Thread: Gyros Explained

Originally Posted by Tripler

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.

The 401 is an excellent gyro for its price, but it is none-the-less a budget gyro.

If you want a gyro that holds well in backwards flight and really sings, then you've got pay a load more dosh.

My 4 helis have the following setups at the moment:

JR Voyager 30 - GY401 & Futaba 9254 servo
JR Airskipper 50 - GY401 & Futaba 9254 servo
TRex 600 Pro - Spartan DS760 & JR8700 servo
JR Vibe 90 - GY611 & Futaba 9256 (I think) servo

The 401/9254 combination is excellent for what it costs and easy to setup.

The 611/9256 is the Futaba flagship gyro and is works impeccably, but it's expensive and is physically bulky.

The Spartan is my newest gyro and I'm liking it a lot. It's a tiny one-box design with a very user-friendly PC interface which after a little bit of tweaking is performing really nicely.

I've also had CSM560s in the past which worked fine with a 9254 servo. The CSMs are sensitive to mechanical failure in the heli and are noted for showing up say a failing main shaft bearing as an intermittent tail-kick, which can be a good thing in my opinion. The PC interface is clumsy and difficulty to use. The 560 has now been replaced by the 720 which uses the same PC interface. A friend of mine has one of these in his 90, and seems to be liking it a lot, but I've never tried one.

I've flown other people's helis with the JR770T and 8900 servo combination and found it very precise but mental! They take some careful setting up and seem to need very high amounts of expo to soften the centre control. This is fine if that's the way you like it, but it's not for me.

A lot of it is down to feel and personal preference, so this is just my 2p's worth.

£125 will get you a Spartan or a CSM 720 which both perform a lot better than a 401, and both will work with any tail servo. By the time you add a servo to the price of the gyro, you're likely to be up near the £200 mark.

Futaba 611 is errrr, about £250 I think and comes with its own matched servo.

Originally Posted by Mojogoes

I'm interested to know what the top 3d flyers use in the way of HH gyro's.............which are the top 3 bee's nee's gyros you can obtain (only the proven units1).

Top three is a bit limiting, and its hard to put them in any order of best of the best to worst of the best, they are all so close, the only thing that you can say is some are better in specific areas than others.

But the general concensus is that any of the following.... Futaba 611, CSM 720 or the Spartan 760 are considered as the current best of the best.

Originally Posted by Mojogoes

^^^Cheers!! i take it that these are all in the £200 to £300 price bracket.

They are there abouts when you include a suitable servo in the price if one isn't included anyway.

Just read it again.

Cleared up a few questions for me. Great document. Thanks

David

Hi guys,
Although I fully understand how rate, heading hold, gyros work and understand the theories behind them (avionics 24 years in the Air Force) I gotta tell ya, the instructions on pages 24/25 in the 400 3D book, suck at best. really confusing. But then again, we never had anything to do with adjusting the gain of our systems. I looked at your page and under GAIN. You state the percentage rate is based on 140 percent. which I get. but how do we get 60% of 140 being 42% I got 84%. do you divide that number in half? In the book the percentages E-flite(I spelled it right!!) gives for examples in, doesn't make any sense to me. I pretty smartbut this is making feel dumber than a box of rocks...AAAARRRRGGG!!! HELP!! I'm Drowning here in confusion...hehe

If your Tx is showing 60% then it represents 60 out of a total of 140 (or 150 for some transmitters).

60 divided by 140 = 0.428 = 43%

Well, now that makes sense. You can see where I was screwing up. Your page makes alot of sense now. But E-FLites' (still spelling it right!haha) manual not so much. Maybe If I made a chart of what they are doing with their numbers it'll come to me...again thanks for the math lesson. Geez, now I feel even dumber..haha

Good evening,
Well it took awhile to chart this out from the blade 400 manual. but what I came up with is this when you see 50% displayed for either rate switch you percentage is 0%.
As you decrease the rate % of a given switch below the actual percentage rate increases, and is in rate mode(E-Flite calls it "non heading lock mode"). As you increase the displayed amount above 50%, you are then in HH mode(E-flite "heading lock mode"). and the percentage increases, although the percentage displayed is actually less than the actual percentage(due to the 140/150%). My numbers seem low, actually about half of what they should be. If I multiply my answers by 2, the actual rate coincides between 0%and 140% Maybe another beer would make them look better!!

Originally Posted by Mojogoes

^^^Cheers!! i take it that these are all in the £200 to £300 price bracket.

CSM 720 £112
Spartan DS760 £125
Futaba Gy611 with 9256 £199

It's a lot more complicated than that. Or a lot simpler. As an engineer designing feedback control systems gain as a % is nonsense. You need to look at the whole system which includes which the servo and the hole you use on the servo to connect to the tail.

From a practical point of view the tx is able to control the way the gyro works by sending it a pulse that varies from about 1 to 2ms. How you vary that pulse is up to you and your tx software and what that pulse does is up to your gyro/servo combination. Different makes of gyros and transmitters behave differently. It's not a mystery it's just badly defined.

What the manufacturers are doing is trying to make it easy for us by hiding the detail. In practice you adjust the number and make the tail wag in heading hold, then reduce the number until it doesn't. Change anything in the loop and you'll probably have to change the number.

Quote......
"What the manufacturers are doing is trying to make it easy for us by hiding the detail. In practice you adjust the number and make the tail wag in heading hold, then reduce the number until it doesn't. Change anything in the loop and you'll probably have to change the number"

Correct this is how i also see it..............changing the head speed higher or lower will either mean more gyro can be dialed in or not i.e the higher the head speed the larger the number etc........if your using a throttle curve thats very much a flat curve and a pitch curve to match like in 3d throttle up mode even more gyro hold can be munipulated because there is little torque differencial from increased or decreasing degree's of pitch...........though i would guess that you would have to fiddle around with pitch settings to get it spot on and not to load the engine/motor............many top 3d flyers and people who teach keep mountains of logs and info on said curves although there are a few "rocket Ronnies" out there that have it all in there heads.....lol