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Old 11-22-2009, 03:25 AM   #1
Need help AGAIN!!!!!
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Default Gyro gain HELP!!!

Hi am am quite new to heli fling, i started with a blade 400 which i had for about 6 months and crashed a million times but i got good at fixing it lol,
Anyway now i have moved on to trex's as they seem to be the main name in electric helis so i bought myself a trex 450 and a trex 250,
On the trex 250 i have the stock GP750 that came in the box
On the trex 450 i have a acer lab Gyro which came on it as i bought this second hand.
Both heli's seem to fly very very well but i do have one quetion. I was told by everyone that my gyro gain on my DX7 should be set to about 70% this making it head hold mode and all that however the only way i can get both heli's to fly right is if i set the gyro to 40% ish. why is this as i am told this should be completely wrong but my heli's both seem to fly ok when i have done some hovering with them.
Not going to go out doing 3d till i get this problem answered as i dont want to smash my new heli's up.
hope someone can help
Tim.
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Old 11-22-2009, 03:31 AM   #2
SamurAchzar
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There's no absolute value for correct gain. Basically on some gyros, above midpoint gives HH, below gives rate mode (it could be reversed if your gain channel is reversed). But the actual gain value differs according to the heli and setup.

The gyros should have a LED for HH mode indication. Observe it yourself, see at what percentage it turns on and at what percentages it goes off.

Anyway, your gain channel might be reversed, making lower values higher gain. Nothing wrong with that really.
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Old 11-22-2009, 04:48 AM   #3
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If your gyro gain must be turned down low in the radio it usually means that the mechanical gain is too high. In other words the servo output arm is too long.Try a closer hole you will have to raise the gain in the radio to compensate for this.

You said it is flying good now; if that is the case you may consider just going with it as is. If it aint broke dont fix it...
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Old 11-22-2009, 06:38 AM   #4
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Thanks for the quick replies, i cant figure it out at all, The heli's both seem to fly fine doing hovering so i might just take them out in the next bit of good weather.
I watched Jasmine on utube do a trex 250 using all the same bits i use, same transmitter DX7 and all the same electrics, in the vid it gets set to 72% but when i do that the servo does not re-centre the heli can fly like it but you have to try and correct the tail yourself, almost as if there is no Gyro there at all. but if i set to 40% which turns the little light red on the gyro instead of green it works.
really odd, i bet its something really simple that i just dont see.
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Old 11-22-2009, 07:26 AM   #5
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To set your gyro gain are you using the gyro menu or endpoints in the gear channel. If you're using endpoints in the gear channel +40 would be a workable setting for many set ups. Using Gear channel endpoints -100 - 0 is Rate mode and +0 - 100 is Head Holding. Using the gyro menu 0 - 50 is Rate and 50 - 100 is Head Holding.
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Old 11-22-2009, 07:26 AM   #6
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I agree that gyro gain is never absolute. Even if someone else owns exactly the same heli, Tx, gyro, tail servo with the same ball distance on the servo arm- you would probably end up with slightly different gain values!

Also remember with a DX7 you have two ways of adjusting gain- either with the Gyro Sense menu or end points via the gear channel. Each different method has different gain resolutions, ie, in the gyro sense menu rate would from 0 to 50 while HH would be 50 to 100. Using gear via endpoints, rate would be -100 to 0 and HH would be 0 to +100.

So now you see that a 40% gain value using the gyro sense would actually be in rate mode, while using enpoints it would be in HH (because it's not a -ve value)!

