Futaba Gy401 Problem

[bodean1111]

Hi guys, first post. I got tired of trying to set up that junk copter x Gyro , and stole my futaba 401 off my Trex for my copter x. Its been sitting along time so my problem may be somthing simple that I'm missing. I am having a problem that is similar to hunting ,but not quite the same. When I turn left or right the tail over travels by maybe a inch and then comes back and locks in HH just fine. My heli flys great other than that, and maybe I'm just being to picky. I am using a didital s9257 servo, for some reason the limit on the Gyro with HH off won't change the servo travel. I had to go into My radio rudder end points to get the correct travel.I don't know if thats has anything to do with it or not .Oh I am using Futaba T9CHP radio. Also Gyro sensitivity in the radio, I had to bring down to 20% to get rid of tail wag. I checked my Trex set up on the Radio and I had it set there also. I have the delay set at zero , but played with different settings anyway.The 401 is set to a didital servo.The delay in the radio is at zero, again I tried different settings just to see. Nothing seems to be binding in the tail.I also changed the ball on the servo horn from the 4th hole to the 3rd hole, no change.I suppose I could forget about it and fly my heli as is, I just don't remember my Trex doing that. Does anyone have any Ideas? or questions? Thanks Jeff

[Skiddz]

End points in the Tx don't set end points for TR servo travel; they tell the gyro how fast to allow the helicopter to yaw (piro). You set the travel limits with the pot on the gyro itself. You'll need to tweak the length of the servo arm to get the limits right.

What's the limit pot set to on the Gyro itself? 100-ish is the "sweet spot" for that gyro.

How are you setting gyro sensitivity? Using the GYRO functions in the radio or using end points on the gain channel?

What's the delay pot set to on the gyro? This will help soften up under/overshooting and bounce..

You sure nothing is slipping in the drive train and you've got enough RPM? Low RPM and a slipping TR drive system will do some weird things.

[Wolfpackin]

Don't use Rudder Endpoints to set the physical limits, it really only changes the piro rate of the heli unless you go very low and that's incorrect.

I was going to say you might have the linkage ball out too far... but now that you've moved the tail servo linkage ball inward try the Limit pot on the gyro again. It should work, physically limit the travel.
If it doesn't have any effect then it might not be functioning and that's a problem.

Make sure the pitch slider is centered on the tail rotor shaft when the stick is centered and servo arm is at 90°.
This is needed because the GY401 doesn't have independent Limit adjustment. So center the slider and adjust the Limit pot to just short of touching on both sides.

Ideally the Limit pot should be somewhere between 80-100%. If not, adjust the tail servo linkage ball in or out to get there.

If you can't get this far because the Limit pot still doesn't change the physical slider throw then I'd say the gyro is shot.

If you can get the mechanical setup right, and you still have the overshoot you might have binding or a sticky slider. Make sure everything is super smooth in the tail pitch control system.

Check out the Finless video's here:
GY401
and
GY401 w/DX7

[Wolfpackin]

And what Skiddz said too...crap, slow again.

[bodean1111]

I will try to answer some of your questions. I set servo limets on the radio becouse the gyro limet does not respond. I was not sure if a didital would be different. The limet was set at 120 , but it don't matter I could only reduce travel in the radio. It now travels almost all the way both way. Im not saying thats the correct way, but that is why I mentioned it. I set radio Gyro sensitivity under just that in the radio,up-cntr-and down. Delay is at zero for didital servos. Rpm I forgot what my thr curvse are at, but I am using Align 430 xl motor. belt slipping I have not rechecked, but you would think that would be more inconsistent. Pitch slider has been centered and tweeked several times, servo horn is at 90 degres.Every thing is really smooth. I think now, that the limet is malfunctioning; just a little surprised becouse it is flying so well other than that little bit of overtravel. In fact the cost of a futaba 401 I think I will continue to run it as is for now, Im not good enough for 3d flying yet anyway.Thanks alot for your help both of you. Jeff

[bodean1111]

I just spent a half hour wrighting a reply to your questions and for some reason it diddn't post. Im not doing all that again. Bottom line is the limet switch is not responding and that is probably what is wronge. I'm not good enough to fly 3d, so for now I will deal with it ,becouse it really seems like a miner problem becouse it really does fly well other than that little bit of overtravel. Thanks guys for your help.Jeff

[cudaboy_71]

if the limit is not responding, then you likely have the ball too far out on the servo horn. try going in a hole.

and, just to be clear: the 401 does not allow you to set the limit in both directions--which is common on today's gyros. so, you need to get the linkages mechanically centered so that your SINGLE limit adjustment works for both directions.

now, when you're setting the limit you need to have the tail deflected fully. definitely helpful to have 3 hands (a helper). someone needs to hold the rudder at full deflection and you adjust the limit pot until the slider is just barely not binding.

this single adjustment MUST work in both directions. if it is binding in one direction and not the other, then your linkages are not centered.

