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HelicopterRadio - Servo - Gyro - Gov - Batt › Slight tail drift in 3D
09-11-2007 10:54 AM  10 years agoPost 1
"Cam"

rrKey Veteran

UK

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I’m flying a TRex 600 with a GY502, 9254, 13mm arm, 50% gain on the Gyro.

2200 headspeed. Thing locks rock solid and holds fine in fast backwards flight.

The tail is loose in tic-tocs and will drift right just slightly (piro right) in static flips. But holds in full power climbouts from the hover.

I don’t know why or what to adjust.

DSX9
EMax V2
http://runryder.com/helicopter/gallery/37491/

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09-11-2007 01:30 PM  10 years agoPost 2
nappyroots2182

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Moline, il

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maybe your dropping headspeed just a bit and the tail is letting go? gain sounds a bit low. does it hunt if you up the gain a few percent?

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09-13-2007 01:54 PM  10 years agoPost 3
"Cam"

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UK

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I thought the gain should be around 20% in heading hold on a 502?

I can increase the gain but I don't want the servo to burn up and trash the heli.

Yeah I think the h/s drops just slightly but the tail is not letting go in any way; just drifts a tad.

DSX9
EMax V2
http://runryder.com/helicopter/gallery/37491/

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09-25-2007 09:40 PM  10 years agoPost 4
dpcarey

rrApprentice

Ontario, Canada

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I have been experiencing the same thing on my little Trex 450 with a 401 gyro. The tail is solid in every manuvre except a stationary flip. When I do tight stationary flips I always get drift (nose right/ tail left).

Sometimes I see as much as 45 degrees drift just going from level to inverted (forward or backward flip = same thing). I have also noticed that the bigger the radius of the flip, the less it seems to drift. The tighter the flip, the worse it is.

I have re-setup my head twice, changed blades and dialed gyro gain up and down. So far, I cannot seem to nail this down. Other than this tendancy, the bird flies straight, true and smooth.

I sure hope someone can offer some more insight here.

Dave

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09-28-2007 06:07 PM  10 years agoPost 5
dpcarey

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Ontario, Canada

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TTT

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09-28-2007 06:42 PM  10 years agoPost 6
MJA

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UK

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There is a limit to what any gyro/servo combo will cope with as far as sudden collective load changes go.If you want the tail to be rock solid never moveing off line hardly, no matter what you throw at it, you might consider going upmarket with the gyro to the GY601/GY611
for the T-Rex600
In other words it might not be a setup issue or an issue with the tail on the heli ,but rather the limitation of how quickly the gyro/servo can correct it.

You say it yaws right,with the rotor direction?
Is your auto unit locked up or very tight?
Really notchy mainshaft bearings might be enough to do it too
Reason i ask if auto unit is tight or locked up
is the extra inertia created whenever the actual rotorspeed exceeds the engine driven rotorspeed would tend to yaw the heli in the same direction as the rotor direction ie to the right or clockwise when looking at the top of the disk.

Tail changes that are opposite to the mainrotor direction tend to be situations where the tail power can't cope or the gyro/servo can't keep up or you have low gyro gain,slow tail servo or
sticking linkages,bad tail grip bearings etc.

If the tail holds very good in everything else but flips it could be related to the sudden cyclic/rotor disk shock loads getting into the gyro sensor.It generally happens more when you use gyro mounting tape that is too soft.Also the standard Futaba double sided gyro foam has a habit of splitting down the middle over a period of time. Things like the rear boom support clamp moveing,battery shakes,canopy shakes etc can get into the gyro too and degrade performance or cause false yaw sensing / corrections .

Martin

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09-28-2007 07:03 PM  10 years agoPost 7
LJS

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Minnesota, USA

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Hi Cam,

I had the same problem with my Swift. It would drift in flips only. I increased the size of the tail rotor blades and switched from plastic to carbon fiber and that took care of it. I did have to turn the gyro gain down a bit after putting on the bigger blades. My Swift uses the JR7703D gyro.

I've also had the same issue with my TRex600N with 611 gyro. The tail drifts in flips. I have the Sport which comes with the plastic "batman" tail rotor blades. I switched to RotorTech CF 95mm tail blades. They are stiffer and have more surface area than stock. I will be trying them tonight. I'll let you know how it works out.

Keep 'em flying.
LJS

Logo 600 VBar, 10S
TRex 600E VBar, 8S
Logo 500 VBar, 6S
TRex 600ESP, 6S

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09-29-2007 04:12 AM  10 years agoPost 8
LJS

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Minnesota, USA

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Hi Cam,

Well, I tried out the new tail blades and they worked great. I gotta tell you that I am not too smooth when doing my flips. I usually put in too much collective. I think that's why the tail was drifting.

