RunRyder RC
WATCH
 3 pages [ <<    <    ( 1 )     2      3     NEXT    >> ] 2143 views POST REPLY
HomeAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › Odd gyro problem - I swear I searched first - SOLVED!
08-14-2010 11:09 AM  8 years agoPost 1
Andypants

rrApprentice

Sydney

My Posts: All  Forum  Topic

Hey guys

Sorry to post on the main page but I'd love your collective wisdom before tomorrow so I can get out and pummel some air in style, or at least with a stable tail.

I fly a T-Rex 500 ESP w/GP780. The tail holds fine throughout most of the flight envelope but when I hit collective either positive or negative, it yaws slightly to the left. Nothing too unusual in that except this - it yaws, then rather than snapping back it stays on its new heading. It's *exactly* as if I'm feeding in a smidge of left rudder but I'm as sure as I can be that's not the case.

So say during a pitch pump, for example, the slight yaw each time will cumulate until it's more or less side-in after for or five pumps.

I suspect my transmitter is at fault, but I'm still a bit of a noob and can't be sure.

SETUP:

GAIN: 67 (no wags)
TAIL SERVO: DS520
THROTTLE CURVE: 100 per cent flat (tried a V-curve too - same result)
PITCH CURVE: 0-25-50-75-100
TRANSMITTER: DX6i
DELAY: none - could this be a culprit?

Any help is very much appreciated -she's flying like an absolute dream except for this one problem and I'd love to get it resolved and make sure she's a happy heli.

Cheers

Andy

PM  EMAIL  Attn:RR  Quote
08-14-2010 11:50 AM  8 years agoPost 2
Saint728

rrProfessor

Honolulu, Hawaii

My Posts: All  Forum  Topic

Maybe its the cruddy gyro that is the problem? I would swap it out for a Futaba GY520 or something like that. I never trusted an Align electronic.

Take Care,
Cheers, Patrick

Check the hotties in my Gallery
http://rc.runryder.com/helicopter/gallery/9019/?all=photo

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
08-14-2010 12:15 PM  8 years agoPost 3
Andypants

rrApprentice

Sydney

My Posts: All  Forum  Topic

Hey Patrick, cheers for the reply. I hear you on the electrics and I'd swap it ALL out for a Logo 400 but cash is tight... I have a Spartan but that's sitting pretty on my 250 and I think they're good friends. I'd definitely not trust anything else with the 250s tail - FWIW I was using a 780 on the 250 too and after an eternity chasing a wag I just got the Spartan and problem solved.

So your suggestion's a good one but not an option right now.

PM  EMAIL  Attn:RR  Quote
08-14-2010 12:18 PM  8 years agoPost 4
z11355

rrMaster

New England

My Posts: All  Forum  Topic

it's not the transmitter. when you pitch pump like that, you're putting a lot of torque into the system VERY quickly and gyro/servo is struggling to keep up w/ those instantaneous demands. In the old days, we might recommend the 'acceleration' setting in the transmitter. do they still even have those?

Other considerations are slightly bigger/better tail blades and/or faster servo. Make sure the tail rotor control is SILKY smooth

but the bottom line is that the current tail system can't counter the instantaneous main torque.

PM  EMAIL  GALLERY  Attn:RR  Quote
08-14-2010 12:31 PM  8 years agoPost 5
Andypants

rrApprentice

Sydney

My Posts: All  Forum  Topic

Hey Z - yep, we sure demand a lot from our systems these days... maybe even a little spoilt? What puzzles me though is I can handle the tail yawing slightly and I understand why... but shouldn't a HH gyro try to return to the point where it last received a rudder input? I think this is what's confusing me. I've had tails yaw before but they struggle back to the last commanded point eventually. This seems like it's independently choosing a whole new heading.

The tail's so smooth it's dipped in oil. I actually think your suggestion of more surface area for the tail could also be a possibility - I have the stock CF blades on at the moment. It makes sense, but as I say, the new heading deal is doing my head in a bit.

Thanks for the reply, and acceleration? Dunno about that... lol!

PM  EMAIL  Attn:RR  Quote
08-14-2010 12:37 PM  8 years agoPost 6
z11355

rrMaster

New England

My Posts: All  Forum  Topic

my hunch is that you're going to end up replacing the gyro.

PM  EMAIL  GALLERY  Attn:RR  Quote
08-14-2010 12:43 PM  8 years agoPost 7
Andypants

rrApprentice

Sydney

My Posts: All  Forum  Topic

lmao - two learned replies, both saying the gyro just flat-out sucks... I sense a trend emerging...

PM  EMAIL  Attn:RR  Quote
08-14-2010 12:46 PM  8 years agoPost 8
menace

rrKey Veteran

Sydney, Australia

My Posts: All  Forum  Topic

i dont know much about those gyros, but i overheard some guys saying they manually trimmed the heli out with the gyro in RATE mode first...not gonna hurt to try

!boo!

PM  EMAIL  GALLERY  Attn:RR  Quote
08-14-2010 12:50 PM  8 years agoPost 9
z11355

rrMaster

New England

My Posts: All  Forum  Topic

certainly no harm in doing that (set up for accurate rate mode) even if you never plan to be in rate mode.

