TruTrak Pitch Servo Issue

Installed the pitch servo using the Tru Trak supplied bracket and hardware. I am concerned that the torque multipier arm could get hung up on the top rear bolt head. I ended up shimming the oposite end with an additional washer to kick the back end of the arm further away from the bolt head. I believe the correct solution is to use a countersunk screw and let the threads protrude through to the servo housing and safe tie the screw on that end.
I know this probably belongs in the A/P section, but it is RV-10 specific.

Anyone else see this as an issue?

Mine has approx 3/32" clearance. We could build a little ramp using epoxy flox
and that would prevent it from catching. It also may be possible to use a truss head screw with sl nut. Contact trutrak to see what the possibilities are.

Inspect that little cable for fraying at every annual. If it breaks you could possibly limit your control movement.

This whole arrangement looks like a poor design to me. You are correct in that if the cable breaks you have a seroius issue with pitch lock up. I don't understand the decision to go to this arrangement verses the roll servo actuator arm. I am going to go with a truss head screw and and locking hardware at the other side. I will give them a call today to discuss.

Let us know what you find out.

I had the same thought about the bolt head when I assembled mine. I don't think it will be an issue. But I'm game for changing it if there is a way to fully remove any possibility of a hang-up.

Phil

Bill,

Have you talked with Lucas at Trutrak?

You may want to post the question on their forum.

bob

A truss head screw with a lock nut is perfectly acceptable. The lateral motion of the torque enhancer body is negligible so there should be no danger of it interfering with that bolt. However, the nice thing about Experimentals is you can do it how it makes YOU comfortable.

Our first iteration of the RV10 pitch servo we DID use the standard arm just like the roll servo. However, we found that it lacked sufficient torque to control the airplane satisfactorily. That left a few options. One was to use a larger stepper motor, but the larger motor has a pretty big increase in residual torque. We could use our high torque servo which would be more than sufficient, but at considerable cost to the customer.

The other option was to use our torque enhancer. This allows the C size servo motor to exert greater force on the controls through the mechanical advantage of a capstan wheel.

I hope this helps.

With quick responses like this and also over on vbulletin I am glad I chose TT AP. Thank you.

Wayne Gillispie said:

With quick responses like this and also over on vbulletin I am glad I chose TT AP. Thank you.

Click to expand...

I've got around 400 hours on my TT AP and absolutely love it. It is one of the nicest autopilots I have ever used(and I have used more than a few), and customer support is superb.

I spoke with Lucas today in regards to both the bolt interference issue and the limit stop on the roll servo. I agreed to send him some photos of the mod to the roll servo bracket that provides a more secure method of attaching the limit bracket. The concern here is an overcenter position if the autopilot were to drive the servo past the hard limits, which are only held on by a couple of #6 screws with minimal thread engagement. The second issue is the top rear bolt head possibly preventing the actuator arm from moving towards the aft position. I am using an 10-32X1.25" screw and locking it down with a nylock nut on the oposite side of the servo.
My biggest concern was pointed out by Wayne, and is the possibility that wire rope comes loose from the force multiplier arm and limits the pitch travel. Lucas mentioned that they had only seen this once and the had rectified the issue by using a different method of attachment at each end of the cable. Non the less, I personally still have a concern, but don't have any ideas how to resolve except lot's of inspection attention.
I am looking forward to flying behind this A/P, I too have heard nothing but good reviews on the product and the technical support.

Below a photo of the "fix" I used for the roll servo limit plate.

Just out of curiosity...why an 8-32 screw. Isn't the original bolt that goes through there 10-32? And with 1 1/8 length, does that give you a good length on the back side to tighten the nut down?

Thanks
Steve

P.S. Does anyone know what the thickness is of the servo+the mounting plate it is attached to in that location?

Brkt+servo= 15/16", so I would use AN23-20 or AN526C-1032R20. Then a AN364-1032A thin nut with AN960-10L washer.

Steve, You are correct, it is 10-32. That is what I ordered AN526C-1032R20 from ACS.

Wayne, One of these days I need to fly over and see your project!

The an23-20 doesn't work because the servo is threaded and the 15/16" grip length doesn't fit through the threads. Wondering if that is why a #8 was used. I will use a ms24693 I think. Or an AN 526

Steve

The AN526C-1032R20 is a countinuous thread #10 screw. http://www.aircraftspruce.com/catalog/hapages/an526.php

Steve, i did forget to mention drilling threads out with #12 drill bit when using AN23-20. Sorry.

Bill, come over on a Sat in about 3-5 weeks, PMH, restaurant on field. I am hoping to have Andy Turner(RV-10) down from PA too. I will let you guys know. HVAC work is finally slowing some. My cell: 606-316-niner,zero,two,zero.

Wayne,
Sounds Great.... Send me an email when you no more
Bill

Below are photos of the pitch servo bracket modification I came up with to prevent the torque arm from swinging loose should the cable break or come off the pulley (I know, the screw is now two short). The nylon does not come in contact with the torque arm.

What nut are you guys using for the AN526C-1032R20 near the forward portion of the servo? The screw just on top of the forward portion where the DB cable plugs into. I can't get a 1032 nut on there as it's too close to the enclosure.

I believe it is an ms21042-3 locking nut. It is the same style as the ones provided by vans to attach the delrin blocks to the doors.

Ditos to David's comments. I too have 400 hours of trouble free service with the standard supplied servo set ups.

Dick Sipp

Just hope you never have to deal with a jammed control......