E-Razor 450 setup - yaw is drifting with centered trims

[creyc]

This is my first time with RC heli's so please forgive me if I don't use the correct terminology.

I recently got an ARF E-Razor 450 and have been having a hard time keeping the yaw in control with centered trims. The copter came with a GY192 gyro and I am using a FrSky Taranis radio with a D8R-II 8-channel RX.

To setup the tail rotor I first bypassed the gyro and plugged the tail servo directly to the RX. I set subtrims to center and the servo horn to be 90 degrees with the tail and adjusted the linkage to set the tail rotor pitch to 0 degrees at this center point. I then plugged the gyro back in and mapped the gyro gain pin to a pot on my radio, which outputs from -100 to +100.

I tried hovering and the craft wanted to yaw left (CCW) pretty badly. As a test, I applied a little right trim on the yaw control and it stopped spinning on its own and seems to operate correctly. I turned the gain pot up until the tail began 'wagging' and then backed off a little, ending around -70.

I don't think this is correct behavior however, surely the gyro should be able to hold the tail in position without the extra trim? Any tips would be appreciated!

[Ozz58]

Not the best gyro, but we might be able to improve it some.

First take it out of HH mode, hover the heli, you will need to add trim to get it to hover straight. Once you have it staying somewhat straight land and take note of tail blade pitch. What we want to do is make the tail blade pitch the same as when it landed but with the trim in the middle by adjusting the linkage, it's a little trial and error but will help.

Now try it in HH mode, it should be better. Trim is not a good thing to use on a gyro, but if you have to use it make sure you center the trim between flights before you plug in your next battery.

Craig

[Imzzaudae]

Please tell me about your transmitter make model.

Throttle and pitch curves. This is important.

How's the blade balance on the main blades do you see any vibration in the tail?

What have you got the gain set at channel 5? Both sides of the switch?

A very light touch on the collective is needed, It is possible to input right rudder when increasing collective without knowing you are doing so!

Will check back in in a few.

[creyc]

Originally Posted by Ozz58

Not the best gyro, but we might be able to improve it some.

First take it out of HH mode, hover the heli, you will need to add trim to get it to hover straight. Once you have it staying somewhat straight land and take note of tail blade pitch. What we want to do is make the tail blade pitch the same as when it landed but with the trim in the middle by adjusting the linkage, it's a little trial and error but will help.

Now try it in HH mode, it should be better. Trim is not a good thing to use on a gyro, but if you have to use it make sure you center the trim between flights before you plug in your next battery.

Craig

Craig; thanks for the advice. To be honest I don't know how to get in and out of heading hold mode. The GY192 manual is rather lacking, and merely states: "Dual mode system: Heading lock mode or normal mode" but gives no indication on how one would go about switching between these modes??

http://www.dynam-rc.com/download/GY1...ion_manual.pdf

Originally Posted by Imzzaudae

Please tell me about your transmitter make model.

Throttle and pitch curves. This is important.

Transmitter is a FrSky Taranis 2.4GHz, mode 2, running OpenTX firmware. I'm not an expert with OpenTX but I understand the basics and this radio has served me very well on other craft.

Throttle is [-30, -15, 0, 50, 100] in normal mode, and linear in both idle-up modes.

Pitch is [-100, 20, 30, 70, 90] in normal, [80, 70, 60, 70, 100] in sport and [100, 90, 80, 90, 100] in 3D mode.

How's the blade balance on the main blades do you see any vibration in the tail?

Blade balance seems OK, no major vibrations at least, and tracking is almost dead-on.

What have you got the gain set at channel 5? Both sides of the switch?

For me, I've got channel 5 mapped to my throttle. I'm not sure which parameter you intended to ask about with this question?

[creyc]

After doing a bit of digging through better gyro manuals it seems (standard??) that a gain value >50% puts the gyro in heading hold, and <50% corresponds with yaw rate mode.

Since my transmitter doesn't use percentages but rather deals with -100 to +100 values directly, I mapped my heading hold switch to send a gain of +30 (or 65%) and in yaw rate I'm sending -30. (or 35%) It's dark now so I won't have a chance to test this until tomorrow but I feel like I must be on the right track at least.

Also, here are my curves in case the -100 to +100 values do not make sense.


Throttle normal


Throttle sport


Throttle 3D




Pitch normal


Pitch sport


Pitch 3D

[Ozz58]

Your setting look good.

Good luck, and let us know how it goes.
Let us know if you need more help.

Craig

[creyc]

I trimmed the tail in rate mode, measured with a pair of calipers, reset trim and adjusted linkage to match and now it's holding strong.

Now I've got a bit of cyclic drift I've got got to get rid of. (About 3 trim clicks right and 4 clicks forward) but I can hold it in a pretty steady hover.

I also noticed the main shaft came out of the box with a fair bit of runout, so I think that is causing some unnecessary vibration.

[Ozz58]

Glad it's working better for you.
Yes, replace the main shaft, vibrations will also screw with the gyro.

Craig

[creyc]

I noticed over the weekend the yaw did not seem very well controlled, even with HH enabled.

Looked a bit further into the tail and noticed the belt pulley on the tail rotor seems to be somehow stripped. It is allowing the pulley to slip and not turn with the main rotor. I'm not sure what parts I will need to fix this, hopefully not too much.

[kenbeav]

cryc, i have a e-razor 450, the tail is a problem with them , the shaft is splined and the pully is pressed on. the problem with mine is if i have a hard landing the pully will slip on the shaft. after that when you spool up the heli will spin round and round. it is not a problem replacing the tail unit, the problem is replacing it so often. it should be a way to fix the pully where it would hold better. if you land hard and not hit throttle hold it will strip every time, so mine has, maybe some could sujest a way to fix this. this is the 3rd one for me, i like the heli, but not the way some parts are made. if someone knows a fix for this i would greatly appreciate letting me know. cryc, you can remove the shaft and pully without taking the whole tail of. remove the two screws that holds the left bering on, take the bering out, then remove the slider and blade holders and the pully and shaft will slide out through where the bearing was. hope this helps