JR G770 and a new tail wag

[FlyawayClyde]

So the one thing I noiticed right off the bat, with this Gyro from the 401.
I used to run my gain setting around 60 to 70% in the heading hold mode.
Now as far as I was able to understand from the Finless videos, ( back when I was learning as a NOOB ) ( I still might be . The 401 use a value that is 1 to 1 in the menu in the Futaba radios.
Ok here is where I am having a little bit of a problem. The G770 is right now turned down to 15% and I'm having a wagging thing going on I just cant seem to get rid of.
I have turned the gain up to as high as 78% and as low as 10% in HH mode and the tail will not hold still.

Will I need to change holes on the servo arms. Will this help at all?
I would'nt think that the setup would be that different from one Gyro to the other??

Erik

[Jerrymac]

Don't know if this will help you any, but I use the G770 with 890 tail servo on my plastic framed Hurri with 550mm blades. I have the ball on the servo arm 15mm out from center.
I am using a DX7 and set gain using Gear travel adjust, and have mine at +28%.
It holds good and no wag.

[FlyawayClyde]

I got out the trusty Caliper, and it told me my ball is out 17.5 from center.
Now I also measured the other bird that is 401 equiped, And the ball is out 13.
Yeah I would probly benifit from moving the ball...

[Mikej]

Sounds like you need to get yer balls movin' Clyde

[FlyawayClyde]

Originally Posted by Mikej

Sounds like you need to get yer balls movin' Clyde

[kahn10]

ya nuts...yeah that'll bump up yer resolution....

[ke6d]

I have 4 of these gyros. They are not supposed to be set up like a GY401. You need to follow the JR770 manual set it up (exactly like what it says)

On my DX7 TX, this is how I set up my Hurricane:

1. Rudder travel: -150%, +150%
2. Rudder dual rate (with Rudder D/R switch on and off) 60% - Rudder dual rate controls how fast the pirouette rate is.
3. Rudder expo: (with Rudder D/R switch on and off) 40% - Rudder expo controls how linear the tail control is around the center. 40% is considered linear.

With the DX7, 50% gain will turn off the gyro
Anything below 50% is rate mode
Anything > 50% is HH mode.

Gain between 51 - 55% is not stable and should not be used for HH.

I only use rate mode for servo travel adjustment. Once that is done, I set all the flight mode to use HH.

65% gain HH is a good starting point. Generally, you want to increase the gyro gain until the the tail started to wag, the back down a couple % until the tail holds solid.

[Jerrymac]

Originally Posted by ke6d

I have 4 of these gyros. They are not supposed to be set up like a GY401. You need to follow the JR770 manual set it up (exactly like what it says)



With the DX7, 50% gain will turn off the gyro
Anything below 50% is rate mode
Anything > 50% is HH mode.

Gain between 51 - 55% is not stable and should not be used for HH.
.

This would apply if using the gyro sensing menu for setting gain, however if setting gain using gear travel adjust ( Gear set to "Gear" instead of "Gyro") then,

0% is no gain , anything above that ( 1% to 100% ) is HH mode
and anything below that ( -1% to -100% ) is rate mode, although -1 to +1 is not recommended.

Also, setting the rudder travel to 150% both left and right will usually cause the heli to piro much faster with torque (left) than it does against torque (right).
Without actually looking, I think I have mine set somewhere around 150% right and 110% left, I think.

[FlyawayClyde]

And all of this is very good information. Now as I am going through the new rebuild since the Meeting with Terra-Frima this afternoon.
I have come to the concolusion that the whole culprit to my problem was a loose bolt working its way out of the new tail hub I had installed after the last crash, the 3point shot.
There was probly nothing wrong with my orginal set-up

[Jerrymac]

Glad to hear that you got it figured out. Loose bolts/grub screws have caused me more problems than I would like to admit to.

[FlyawayClyde]

I do a pretty good pre-flight, but I had missed this.

[ke6d]

Originally Posted by Jerrymac

Also, setting the rudder travel to 150% both left and right will usually cause the heli to piro much faster with torque (left) than it does against torque (right).
Without actually looking, I think I have mine set somewhere around 150% right and 110% left, I think.

