[Cougar429]

Posts not relevant to this subject will be removed after a few days to keep the thread on topic.

SETUP: HEADING HOLD GYROS

There have been repeated questions about Headlock Gyros and the problems they can cause. This is not limited to the ESKY, Logitech, Telebee, Futaba or others, since all of the info I've been able to review has them all similar in function or gain control.

Most can be described as adaptability or setup issues and take only a few minutes to describe how and why they react the way they do.

Note: The solutions I'm describing is not to correct for a servo POSITION or tail pitch control problem, such as a servo that requires adjustment along the boom to give proper pitch range or a tail pitch mechanism with binding or built in control problems. It also does not deal with a gyro MOUNTING error, since there is more than one method or location these units can be attached. Most will give detailed instructions as to how and where they should be mounted. Be advised, though, some are even more sensitive as to the type of double sided sticky used to adhere them. I've even seen some cases where there are two layers of sticky with a metal plate in the middle to have the gyro react correctly, but we're getting off topic here.

One thing that should be of prime consideration is the fact the better the gyro, the more vulnerable it is to vibration. That's the reason the sticky pad is all-important. It not only isolates the gyro as best it can from airframe vibes, but still transfers information into the gyro sensor to what the heli is doing so it can correct for angular changes. The problem here is that these two factors run counter to each other.

So, you MUST do all you can to reduce vibrations in the heli, something that's damnably difficult the smaller the machines get since there's not a lot of mass to counter or nullify harmonics from what starts it in the first place. One of the biggest sources seems to be the tail rotor system. Since it spins so fast even a slight physical difference or imbalance can have major effects on the gyro. To top it all off most gyros are mounted very close to the tailboom, and if anyone has read the bio of Barnes Wallace, (of Dambusters fame) you will see that any vibration waves in the tailboom, regardless of where in the airframe they initiate, actually reflect off the tail end and head right back to the anchor point in the fuselage. Guess where the gyro is mounted, eh? I once had a bit of fun chasing a little bugaboo where an out of true tail rotor hub and a motor that went out of balance after a bit of a doink created harmonics in the ariframe at or darned close to the main rotor freq, which had me looking in the wrong place for the source for far too long.

In regards to any gyro premounted on what is euphemistically called an "RTF" machine, the first thing you should do is cut off anything such as a wire tie that secures the gyro to the frame and check the sticky, replacing it if at all suspicious of how well it holds. That tie does nothing if the sticky is good other than transmit vibes into the gyro. You should also make sure the gyro is not touching any structure as that will do the same. One other important point is to ensure the gain, signal or servo wires are not fastened down so they put tension on the leads. Along with perhaps shortening the life of the insulation, this also transmits vibrations from the airframe into the gyro body and sensor.


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SOME IMPORTANT POINTS ABOUT THE ONBOARD GAIN POT:

The user must take heed that when the REMOTE GAIN lead is plugged into a receiver channel, that gain signal overrides the physical gain pot on the gyro itself, rendering it inert. The other fact that seems to crop up often is that with that onboard pot active, (such as with it unplugged or on a gyro that does not have remote gain) ANY change to settings you make won't take effect until the powering down and reset procedure is followed. With the remote lead plugged in and seeing a signal gain can now be adjusted on the fly with any changes felt immediately. I don't know why the difference in how that operates.

I've also heard reports of differences in how the gyro reacts to leaving the gain lead disconnected or plugging it to ground. Some lock the gyro in HH mode with the onboard pot active if left disconnected, others go to rate mode with it plugged to ground. Any information regarding that subject would be appreciated.
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TEMPERATURE COMPENSATION AND DRIFT
Most of the drift issues are caused from not allowing the gyro to stabilize correctly. Any with the "TEMP COMPENSATING CIRCUITRY" require sitting in the flying environment for at least 15 minutes to acclimate. However, powering up for at least 5 minutes in that environment speeds this process. Once that time period is complete, powering down for a few seconds and back up again should reset the gyro and unless the environment changes drastically, remain stable throughout the flight.

