SpartanRC DS760 Gyro Review and Setup Vids

[leeph]

Originally Posted by Tomas Ahl

If you set it up with 0 pitch when the servo is at 90 the gyro will have to use quite a bit of the servo's right rudder direction travel (the direction the 8 degrees goes into) only to get to the natural neutral state. After that you'll have a huge differential between left and right rudder due to this fact, possibly to the extent that the servo bottoms out to the right for you if demanding much right rudder pitch for whatever reason.

I don't agree with this.

If you add the 8 degrees tail blade pitch with the servo horn at 90 degrees, there is still the same limit of tail blade deflection as when you set the blades at 0 degrees with the servo horn at 90 degrees. The limiting factor here is the tail pitch slider - you don't magically get more deflection in either direction by setting the blades with pitch to hold the tail in rate mode. All that happens is that the gyro adds the the required pitch in AVCS to hold the tail - there is still only a certain amount of deflection left in that direction as when you add the 8 degrees mechanically.

The servo will not 'bottom out' in either scenario since you will have set the gyro endpoints to achieve full tail slider movement in both directions without binding, and you will also have set the servo horn ball link far enough out so that you get full tail pitch slider deflection without pushing the servo out of 45 degrees in either direction.

So really, as has been stated so many times on this forum before, the only reason to set the 8 degrees of pitch in the blades is if you want to fly in rate mode and not have the heli drift/pirouette.

In fact, when I had my gyro gain on the gear switch, I did once take off in rate mode accidentally (without the 8 degrees pitch) and there was tail drift, but it was in no way uncontrollable as some have alluded to. Now I fly solely in AVCS with the gyro gain mixed with the flight mode switch, so I can never accidentally fly in rate.

Just my tuppence worth, feel free to correct me if I'm wrong!!

James / leeph

[marcosp]

Originally Posted by leeph

So really, as has been stated so many times on this forum before, the only reason to set the 8 degrees of pitch in the blades is if you want to fly in rate mode and not have the heli drift/pirouette.

What you state is right as far as travel limits. However it is geometrically convenient for the servo to be at 90 degrees where you need the best precision/resolution, that is, at 8º aprox.. I really do not know if the difference can be felt, but the math says it should work better. My grain of salt.
Marcos

[leeph]

Originally Posted by marcosp

What you state is right as far as travel limits. However it is geometrically convenient for the servo to be at 90 degrees where you need the best precision/resolution, that is, at 8º aprox.. I really do not know if the difference can be felt, but the math says it should work better. My grain of salt.
Marcos

Yeah, I see what you mean in that respect. However since we're talking about a Spartan DS760 that will only drive digital servos (the digital potentiometers of which are obviously superior to analogs) their performance when operating outside of centre position ought to be as good.

[Tomas Ahl]

Originally Posted by leeph

Yeah, I see what you mean in that respect. However since we're talking about a Spartan DS760 that will only drive digital servos (the digital potentiometers of which are obviously superior to analogs) their performance when operating outside of centre position ought to be as good.

Yes and no. If you re-read the post I responded to in the post you quoted from maybe you see what I saw, a more general question for reasons of the tail rotor pitch offset than what pertains to the DS760. I mean, the guy has a gyro that works perfectly for him and yet he asks about the 8 degree pitch offset and why it is/was done.

Otherwise I agree with you given that a proper mechanical set-up has been done including a good servo horn radius being used. But reality tells me that this, very sound and reasonable point I must add, isn't always observed especially by newcomers to the hobby. Thus my statement about the tail servo possibly bottoming out.

Another reason for the offset practice is/was that older gyros might not hold the tail properly if they are handed the throw differential incurred by not implementing the pitch offset. But, this does not belong in a thread about the DS760.

[Mathias]

So, what's the proper binding procedure these days with firmware version 2.0? 5% gain, rudder stick to the left?

[Mathias]

Anyone?

[raptorheli2]

http://www.spartan-rc.com/resources/...=42&category=2

[Mathias]

Thanks!

[Nick Adams]

Originally Posted by Angelos

Half correct Ade. 760us or 1520us is the pulse width (time from start to end) that makes the servo go to mid-point. Here is a copy of a post I made on another forum a few weeks ago....

There has been a lot of misinformation and confusion about what people call frame rate so I will try to shed some light and also explain what is beneficial and what is not.

