Gyro Differences

[Tony]

Tony submitted a new Article:

Gyro Differences

(Piezoelectric Gyro)
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The first type of gyro is the piezoelectric gyro which uses a quickly vibrating crystal. As the crystal vibrates, an applied rotational force will cause disturbances in it’s wobble which create a small, but measurable electric current proportional to the rate at which the gyro is rotated.

A disadvantage of piezoelectric gyros systems is that they’re very temperature sensitive and going from hot to cold or vice versa will cause them to act erratically. Most have built in temperature protection circuits, but they’re not perfect, so if you’re going to take a gyro from warm your car and fly in cold weather, give it 10 or 15 minutes to adjust before flying.

(Mems gyro)
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The second and most modern type of gyro is the MEMS or Micro Electric-Mechanical System gyro.

MEMS are molecule sized machines that are fabricated on top of a piece of silicon, along with the electronics to interface to them. They vibrate at a high rate just like the piezoelectric gyro and as the gyro rotates, so does the displacement of the mass and the signal generated by the gyro.
Besides the different makeups and types of gyros, there are two primary ways that gyro’s operate, rate and heading hold mode.

Rate Mode Vs. Heading Hold Gyros

There are two types of gyro functions, rate mode and heading hold.​

Rate Gyros

Rate gyro’s are often used in scale RC helicopters because they lend themselves to a more realistic flying experience, while heading hold gyros are used by almost everyone else because they make flying easier.
The only time that we will use rate mode on the gyro is when we are setting it up. The reason for this, is that the servo will always go back to center when you release the stick.

Heading Hold Gyros

Heading hold or heading lock gyros are a conceptually simple extension of rate gyros.
In a heading hold gyro, a built microprocessor that keeps track of and remembers how far the helicopter has turned from its set position. Based on the deflection from the set position, the gyro will control the rudder servo such that the gyro returns the helicopter to the set position.

Therefore, as you increase the throttle or headspeed of your heli, the head holding gyro will counter the main rotors thrust automatically keeping your heli’s tail in its original position.

Heading hold gyros are very popular and pretty much standard among RC helicopter pilots for that very reason – they’ll hold your tail in a constant position no matter what you’re doing as long as you don’t input a rudder command, even if you’re doing 3D aerobatics or flying in a strong wind.

With a head holding gyro, the rudder signal from your transmitter no longer directly controls the tail – it simply tells the gyro how many degrees to turn per second. It will also reset the gyros stored position to the new position you move your heli to.

In conclusion, only purchase a head holding gyro unless you are wanting to go scale. And even then, learn on a head holding gyro first, then progress onto the scale heli's and rate mode gyros.

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[tim]

yeah had the old eflite g90 an would wag an break loose on my 450se it was ok just to fly gradually but defitenly not for pitch pumps or sudden throttle burst. it would wag or not hold wen i turn the gain down, so there wasnt much in between but u can put mixing in but its a process of scripples of settings? i never done the mixing in a transmitter. theres so called tail lock gyro too an thats were u put mixing in jr had one forgot the name of it. what is that mixing called? revo mixing think revolution mixing program the head speed with the gyro if it was tail lock or an non heading hold or if it didnt hold to well u could use it. it slowed down the mtr rpms or headspeed an help compensate for the tail an the gyro to catch up. i think thats what it did.

 

[tim]

well my tailblades are shot got new pair on order concrete finally grinded the ends down now its waggn an vibrateing there outta balance an size ooh it looks nasty watchn the tail wag an vibrate,lucky i only flew it once an that was sunday at the field it was windy bad atleast 20mph burst of wind it wasnt the gain to high blades were ate up at the tips grinded down. ouch!

 

[Rc-Help Member]

I've tried several different brands of gyros cheap and costly, the two most expensive being the Futaba GY401 and the Align GP780. So far the GP780 has beaten all of them out on performance.

 

[Tony]

Tim, all gyros will have some blow out if you do a pitch pump in normal mode. If you put it in idle up however, they will hold much better. Just the nature of the beast.

 

[tim]

yeah i run heading hold in stunt an normal mode very seldom use regular rate mode wich is fun to fly cause you actually have to control your tail a bit more,the real 401 ive got has been beat an busted an glued back together an taped its 5 years old and has been in alot of crashs but until a week ago it started twitchn, so i put the spartan qaurk on it tiny little gyro an it holds tight in pitch pumps,i usually run my gain up to just get atiny wag. belive Futuba was the first to come out with avcs smm technology with the 401 now ever one has jumped on that bandwagon. on the otherhand the eflite g90 i still got it too just sittn around an that 48 v the 13 dollar one came off the blueray pe. needa put the old 401 on sumthn with a scale body just to fly around no 3d! or get a clone 250 an c how those little things do shouldnt be that bad to fly since i run negative 15%expo in my cyclics already on my 450 pro.

 

[tim]

just thought i would write something in here! you know i like the way they made the spartan qaurk to me its simpler than the regular 760. just press the button an wahh lahh,think all gyros need to adapt to the climate change it seems to work better i experimented it was 56 degrees outside one day an i took the heli straight out an flew it an it kinda acted loose in the tail, took it out the next day an it was around in the 50;s an let it sit there for bout 15 minutes an wen i flew it the tail felt more locked in an ive notice that over the years in flying in cold weather how its seem to done that an it mostly tells u in the manuel about the climate change how a gyro reacts in a small way.

 

[cweeks0515]

i am a noobie trying to figure out setups with phx sim. I like the scale models as they seem more docile-- I think based on tony's article I am finding out why. They are tail rate gyro physics as opposed to the hh gyro setup. At least based on my very anecdotal response the flying behavior of the same bird with tr vs hh gyro is remarkable. I can barely make circuits with the HH set up, with the tail rate setup I find the banked turns remarkably easy and stable!! No side slipping to recover from etc etc. Hovering is easier of course with the HH set up. It would seem to be based on my sim feedback that what I would like to see would be a programmable gyro that I could configure for either rate or HH?? Is that possible??What am I missing in my flight skills that is creating this substantial difference-- and will I observe this phenomenon when I get into the real bird set up with a HH gyro ?? Pretty scary!!

 

[Tony]

On the sim, the scale models are made to react a lot slower to stick input. You can do this with all of the others by adding expo to the channels. It will slow down the servos in the beginning of the stick movements. And for stability, the HH mode will be more stable than rate mode if you have it setup correctly.