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INSTALLATION

A problem that seems to crop up repeatedly is uncontrolled tail spinning. True for both regular and digital servos and depending on the tail servo used, the direction of motion is critical as to how the gyro and servo work together. There are ways around this, but I'm making an assumption this post is intended for those climbing a steep learning curve and I want to keep the info overload to a minimum.

Some servos move in the identical direction as other makes, but this is not guaranteed. With a servo travelling opposite to perhaps one removed, reversing either the servo direction switch on the transmitter or gyro itself will NOT correct for this. The signal path from the transmitter control is through the receiver and gyro, then on to the servo, with the gyro having no direct effect over which way YOU command a movement. In effect, the gyro reverse switch will not affect your direct control over the tail. It only has an effect of altering the direction of the corrective commands the gyro gives the tail.

Where this will get interesting is if you have installed a servo with reversed direction or have the gyro switch in the wrong position. Having either reversed will mean any corrective or commanded signal will make the servo go the wrong way, adding tail movement rather than damping it out. I've had it happen, and you won't believe how fast these things can spin about the main axis if the tail hits full limits.

I hope this covers most of the questions regarding these gyros. They are a great addition regardless of the type of flying and can seriously reduce the workload when you are learning to hover for the first time. Just be sure to read the documentation for your model for specific characteristics and setup instructions.

p.s. I found a little trick for cancelling drift on my HH gyros I wanted to pass along. If, after the warm up period is over, you still encounter drift, flip the switch on the Tx rapidly between HH and RATE for a few seconds and then END with HH mode selected. The gyro should reorient itself and recenter the neutral point. This MUST be done with the heli on the ground and rotors stopped to reduce vibrations. The Tx rudder trim must also be centered.

[Beerwiser]

Nice write up as always Cougar . For those who don't know finless bob has some setup up videos on certain gyros. You will have to join to view them and use the search to find your particular gyro as its not very well organized. They can be found here:
http://www.helifreak.com/forumdispla...=60&order=desc

[jmcintosh]

Whenever I am unsure of a new gyro setup, I always throw the training gear back on. If you do get a reaction you were not expecting at least there is a wider base of support. Good write up. I learned everything I know about gyro's from the complex instructions Futaba and JR put out and hopefully a plain english writeup will help new guys out.

[funtvrk]

would you install a tall lock and a head hold gyros on one heli?

[Cougar429]

I don't really understand your question. A Heading Hold gyro does just as the name suggests, ie. maintain the heli pointing in the same direction until commanded by the transmitter.

The term "Tail Lock" may simply be another name for the same function. Since this is used to control the tail servo two systems tied together would likely conflict or not work at all.

[jathca]

I bought my son an axe cp (helimax) we have had it hovering about five times now, three attempts ended in crashes that left the heli unable to fly. He's getting discouraged and Mom's getting ready to cut off the repair fund. Would a head lock gyro be a good idea? Is there anything out there to make the heli return to stationary hovering when you let the sticks return to the neutral position? or should I be looking at a fixed pitch heli intstead? thanks

[waylander]

The axe cp is about the worst learning heli there can be in this day and age. I'd suggest you start a different thread to not clutter this one up as what you're asking has little to do with a HH gyro. What you're looking for is a stabilization system. A good one will cost more than your heli.

If the axe cp is his first heli then put it on the shelf or sell it, get a blade msrx instead and learn on that first.

[jathca]

thanks for the response and advice, waylander.

[HAL9KPCM]

After being out of the hobby for about 18 years... I've kept my promise to myself to get back into it with a JR 260Z Sports gasser. I did my initial test run with the Futaba 750 gyro in normal mode (that's what I was used to 18 years ago) and everything ran fine, but needed more cyclic control input. I fixed that and the next flight went well. My stator gator finally arrived and I put that on and at the same time, I set the gyro to AVCS mode. Everything is solid, good cyclic response, solid rotor speed and response... but am I correct in assuming I have a little too much tail rotor gain?... it has a sexy little fast tail wiggle of about two inches or so.

Things sure have changed in 18 years.

[waylander]

Typically, if you see a fast wag then yes you have too much gain on the tail. What setting do you have it on now?