AllMYRC.com-A Radio Control Helicopter, Airplane and Car Community » R/C Helicopters » Ask the Pro's » Bert Kammerer

[OlegM]

Hello, Bert,

In the second Smack Talk episode you mentioned that you and Bobby do check that helicopter does not pirouette when gyro is in rate mode and then you set gyro limits. Personally, I set the rate mode for some of my models and do not set for others just for experiment. Actually, I do not see any difference between these setups.

It would be great if you can tell, what difference in model behavior do you see when gyro is setup with rate mode and without it. What moves (maneuvers) could show the difference. Of course we talk about flying in heading hold mode.

My models are:
former Trex 450 + Futaba 401 without rate mode setup.
Trex 500 + Align GP750 without rate mode setup
Trex 600 + JR770 with rate mode setup.
Rave450 + Spartan DS760 with rate mode setup.

Thank you in advance.

[bert]

Hello,

Most gyros nowadays are "smart" enough that they do not need to be setup the way we do. For the most part you can get away with just zero pitch on the tail at center and the gyro would work just fine. However, I have always had this theory (and I might be wrong as there is a lot of debate about this) that the logical way to do it is to center it in rate mode with enough pitch so that the heli does not want to pirouette in any direction. I have always believed that this puts less load on the tail servo (not gyro) during hover and in instances when tail correction is not necessary.

Again, there is a lot of debate about this and I really don't think it matters much.

Bert

[OlegM]

You are right, there is a lot of debate about this. Well, I thinks with all said, it is wise to assume that any setup is correct while it allows a pilot to fly.

Thank you for the input, Bert!

[ualdrivr]

Originally Posted by bert

Hello,

Most gyros nowadays are "smart" enough that they do not need to be setup the way we do. For the most part you can get away with just zero pitch on the tail at center and the gyro would work just fine. However, I have always had this theory (and I might be wrong as there is a lot of debate about this) that the logical way to do it is to center it in rate mode with enough pitch so that the heli does not want to pirouette in any direction. I have always believed that this puts less load on the tail servo (not gyro) during hover and in instances when tail correction is not necessary.

Again, there is a lot of debate about this and I really don't think it matters much.

Bert

+1, I am with you on that Bert. Most problems I've seen out there with the tail not holding have to do with mechanical setup or binding. Rate mode setup is important IMHO

[saigonheli]

Hi Bert,

I have the similar questions, I hope you can help me to clarify.

Background

I have used GY401 & GY 611. So far I have never able to adjust the gyro to keep the tail hold straight as It supposes to be. Below is what I have done.

1. Put gyro on rate mode using Tx.
2. I ensure my servo arm is 90 degree with body.
3. Adjust the linkage length so that the pitch slider on the tail blade is in the middle of the "total" throw of the tail shaft.
4. I use Zeal tape (thick green double size tape, I also have used the stock double size tape) to mount the gyro sensor, I do not use the strap over the sensor.
5. Start hover the heli with 75% gain for GY401 and 33% gain for GY611.
6. when hover or flying my heli, I do not see it vibrate, it looks quite smooth in fly.

Questions

1. The is way, that I mechanically setup tail control, correct?
2. In the rate mode, I really can't get the tail hold straight when pointing to the wind direction. I am not sure why?
3. I have read and watched setup guide video, it mentions that when the pitch slider is in the middle of "total" throw and if the tail blades are folded, the tip-to-tip of blades is about 3 cm apart. I think, this is very similar as OlegM mentioned 8 degree or so. I think, your answer is it does not matter for today gyro?
4. When saying, tail holds straight. Does it mean absolute straight or it will drift abit?
5. I saw many cases that the GY sensor is "secured" with a additional strap, does the strap work as a double-tape-failure preventor or to stabilize the sensor?
6. With my setup, I always trying to control the tail while hover or flying. I know I've done something wrong but I do not know what wrong? Can you give me some guide line or experience to setup GY?

Thanks in advance,

[bert]

Hello,

With the 401 and 611 you have to set your tail blades so that in rate mode there is no drift. If you are setting up the heli so that the pitch slider is at the center of travel, you might be close, but you still might have a drift in a hover, these gyros will not work well that way. Simply hover the heli, observe the drift, land, adjust your linkage (long tail push rod) as required and repeat until you eliminate all the drift.

As far as tape, zeal never worked for me, I use stock gyro tape, the tape can't be too lose or too tight, find a tape that holds the gyro securely with very little dampening. Velcro is not necessary, some people use it, but it is just a "peace of mind" item, nothing more.

Finally, once your helicopter is not drifting (a very slow drift of about 45 degrees per second is acceptable), go ahead and reprogram your gyro limits, make sure the slider moves all the way to both ends.

Hope this helps!

Bert

[saigonheli]

Hi Bert,

Thanks for quick reply. I just want to clarify your instruction abit more.

a very slow drift of about 45 degrees per second is acceptable

I supposed you meant 4.5 degree per second?

Simply hover the heli, observe the drift, land, adjust your linkage (long tail push rod) as required and repeat until you eliminate all the drift.

then

... go ahead and reprogram your gyro limits, make sure the slider moves all the way to both ends.

If I adjust the long tail push rod to eliminate the drift, then the pitch slider is off the center of travel. What gain % in the rate mode that I should start with?

Now if I want the slider moves all the way to both ends then I have to use travel adjust function on the radio which means the throw for each end will be difference from the neutral point? As I understood the throw adjustment on the GY unit gives the same throw for each end therefore I can't have the slider move all the way to each end if I use travel adjust on GY unit.

Thanks and Regards,

[bert]

4.5 is too exact lol, 45 might be too much. Just use common sense, the heli can drift, but very little, all my helis have very little drift, almost nothing in rate mode during a hover.

I understand that the pitch slider will be slightly off center if you adjust the push rod to eliminate drift, this is OK. As for gain, use the same numbers in rate mode you use for heading hold, you are not going to fly the helicopter in rate mode, you are just hovering it, so the gain is not too critical, just use a rough number.

As for the throw, yes on all my gyros the throw is a bit different on each side. With the 611, this is OK because you can specify different throws for each side, on the 401, just set it up so that it reaches all the way to the side that is farther and it binds to the side that is closer, this is perfectly acceptable. It will never bind in flight because it will never get there.

Bert

[saigonheli]

Thanks.