Weird Rotation

[spfdheli]

Hey helifreaks,

Tonight I took my maiden flight with my 400!! I had an issue that I was hoping you guys could help me with! When I spool up the heli it begins to rotate counter clockwise as if I was holding the rotor stick to the left. I was able to trim it out while it was on the ground with A LOT of trim. Almost all the way left. Then once it got in the air it would do it again but not as wildly (still enough for me to lose control and slap the ground) . I was able to add more left rotor in the air and straighten it out for a moment. So what could the problem be? Once I get it in the air again I guess I could try to trim it out again but I think there is probably an easy fix I am over looking. Is it my servo position on the tail? I did remove it this week to try and mount my align ds520 tail servo but ended up having to order the tail mounts. Or is it something with my controller? Or could it be the tail gyro? I just set everything back to stock (by resetting the controller). I have the controller turned down so its a little easier to fly right now but that shouldn't affect the rotor. I am just confused! I broke my landing skid tonight so I am about to order some parts: T-rex 500 skid, servo arms for my ds410m, tail mounting unit for my ds520, and a main shaft retaining collar (original owner lost it). So I was hoping to get an answer soon so I could order any part I may need with this order! Let me know what you guys think!

[Bee_random]

What gyro do you have on?

Also what transmitter?

[spfdheli]

Dx6i and the gyro is a hobby king hk401b DS is off and DR is reverse. I am not sure exactly what that means but those are the current settings.

[Bee_random]

What you're describing is 'drift'. This is usually corrected by increasing the gyro gain. on the DX6i the gyro gain is 0-100%, where lees than 50% is rate mode and greater than 50% is head hold (HH) mode. FYI 50% just confuses the hell out of the gyro, so stay clear of this. Normally the setting for HH mode is approximately 67%. But you ought to set the tail up in rate mode to give the gyro the best opportunity to correct for drift.

There are a heap of setup videos that I recommend watching. However in bullet point summary;

• Set all trims and sub-trims to zero
• Set the end points of the rudder so there is no binding (re-check this during set up steps below)
• Get into a gentle hover in rate mode (<50% gain) - look for what direction the tail is drifting (it will, and you will need to compensate on the transmitter - NOT trim)
• Adjust mechanically the servo position (or rod length) the position of the tail pitch slider and test again. Keep testing until the tail is pretty stable in a hover with constant collective.
• Then switch to HH mode with gain set to 67% and test.
• If the tail drifts, then increase the gain 2%.. keep going until it stops drifting (make a note of this).
• If the tail is wagging (swinging from side to side) then reduce the gain in 2% steps until it stops - adjust further to suit.
• Most folk will increase the gain until it starts to wag and then back it off a bit.

This should give you a stable tail. You should not need to use trim on the tail - ever.

Other sources of problems may be;

• Bad gyro (yours is a clone, so I wouldn't rule this out)
• Vibration - always keep to an absolute minimum

I hope this helps, B

[spfdheli]

Thanks a ton Bee! I will try this out as soon as I get the new landing skid and parts on!

[spfdheli]

Well I ordered all the parts to get things working. Installed the new landing skid after drilling the new holes. Mounted the servo on the tail and installed the shaft retaining collar that was missing. I got everything dialed in and when I took it out as I spooled up the heli the tail would glitch and throw the blades all the way left. I tried many things to try and correct the problem and came to the conclusion that the gyro is bunk. Luckily I had already purchased a Tarot ZYX gyro to do a FBL conversion. So I went ahead and ordered the Tarot 450 FBL head and Castle Creations 10amp BEC. Just need to wire them up and get the gyro configured.

[Bee_random]

A few pic's to help your build..

[spfdheli]

Originally Posted by Bee_random

A few pic's to help your build..

Bee you are an absolute life saver! Thank you so much for all the help from the very beginning of my CP heli experience! I owe you a lot, thanks again and I hope to get everything installed Sunday evening!

[Bee_random]

Welcome. Just passing on the kindness other folks here have shown me.

[longiotti]

Originally Posted by Bee_random

What you're describing is 'drift'. This is usually corrected by increasing the gyro gain. on the DX6i the gyro gain is 0-100%, where lees than 50% is rate mode and greater than 50% is head hold (HH) mode. FYI 50% just confuses the hell out of the gyro, so stay clear of this. Normally the setting for HH mode is approximately 67%. But you ought to set the tail up in rate mode to give the gyro the best opportunity to correct for drift.


There are a heap of setup videos that I recommend watching. However in bullet point summary;

• Set all trims and sub-trims to zero
• Set the end points of the rudder so there is no binding (re-check this during set up steps below)
• Get into a gentle hover in rate mode (<50% gain) - look for what direction the tail is drifting (it will, and you will need to compensate on the transmitter - NOT trim)
• Adjust mechanically the servo position (or rod length) the position of the tail pitch slider and test again. Keep testing until the tail is pretty stable in a hover with constant collective.
• Then switch to HH mode with gain set to 67% and test.
• If the tail drifts, then increase the gain 2%.. keep going until it stops drifting (make a note of this).
• If the tail is wagging (swinging from side to side) then reduce the gain in 2% steps until it stops - adjust further to suit.
• Most folk will increase the gain until it starts to wag and then back it off a bit.

This should give you a stable tail. You should not need to use trim on the tail - ever.


Other sources of problems may be;

• Bad gyro (yours is a clone, so I wouldn't rule this out)
• Vibration - always keep to an absolute minimum

I hope this helps, B

so when you are setting this up my <50% I should be at like 43% then try and hover?
I have the factory Gyro.

[Bee_random]

There or a wee bit lower. It's not as important as in HH mode.