TruTrak Pitch Servo Clearance RV-7A

I recently ordered the Gemini AP and servos from TruTrak. I received my servos today and although I didn't have a lot of time, I thought I'd at least see how the pitch servo fit. Years ago I installed the Dynon pitch mounting bracket while building my plane. The TruTrak bracket appears to be the same. I did notice that Dynon calls out mounting the bracket 3.43" from the center point of the bellcrank and TruTrak calls out 2.5" or something. (It's called out on the new instructions I received with the kit although it's not shown on the attached TruTrak sheet.) Also Dynon says to use a 6" push rod TruTrak says 5.739". Anyway I appear to have an issue even with the longer rod. (Picuture has 6" rod) The issue is the elevator tube hits the servo arm before the elevator hits it's "up" control stop.

Both the Dynon and TruTrak instructions show the servo arm clocked pretty close to 1 o'clock when the bellcrank is at 12 o'clock position. Is there a reason for this? I ran out of time but I'm guessing a little longer pushrod and the servo arm clocked closer to 12 might create the necessary clearance when the elevator goes up. Moving to the "center" hole on the servo arm may also do it.

Again this was just thrown together quickly as a quick "test fit" I haven't safety wired anything and the large washer on the servo arm isn't installed yet.

I figured I wouldn't bug TruTrak yet cause I know they're buried.

Any thoughts?

Dynon Install Sheet


TruTrak Install Sheet


Elevator Nuetral Position


Elevator Up Position (approaching stop) Elevator tube contacts servo arm.
May need a 3rd spacing washer on the bellcrank end too as the rod comes pretty close to a rivet.

Match the neutral position of the trutrak drawing by lengthening the control rod to more than 6 inches.
Comparative geometry says a trutrak servo in a dynon position MUST use a rod that is longer than 6".

The bracket positions are different by 3.43 - 2.8 = 0.63
Adding this to the Trutrak arm length spec gives 5.739 + 0.63 = 6.369

Try lengthening the rod.

Check for overcenter when done.

If you change to the shorter hole on the control arm, will you still not overtravel the servo! If so, then moving to that hole will work and give you more torque also. Otherwise, a longer pushrod (or lengthening that one if you have enough threads) should work.

Jeff, I sent you an email with the current drawings. My apologies to you (and everyone else!) but the drawing on our site is out of date. I'm fixing that right now. Thanks!

No worries Lucas, you sent the updated drawings with the servos. I just referenced the online drawing last night when I made the post. (Left current drawings at the hangar.)

Just for reference, here is the current TruTrak drawing as of 1/7/15.

boom3 said:

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Just an FYI on the above picture, I highly recommend removing the portable ELT antenna attached to the ELT mount or properly secure it so it won't come loose, I find these laying in the bottom of the fuselage all the time and it's a serious FOD hazard

It doesn't matter if the antenna falls loose when the unit is mounted in the cabin somewhere but when mounted inside the empennage you should just remove it (you're not going to get to it anyway if you crash so what's the point).

Is the bell crank mounted correctly? Doesn't appear to be mounted at the same height as shown on the drawings.

Walt said:

Just an FYI on the above picture, I highly recommend removing the portable ELT antenna attached to the ELT mount or properly secure it so it won't come loose, I find these laying in the bottom of the fuselage all the time and it's a serious FOD hazard

It doesn't matter if the antenna falls loose when the unit is mounted in the cabin somewhere but when mounted inside the empennage you should just remove it (you're not going to get to it anyway if you crash so what's the point).

Click to expand...

Great idea Walt! Thanks for the heads up.

SMO said:

Is the bell crank mounted correctly? Doesn't appear to be mounted at the same height as shown on the drawings.

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The bell crank is mounted per plans, I think there's just a bit of an illusion from my iPhone pic.

Adjustment required?

I had the same issue. If I remember correctly, when I got all the linkage and arm square to each other, the problem went away. The clearance was still close, but not touching. It also pretty much eliminated any concerns of the arm going over-center, but I still mounted the anti-over-center gizmo Dynon sent with the kit.

Does servo orientation matter?

My -6A was constructed with the bellcrank on the other side of the keel -- if I mount the servo as pictured in the drawing, the actuation rod does not line up and interferes with the bracket. If I turn the servo around and mount it on the bracket side, everything lines up with no interference. My question is: does the orientation of the servo matter, facing left or right?

I have an email into TT, but its a weekend (and I saw the gang at the LSA show) and I would like to get the pitch servo mounted.

Thanks,

Ron

It doesn't matter which way it goes. If it is controlled wrong, either install or remove the pitch reverse jumper on the back of the programmer.

Thanks, Jesse

I was hoping for that, and I believe that the 385 includes in its setup the ability to do the reverse from the control head.

Ron

You are right. It looks like they added the level switch and moved the pitch reverse to the setup. Even better!

Jesse strikes again! If it's backwards and you have a Vizion, just use the setup menu reversal. Easy peasy!

Good thread. Not a lot of instructions on mounting servo bracket to airplane. Most people riveting ? What about aileron servo bracket ? Would anyone mind describing or throwing a picture up of your attachment method? Thanks

erikpmort said:

Good thread. Not a lot of instructions on mounting servo bracket to airplane. Most people riveting ? What about aileron servo bracket ? Would anyone mind describing or throwing a picture up of your attachment method? Thanks

Click to expand...

I riveted in the pitch servo bracket. For the aileron servo you just swap out the bottom bell crank bracket with the one supplied.



Roll Servo.
Oh and you can't really see it in this picture but there is a small another small bracket on top that angles up and attaches to one of the top bell crank bracket bolts.

thank you! pictures help

boom3 said:

Just for reference, here is the current TruTrak drawing as of 1/7/15.

Click to expand...

Glad I saw this. THANKS! I have been rehearsing the pitch servo install in my mind for a couple weeks now and hope to tackle it this weekend. I printed the drawing above today and it is STILL the old drawing.