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Autopilot Servo Arm too short
http://t18.net/thorpforum/viewtopic.php?f=13&t=8674		 Page 1 of 1
Author:  MartyG [ Thu Jan 20, 2022 9:52 am ]
Post subject:  Autopilot Servo Arm too short
Has anyone else experienced a problem with installing a pitch servo for an autopilot on their T-18?

I have GRT brand servos, but they look about the same in geometry as most other popular servos. When I hooked it all up (I should have thought to try this beforehand) the throw of the elevator tube from stop to stop is much more than the throw of the servo arm. I spoke with a friend who had this problem on his Tailwind and he just made an extension on the servo arm to fix the problem. This was my first thought also, but it also increases stress on the shear bolt on the servo.

Is there another solution that I should be thinking of? Anyone who has installed an AP on their Thorp, I would love to see some pics to spur some thoughts.
Author:  Ryan Allen [ Thu Jan 20, 2022 1:34 pm ]
Post subject:  Re: Autopilot Servo Arm too short
I have Dynon autopilot system. My pitch servo required an arm (basically a piece of aluminum tubing with rod ends on both ends of the tube) to reach from the servo to the elevator tube. My pitch servo is mounted on the side of the tunnel/elevator tube cover located in the baggage area. Sorry, no pics handy.
Author:  Mduroch [ Thu Jan 20, 2022 1:52 pm ]
Post subject:  Re: Autopilot Servo Arm too short
Hello All,

Can you guys share some photos? I am planning to install a Bendix/King Xcruze this year.

Thanks!
Mike Durocher
N2WB
Author:  MartyG [ Thu Jan 20, 2022 2:47 pm ]
Post subject:  Re: Autopilot Servo Arm too short
I don't have great pics but I snapped a couple quick ones of my mount at least. Mine has a rod connecting the servo to the elevator tube also, but the travel isn't enough. **the rod is not connected in the photo. It is parallel with the elevator tube when connected**

I called GRT and they are going to send me a longer arm that bolts up to the servo, we will see if that's enough. Otherwise, I think I'm just going to have to make an extender out of some aluminum to get it to the right length.

No matter what I do the pics show up upside down, sorry about that.

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Author:  david read [ Thu Jan 20, 2022 9:35 pm ]
Post subject:  Re: Autopilot Servo Arm too short
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I took this pic for something else but it shows how I mounted my MGL avionics servo. That is a smoke oil pump beside it.
Author:  bfinney [ Sat Jan 22, 2022 3:31 pm ]
Post subject:  Re: Autopilot Servo Arm too short
This is my install of a Garmin GS28 servo, I had to get the longer servo arm, needed 1.75" throw and the standard arm max is 1.5". The servo is mounted on the aft side of the -571 bulkhead (the aft bagage compartment bulkhead).

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There is something happening when photos are included, this is upside down (rotated 180deg), it displays just fine on my computer.
Author:  Mduroch [ Mon Jan 24, 2022 12:06 pm ]
Post subject:  Re: Autopilot Servo Arm too short
GREAT!

Thanks for all the photos! I appreciated it.

Mike Durocher
Author:  campipilot [ Sun Feb 06, 2022 11:26 pm ]
Post subject:  Re: Autopilot Servo Arm too short
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Author:  campipilot [ Sun Feb 06, 2022 11:30 pm ]
Post subject:  Re: Autopilot Servo Arm too short
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Author:  MartyG [ Mon Feb 28, 2022 11:07 am ]
Post subject:  Re: Autopilot Servo Arm too short
Just wanted to update this with my final solution and a pic. The longer servo arm that GRT supplied me worked perfectly. I now have full elevator travel with only about 45 degrees of travel either way off center. Looks like it's all going to work out!
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Author:  Tony28031998 [ Thu Nov 02, 2023 3:42 pm ]
Post subject:  Re: Autopilot Servo Arm too short
Hi Marty!

I am looking at GRT avionics too, and I wanted to know what rod length you got for your pitch and roll axis for your autopilot? THanks
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