Elevator servo horn ball link binding / insufficient throws

[kennyd1gital]

I just received my N5c kit last week and did 90% of the build over the weekend. I'm still waiting on my V-Bar to show up so I can finish the build and do the initial setup. In the manual, it says for a flybarless setup, you should place the ball link balls on the servo horns 10mm from the servo horn center for better resolution. I attempted to do that, but on the elevator servo, there doesn't seem to be enough throw before the sides of the ball link hit/bind on the inner portion of the servo horn, where it attaches to the servo spline (because the elevator balls are mounted on the inside/underside of the servo horn). I'm running Outrage Torq 9180 servos for cyclic. I have temporarily moved the balls on the elevator servo horn out to 13.5mm from center and the throw seems to be closer to where it should be, but from what I understand, all three cyclic servos should have the balls the same distance from center. Is there something that can be done so that I can mount all the balls 10mm from center and still have sufficient throws on the elevator? Or am I stuck mounting the balls 13.5mm from center on all cyclic servos?

[Chris Sexton]

Well every servo is a bit different.  The recommended 10mm is a starting point. If you need more throw to get the resolution you need, then move the balls out. But yeah you need to move them all out or the FBL unit will have issues.

I can tell you from personal experience, the OutRage Torq cyclics have a TON of resolution because of their drive train. I am not surprised you need to move the balls out.

[kennyd1gital]

So in other words, I should be okay moving them all out to 13.5mm? I'll still have good resolution at 13.5mm from center as opposed to 10mm from center?

[Chris Sexton]

Yes, I think you will be fine. Once you get to the FBL tuning part, you can tweak the ball position completely, but if it takes 13.5mm to get the throw you need without binding, then that is the place to start.

[Brandon Bartolomucci]

I have JR8717 Cyclics on mine and they are all at about 13.X millimeters to get proper throw and resolution as well.


Regards,
Brandon Bartolomucci
Sent from my iPhone

[kennyd1gital]

Alright, I'll try it with the balls at 13.5mm from the servo center. Thanks for your input guys.

[nick.m]

now this may sound a dumb question but do you mean by resolution 

[Brandon Bartolomucci]

Edit. Sorry wrong thread reply.

[RichL]

now this may sound a dumb question but do you mean by resolution 

Nick, Chris's reference to resolution refers to how small a movement can be made by the servo and the ability of the servo to hold a very specific position.  A few things effect servo resolution.  One, the configuration of the gear train. Two, size and number of the teeth on the gears and three, the ability of the servo motor to make very small movements. Frequency also comes into play, a higher frequency servo is capable of receiving and executing more instructions in a given time frame than a servo operating at lower frequency. Moving the ball and linkage further out on the servo arm (13.5mm) will mean that a small movement of the radio gimbals will translate into a larger movement of the attached control surface (in this case the swash plate) compared to the ball's original position (10mm) closer to the center of the servo horn.  A servo with higher resolution will be able to execute smaller more precise movements and mitigate some of the oversensitivity gained from the extra travel in the control surfaces.  Typically having linkages closer to the center of a servo horn offers speed and precision.  Moving linkage further out on the servo horn offers a mechanical torque advantage and more travel.

 
Rich

[kennyd1gital]

Great information, Rich. Thanks for sharing that with us!

[nick.m]

many thx for explaining that rich 

[copenhagen]

I have been fighting this issue.  It has held my N5c TT out of the air for months now.  (18 credits of Mechanical Engineering hasn't helped)  Anyhow, I stayed up until 2am last night trying to get 10mm radii to work, and no dice.  I tried putting small washers beneath the offending horn to move it out to prevent the binding with the Outrage Torq servo, but I feel that I would have to lose more torque transmitting spline surface than I am willing to part with in order to accomplish this task.  I'm about to try 13.5 and call it a day.  I also tried the Quick UK horns, but their spline had an extra half mm on the OD vs the Futaba horn, so even though I was able to mitigate the binding on the servo by using a minimal amount of washers to set the horn out, I still had binding on the spline at extreme collective/elevator combinations.  I was only running 12 degrees of pitch.  I tried lengthinging my swash links one turn at a time until I was at damn near 24 mm, and that still was not enough to eliminate that binding...so...I'm 6 setups into my N5c, and she has still never had a drop of fuel in her tank!

[Tommy Wagner]

Copenhagen

What FBL system are you using? Torq has the same spine as futaba so the 4 star wheel should get you there.

Pics would help us also mite be something simple.

[copenhagen]

Tommy, to answer your questions, here is a post I just made on the V-Stabi forum:

I am setting up a Synergy N5C TT. I am using Outrage BL 9180s for my collective servos. I am unable to obtain a bind free setup with 12 degrees of pitch and a resolution between 80-100 per the V-Bar menu. If I use 10mm radii on my horns, I get binding at extreme collective/elevator combinations on my elevator servo. This is because the design of the Synergy dictates that the balls be on the inside of the horn rather than the outside for this particular servo. This problem is magnified by the fact that the Outrage servos have a larger than normal aluminum base housing their spline. When I try 13.5mm radii, I am able to obtain a bind free setup. The problem now is that in the collective travel setup I get 12 degrees of pitch at "69," and 13 degrees of pitch at "75" within the V-Bar. Is it ok to run the V-Bar at values this low?

I am going to try a set of 12mm radii horns today, but after 7 failed setups, I am not keeping my hopes up.

[cyprusflyer]

Just a thought for a little more room beneath the elevator servo horn.
Be advised that Mikado links are also 2.5mm thread, in fact I have used the N5 pitch links on a Logo 600 to convert to the new head, they were the perfect size.
Mikado balls are a bit smaller so nothing stopping you fitting the smaller balls on the servo arm and the mikado links to the pushrods just at the servo end!
It would make absolutely no difference to the geometry, the key here is the same 2.5mm thread.
No worries about those links, my TDR uses them at 150 mph + lol