, and when you circle to the left you're always pushing a little to keep it from stopping.

Inverted is the opposite. When inverted and tail-in, the tail rotor is pushing to the right and the heli has to tip slightly to the left. Again, right rudder tips the nose down and left rudder tips it up. But since you're inverted you have to push while in right rudder turns (turns to the left from our perspective) and pull a little in left rudder turns. You need different compensation depending on orientation, so my approach requires a radio that can do stick switches.

So first I setup a stick switch that was off for the bottom 50% of the throttle stick and on for the top 50%. I have a JR 11X, but I'll assume you can figure out the steps on your radio.

Then I setup two program mixes. First I setup a RUDD->ELE mix at -14% that's always on. Then I setup a RUDD-> ELE mix at +28% that only on with the stick switch. The result is -14% while inverted and +14% while upright. Depending on radio capabilities, there are probably many ways to actually achieve this.

At any rate, the result is a surprising improvement in my opinion. I can actually do very slow and moderate speed piros with little to no correction. Circles are significantly improved as well, with much more neutral handling in all directions.

I considered adding more mixes to add back in a little bit of the lost tilt, but so far that doesn't seem to be necessary. I might do it with time, but for now I'm enjoying a much more neutral heli. If you have the interest and a radio that can do this, give it a try and let me know if I'm just imagining the improvement.

Cheers,
Bill
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Old Dec 20, 2014, 02:54 AM
B5003D, 130X, Ncpx
notaclue's Avatar
United Kingdom, England, Redditch
Joined Sep 2014
63 Posts
It certainly helps indoors. Gonna try it outside and see if there's any horrible effects. If it's ok I'll be doing the 130x program next.
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Old Dec 20, 2014, 10:59 AM
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CatBird's Avatar
Louisville, Colorado
Joined Oct 2007
379 Posts
I'm glad that seemed to help you out indoors. I have yet to get it outside and try full rudder as well. I thought that I might try a curve mix if the elevator causes wobble at full rudder input. I'm not sure what to expect during a really fast pirouette.
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Old Dec 20, 2014, 11:00 AM
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gauchopuro's Avatar
Aurora, CO
Joined Feb 2005
73 Posts
Catbird/Bill, thanks for those details! I'm definitely going to give that a try. What do you mean by "lost tilt"?
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Old Dec 20, 2014, 08:20 PM
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CatBird's Avatar
Louisville, Colorado
Joined Oct 2007
379 Posts
Quote:
Originally Posted by gauchopuro View Post
... What do you mean by "lost tilt"?
I'll explain what I was thinking, though I'm not 100% sure it's necessary to counteract.

Hold your Nano in front of you tilted to the right as it would be in a hover. It might help to exaggerate the tilt to something like 30 degrees. Holding the head and keeping the main shaft as steady as possible, rotate the heli 90 degrees in either direction. Obviously you'll notice that the nose is now pointing up or down, and that's what the mix I suggested is trying to address. You'll also notice that the heli is no longer tilted to the right. That's what I meant by, "lost tilt."

Initially I thought I'd want to mix in a little right aileron (regardless of the rudder direction) while upright and a little left aileron while inverted. I was thinking this would keep it from "sliding" to the left during turns, but I don't feel like I'm seeing it do that. I am wondering whether the gyros are sensing the yaw+pitch and counteracting it with a bit of right roll. Or perhaps it's just that we are accustomed to constantly balancing aileron and rudder throughout turns, and the affect is too subtle to feel like anything.

At any rate, that's what I was thinking. I will try to look for this and report back if I find that any additional mixes make it feel even more neutral.
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Old Yesterday, 10:02 AM
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gauchopuro's Avatar
Aurora, CO
Joined Feb 2005
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That makes sense now. With that added understanding I would think that aileron correction would be just as important as elevator correction, but as you said there may be other factors at play there. But regardless, it should be possible to mix out all of the drifting tendencies.

I wonder if anyone else has ever experimented with this? When I got started flying planes several years ago, the manual that came with my radio has several pages dedicated to tuning planes and flybarred helis by adding custom mixes to counteract unwanted tendencies. I didn't even think of doing this with a flybarless heli until now.

I wonder if there's anything that piro comp does that can't be done with radio mixes? Piro comp algorithms running on the FBL controller do have access to the 3 axis gyro readings, which is something that radio mixes can't get. But I wonder if piro comp algorithms make any use of those values?

My nano qx quadcopter feels significantly more stable and locked in than my nano cpx. I'm interested to see if adding these mixes will make a difference.

Also, I wonder how well these mixes would cope with piro flip maneuvers? That's something I won't be able to comment on for a long time, because piro flips are far beyond my skill level right now.
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Old Yesterday, 10:43 AM
JKasprak
propchief's Avatar
Fayetteville, NC 28304
Joined Jan 2010
855 Posts
Quote:
Originally Posted by gauchopuro View Post
I wonder if there's anything that piro comp does that can't be done with radio mixes?
Yes - a mix will only add a gimbal movement based on a gimbal movement. Piro comp makes constant corrections.
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Old Today, 01:15 AM
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CatBird's Avatar
Louisville, Colorado
Joined Oct 2007
379 Posts
Correct, I titled my ideas "Poor Man's Piro Comp" because any mixes will definitely fall short of what an onboard program can do given access to all of the gyro values. My goal was to see if I could make it a more neutral bird for general indoor flying. I agree, it would be cool if someone could comment on the impact to hard 3D (not something I can do).

As for the Nano QX, it should not need any compensation. With four blades all in the same plane and two spinning each direction, it should not have any of the challenges that a traditional heli has. Of course it's also only flyable with considerable computer oversight. But it should piro exactly the same in either direction; that's been my experience with the QX.
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Old Today, 11:28 AM
Registered User
Tucson, Az
Joined Feb 2007
8,510 Posts
I convered a couple of my older birds to bl main. More and more of my micros are now bl. My newest Nano CP-X is still stock. it flys fine but when you have bl birds kinda hard to not upgrade it.
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Old Today, 03:03 PM
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United States, CA, San Jose
Joined Jun 2012
1,377 Posts
Quote:
Originally Posted by Jasen40 View Post
Fun days, my 21 day old brushless upgrade quit me last night. The esc would no longer arm.
I placed a support call, and was told that since it worked on day one that the warranty period was over. He wanted to sale me a replacement kit. I promptly reminded him of the kit's one year warranty, I was told there is no such warranties on their products It took a bit of work to get him to look up Horrizon's documentation. Once he figured out I had done my home work, he offered me a replacement. It's great that I am getting my in warranty item replaced, but why do they try to convince the customer that the products have tail light warranty.
Horrizon decided just to send me a replacement ESC, witch did not fix my issue. I guess I have a bad motor or a loose wire on the plug.
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