Do you know which method you are using to adjust the gain?
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Old 11-22-2009, 07:28 AM   #7
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Quote:
Originally Posted by GreenCello View Post
To set your gyro gain are you using the gyro menu or endpoints in the gear channel. If you're using endpoints in the gear channel +40 would be a workable setting for many set ups. Using Gear channel endpoints -100 - 0 is Rate mode and +0 - 100 is Head Holding. Using the gyro menu 0 - 50 is Rate and 50 - 100 is Head Holding.
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Old 11-22-2009, 07:47 AM   #8
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I used the gear channel and set it to gyro, Then i go to the gyro sens menu (this menu is not there if you dont set the gear to gyro) and set the gain value under the bit where is says Rate.
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Old 11-22-2009, 07:53 AM   #9
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Hi, i use the gp 750 on my t-rex 500, red light means you are in rate mode and green light means you are in heading hold.
Need to check your values in your radio to verify you are in rate or HH by the color of the light.
Hope this helps.
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Old 11-22-2009, 08:02 AM   #10
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Yeah thats what i thought, the light on the gyro is red which means its in Rate mode as far as i am aware, i have had the heli out like this and it seems to fly fine, If i turn the light green on the gyro the servo does not re-centre itself automatically so. and the heli is way out of control.
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Old 11-22-2009, 08:11 AM   #11
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I am having this problem with all my heli's using this radio set so i do beleave its a problem with the settings in my transmitter.
I have a blade 400 with stock gyro
a trex 450 with acer lab gyro
the trex 250 with a GP750
and a belt cp with a esky Gyro,
All these heli's are supposed to use the head hold mode but i cannot get them to work like this i seem to have to set them to rate mode.
Its all very strange.
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Old 11-22-2009, 08:58 AM   #12
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When your gyro is set to heading hold mode the tail pitch slider will not return to center untill the heli moves in the intended direction. Try this, set the gyro to HH mode and move your rudder stick to one side or the other. Then physically move the heli with your hand in the same direction you gave the input. As you start moveing the heli watch your tail rotor, it will start to correct itself. If you move the heli far enough the gyro will push the tail rotor past center as it is trying to keep the heli from piroeting. Hope this helps.

With what you have described so far though your gyro is working fine when you put in rate mode. It may not seem like it to you but that is how they work in heading hold mode.
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Old 11-22-2009, 10:02 AM   #13
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Thanks to everyone for you replies and Nargargle you where right, although it did seem really weird the way the servo was behaving i just tried it fling and it actually seemed to work fine even in the wind we have here today. The other problem i had is that i had set the limits wrong which was making the slider on the tail pitch get stuck at one side thats why it seemed so out of control.
I had a bit of tail wag at 70% on the trex 450 so lowered it to 65 and all is good.
I would like to know what the difference is between head hold and rate mode and why my heli seemed to fly fine in rate mode.
anyway many thanks to all, no doubt i will have another issue before long.
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Old 11-22-2009, 10:19 AM   #14
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Glad to see you are getting there pal

To answer your question on the differences between rate/HH in simplistic terms.... when you are flying in rate mode the gyro is acting as "tail dampener". The gyro will resist say a crosswind only a certain amount before the tail weathervanes with the wind direction. When you are flying in HH the gyro attempts to hold the helis heading regardless of wind direction, headspeed change etc. That is untill you give a rudder command. As a rule the more expensive the gyro the better it will be at holding a heading due to the more sophisticated gubbins inside!
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Old 11-22-2009, 05:11 PM   #15
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Quote:
Originally Posted by Need help AGAIN!!!!! View Post
Thanks for the quick replies, i cant figure it out at all, The heli's both seem to fly fine doing hovering so i might just take them out in the next bit of good weather.
I watched Jasmine on utube do a trex 250 using all the same bits i use, same transmitter DX7 and all the same electrics, in the vid it gets set to 72% but when i do that the servo does not re-centre the heli can fly like it but you have to try and correct the tail yourself, almost as if there is no Gyro there at all. but if i set to 40% which turns the little light red on the gyro instead of green it works.
really odd, i bet its something really simple that i just dont see.
I'm a bit confused - are you talking about one setting for both helis??

Each gyro needs its own way of setting up, I advise reading the manual for the gyro you are having trouble with and setting it up from that.

Actually I'm very confused . 1 heli + 1 gyro = 1 setting.

Also 50% on the DX7 is the midpoint - usually between the gyro modes. For instance my GY401 runs on 75% for HH mode and 25% for rate mode. On that basis 40% sounds like rate mode with very low gain.
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