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Getting frustrated... need help!

Derived42

Junior Member
#1
Hello everyone! I hate my first post to be one where I'm begging for help, but I'm getting frustrated.

About 2 weeks ago I finished my Tricopter based off of David's 2.5 design. For the first week or so, it flew great. I wasn't doing anything crazy, just trying to get the feel of it. At that time I was also flying it in Acro mode. Since then I found that acro was a little too touchy on the throttle for me, so I decided to go to Heli mode and change the throttle curve. It was also at that time that I replaced the #2 prop to be counter rotating and also reversed the motor.

It seems to fly ok near me. When I roll right or left for a bit and it gets away, it seems to start bucking. This also happens if I pitch away from me and it travels a good distance. It's almost to the point where my transmitter doesn't seem to send input.

I'm using the OrangeRX 620 (no sattelite) and I have the antenna on the battery/camera mount pointed up vertically. I did a range test the other day and about 100 paces away (with low power) it lost signal.

Would bad signal cause it to buck like that or are there multiple problems? I've ran out of replacement wood booms so I have some on order. Feel free to ask a bunch more questions because I'm pretty much lost right now.

THANKS!

Edit: I should mention that I'm using a DX6i as my transmitter.
 
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Craftydan

Hostage Taker of Quads
Moderator
Mentor
#2
hmmm . . . probably not the tx link. Try this and you'll see:

Remove the props, arm and throttle up, then turn off your transmitter. You'll likely see the motors cut off compleatly. Try turning on the TX again, and you'll see a second or two lag before the TX reconnects. TX failure is far more likely to drop like a stone rather than to be difficult to control.

At 100 paces, the transmitter test *should* fail. the spektrum manual states the TX test should be run at 30 paces.

So it's probably not your Tx . . . I'm thinking it has more to do with speed rather than distance. If you're like me, flying close in as opposed to far out has longer flight times, even though I'm zipping arrond. for me, it's speed. It feels like I'm going the same speed, but I really push quite a bit harder when I'm not not in danger of crashing into me! So that's "why" it's failing in the bigger area, but what changed?

two things:
- first did you balance the prop -- speed sensitivity is usually from the increased vibe. It can tollerate a little at low speed, but go faster . . . the vibe becomes enough to confuse the flight board.

- what side of the servo are you on? whaen you swapped rotations, you swapped where "center" is on that servo. Most servos are poorly suited for Tri's. They seem just fine, but most tend to have a deadband around the center and some servos has trouble in spots getting the servo arm at the angle commanded. Some are better than others, but few are designed to work well for tri's. An idea . . . move the "center". Go ahead and move the arm one click on the mounting sprocket, and readjust your offset on the servo. This will place you on a diffrent range on the servo's throw, and if you've got a bad spot you've wandered onto, this should help. now you may loose some yaw authority in one direction, but if it still tracks fine, you at least know what was giving you trouble.
 

Derived42

Junior Member
#3
hmmm . . . probably not the tx link. Try this and you'll see:

Remove the props, arm and throttle up, then turn off your transmitter. You'll likely see the motors cut off compleatly. Try turning on the TX again, and you'll see a second or two lag before the TX reconnects. TX failure is far more likely to drop like a stone rather than to be difficult to control.

At 100 paces, the transmitter test *should* fail. the spektrum manual states the TX test should be run at 30 paces.

So it's probably not your Tx . . . I'm thinking it has more to do with speed rather than distance. If you're like me, flying close in as opposed to far out has longer flight times, even though I'm zipping arrond. for me, it's speed. It feels like I'm going the same speed, but I really push quite a bit harder when I'm not not in danger of crashing into me! So that's "why" it's failing in the bigger area, but what changed?

two things:
- first did you balance the prop -- speed sensitivity is usually from the increased vibe. It can tollerate a little at low speed, but go faster . . . the vibe becomes enough to confuse the flight board.

- what side of the servo are you on? whaen you swapped rotations, you swapped where "center" is on that servo. Most servos are poorly suited for Tri's. They seem just fine, but most tend to have a deadband around the center and some servos has trouble in spots getting the servo arm at the angle commanded. Some are better than others, but few are designed to work well for tri's. An idea . . . move the "center". Go ahead and move the arm one click on the mounting sprocket, and readjust your offset on the servo. This will place you on a diffrent range on the servo's throw, and if you've got a bad spot you've wandered onto, this should help. now you may loose some yaw authority in one direction, but if it still tracks fine, you at least know what was giving you trouble.
Thanks Dan! I'll try the tx off thing tonight.

I did balance the props at first, but there have been times where the props have been scuffed up or maybe they're warped. I didn't balance the motors.

As far as the servo, the "bucking" is usually a roll buck. I haven't seen much trouble with the tail. As info I have a digital metal gear servo. 380max I think.
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#4
dunno about the servo, but the left-right bucking sounds like vibe being amplified by the shock mount (you do have the board shock mounted, right?)

I had mine mounted in a frame-foam-sandwich with a foam pad on the bottom and cut earplugs in stratigic locations along the top. One of the pads got loose once and WOW what a ride! Once the board accelerated more than a little, the missing pad allowed the board to warp ever so slightly casuing it to amplify the motion. Suddenly the throttle started surging up and down as it shook the board up and down -- doesn't take much of that to stop flying. Fixed the pad once I noticed it, and it flew like the magic had returned!

While I won't rule out your servo, since it's mostly left/right I have a hard time believing it's the problem. If the bucking was coupled with a wild tail osscilation or servo flopping, then maybe . . .

