New 3400G Tail Servo - Having trouble with throw

[GreenBar0n]

I took the advice of a few knowledgeable members here and went with the JR Heli-servo pack (285's,3400g). At this point I have only installed the 3400. I was able to get the 3400 to screw in to the middle post on the frame.
Did everybody else just use one screw per side of the servo?

I used the smallest servo horn, with the shortest lobe, that came with the 3400. The angle of the JR horn slopes toward the tail and the ball is in the top or second hole for that horn. The ball link is mounted on the servo-body-side of the horn.

The control rod has a really straight throw to it, there is no binding or dipping, but the travel is way too long. The ball link contacts the servo only when the horn leans towards the tail, towards the nose the servo doesn't contact anything, works fine.

I attempted to adjust the Travel Adjustment setting in the dx6i interface. My rudder is set at factory which is 90. I changed the values over and over and the desired effect is not what I am getting. The Travel Adjustment setting seems to slow the rate of the servo motor-speed as opposed to restricting travel length. I can't get the throw to be the right distance and maintain decent speed.
I am obviously missing something here.

Another serious problem I am having is that it seems the 3400 never goes back to its original center. I have to jockey it left and right to get it back to center.

I tried to make as much sense as possible out of this, but I am brand new to Heli and could use some help if you can spare it.

Thanks for reading.

[Heli Jim]

Did you change the setting on the gyro to "DS"? this servo is a true digital and the gyro can work in digital mode.

The servo doesn't really center when the heli is sitting still. I just read an article on another board about how to set up your tail servo and I'll post a link to it. I found the article explained a lot of things.

Also, make sure to test the gyro to see if it is working in the right direction for this servo. There are directions
on how to do this in the manual that came with the heli

I found that I had to reverse the servo AND reverse the gyro. The reverse for the gyro is ON the gyro as is the switch for "DS": mode.

Here is a copy of that post about setting up the servo.
I found it on the Rotory Modeler forums.

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Re: servo creep
02-28-08 05:04 PM - Post#86460
In response to jetss

Here is a start.

With TX ON only:

Put TX rudder travel adjust at 60 on both left and right stick adjustments.

Gyro Menu shows gain at 64 on 1 switch position and maybe 60 or so on the other position as you flip the gear/gain switch. Next look at your rudder digital trim lever and make sure you are at ZERO with the hash mark in then center on the TX screen. Flip to ID stunt mode and check then HOLD as well. Make sure the hash mark is centered on the screen when you flip into these modes.

Next go into sub trim and make sure the rudder channel has NO sub trim number. Shut off TX.

Remove plug of t/r servo plug from the gyro. Go to channel 4 of your receiver and unplug gyro and plug in the rudder servo along. Now turn on TX and plug in heli. You may want to disconnect the motor to be safer...your choice. With the rudder stick centered look at servo horn on servo. Move the rudder stick to see servo move. You can check for binding this way and check for the center. I recommend that you put the servo horn on the servo with the horn facing SLIGHTLY forward. You could put it at perfect 12o'clock with the TX stick centered but you will likely see binding if you move the rudder stick. Advance the servo horn 1 tooth or slightly forward to put the horn say at 11o'clock vs. the 12 for perfect vertical. Now with TX still on and rudder servo horn at this slightly advanced location look at your t/r pitch slider at the rear of the heli. Adjust your t/r rod length so the SLIDER on the t/r output shaft is almost centered as it travels on the shaft. You may need to lengthen or shorten the rod. OK not a problem just remember to have the TX on and your servo horn in the slightly advanced position.

Now shut off the heli. Reconnect the gyro to channel 4 then the servo to the gyro.

Make sure to reconnect your motor if you disabled it.

You should be very close to now have a good flying tailrotor on the B400. You may need to adjust your gain a little but it should be very close. ALSO if you notice the t/r servo creeps a little you could NOW go into the sub trim for the rudder channel and add a few numbers to help stop it. I usually HOVER the heli and make this adjustment. IF you add a number and the servo moves faster you went the wrong way...remove the number and add some the other way. Same as if you hover...if it moves/yaws more...take the number off and go the other way.

You could use the rudder trim but that is not as fine an adjustment as sub trim. PLUS sub trim work in all flight modes where as rudder trim is separate...so you'd have to adjust your rudder trim lever in each mode...normal - id - hold. Your choice.

GOOD LUCK!

____________
Best Regards,

Ron Osinski
aka - GMRO

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I found this to be VERY good advise.

[LockMD]

I attempted to adjust the Travel Adjustment setting in the dx6i interface. My rudder is set at factory which is 90. I changed the values over and over and the desired effect is not what I am getting. The Travel Adjustment setting seems to slow the rate of the servo motor-speed as opposed to restricting travel length. I can't get the throw to be the right distance and maintain decent speed.
I am obviously missing something here.



I never changed the rudder setting. In HH mode it will not center, its doing what is should HOLD - you have to set center in rate mode Gyro = less than 50% I dont think you'll be able to set the limits exactly on the stock gyro but try moving the ball closer to the center on the servo. The only way I was able to get my limits set correctly was by adding a GY401.

[GreenBar0n]

Thanks for the reply Heli Jim, I have set the switch on the g110 for DS and REV.

I understand now about the centering and that while the bird is not moving there will be no t/r center, thanks for the heads-up.

The thing that I am having the most trouble with still is the servo ball contacting the servo body. I am trying to set a limit on the servo travel, but can't.The servo continually drives past the limits I set for it.