Anyway, the 95 mm RotorTechs worked great. Even with some very aggressive collective pumping the tail held great. I was surprised to find that I didn't have to lower my gyro gain. But I had initially set it to what the guys recommended for the 600N Pro. Since I have the Sport, I may have had my gain set too low for the smaller tail blades.

I'll bet you will have similar results if you go to larger tail blades.

Keep 'em flying.

LJS

Logo 600 VBar, 10S
TRex 600E VBar, 8S
Logo 500 VBar, 6S
TRex 600ESP, 6S

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10-08-2007 01:39 PM  10 years agoPost 9
"Cam"

rrKey Veteran

UK

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MJA nice reply thanks.

LJS you get the same 'drift-in-flips-only' with a 611? that sucks.

For static flips you need a lot of 'pop' thats a lot of collective very quickly. Its more like impulse than acceleration as its a big force over a very short time so you load the rotor up but the heli dont go nowhere! Get the pop on only for a split second as you give cyclic and then head back to the middle on the collective for knife-edge. Then I 'pop' it again when inverted before getting back to skids down. That way the flip's completely stationary.

I wasn't trusting the battered old 502. But I think it may be a motor loading issue. Although the tail slider's not maxed-out so it must be the gyro response. Maybe if the h/s drops, the gyro really needs more gain at that point to hold, and that's why it drifts.

I should really set the GY502 to AVS and use two gain positions on the switch for hold, then only go to higher gain when doing a flip. That might show if there's anything to the above idea.

DSX9
EMax V2
http://runryder.com/helicopter/gallery/37491/

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10-08-2007 02:20 PM  10 years agoPost 10
LJS

rrKey Veteran

Minnesota, USA

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Hi Cam UK,

Thanks for the tips on doing the flips. I was doing them again last night, but they weren't pretty. Tail was holding, but I don't seem to have the collective figured out. Will try popping it next time. It makes sense that that would work.

Thanks again and keep 'em flying.
LJS

Logo 600 VBar, 10S
TRex 600E VBar, 8S
Logo 500 VBar, 6S
TRex 600ESP, 6S

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10-15-2007 01:29 AM  10 years agoPost 11
MJA

rrKey Veteran

UK

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wasn't trusting the battered old 502. But I think it may be a motor loading issue. Although the tail slider's not maxed-out so it must be the gyro response. Maybe if the h/s drops, the gyro really needs more gain at that point to hold, and that's why it drifts.

I know what you're saying,but it doesn't explain why you are getting a nose right yaw when looking at the top of the disk.The nose right yaw would be comeing from the gyro's ability to correct when rotordisk is unloading
or due to extra drag about the mainshaft axis through to the main heli body system

Another possibility is it could be a cyclic phasing shift issue due to sudden changeing headspeed.
The situation i'm thinking of is where you give pure fore/aft cyclic
but are getting a little unwanted aileron effect as well.

Taken to the extreme and to demonstrate what i'm getting at.Say you flipped the disk back (so you were looking at the top of the rotor disc near vertical)
,then forward flipped with a deliberate mix of full forward and full left cyclic held in at same time,by the time the disk got to near the horizontal the nose of the heli would be pointing fully to the right.

If this were happening on a smaller scale due to unwanted cyclic due to sudden loading/unloading & headspeed changes it might give the appearance that your nose was drifting right in the flips

What is your general cyclic trim like in the hover,is it much away from neutral.Did you check the swash/paddles very carefully for any unwanted cyclic interaction throughout the collective range


I should really set the GY502 to AVS and use two gain positions on the switch for hold, then only go to higher gain when doing a flip. That might show if there's anything to the above idea.

That's a good idea if you can get away with it not just hunting all the time on the higher gain setting.

Martin

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10-16-2007 10:49 AM  10 years agoPost 12
"Cam"

rrKey Veteran

UK

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It might be the phase. I think the whole align head is pretty sloppy.

Yes the nose drifts to the right slightly so the blades are driving the tail round a tad.

Tail holds fine when unloading the disk. (Get slight overspeed flying in 'gas' mode).

I really dunno what's up. Some helis fly perfect, others always seem to have some gripes.

DSX9
EMax V2
http://runryder.com/helicopter/gallery/37491/

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10-25-2007 02:35 AM  10 years agoPost 13
"Cam"

rrKey Veteran

UK

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Learnt a bit more

I've read this:
http://www.runryder.com/helicopter/t380698p1/

Now I'm thinking to mix some collective to the gain channel!
On a free mixer I could just turn it off for normal fast flight if the tail hunts. Being able to mix rate of collective would be a better solution but it's not an option.

I always thought a heli should fly true just on mechanical setup.
I guess 3D pushes everything a bit!

DSX9
EMax V2
http://runryder.com/helicopter/gallery/37491/

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HelicopterRadio - Servo - Gyro - Gov - Batt › Slight tail drift in 3D
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