Look carfully at how the board is mounted, and look into rebalancing/replaceing that prop (a dinged prop is turbulant prop, and a turbulant prop is a vibrating prop). Get the vibe down, and the flight charactersistics will improve, hopefully enough to fix your problem.
 
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Derived42

Junior Member
#5
dunno about the servo, but the left-right bucking sounds like vibe being amplified by the shock mount (you do have the board shock mounted, right?)

I had mine mounted in a frame-foam-sandwich with a foam pad on the bottom and cut earplugs in stratigic locations along the top. One of the pads got loose once and WOW what a ride! Once the board accelerated more than a little, the missing pad allowed the board to warp ever so slightly casuing it to amplify the motion. Suddenly the throttle started surging up and down as it shook the board up and down -- doesn't take much of that to stop flying. Fixed the pad once I noticed it, and it flew like the magic had returned!

While I won't rule out your servo, since it's mostly left/right I have a hard time believing it's the problem. If the bucking was coupled with a wild tail osscilation or servo flopping, then maybe . . .

Look carfully at how the board is mounted, and look into rebalancing/replaceing that prop (a dinged prop is turbulant prop, and a turbulant prop is a vibrating prop). Get the vibe down, and the flight charactersistics will improve, hopefully enough to fix your problem.
I have some pre-balanced props standing by and I'll replace all of them.

As for shock mounting, I have the board on some kyosho gel sitting right on the frame. Maybe I'll go, frame->gel->another surface -> gel -> KK2.
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#6
I have some pre-balanced props standing by and I'll replace all of them.

As for shock mounting, I have the board on some kyosho gel sitting right on the frame. Maybe I'll go, frame->gel->another surface -> gel -> KK2.
ooooh . . .going with the fancy foam ;)

I wonder if it *might* be sloshing too much when vibed. The gel padding is great to cut out high frequency vibe, but the shake might be form the remaining low-medium freq vibe. I'd definitly try the props first, before you re-mount, and possibly try the balancing the motors before that too.

It's an interesting idea, but I'm not sure the double-decker-super-foam sandwich will cut the frequencies that are beating your copter up.
 

Derived42

Junior Member
#9
Tried the tx test. Did exactly what you thought it would. Going to try props next week and also change around the position of the motor wires. They weren't about 2cm away from the prop. Going to route them on the side of,the arms instead of on top.
 

Cyberdactyl

Misfit Multirotor Monkey
#10
Also . . .are your plates G10 or carbon fiber?

And if CF, do you have 620's antenna pasted or very close to the plates?

If you have David's G10 plates and/or your antenna isn't taped length-wise down your carbon fiber boom, ignore me. :p
 

kah00na

Senior Member
#13
When you had all three propellers going the same way, did your KK2 board know all three were spinning the same direction? I would guess you did since it was flying well. When you swapped the rotation of the second motor, did you just switch a couple of wires to it or did you go in to the KK2 settings and specifically change the setting so that the KK2 knows that the second is spinning the opposite direction now?
 
#14
When I was flying with all three the same rotation, I never changed the setting on the KK2 board. I was under the impression (from reading) that it didn't matter what rotation the KK2 had stored.

Now with having the #2 motor being counter-rotating the KK2 is setup exactly how the copter is.
 
#15
Wanted to post some pictures of my setup to see if it would help figure out the problem. Got the new booms today so I'll be taking her out tomorrow at lunch to see how she does. Let me know if anything looks out of the ordinary. THANKS!


General Layout:
photo.jpg
Wanted to show how I was balancing (with tape on trailing edge):
photo_1.jpg
photo_2.jpg
Showing that the prop is indeed balanced:
photo_3.jpg
How the KK2 is mounted on the board and the PID settings:
photo_4.jpg
photo_5.jpg
photo_6.jpg
These are the props I was using during the problem (notice how they are pretty damaged on the edges):
photo_7.jpg
photo_8.jpg
 

xuzme720

Dedicated foam bender
Mentor
#16
When I was flying with all three the same rotation, I never changed the setting on the KK2 board. I was under the impression (from reading) that it didn't matter what rotation the KK2 had stored.

Now with having the #2 motor being counter-rotating the KK2 is setup exactly how the copter is.
It doesn't on a tri since the yaw is controlled by the tail tilt. If you have all three props the same, you need more offset on the tail (tilted to the right) to counteract the torque produced by the props, but the board will counter that on it's own as well so it's not much of an issue.
 
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#17
It doesn't on a tri since the yaw is controlled by the tail tilt. If you have all three props the same, you need more offset on the tail (tilted to the right) to counteract the torque produced by the props, but the board will counter that on it's own as well so it's not much of an issue.
Thought so. Glad to know I'm not crazy :)
 
#18
Took it out today and broke two booms because of the problem. I had my friend take a video of it.


If you notice where the annotation is, it starts to buck a little bit. Exact same problem as before.

Let it be noted that I HAVE NOT balanced the motors.
 

xuzme720

Dedicated foam bender
Mentor
#19
It's a little far away in the video to see just what's happening but I have to ask, have you tried going back to plane mode and see if maybe there isn't some sneak setting in the heli setup in the radio? Seems like your issue started when you swapped templates...
 
#20
It's a little far away in the video to see just what's happening but I have to ask, have you tried going back to plane mode and see if maybe there isn't some sneak setting in the heli setup in the radio? Seems like your issue started when you swapped templates...
I haven't. I could never get comfortable enough with acro mode to fly faster. What setting would make it go wonky when flying faster? I don't know much about heli mode so I'm curious.