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04-27-2004 12:24 AM  13 years agoPost 1
vaportrail OLD

rrApprentice

Anchorage, Alaska

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My x-cell gasser has developed gyro drift in HH. I have a 401/9253 combo that has worked great since I got it, 35 flights. I changed to the cnc tail gearbox and pro 2k tail pitch mech and flew it a couple of times without incident. On my last 4 flights, the tail won't hold in hover. It drifts torque-wise. This is the only change I've made. If I punch it, the tail holds fine. It moves away very slightly, but comes right back.

I checked for trim and subtrim in the tx and found nothing. The tail control is smooth as ever.
I increased the gyro sens from 53 to 75 (Futaba 9C) with no change (no wag either.)
I richened the mix just incase that was it but no joy.
The problem is worse the higher the rpm. At 1400, the drift is about a degree a second. At 1700, it's 5-10 degrees/sec.

Could this be the gyro going bad or should I look for something else?

I'm open to suggestions. I have another gyro coming back from hobbyservices but don't expect it for a few weeks.

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04-27-2004 01:07 PM  13 years agoPost 2
staraero1

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Atlantic City, New Jersey

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Check your mounting tape for security. Check your tail rotor linkage for draging. Have you fliped the gain switch fast back and fouth three times to check for gyro centering? Check that as well.

If you don't find the trouble in these obvious places, send it in for service before it does something really bad. Look over the whole setup for an obvious problem first. If it clearly is not any of the standard problem items you got one going bad.

Staraero1

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04-27-2004 10:58 PM  13 years agoPost 3
vaportrail OLD

rrApprentice

Anchorage, Alaska

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I checked the mount pad and it is still good. I have a velcro strap over the gyro to prevent it leaving in a crash but that has always been there. The linkage is as smooth as ever. I think this is either vibration related or a failing gyro. I will work on the vibration angle for now. Since it holds during rapid power changes I am suspicious of vibration.

Thanks for the suggestions.

chuck

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04-28-2004 01:00 AM  13 years agoPost 4
scottc

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shakopee minnesota..USA

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awhile back i was buying gents 9253 servo and the reason he was selling it was it was on a gaser and there was not enough torq to hold the tail on his gaser,this just a thought for you

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04-28-2004 01:03 AM  13 years agoPost 5
staraero1

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Atlantic City, New Jersey

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Vibration is probably the issue in your case. You could try to retrim the center in the gyro, and then adjust the ball link in rate mode, one turn at a time at the servo arm to achive a no drift condition with hover tests in rate mode. Then switch to heading hold mode and try it.

I would suspect you will find a vibration problem of some sort, or possibly even some servo problem. Let us know what you eventually find is the trouble. Thanks.

Staraero1

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04-28-2004 01:32 AM  13 years agoPost 6
2LTime

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Walworth,NY

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When I rebuilt my raptor last time I left a washer off one side of the spindle. It didn't really vibrate that bad but the tail did the exact same thing you describe. Noticed my mistake and replaced the washer, Tail was perfect again. It was a 401 gyro. Look for vibration.

Jeff

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05-15-2004 12:25 AM  13 years agoPost 7
vaportrail OLD

rrApprentice

Anchorage, Alaska

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Fixed the problem

I remembered the one thing I had changed since the last time my tail held well. I had always had a tie wrap around my gyro (see my gallery) and it worked fine but I always heard that securing the gyro too tightly wasn't a good idea. So I replaced the tie wrap with a velcro strap (the idea was to contain the gyro in a crash so it doesn't tear loose and beat itself to death, learned that lesson on my raptor.) I didn't think of this right away though. I checked the gyro pad and found it deteriorated. AH HAH! Replace that (still with the velcro strap) but it still drifted. So I stuck another tie wrap on it and it works like a champ.

My theory: I have the gyro on a platform made from the original gyro platform support brackets, just stuck together without the carbon plate. It has an arm (think physics) but is very rigid so the gyro felt whatever the frame felt vibration wise. That is with the tie wrap. With the velcro, the gyro wasn't forced to move with the bracket and set up some kind of resonance. The higher the rotor rpm, the worse the drift so it was definitely vibration related, although the heli is much smoother at 1700 than it is at 1500 at least at human visible freqs.

If my logic is invalid someone please let me know because this drove me crazy. I was laid up after surgery for a few weeks and today was the first chance I've had to fly.


The real point of terrorism is not the act itself, but our reaction to the act.

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05-15-2004 02:49 AM  13 years agoPost 8
scottc

rrKey Veteran

shakopee minnesota..USA

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i like the heli you got there,as for the gyro mount iam not sure of it but if it works so be it,as long as you know where the problem is try try this out ,get a horzital tail fine mount and make a small square bracket for the gyro to mount on and put it behind the tail servo and see if that works for you ,just my though here.

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05-15-2004 07:08 AM  13 years agoPost 9
vaportrail OLD

rrApprentice

Anchorage, Alaska

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I saw one with the gyro mounted in front of the start shaft (which I don't use) so the next time I get bored I will probably move it there. It will be under the canopy then. I put it where it is because I had to move it from the stock location below the tailboom because of the muffler upgrade. I had the wires neatly spiral wrapped (can't see in the photos) so got lazy. It is working fine now but I do want to move it. Just can't bring myself to fix it since it isn't broken anymore. Anybody think the position is bad for the long term health of the gyro?

Thanks to everyone for their advice.

chuck


The real point of terrorism is not the act itself, but our reaction to the act.

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05-15-2004 09:04 PM  13 years agoPost 10
Stretched

rrApprentice

Mobile, Alabama

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SHAZAM!!!

Chuck, I am glad you posted this question. I am having the same exact problem. I too have only noticed this recently. And when you said you remember noticing it after the velcro strap, and now the fix by taking the strap off, you also solved my problem as well.

I reconfigured my battery tray about 3 weeks ago, and bought some new foam, and straps to get a cleanner look. I also put a strap on my gyro in the event of a crash. Thats about the time I noticed it. It just slightly wanders to the right in a hover. Normal mode is trimmed perfectly, and I also tried resetting the center, to no avail.

I will take the strap off, and try your tie wrap method.

Thanks!!


Scott

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05-16-2004 04:05 AM  13 years agoPost 11
Stretched

rrApprentice

Mobile, Alabama

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Yep, that was it.


Took the strap off and now she is as solid as a rock again.

Thanks,

Scott

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05-16-2004 05:58 AM  13 years agoPost 12
vaportrail OLD

rrApprentice

Anchorage, Alaska

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The gyro must be shaking too much on the pad with just velcro. That should also mean it is shaking without any support which is how a lot (most?) are done. Weird! I've had a tie wrap on my r50 ever since my last chicken dance It was tough watching the gyro swinging around beating itself to death until I could shut it down. I never gave the tie down any thought before and on the raptor, it worked fine with nothing but the pad. And it works with the tie wrap too! No complaints I guess.

Chuck


The real point of terrorism is not the act itself, but our reaction to the act.

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