Head locking question

[EatMorePizza]

my heli is in HH mode and the tail creeps slowly to the right. Should I adjust the trim or sub trim?

[vandelescrow]

Yes and no. If you adjust the trim or sub trim, you have to remember to set it back to center each time befor you turn on your heli's receiver. The reason why is when the gyro initializes, it is looking at the signal it receives from your transmitter. What ever the transmitter is sending, the gyro thinks is center. So say the first time you adjust the trim 5 points to the right for it to hold, you forget to reset it for gyro initialization, you now have to give it 10, then 15, 20 etc.

With that said, you need to find out why it is drifting. Did you set the gyro (at the gyro, not the transmiter) the "limit" it can have the servo move so it goes to the full travel yet not bind? Is your gain set high enough? it should be set as high as possible so the tail does not hunt. Is the linkage able to move freely?

Lastly for others to be able to help you, what gyro and servo are you using?

[EatMorePizza]

ohh sorry I forgot that. Thanks.

Im using the new jr770/8900g servo combo.
About the limit, I adjusted the pot just a bit less of binding. Only thing is that which way should I look for binding? Left or Right? I ask because the slider isnt perfectly in the middle. Its at the 4mm setting.

Tomorrow ill check the rate.
thanks

[vandelescrow]

I do not know that servo gyro combo so it would be best for someone else to chime in here. However for your question about where the slider should be, I would recomend you go to http://www.raptortechnique.com/index.html you should be able to find your answer there.

edit/
about the binding, both directions. But if you have it set so it is just below the point where it will bind, then this is NOT what is causing it to drift. I mentioned it because if the gyro is at its full limit and you still have room to spare, then it may not be moving far enough to hold it. But this is obveously not the problem. Just to be cureouse, do you know your head speed? I know on electics if the head is not high enough the tail will never hold, I'm sure it can hold true on nitro's.

[EatMorePizza]

I do not know that servo gyro combo so it would be best for someone else to chime in here. However for your question about where the slider should be, I would recomend you go to http://www.raptortechnique.com/index.html you should be able to find your answer there.

edit/
about the binding, both directions. But if you have it set so it is just below the point where it will bind, then this is NOT what is causing it to drift. I mentioned it because if the gyro is at its full limit and you still have room to spare, then it may not be moving far enough to hold it. But this is obveously not the problem. Just to be cureouse, do you know your head speed? I know on electics if the head is not high enough the tail will never hold, I'm sure it can hold true on nitro's.


You know come to think of it My engine was acting up. It was running a little sluggish. When I wipped the tail quickly I felt lost of power in the heli. So I think my head speed is to low. Should I have the throttle more than 50% at half stick just so the rudder has enough power?

Well I just got my os37 today so im installing it this week. Ill post back.. thanks

[vandelescrow]

That would depend on your pitch curve. I recently just changed mine to linear on both throttle and pitch and I found my head speed is higher in a hover than it used to be. It now hovers at apx 3/4 stick.

One other thing I thought of after I posted my last. Is your tail rotating the correct direction? When you rotate the head counter clockwise (the direction it spins when under power), the tail blades should be turning counter clockwise as looking at it from the right side of the heli (the blade going up is toward the front of the heli). This will allow the blades to use the down force of the air from the main blades instead of having to counter the air flow and generate its own.

[EatMorePizza]

Dont the main blades rotate Clockwise? If so mine are good.
What do your pitch and thr curves look like. Also I noticed on my cp pro and all the 3d heli's on the sim when I enter stunt mode the throttle is constant, but I seen people apply the "V" throttle curve. WHich is used more?

And should mid stick be +6 deg or 0 deg

[vandelescrow]

OOPS, yes the main blades do turn clockwise, I guess I had a brain laps.

For normal mode my throttle curve looks like "/" 0, 50, 100, The other modes it is a "V" not sure the numbers, I use a governor so it doesn't matter much. I'd start with 100, 70, 100. Adjust the middle number as needed so the engine does not over rev at 0 pitch yet keeps the rms's up for what ever maneuver you will do next.

Pitch curves are all the same "/" 0, 50, 100.

Now there is one thing you can do. If you are getting more pitch on one end of the scale than the other say -12 +14, only set the pitch curve to 100 for your throttle hold. I've been told by a vary good sorce that a heli can still produce lift at +14 degrees pitch at 800 rpm. For an autorotation, I would not recomend using that much pitch except for about 1 foot off the ground for a little extra hang time.

/edit
You asked about the sim, constant or V. You need a V because as you give it more pitch your putting a bigger load on the engine. I've even read somewhere that (if you have enough points to set in your pitch curve) that it looks like a "Y" 100, 90, 70, 90, 100. These numbers were just an example. I don't know why the simulators do it like you described unless it is using a governor. One of my sims (Reflex) I cant turn off the governor or the heli will just sit there idling all the time.

[iher]

Well if the main rotor was turning the other way, I am sure you would not even have the chance to check the drift :)

I had that same problem and it was caused by:

1- rpms. if its too low it will probably drift.
2- sticky ball links or control rod. remove ball link to the servo horn . and move it back and forth. It should feel ....or should I say : You shouldn´t fell anything . No resistance whatsoever.
Check that ball links do not stick. they should rotate around the ball with no friction. you can use a JR ball link sizing tool.

3- play. Check that you have no play at all. If ball links are a bit loose( if they can move back to front on the ball in the direction of the axis of the screw that holds the ball....then replace)

4- Gyro placement. if it is too close to the main rotor axis in some cases it matters. according to some people: on a AVCS ( Heading hold) gyro it should not matter because it measures the angular velocity where ever you install it on the heli.........well my experience proves otherwise. install it as far as possible.

hope this helps

[EatMorePizza]

very usefull info here. Thanks

[archiebald]

Well if the main rotor was turning the other way, I am sure you would not even have the chance to check the drift :)

I had that same problem and it was caused by:.......


.....4- Gyro placement. if it is too close to the main rotor axis in some cases it matters. according to some people: on a AVCS ( Heading hold) gyro it should not matter because it measures the angular velocity where ever you install it on the heli.........well my experience proves otherwise. install it as far as possible.

hope this helps

The people are correct. The ANGLE the gyro rotates through is the same whether it might be mounted on the
axis of the main shaft or at the tip of the tail boom. Ain't gonna be one smidgeon of a difference as far as the gyro is concerned.

I had the same problem a year or so ago with a GY401 causing very slight right drift. After going through all the usual stuff, I found this http://www.futaba-rc.com/faq/faq-gyros.html#q313

I mounted mine in the original location (just behind the main shaft) on an aluminium plate with a layer of foam tape top and bottom (tape / plate / tape / gyro) and it solved the issue completely. Whether it was the plate itself, or the extra shock absorption I can't say, but I am guessing the latter.

iher,
I wouldn't mind betting that your problem went away simply because of new mounting tape or slightly different vibration pattern in the new location.

[iher]

archiebald
You are right, theory dictates location shouldn`t matter, so it probably was some sort of interference. Electric, magnetic o vibration....who knows.
I tried many things . More foam , bottom plate, rotating it 180, and I had the same result. I guess maybe (it was for a Trex) it was the close distance to the motor.
I guess other people's experiences result in a spot to locate the gyro that takes into account all the possible problems and ends up being the most suitable.
So by going back to that Gyro location,the problem was solved......A little experimenting never hurts