Gyros Explained

[Steve]

New updated version is now available via the original link in the first post.

There's one more diagram I want to add, but probably won't get a chance until after my hols next week.

[Steve]

That's it, all done now I think.

I've found some unexpected time this evening to do the last diagram, so it's pretty much complete now.

Enjoy!

Cheers.

[gareth08]

Ha ha - in other words it's like a miniature version of the Airbus aircraft - lots of jiggery pokery which makes you think you're flying

[JayLex]

Where did it go? I wanted to read it and now just gettting a not found error, any chance of fixing it or uploading it again as would be great to remind myself of stuff.

[Ashley Davis]

http://www.trextuning.com/modern-gyros.php

[PKNEC]

Many thanks for your article,it has saved me a lot of aggro

[Steve]

Many thanks for your article,it has saved me a lot of aggro

My pleasure.


PS You know where the thanks button is....

[funfreex]

Have just had chance to read through your article and it has certainly clarified a lot of misunderstandings I had about gyros. Thankyou.
Although: i could not totally work the mechanical adjustment out for torque compensation.
If a mechanical offset is made then that means the rotor shaft will have less travel one way than the other?
So setting the end point adjustments through the gyro will also leave you with more movement one way than the other (if the gyro has only one pot that restricts both left and right throws). Have I got that right?

[Steve]

Have just had chance to read through your article and it has certainly clarified a lot of misunderstandings I had about gyros. Thankyou.
Although: i could not totally work the mechanical adjustment out for torque compensation.
If a mechanical offset is made then that means the rotor shaft will have less travel one way than the other?
So setting the end point adjustments through the gyro will also leave you with more movement one way than the other (if the gyro has only one pot that restricts both left and right throws). Have I got that right?

Some might say this is unnecessary with modern gyros, but it certainly makes mechanical sense to me. You set the rudder servo arm one or two splines off from the 90 degree position in the direction that gives you left rudder. Then adjust the push rod to get the pitch slider in the middle of the tail output shaft, set your gyro-to-servo endpoints as usual and finally go through the whole mechanical trimming process in normal rate mode for the gyro until you get the steady hover.

Once all this is done, You've found the natural hovering center of the heli, the pitch slider and endpoints are all in a good position, and all this is happening with your servo being slightly off-centre, giving you the mechanical advantage with and against the blade rotational torque.

[Mojogoes]

^^^ Yes i can see why this would work as setting the rear tail up in natural isn't what you really want as it will not be counter acting upon the torque created , but its quite a hard thing to do (in ones head) when you've been taught to put the arm in a 90* position.

So manager am i thinking in the right way thinking that the way you have discribed puts the centre point slightly forwards where the torque is nutralised plus the HH will also take this as centre point etc..........if its repeating some of what you have stated i appoligise as i like to think it out allowed as it were so i can get it straight in my own head!!........lol.

[Steve]

There are 2 schools of thought on how you should setup the centre position of the tail pitch slider - (a) you set it so that the heli holds a steady hover in 'normal' mode, and (b) you set it in the middle so that all the bell-cranks and push rods etc are at 90 degrees, and leave it up to the gyro to do all the fancy stuff in heading hold mode.

When I wrote the original piece, it was written very much around option a. However, I've since done some experimenting with a ubiquitous GY401 gyro and 9254 servo and found that it actually works and feels better when setup like option b. In addition to this, most modern helis have the geometry of their tails manufactured in such a way that anything other than a full 90 degree/middle of the pitch slider setup just looks wrong, and gyros that have independent right and left hand travel throws seem to work best with equal left and right hand travel throws (usually pretty close to 100% each way), which also lends them to option b, as option a would typically give you say 70% one way and 130% the other way.

One other thing that I have found recently is that your tail servo hardly moves at all left and right during flight, which further adds to the centre position/equal throws argument. I think you'd be surprised at just how little the servo moves even when piro-ing at full rudder stick, unless of course you've got a really high piro rate setup.

The amount that the servo travels on the bench is kinda important in ensuring that the servo never over-stays its welcome at the end points, but during anything but extreme flight, it's hardly ever going to get anyway near that degree of offset.

The gyro-servo setup is a closed-loop control system, so the gyro controls the servo to attain the desired rotation speed (or straight hover) as fast as possible. Couple this with the fact that modern tail servos are blisteringly fast means that within a fraction of a second of the gyro requesting an input from the servo, it's almost already done it (if you know what I mean), so the amount the servo has actually moved is generally tiny before the system settles down again into a steady-state.

Anyway, I've now come to the conclusion that with modern gyros and tail servos, a 90 degree/centre pitch slider setup with the gyro just set in heading hold mode (i.e. forget about 'normal' mode) works best.

Change of heart, maybe. Every day's a school day.

[Mojogoes]

Well put!! I know these types of gyro exist already so what do you think about the dual gyro systems which control the swash plate as well as the tail and what kind of new manauvers do you think will be born out from using such units/G systems.........i believe that they use a camera in conjuction to verify that the crafts heading and speed but only down to a certain speed as any slower than say 5mph carn't be detected is this correct.

[Steve]

Well put!! I know these types of gyro exist already so what do you think about the dual gyro systems which control the swash plate as well as the tail and what kind of new manauvers do you think will be born out from using such units/G systems.........i believe that they use a camera in conjuction to verify that the crafts heading and speed but only down to a certain speed as any slower than say 5mph carn't be detected is this correct.

Are you on about the flybarless system or the auto-pilot thingy?

Either way, neither use a camera.

[Mojogoes]

Are you on about the flybarless system or the auto-pilot thingy?

Either way, neither use a camera.

It must be pretty new as a friend who flys and who really knows is stuff with electronics was telling me the other day that this thing used a camera in the way i've discribed..................he's probably still getting live pic's of the police bolco these days but i guess its a perk having fit the first system in for them some years ago.

[Tripler]

Fairly new to this game and have 401/9254s on most of my helis.

I’ve always set them up as per Managers B option but with a slight bias +/- 90deg to compensate for the main rotor in the linkage to the rear rotor.
Correct me if I’m wrong but doesn’t the 401 set its own centre point and remember it in HH which is usually off centre for hover and normal ff.

I’ve also found doing it this way gives me a gain setting every time of 58 for normal mode and I drop it to 55 for Idle up 1and 2.

Never had any problems setting them up this way and for my type of flying sport/ mild 3d the tails on all helis have remained rock solid.

I did notice the 401 doesn’t seem to like backward flight and can kick out occasionally (not that I do much backward flight)
thought it was my setup until I read some experts comments on here and found the 401 is prone to this.