@LockMD Thanks for the reply, I was wanting to get the 401 in a week or so, but was hoping I could test out the new servo on the g110 in the mean time.



http://i83.photobucket.com/albums/j303/GreenBar0n/3400G.jpg

[Heli Jim]

If the ball is hitting the servo, then you will have to put the ball on the top of the arm.

YOu should still be able to have the pushrod line up OK.

I ended up with a travel adjustment of 60 both ways and I used the round wheel and used
a placement of 2nd hole in from outside to start with.

[sokal]

unfortunatly for now you will have to fly knowing were our limits are manually
no cure o it with stock gyro like lockmd said oving ball closer to the scew will limi sme not all

[sokal]

use the smaller arm the 4-way with one hole on each its the closes u can get to the screw or if u find that JR roundwheel
and put the ball on the outside for now that way when the servo moves fwd wont bind against servo

but the 401 is your best bet

[LockMD]

@LockMD Thanks for the reply, I was wanting to get the 401 in a week or so, but was hoping I could test out the new servo on the g110 in the mean time.




Oh you can fly with stock just fine, you wont be putting enough on the stick to cause binding while you are in the air. and like the others say, change the ball link so it facing you (out) away from the servo

[GreenBar0n]

Thanks for the good advice. I am going to try moving the ball to the outside, and then the round wheel. Sounds like the 401 will be necessary sooner than I had hoped.

[LockMD]

I didnt use the round wheel, I'll post a pic of my tail in just a sec......

[LockMD]

Pretty much did the same used the star and cut the other three legs off I am using the whole closest to the screw though and my cyclics I left the star horn intact here are the pics:

[sokal]

i used the smaller arm
http://www.helifreak.com/attachment.php?attachmentid=40644&stc=1&d=1204506988
http://www.helifreak.com/attachment.php?attachmentid=40645&stc=1&d=1204506988

[GreenBar0n]

Thanks alot for the reference pictures, this helped alot. I ended up moving the ball to the outside of the horn and to the 1st hole as was recommended. It came together so easy after that I was shocked. Much thanks and appreciation to you guys, this is an amazingly helpful and cool forum.

Just to clear up one thing, sokal, how were you able to run the ball link on the inside of the horn and on the 1st hole without contacting the servo chassis? Is it because you screwed the servo to the boom mount from the backside that you are able to attain the necessary clearance? Does that configuration twist or shift the control rod excessively?

Thanks again.

http://i83.photobucket.com/albums/j303/GreenBar0n/3400Gballoutside.jpg

[sokal]

i reversed the servo mount
and i have the 401 so the limit is right before the rod hits case
i did this because it gave me a strighter shot down the boom
and the ball clears just fine

[GreenBar0n]

and i have the 401 so the limit is right before the rod hits case


So the 401 can automatically sense the ends of the servo throw, or it has better coordinate programming from the radio?

[sokal]

the 401 has a limit POT which controls the servos throw
http://www.helifreak.com/attachment.php?attachmentid=40676&stc=1&d=1204530878

[GreenBar0n]

the 401 has a limit POT which controls the servos throw

I will be going with the 401 in a week or two here hopefully, thanks for the help.

[skigolfmike]

I installed a DS3400G on my bird last night. Basically, I tried several things to get rid of the rebound with the DSP75. I turned the delay up to 40 and even put it in analog mode. The bottom line was by the time I got the rebound out the setup was only slightly better than what I had with the stock 110 gyro. So, ..., time to replace.

What I did setting up was to look at the centering and throws I had on the DSP75, then compare it to the 3400. I was flying in the 3rd hole with the DSP75, which is .355" from center. The DSP75 was moving about 60* total throw. The 3400 has more throw, so I looked for a servo horn for the 3400G with a closer hole to center. I found an arm with a hole .300" from center and I started there.

OK - I hooked it all up, turned on the radio with the gyro in HH mode, and switched it to analog mode. Guess what, too much throw. I used the Travel Adjustment to find the endpoints. It turned out to be 45%. So, I'm going to need a hole about .250" from center to make this work. Will have to look at this tonight. Will post pics when I get it done.

[sokal]

dont use servo end point in the tx
all should be center subtrim and trim
see my pic for servo horn used

to center servo do so in rate mode then put horn on
on gyro do
DS on
dir norm
delay 0 (only for analog)
and about 90-100 on your limit

70 in TX for gyro is good start

no need for trim or subtrim on tail

[skigolfmike]

OK - got it figured out. I found a servo horn with a hole closer to center. It's .270" from center. I had to grind the servo horn slightly for clearance. I centered the servo, set the travel in the TX @ 100%, then adjust the endpoint in the gyro, Simple. Sokal's direction work.

Here's some pics:

1st is several control horns. The arm on the left, the inner hole is at .300", on the right it's .270", the 3rd hole on the stock arm is .355"
2nd is the servo installation. I had to use different screws, but it's in the stock location. I also had to turn he ball link at the TR end about 3 turns in to recenter.
3rd is the gyro setup. Delay is set to zero and endpoint pot is tweaked toset throw.
Last is my 2 helis. Note: the CX2 isn't even close to stock.

[GreenBar0n]

Nice work, have you flown it yet?

[skigolfmike]

Not yet. We got a foot of snow starting yesterday at noon and it's still snowing. Maybe tomorrow. We have an indoor fly-in tomorrow evening, I'll get to fly it then. Maybe I'll get someone to shoot a little video.

[skigolfmike]

Here's a little better pic of the TR servo installation.