First some background information. The servo position is controlled by an electrical pulse or variable duration which in electronic terms is called pulse width. The pulse repeats at constant intervals and this repetition frequency is also known as frame rate. The majority of RC receivers will produce a frame rate of around 50Hz which means that they will instruct the servo where to go 50 times each second. The position of the servo horn is defined by the pulse duration. For a typical RC servo a pulse duration of 1520uSec means that the horn should be at the mid-point of the servo travel. If the pulse duration becomes shorter or longer the servo horn will move clockwise or counter-clockwise respectively.

As gyros evolved it was apparent that 50Hz was not enough to achieve the desired performance as the time intervals between pulses were too long. So manufacturers starting pushing the frame rate up. JR gyros went to 250Hz and Futaba pushed as high as 333Hz. This allowed the gyro to talk to the servo more frequently but the position command remained the same (1520uSec still means mid-point).

Then the GY601 came along to create confusion with the non standard 760uSec. With this system the servo travel mid-point is at 760uSec as opposed to 1520uSec. In theory by shortening the pulse to half it can reach the servo faster and therefore the servo can react sooner. In reality the benefit is negligible as the savings are less than 1mSec. Considering the inertial of the motor windings and the helicopter as a whole 1mSec does not give any noticeable benefit. In my view the only reason for doing this non-standard 760uSec system was to lock customers to a specific gyro/servo combo.

So when buying a new servo the important things to look at are… speed, torque and 333Hz frame rate. With the exception of the older JR servos 8700G etc most new digital servos will work at 333Hz. This includes all Futaba servos and therefore the S9254 will work as good as the S9256 since they have the same torque and speed spec but perhaps a little hotter due to the lack of metal case.

-Angelos

Angelos .... You are the man .... you do know that dont you .... the information you offer to people at no cost is a great thing .... your knowledge and your willingness to help others is very helpful ... thank you so much for all your inputs and for the DS760 you deserve all good things that come to you ... cheers mate from all us in Australia and all those on Helifreak, Im sure they all wont mind me saying that on there behalf .. haha

[TMoore]

Originally Posted by leeph

Yeah, I see what you mean in that respect. However since we're talking about a Spartan DS760 that will only drive digital servos (the digital potentiometers of which are obviously superior to analogs) their performance when operating outside of centre position ought to be as good.

Digital and analog servos use the same pots.

TM

[esmoglo]

I have the JRDS8900G digital tail servo what are the correct setting? 1520u and 333Hz? Just let me know...


Angelo

[raptorheli2]

the information you need is in the manual (below link)

http://www.spartan-rc.com/products/d...user_guide.pdf

1520/333 or 1 flash in other words.

please take the time to read the manual, it will stand you in good stead should you need to tweak anything at field.

cheers

[esmoglo]

Yea thanks but that Servo is not listed in the PDF I checked it.

[raptorheli2]

servo list is on page 6 of the manual. (8900G is listed there)

1520uSec servos capable of 333Hz
Futaba S9253 / S9254 / S9257 / S9650 / S3153 / S3154, JR 8900G /
3400G, Sanwa ERG-WRX, Airtronics 94758 / 94761, Hitec 5925MG /
6965HB, Robbe FS61BB, LogicTech 3100G

1 flash during setup is what you are after.

cheers

[esmoglo]

Ok I have the older book and its on page 8 and it lists the 8700G, I just printed the new one and I see it on page 6.

Its 1520uSEC at 333Hz thats nice!

Angelo

[raptorheli2]

since the 760 launched the manual has had the 8900 listed but not the 8700 if memory serves correctly.

a bit of useless knowledge for you as to how that happened-

the 8700 was added at a later date due to demand for the 8700/2400/3400G. this meant a 3rd option was required in the set up sequence (1520uSec/250Hz/3 flashes). the very first 760's only had 1520/333 and 760/333 respectively. so in essence if you have 8700 in there then you should have 8900G on your list as 8900 was there first. hope that makes sense :-)

glad your all fixed up, enjoy

cheers

[ualdrivr]

Very long thread this one, I don't know if anyone has mentioned it yet, but I found out that in order to update firmware on my Spartan with a AR 7100/R RX, I have to power the TX and RX.

Bob's video shows only RX powered with a 4.8 volt battery. I found out that this can not be done with the AR 7100/R. You need to turn the TX on and power the heli normally, otherwise the Spartan is not powered.

[MrWolf]

Deleted

[Dumb Thumbs]

I'm searching around gyro threads looking for ideas for what I want to put on a new 450 I'm building. Man, this DS760 looks like a lot to be messing with.
Is it really worth all the trouble?

[raptorheli2]

what trouble?

for a 450 get a quark, lick it, stick it, fly it....job done. you won't be dissapointed.

cheers