A/P and Dynon servos

FYI to builders...pondering servo size (strength) when installing their autopilot system. I have a STOL 750 with two axis autopilot ( Dynon SV-32 servos.)   During my 40 hr test phase I was having problems getting the autopilot pitch servo to not slip - esp. in turbulence.  Went thru the whole setup routine per Dynon, but no joy, airloads were too much for the servo as the A/P worked to maintain selected altitude in anything but smooth air.  Even then, in smooth air, during prolonged turns, the slipping would occasionally occur as the A/P worked to hold altitude.  Finally decided to step up the pitch servo to the next size servo (SV-42) which has a bit more torque.  Installed it today and it seems to have taken care of the problem.  Kudos to Dynon for allowing a swap of the servo I bought 3 years ago for the new servo.  Evidently it was no big deal, they would rather it work right and they make it easy to resolve issues. 

So, my advice for those outfitting their CH750 with servos from Dynon, install the SV42 servo (at least for the pitch servo) which should work fine for our aircraft.  HTH someone...

Dave

Views: 783

▶ Reply to This

Replies to This Discussion

Permalink Reply by Tim Jones on April 13, 2018 at 11:22pm

Thanks for the info David.  Do you have the Y-stick or dual stick option?

Permalink Reply by David J. Beaulieu on April 14, 2018 at 8:34am

Y stick...

Permalink Reply by Ken Ryan on April 14, 2018 at 11:01am

Good info Dave. When you swapped servers, did you need to re-do the connections to the controls? It looks like the motors are identical except the bigger versions are longer in the back, making me think the swap should be pretty painless. I have the 32 in the airplane I am currently building and fear I might run into the same problem.

Permalink Reply by David J. Beaulieu on April 14, 2018 at 2:01pm

Ken, relatively painless affair.  No change of the physical setup to flight controls or servo mounting. Have the correct connector and shell (DSUB 9 pin male) for the new servo wires, dsub male pins to crimp and your done with electrical!  The SV software detected the new servo and did a software update to the servo.  I then had to run the servo calibration and test.  Ground and flight check and done!  Only downside to the 42 is it indeed physically larger (just a bit) and approx one pound heavier with slightly more current draw (which is really not an issue for our wire size and C/B's)  I would suggest doing the swap earlier (unused servo) might get you a new servo versus a re-manufactured servo like I received.  Just a note regarding physical setup.  In  an attempt to get more torque from the SV32 servo during my testing I had gradually moved the relay rod from the outermost hole of the servo arm to the middle and finally the innermost hole.  At the innermost connection, I was able to jam the flight controls (on the ground) for the elevator while checking range of motion, etc. due to overcenter geometry.  The torque output of the SV32 at the innermost connection point is the same as the SV42 at the outermost point of connection to the servo arm.  That's when I elected to swap servos. The angular deflection at the outermost points of the servo arm is much less then when connected at the innermost point for same control deflections and makes setup of the physical connection geometry a bit easier.  Hope that makes sense, the Dynon literature is very good and emphasizes all the above "take-aways" I experienced.  Good luck with the build!!  Glad to take questions if you got any later on.

Cheers!

Permalink Reply by Ken Ryan on April 14, 2018 at 2:17pm

Thanks Dave. 

Permalink Reply by KENNY MCLAIN on September 17, 2024 at 8:59am

Do you have pictures of the mounting , fixtures and connections of the servoes?

RSS

New from Zenith:

Zenith Planes For Sale 
  

Classified listing for buying or selling your Zenith building or flying related stuff...

Custom Instrument Panels
for your Zenith:

Custom instrument panels are now available directly from Zenith Aircraft Company exclusively for Zenith builders and owners. Pre-cut panel, Dynon and Garmin avionics, and more.

Zenith Homecoming Tee:

Zenair Floats

Flying On Your Own Wings:
 A Complete Guide to Understanding Light Airplane Design, by Chris Heintz

Builder & Pilot Supplies:

Aircraft Insurance:

 
 

West Coast USA:

 
Pro Builder Assistance:

 

Transition training:

Lavion Aero

K&S Aviation Services

Aircraft Spruce & Specialty for all your building and pilot supplies!

How to videos from HomebuiltHELP.com

Developed specifically for Zenith builders (by a builder) these videos on DVD are a great help in building your own kit plane by providing practical hands-on construction information. Visit HomebuiltHelp.com for the latest DVD titles.

© 2024   Created by Zenith.Aero.   Powered by

Badges  |  Report an Issue  |  Terms of Service