Understanding Gyros + Setup

[Guest]

Does anyone have a good link to any articles explaining in layman terms the ins and outs of gyros, especially from a setup point of view.

What I mostly do not understand well at the moment is the whole gain thing and the relationship with rate mode and HH.

I have a DX7 and in the menu you can set up the gyro gain in the Gyro Sens menu...this seems the correct way to do it but the guy who re-setup the TX for me did it a different way...on the gear settings in travel adjust with +74% and -74%.

This seems to work but what happens if they were set to say +90% for HH and -10% for rate mode and how does this relate to the screw setting on the gyro itself? Does the screw just have to be bang in the middle?

Hope that is not too confusing - I can not seem to work out the logic of these things and as I am planning to get a better gyro (my cheapo one can not cope with the higher head speed it seems) I thought I should properly understand them first.

I watched this vid from 2/3 onwards but still stuck:
http://video.helifreak.com/tmp/70cac...1bb2/dx7v3.wmv

Cheers,
Jack

[snapshot]

Rate mode applies an opposing force to any movement of the tail. So if it is hit by a side wind and starts to move the gyro will try to oppose this force to hold it in position. So it knows it has moved left so it moves the tail right but it doesn't know where the original position of the tail was. Some scale flyers use rate mode as the tail will follow a turn even when you have finished applying rudder/yaw and then the tail will act like a weather vane in straight flight and straighten itself up.

Heading Hold will hold a position not just apply a force to counteract it, so if wind hits the tail and starts to move it a heading hold gyro will try to return the tail to the position it was in before the wind hit it.

The gain basically alters how sensitive the gyro is to movement, in HH not enough gain and the tail will drift. too much gain and the tail will wag. In rate not enough and the tail drifts left and too much the tail drifts right. Thats why there is 2 different settings for rate and HH and also because they are normally set at opposite ends of travel e.g. -50% for rate and +50% for HH but these values will most often be different from each other.

Kind of the tail has moved, I better do something..... Oh yeah I better do something (Tail has drifted - low gain) or the tails moved correct it, done it too much, correct it the other way oh no, gone too far the other way, correct it.(Tail Wag, too high a gain)

Setting up a gyro is down to how the gyro's manual says, so it's not easy to give a definitive answer. Some/most require a mechanical setup of 8degs left yaw(Tail moving right) to counteract blade torque and then follow the manual!

The one thing that most people have problems with is yaw input to the gyro. This determines the rate of change of the tail rotors not the position of the servo.

Changing dual rates or atv of the rudder channel alters the sensitivity of the gyro to rudder input, lowering the atv or the dual rates just slows down how fast the tail moves according to rudder input, thus altering piro rate. You can set the rudder to 10% of full travel using atv's and you'll just see that the tail rotor just moves very slowly to it's limits, as you increase the atv the tail rotors will move faster to their limits. So rudder travel in the transmitter has no effect on actual tail rotor travel - that is set by the gyro in HH anyway.

Many people ask that question so I thought I would add it here.

I hope that helps a bit.

[Guest]

Wow, thanks for taking the time to explain that. Really appreciated.

So, can a gyro not be setup without the tx just by using the screw on it?
What I am still confused about its that there is 2 places to set the gain - one on the gyro and one on the tx...am I wrong?

[Grant85]

This is very detailed mate and may help you :
Capi's Gyro 101 - HeliFreak

[snapshot]

Wow, thanks for taking the time to explain that. Really appreciated.

So, can a gyro not be setup without the tx just by using the screw on it?
What I am still confused about its that there is 2 places to set the gain - one on the gyro and one on the tx...am I wrong?

That depends on the gyro, I have never personally flown with the industry standard 401, so cannot comment on that gyro. All I can say is all gyro's are different.

I believe some gyro's can have the gain set on the gyro when no signal is present on the gyro's gain channel. This was when multi channel radios i.e. more than 5 were prohibitively expensive. This would allow the gain to be set on the gyro without using a channel. I use logictech and spartan gyro's, these have no gain setting dials on the gyro itself, it's all done by end points on the aux channel.

[electricsceadu]

the 401's gain is set in the tx
you have a limit pot that limits the movement of the servo
the other is a delay to stop the tail from bouncing on a sudden stop (set to 0 on the 9253/9254 matched servo)
the reverse is on a dip switch
and the other dip switch is the servo type analogue or digital (some ditital servo's use the analogue setting due to the frame rate of the servo)

[Guest]

Ah, it is making more sense now. I was under the impression that they all had onboard gain control. Cheers!

I expect if there is a gain dial on the gyro that also has a gain lead for the aux connection on the receiver the dial is over ridden by the output of the tx.

[electricsceadu]

not all gyros have the gain controled via the tx

the futaba gy240 is similar to the 401 in looks but the gain is set on the gyro (you also can't go from rate to hh in flight as it is switched over on the gyro)

if we also look at a simple rate gyro like the csm180 the gain is also set on the gyro


it is always best to read the instuctions to whichever make of gyro you have as they all have their own way of setting up

[Butuz]

The GY240 is quite a good gyro - easy to set up and holds the tail well for learning. I like mine

Butuz

[unwind-protect]

I expect if there is a gain dial on the gyro that also has a gain lead for the aux connection on the receiver the dial is over ridden by the output of the tx.

That's right.

For more information, you could try:

Gyro - RC Helicopter Wiki

Tail setup - RC Helicopter Wiki

Controlling gyro gain - RC Helicopter Wiki

None of which are perfect---improvements welcome