[Skiddz]

Originally Posted by bodean1111

I just spent a half hour wrighting a reply to your questions and for some reason it diddn't post. Im not doing all that again. Bottom line is the limet switch is not responding and that is probably what is wronge. I'm not good enough to fly 3d, so for now I will deal with it ,becouse it really seems like a miner problem becouse it really does fly well other than that little bit of overtravel. Thanks guys for your help.Jeff

As a new user, your posts need to be approved by a moderator so a little patience is warranted. We're not logged in all day waiting to approve posts, although we do try to limit the "delays" for you guys. It's an unfortunate requirement so we can weed out the bots, spammers and malcontents. This moderation period passes quickly for most users.

[Robertwav1]

Having the same issues on my 401 so this thread is very helpful to me as well. Sometimes with all the other things going on in life you forget some of the basic stuff you learned in the beginning. I have one more test flight to do before I condemn the gyro which has been suspect for a while now.

[bodean1111]

I already moved the ball on the servo horn from the forth hole to the 3rd hole. If I move up one more to the second hole, the rod that exstends to the tail will be in a bind becouse with that servo hole will be two far away from the tail boom. I don't think it will run smooth enough. Do you still think that is what is wrong? ......... P.S. To the moderator sorry if I seemed impatient with my post, I just didn't realize thats how it works for new members. I am actually a little embarresed My apologies. Thank You Jeff

[cory r]

Take it to the field or find a local Freak. Sounds like something is getting lost in the explanation. Ones who have been using 401's since the dawn of time (like myself) may leave miniscule details out. There are a bunch of things that need to be done at the same time, which is much easier just to show.

[cudaboy_71]

Originally Posted by bodean1111

I already moved the ball on the servo horn from the forth hole to the 3rd hole. If I move up one more to the second hole, the rod that exstends to the tail will be in a bind becouse with that servo hole will be two far away from the tail boom. I don't think it will run smooth enough. Do you still think that is what is wrong? ......... P.S. To the moderator sorry if I seemed impatient with my post, I just didn't realize thats how it works for new members. I am actually a little embarresed My apologies. Thank You Jeff

well, if you're not sure you can take the pushrod link off of the tail ball completely. then the pushrod is free to move from endpoint to endpoint without mechanically binding. again, with a helper holding your rudder stick at full deflection (either direction--it doesnt matter) for you, see if the limit pot has any affect on the position of the pushrod.

remember, we're talking milimeters here. you're not going to see a lot of change.

if the limit pot IS affecting the the throw in the test above, then the limit pot IS working, and you still have too much throw from your servo. you need to move the ball on the servo closer to the center of the horn. if this is a problem you need to modify the installation. somehow move the servo closer to the boom?

if the limit pot is NOT affecting the throw in the test, then you have another issue. not saying the gyro is bad. but, something is not set up or working correctly.

[bodean1111]

Sorry for not responding sooner. I want to thank everyone for there help. I did get the limet pod to work, the problem was not with the gyro.The little L shaped bracket on the tail hub slider, where the rod that comes from the servo attaches; had a a crack in it. It would work fine under long strokes, but trying to set the limet it would just open the crack. The pitch just would not move for the small amounts needed for the limet adjustment. I fixed that but, still had the same problem with the tail in flight. I moved the servo ball from the third hole to the second hole, I did notice it got better. The rod between the tail and the servo is not such a straight shot down the tail anymore, but I moved the ball to the first hole on the servo horn. It helped alot, the tail only over travels a little before locking in HH. I may or may not try to modifie the servo holder and a smaller servo horn. Im just surprised that with all the 450 class helis out there with the 401 on them that a mod like that would not be more known. I'm just glad I got it figered out, thanks to help from you guys. Jeff