Question relating to the DS410 and 420 Servo's

[Starcruiser]

I am waiting to take receipt of my very own Trex 250SE super combo this coming Tuesday (if UPS stays on schedule) and wanted to know if the servo's that come with this kit are either;

1. Programmable
or
2. Adjustable (mechanically)

I ask since I want to center the servo arm if the spline is not quite right. Now I know you can use sub-trim to fix it (adjust the servo arm position), but I am looking to get a mechanical center if at all possible. Some may think that I am taking this a bit too far but this is a hobby and I like to tinker and I am a little OCD at times so bear with me

I have been reading quite a bit on the forum and the debate on sub-trim or not to sub-trim and it was brought up that some servo's have a way where you can mechanically center the output shaft. A screw in the base of the horn that allows you to loosen and adjust it to tweak the horn position.

Since I have not used or played with the align servo's so I am hoping that some of you folks could fill me in on these servo's.

I plan on making a few upgrades already to "bling" it out but most are to avoid any of the pitfalls this little bird has and a few to make it more reliable.

Now I could replace the servo's with a programmable servo to provide the adjustability I am seeking but would rather work with what I already have coming.

So TIA for any feedback.

[jamesb72]

I don't believe the DS410/20 are programmable or adjustable electronically, so if you want this you will need to buy programmable servo's and the software/hardware to program them.

Seems a lot of money for nothing though, you should be able to mechanically/subtrim a perfect setup if you spend half an hour or so on setup, is it worth all that money to save half an hour ??

I'd at least fly the SE supercombo stock to see how you get on, before spending half as much again on servo's and programming gear !

[oliverdots]

If you can open the servo's, can't remember as my 250 is at work, could you simply move the gears round a tooth or two to get a level servo horn? I agree with the last post, nothing wrong with subtrim, apart from on the rudder servo, (which doesn't need to be dead centre anyway).

[wlfk]

Don't worry too much about the OCD - it's not altogether a bad thing in this hobby!

[Besen]

This has been debated elsewhere in this forum, but I use subtrim on my rudder servo and it seems to work fine. You just have to re-bind after trimming. To be fair I'm still in the learning to fly phase, but I centered the horn with subtrim and I get no drift in HH mode.

[Starcruiser]

Originally Posted by jamesb72

I don't believe the DS410/20 are programmable or adjustable electronically, so if you want this you will need to buy programmable servo's and the software/hardware to program them.

Seems a lot of money for nothing though, you should be able to mechanically/subtrim a perfect setup if you spend half an hour or so on setup, is it worth all that money to save half an hour ??

I'd at least fly the SE supercombo stock to see how you get on, before spending half as much again on servo's and programming gear !

I thought that might have been the case with these servo's but wanted to ask someone who has them to see if that was really the case.

I have 450's so I have trimmed them mechanically as far as I could then used sub-trim to finish them off. I agree with the cost for different servo's versus time, but I read elsewhere here about sub-trim and The affect it has on the servo's travel, I do realize that as long as the sub-trim value is not excessive I shouldn't have any major issues. I am wondering if I should have purchased the kit and bought the electronics separately instead and got myself some HS-5065's instead for the cyclic and another JR tail bundle. Well I will work with what I have and see how it works out.

Originally Posted by oliverdots

If you can open the servo's, can't remember as my 250 is at work, could you simply move the gears round a tooth or two to get a level servo horn? I agree with the last post, nothing wrong with subtrim, apart from on the rudder servo, (which doesn't need to be dead centre anyway).

\

I was considering this exact point actually, i.e. opening the servo and shifting the gears a tooth one way or the other if the servo horns do not line up the way I would like. I have to disagree with you though on the tail servo and would want that one to be 90 to avoid geometry issues. As I said above I will check it out and see what I end up with and then decide what to do. I figure I will post my findings here as I build to share my experience with the rest of the HeliFreak community.

Originally Posted by wlfk

Don't worry too much about the OCD - it's not altogether a bad thing in this hobby!

Well I will try not to worry about it. I consider this a hobby and it gives me something to tinker with. I am an engineer by trade so I strive for perfection in what I do as well as to find the best solution, so this is a trait I have I guess

Originally Posted by Besen

This has been debated elsewhere in this forum, but I use subtrim on my rudder servo and it seems to work fine. You just have to re-bind after trimming. To be fair I'm still in the learning to fly phase, but I centered the horn with subtrim and I get no drift in HH mode.

Yep I read that thread from start to finish and I am still subscribed to it Just trying to see how close I can get to a mechanical setup with out using electronic adjustments is all. I am new somewhat to this hobby, been flying for about 9 months now, still learning, this site (others too) is great for picking up info and tricks as well as sharing ideas and asking for guidance from others who have been there and done that already, thus the reason for the post.

Thanks to all for responding.

[EtheAv8r]

Originally Posted by Starcruiser

......... I have to disagree with you though on the tail servo and would want that one to be 90 to avoid geometry issues. .......

Err no I disagree, it is perfectly acceptable to have the rudder servo offset from 90, and could even be desirable.

The normal method is to set 90 and then adjust control rod or servo mount position on tail boom to give a 6 or so degree offset on tail totor to counter torque from Main rotors at neutral. So neutral on the stick is not neutral or midpoint on the tail rotor. Actual flying neutral is some 6 - 8 degres offset (to yaw left if main rotors turn clockwise viewed from above). The tail slider is built symetrical - equal movement either side of 0 tail pitch, but the flying neutral being offset means you actually do not have equal tail slider movement either side. It is asymetric, with more movement one way that the other. Therefore this 90 setup creates a geometry issue. If you offset the tail rotor you can equalise the mechanical servo movement with the tail slider movement and reduce or even eliminate geometry issues, and not need different EPA settings left and right.

Both ways work, but mechanically an offset arm is argauably better than a 90 arm.

[Starcruiser]

you are saying the tail/bell crank arm or the servo arm?

To be clear I was referring to the servo horn/arm. I do realize that, depending on the heli, the tail blades might have a few degrees of pitch when the bell crank arm is at 90 while others may not. I like to set up my tail in rate mode to eliminate any drift while my servo horn/arm is at 90. This of course will cause the tail blades to have some pitch to offset the rotational torque of the mains. This will also cause the tails bell crank/arm to be a little off of 90. When I set this up I usually move the servo mounts (slide them) to adjust the tail pitch.

Now depending on how the servo arm/horn is setup (distance from the center point of the horn/arm) the ATV travel may or may not have an impact on the actual travel distance of the servo. Also I realize it is desirable to have the servo travel no more than about 35 degrees I think it is, to maximize tail servo response. So it is a balance of servo travel to ball placement on the servo horn/arm to provide the best response and travel. There are formulas that help determine the best position of the ball on the horn versus bell crank travel. But as a rule of thumb I use between 8 to 10mm to start.

So when I set up my tail I keep my tail servo at 90 and the bell crank might be offset depending. The other consideration is the Gyro setup and travel adjusts so that brings in another set of variables. So the short of it is everyone has a slightly different requirement when setting up their tails.