PM  EMAIL  GALLERY  Attn:RR  Quote
08-14-2010 01:39 PM  8 years agoPost 10
neilg.

rrVeteran

north of borston

My Posts: All  Forum  Topic

why is it always the gyro?

just because i fly like crap doesn't mean i didn't see a diffeence when i trashed the DS420 tail servo and replaced it with a S9257. i made that decision based on this.

the torque was doubled with the S9257
the speed was the same - .08
i had one laying around

In Nomeni Patri Et Fili Spiritus Sancti

PM  EMAIL  GALLERY  Attn:RR  Quote
08-14-2010 01:47 PM  8 years agoPost 11
rotormonkey

rrKey Veteran

Ottawa, ON - Canada

My Posts: All  Forum  Topic

imo z11355 hit the nail on the head. The servo just isn't getting over quick enough to counter the sudden torque. I'm not sure bigger tail blades will help since it clearly has the authority to counter the torque once the tail servo reaches where it needs to be.

I for one don't really think the gyro is at fault here. Yeah there's better gyros to be had for sure, but that ain't your problem. The issue is your servo can't travel to where it needs to be quick enough.

The solution?

Try moving the ball for your tail's pushrod on the tail servo out further from center. This means that the servo will have to travel less distance to get where it's going thus sort of increasing the servo's speed.

The downside of doing that is that it'll have less torque, and less resolution. If you get too far from center you'll have a constant wag that won't go away no matter how low you make the gain in your radio.

My suggestion is to try putting the ball link on your tail servo one hole further on the horn from center. See if it helps. Note that you'll probably have to tweak your gain and you'll definitely have to re-do your limits on the gyro to avoid binding.

As for the tail stepping out, and not returning to the original heading, that might be expected behavior for that gyro. Think about it. Suppose you're in backward flight, and you bog the motor, the tail blows out 180 degrees. You sure as hell don't want that gyro trying to turn your heli around on it's own again. Every gyro has a point that it just gives up and accepts the new heading. Could be that particular gyro has a pretty narrow margin.

Anyway good luck! Let us know how it works out.

If it can't hover, it ain't worth flying.

PM  EMAIL  Attn:RR  Quote
08-14-2010 01:48 PM  8 years agoPost 12
Andypants

rrApprentice

Sydney

My Posts: All  Forum  Topic

Yep -I set up the tail with 0 per cent gain... doesn't get much more rate than that lol... servo horn at 90 degrees, dead centre zero pitch tail blades...

I solved a not-dissimilar problem on my 250 by employing the Spartan method... but as I say, my noobishness can't process a HH gyro not holding the heading but choosing a new one a few degrees off after a high torque load... yaw I understand but not that... damn Align...

PM  EMAIL  Attn:RR  Quote
08-14-2010 02:03 PM  8 years agoPost 13
Andypants

rrApprentice

Sydney

My Posts: All  Forum  Topic

I think Rotormonkey is on the ball... I'm gonna try increasing mechanical gain and see how we go... thanks for explanation re gyro just accepting defeat. We have awesome machines and it's easy to expect too much. They can only go so far and the rest is up to collective management and fleet fingers.

Thanks so much for the help guys. I'll post on this thread again soon once I get it all sorted out.

PM  EMAIL  Attn:RR  Quote
08-14-2010 02:10 PM  8 years agoPost 14
neilg.

rrVeteran

north of borston

My Posts: All  Forum  Topic

more tail weight? (i.e.) a nut on each side of tail grip cap screw

In Nomeni Patri Et Fili Spiritus Sancti

PM  EMAIL  GALLERY  Attn:RR  Quote
08-14-2010 02:12 PM  8 years agoPost 15
Andypants

rrApprentice

Sydney

My Posts: All  Forum  Topic

Ah... Chinese weight mod? Works for the 250SE... not such a crazy plan. Why in hell do they call it that?! Cause it's cheap and effective?

PM  EMAIL  Attn:RR  Quote
08-14-2010 02:37 PM  8 years agoPost 16
Ronald Thomas

rrMaster

Gainesville, Fl, USA

My Posts: All  Forum  Topic

Larger tail blades will give the tail disc more leverage to combat the torque. I would try those first as it is a simple check.........Ron

Team MikadoUSA 480XXTreme, 550SX, 600SX, 700XXTreme, 800XXTreme!!

PM  EMAIL  GALLERY  Attn:RR  Quote
08-14-2010 02:43 PM  8 years agoPost 17
cudaboy_71

rrElite Veteran

sacramento, ca, u.s.

My Posts: All  Forum  Topic

Why in hell do they call it that?! Cause it's cheap and effective?
because the original mod looked like this:

compare with these chinese weight balls:

if it ain't broke, break it.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
08-14-2010 02:54 PM  8 years agoPost 18
Andypants

rrApprentice

Sydney

My Posts: All  Forum  Topic

I gotta pair of them! They do nothing for headaches but are still fun n tinkly. Thanks for the explanation.

PM  EMAIL  Attn:RR  Quote
08-14-2010 03:33 PM  8 years agoPost 19
Aaron29

rrProfessor

USA

My Posts: All  Forum  Topic

..

PM  EMAIL  GALLERY  Attn:RR  Quote
08-14-2010 03:34 PM  8 years agoPost 20
z11355

rrMaster

New England

My Posts: All  Forum  Topic

I'd agree w/ rotormonkey on the mechanical gain idea but MG is a odd beast.

ball in too far and the servo has to move too far to compensate. that is what he's suggesting is happening and may well be.

On the other side, ball out too far starts messing w/ servo resolution and the size of the tail disk. Can start seeing a nervousness in the tail.

But DEFINITELY worth a shot.

PM  EMAIL  GALLERY  Attn:RR  Quote
WATCH
 3 pages [ <<    <    ( 1 )     2      3     NEXT    >> ] 2143 views POST REPLY
HomeAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › Odd gyro problem - I swear I searched first - SOLVED!
 Print TOPIC  Make Suggestion 

 9  Topic Subscribe

Friday, August 17 - 5:50 pm - Copyright © 2000-2018 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online