kiwiflyer
Heliman
Location: New Plymouth, New Zealand
| T12fgh. Tx and GY611 amp both display the gain.
Excerpt taken from "littlerotors":
This is where a lot of people make mistakes… This section is related to Futaba gyros only as that’s the only ones I use and they are the best gyros on the market at the moment.
This gyro is a GY601, but the same principles apply to the GY502 and the GY401 as well.
First up: YOU DO NOT HAVE TO TRIM THE TAIL IN NON-HEADING HOLD FOR THESE THINGS TO WORK!
That’s a carry over from the old days when you had to first get your tail to hold when the gyro is in rate mode by mechanically trimming the tail linkages.
YOU DON’T DO THAT ANYMORE (for Futaba gyros anyway).
You’d be amazed how many people I come across who have problems with their tail and have tried to set up their tails the old skool way.
Futaba gyros don’t care where center (ie where the tail is holding) is. All they care about is the limits that they can move their servo between so they can do their job.
What IS important is that the limits in each direction are the same.
But Si, you aren’t making any sense! We need to set the trim in rate mode!
The reason why you don’t set the trim in rate mode is because the tail trim will be different depending on a LOT of different combinations such as hovering head speed and hovering pitch to name the two main components. You might get the tail spot on mechanically with one combination, but as soon as you go into Idle Up where the headspeed increases, the trim will change. If the engine goes lean or rich, it will change, so what’s the point? The gyro really doesn’t care.
Why is it important to have equal travel on both sides, and why should those values be large???
The gyro wants to know how far it can move the servo to the left and right to make the appropriate compensations. It’s important that these values be equal so the gyro gets a linear progression when it tells the servo to move.
Remember earlier in this article I talked about servo resolution and why you should have your ATV’s set to a relatively high value (ie about 100%)? Well the same goes for the tail servos, the gyro is a finely tuned instrument capable of making minute adjustments to keep the tail steady. If you have cut down the amount of servo resolution by having a low limit value (ie 80% for gyros), then you’re making life harder for the gyro than if you had that value at 120% which gives the tail servo more ‘room to move’.
Another bit of evidence that Futaba gyros want equal limits on both sides is with the GY401. Both the GY601/611 and the 502 have independent limits for both sides, you can set the values to what you want, but the 401 doesn’t. It only has a total limit value, not independent values, it REQUIRES that both sides of travel are equal. You’re required to adjust your mechanical linkages so that the 401 can use the total amount of travel. You should do the same for your 502, 601/611.
Make sure that your tail servo is operating in the correct direction, and also, that your gyro is working in the correct direction.
How do I check my gyro’s direction?
My way is pretty basic, once I’ve established that the tail servo is going in the right direction, I look at which way the servo horn when I move the rudder to the right. Then I grab the boom and swing the nose of the helicopter to the left and make sure that the servo horn moves the same way as it did when I moved the rudder stick to the right. If it didn’t, then you need to alter the gyro’s direction.
Ideally, you want to set your gain to about 37% or so.
On the GY601/611 on my 3D models I have the mode set to 3D. I found that the gyro seemed to perform a little better during pirouetting maneuvers in 3D mode, but it really doesn’t matter much.
How do I know what servo horn to use on the tail?
Ideally you want the tail servo travel to be about 120-130% so adjust your servo horn’s length until you can obtain that. |
