Shimmy!

[denvoyager]

Hi, I tried my A3L gyro out yesterday, and it went well, but I noticed a slight 'shimmy' as the plane ( an Artic Cat - being used as gyro test bed, prior to my Mig 21 !) flew along. I didn't run the gyro all the time, just a few passes to confirm the 'shimmy', and then landed with no problems. I had it on mode one, with mode two inactive.
I'm new to this, and just wanted to check my next move with members who are more experienced with gyros, particularly the A3L. Keep safe, everyone, and thank you, diolch yn fawr, from Den, Cymru (Wales)

[OV10]

denvoyager Your "shimmy" is most likely because you have the gains set a little too high.
Gain settings are usually established by increasing until a point where a "shimmy" starts to occur and then back of the control a degree or so and you should be good to go.
Best regards,

[xviper]

Also, the gains used in an Arctic Cat will not necessarily be the same for your jet. Each plane may require a different gain setting for it to fly to max speed without the oscillation. Unless you are flying the plane is "3D", best to turn the 3D gain to zero.
PS. I also used to use a "MAKO" as my test bed for gyros and receivers. The Cat is similar to the MAKO and has a lot of vibration, so mounting the gyro on a sticky cushion is best. I also had an Arctic Cat until a flying buddy lost it in a horse pasture.

[denvoyager]

That's great, thanks very much. I'll try that out and I think it'll be fine. I know I have to reset it for the Mig 21, I just figured my beat up, experimental, Arctic Cat would be a good intro to gyros, and a lot cheaper if a glitch happened! Diolch yn fawr, Den, Cymru

[Grantham Kid]

With the A3L you can adjust the gain from your TX while you are flying. This is the one good point with these Gyros.

[denvoyager]

Thanks, everyone!
Your replies have really helped me a lot. I backed off the gain about 10 degrees, and it steadied beautifully in flight - quite majestic for my beat-up old foamy! Gkid, I haven't got as far as setting a pot for transmitter gain /master control yet, but now I know how small the alterations need to be, will attempt it sometime soon (NOT on my Mig or Me 262!). It's probably the thing one should do first, as the Pot slots are ridiculously small for my septuagenarian eyes.
I must say I found the A3L very easy to set up, and am very pleased with it. Keep safe everyone, diolch yn fawr, Den, Cymru (Wales)

[xviper]

Thanks, everyone!
Your replies have really helped me a lot. I backed off the gain about 10 degrees, and it steadied beautifully in flight - quite majestic for my beat-up old foamy! Gkid, I haven't got as far as setting a pot for transmitter gain /master control yet, but now I know how small the alterations need to be, will attempt it sometime soon (NOT on my Mig or Me 262!). It's probably the thing one should do first, as the Pot slots are ridiculously small for my septuagenarian eyes.
I must say I found the A3L very easy to set up, and am very pleased with it. Keep safe everyone, diolch yn fawr, Den, Cymru (Wales)

10 degrees on an A3L is quite a lot, so that tells me that the gain was waaaay too high. Anyway, if and when you plan to use a "master gain" on your TX, it's best to use the rotary knob to control an empty port on the receiver - typically on AUX2 or AUX3 but if your gear or flap channel is not needed for your plane, then those can be used and the knob can be assigned to control one of those, so long as you INH the switch for that channel. Insofar as very small adjustments on the gain pot on the A3L, once you assign a master gain, know that now you can control the gain pot setting on the A3L in terms of a percentage of the percentage. That is to say, the knob goes from zero to 100%, so if your gain pot is set at say, 25% of it's full possible travel, then the knob can tell it to go from 0% to 25% and the movements on the knob are not nearly as tiny and can be done while in the air.
Bad vision can plague even younger people and 70 something isn't really considered "old" anymore. I'm in that category and yes, there are times when I feel really old when the aches and pains hit, but on the most part, it's not so bad. There's always bifocals to help with the eyes. Worse comes to worse, there are Coke bottles. Besides, I understand that people in Wales can get to a ripe old age and still be really lively. I mean look at Tom Jones.
So, just for you, I'll do this post in GIANT print.

[denvoyager]

Thanks for that, xviper - I'm testing an Eagle Tree Guardian now, and am using the Master Gain for the first time. Will maiden it this morning, so fingers crossed! Don't understand INH? Not sure how to set the gain pot on my simple FlySky transmitter! It's centered and seems to be happy at that. The main thing is that, thanks to everyones' advice, I'm happy with the way the gyro is performing, and, I'm sure, in a couple of months will wonder why I needed help!
Take care everybody, Den, Cymru (Wales).
P.S. The welsh person I loved best was 'Shirl', Shirley Bassey of 'Goldfinger' fame. She appeared at one of the rugby matches to sing the anthem draped in a silk Welsh Dragon Flag, and although in her late seventies, looked stunning!
P.P.S. I can still see mastheads over the horizon 40miles away (I live on the Atlantic coast - the next land is Florida!), it's 4mm slot heads that catch me out!

[xviper]

Don't understand INH? Not sure how to set the gain pot on my simple FlySky transmitter! It's centered and seems to be happy at that.

"INH" means inhibit. It's a term that's used in Spetrum transmitters, so don't know what is used in a FrSky. It should be in what Spektrum calls the "system setup" menu for your model. In there, you should see something that allows you to see "channel assignment" and "port assignment". You must determine which channel your rotory knob controls. In Spektrum, the rotory is defaulted to AUX2 and AUX3. If you plug the master gain into one of those, then the rotory will control it. If you plug it into some other unused channel/port, you must go into the menu and tell the TX to NOT (ie, INH) use the switch or stick that normally controls it, otherwise you'll have 2 control inputs for the same channel.
The rotory knob on a TX is not really called a "pot" and you should consider it to be a proportional adjustment of the gain you have set on your gyro. On Spektrum, when you turn the knob, it sends out a signal that is from -100 to +100 (not sure but it might be in units of micro or mini volts). Your gyro then sees this signal as being 0% to 100% of whatever the gain is set at. If yours is centered, it should mean that it is telling the gyro to use 50% of whatever it's set at. There will always be exceptions to this as in Lemon gyros or when "3D" gain is also dialed in. The easiest for those new to gyros is to forget about master gain on the TX and just set the gain on the little pots on the gyro. Don't even plug in anything for master gain or gain mode on a switch.