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Dynon AP Pitch Servo Installation SV42T

P

plhamilton

Member
Hi There,

I am in the process of installing a SV42T pitch servo in the tailcone of my RV-10. I acquired the correct installation kit from Dynon, but there are a couple of questions that I can not answer.

1. The Dynon Autopilot Servo Installation Guide. There seems to be nowhere in the document that actually describes the drilling of the bellcrank. It is described in the diagram on page 8 as 2.5" from the axis of the main bearing, but nowhere does it state the actual diameter to be drilled. I am guessing it is drilled #19 to provide a clearance fit, and that the 2 remaining AN960-10s are used between the two sections of the bellcrank to ensure rigidity when tightening. Has anyone gone down this path before and if so, what were the results?

2. The Aluminium Spacer that I have been provided has been drilled slightly off axis. Is this normal, or is this a defect?

Any and all thoughts would be appreciated...

cheers

Paul
 
I'm away from home at the moment but back in a few days - I'll check it out if no earlier reply. Don't remember there being an issue.

IIRC, the hole is #12 to take a AN3 bolt.......

The spacer is just a spacer. I don't think it matters if it is slightly off axis.
 
The hole in the bell crank will be the same size as the hole in the rod end bearing, #12 for an AN3 bolt.

It sounds like the spacer wasn't drilled correctly, but as was already mentioned, it shouldn't matter as its just a spacer (unless it has a very thin wall somewhere due to the bad drilling).

I've never put any washers between the bell crank plates. If I was worried, I'd put an aluminum plate with a couple of rivets holding it in place.

As far as the exact location, the 2.5" is for the correct leverage. From there it's a matter of getting full travel on the elevator with the servo connected. It's usually, IIRC, about 1" from the eft edge.
 
Thanks - Star washers?

Hi Paul Thanks for the pix. One other item that I thought was strange about the installation, was the fact that the star washers are directly against the bracket, rather than against a nice smooth AN960. Did you go with the instructions here or did you add a washer to prevent gouging the primer and bracket? :confused:

cheers

Paul
 
Hi Paul,

I try an avoid star washers on aluminium as they cut through the primer and Aldine into the bare aluminium, where there is an increased likelihood of galvanic corrosion. Just a personal preference. Doesn't happen of course with a flat washer.

Cheers

PaulH
 
Update from Dynon

I received an update from Dynon regarding the use of the star washers.

http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1368959028

Bottom line is they seem to now be recommending that the bolts be installed without star washers, without an AN960-10 and with safety wiring. By reading their response, I am guessing that they want to ensure minimum chance of binding between the linear output arm and the bolt head.

cheers

Paul
 
I am way behind you guys, but I have begun construction on my 10 empennage. At what point do I need to consider pitch servos and manufacturers to entertain? I want to install an autopilot, but am not sure when I choose the type, if Van's has suggestions, etc.
 
The pitch servo install would be easier if done before you attach the tail cone to the fuselage, but it would not be a big deal if you waited till later. It is a simple install.

Jim Berry
RV-10
 
Concur with Jim. You can wait until you choose your avionics. Having said that, when you get to the the fuse I would recommend pulling some wire for the servo regardless of brand before you close up cabin top on. Even with conduit, IMO it's easier to pull wire before that forward top tailcone skin is installed because you have open access at that point. Once that skin is on, you're working through the baggage door. But even then it's still doable (been there done that).
 
I agree that it's a good idea to run conduit and go ahead and pull wire. The servo installation is not hard through the baggage door. Your kit should have a mounting bracket, so it wouldn't hurt to at least make sure that fits. For the TruTrak install you will need 8 wires, 20AWG for power & ground (can ground locally if you want) and the others can be 22awg. Shielded bundles are nice to work with or Stein's servo cable with the snake skin over it. The Dynon requires 7 wires, same gauges as mentioned, but at least 2 pairs should be twisted together, which you get with a 4-conductor shielded bundle of 22AWG. I'm not sure what GRT, Garmin or Trio use, but I can't imagine it being more than TruTrak.

The same goes for the servo in the wing. Run wire but install later, except TruTrak only uses 7 wires like Dynon in the wing.
 
dspender said:
I am way behind you guys, but I have begun construction on my 10 empennage. At what point do I need to consider pitch servos and manufacturers to entertain? I want to install an autopilot, but am not sure when I choose the type, if Van's has suggestions, etc.
Click to expand...

The reason I decided early and started the installation while working on the tailcone is that I will be driving ~100km to the airport where I plan on doing my integration. I therefore wanted to make sure that each component for integration was as finished as possible to minimise the number of take apart cycles that i incur later on.

If you are planning to go dynon sky view I would suggest that you get the SV42T servo installation kit and do it now. It will save you removing the bell crank later on. It is cheap(ish :cool:) and will allow you to finish that part completely early.

Cheers

Paul
 
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