This is correct. 150% is a starting point. One needs to get the the heli up in the air then do a few piros left then a few piros right. Lower the ATV % on the one that is fast until piro rate on both direction are the same.

Mine is about 150% right and 130% left.

Once this is set, the over piro rate is set by increasing/decreasing the rudder dual rate %

[Jerrymac]

Originally Posted by FlyawayClyde

I do a pretty good pre-flight, but I had missed this.

I haven't had that problem on my Hurri yet, but many times on my smaller helis since there are a lot of screws in them that go into plastic. Any screws in metal I use the purple, low strength electronics grade loctite, but haven't found a good way to keep them tight in the plastic.


Ke6d, what tail servos are you using with the G770's. Any in particular that you use that you think work better with it than others. I am using the older DS890G and it seems to work pretty good for the price.

[mysticmead]

a little drop of CA will keep screws tight in plastic..

[ke6d]

Originally Posted by Jerrymac

Ke6d, what tail servos are you using with the G770's. Any in particular that you use that you think work better with it than others. I am using the older DS890G and it seems to work pretty good for the price.

The Futaba 9254 servo works really well. I also have a JR DS-8900G servo on my T-600. I can clearly tell that the 8900G works a lot better than the 9254. You probably won't be able to tell if one tail servo works better than the other until you start pushing them hard. On my T-600, I could fly backward figure eight at 30 mph into cross wind and the tail does not even sway. Fast tail down funnels into crosswind is also a good way to check out the tail.

[FlyawayClyde]

Yep:o
It's true I'm still a NOOB

[Jerrymac]

Originally Posted by FlyawayClyde

Yep:o
It's true I'm still a NOOB

Yeah, me too. Since I can't even fly FORWARD figure 8's at 30 mph yet, I guess I won't have any problems with the tail holding.

Mystic, thanks for the CA tip. Is it hard to get them back out later? Gotta remember the screws in some of the cheap helis are pretty cheap too.

[bobbybe]

i actually had my tail blow out on the hurri for the first time the other day doing fast reverse 8's... heehee i must be getting better

401/s9254
k6ed- should i change the gain now that i'm getting into harder flight? doing a lot of reverse and inverted stuff now and i'm scared that it'll blow out again at a critical junction

[FlyawayClyde]

Originally Posted by Jerrymac

Yeah, me too. Since I can't even fly FORWARD figure 8's at 30 mph yet, I guess I won't have any problems with the tail holding.

Mystic, thanks for the CA tip. Is it hard to get them back out later? Gotta remember the screws in some of the cheap helis are pretty cheap too.

I can still crap my pants when I do nose in

[ke6d]

Originally Posted by bobbybe

401/s9254
k6ed- should i change the gain now that i'm getting into harder flight? doing a lot of reverse and inverted stuff now and i'm scared that it'll blow out again at a critical junction

I know what you mean Bobby. It is down right scary if you are not expecting or preparing for it. The 401 is working decently but it does hold solid in fast backward fight during the turn with crosswind. When it decides to let go, the heli is doing 180 degree turn in a instance I used to have 4 GY401s but now switched to either JR770, Spartan or Vbar.

You can try to adjust the tail in rate mode first, then switch to HH and increase the gain until the tail started to wag. Lower the gyro gain a couple % until the wag is gone. It is also helpful to get the travel adjust pot to be around 90-100% for full tail slider deflection. If the pot value is too little, you want to move the servo horn hole in (too much mechanical gain) If this value is > 110% (to little mechanical gain), move the hole out. Keep experiment with the tail setup until you get the best combination that you like. I have seen awesome performance with the GY401 on quite a few helis at the field flown by extremely good 3D pilots, but I could never set mine up to work that well

If you still could not get the tail to behave well after tweaking around with the mechanical and gyro set up on the 401, you can always sell it and buy a used JR7703D. This is what I did to all my 401 It is like a $25 upgrade to the gyro (I have seen 7703D gyro goes as low as $90 on RunRyder and Helifreak)

Good luck with troubleshooting the tail (I used to spend so much time troubleshoot the tail to get it perfect so I know how difficult it is to get it just right)