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TruTrack stops

LettersFromFlyoverCountry

LettersFromFlyoverCountry

Well Known Member
I've had the Digitrack for the right wing for about 6 years, but with the wings being mounted, I'm just getting around to final installation. And, because I've had it so long, god only knows where all the parts are.

According to the TruTrack Digitrack installation guide:

To protect against this mechanical stops are supplied with the servos. These stops are drilled so that they can be mounted at different angles as required (18? intervals).
In addition to the proper use of the stop it is important to know the amount of travel on the primary control that
the servo can handle. With the push rod connected to the outermost hole (1 ??) the travel on the primary cannot
exceed 2 ??, the intermediate hole 2 1/16?, and the inner hole 1 5/8?.
It is important to note that the servo travel should be very nearly the same in both directions

I'm looking for an image or something of the servo that includes an image of what the stops look like that are to be installed, because I have no idea what the instructions are referring to.
 
If these are the same as Dynon ( I suspect they are - the installation verbage matches almost exactly that from the Dynon package), they'll look something like this (via GIS) :

CIMG1401.JPG
 
Hmm. I got nothing like that with the unti when I bought it. I'm kinda wondering if there were stops for the unit when I bought it?

You around on Sunday? I gotta hoist the right wing up for fitting.
 
I believe that TruTrak depends on the Vans stops

I put in my TruTrak servos 3-4 years ago, and may be off on this, but I believe that TruTrak depends on the control stops that are built into the RV-9. Likely the same on the RV-7.
 
Bob Collins said:
Hmm. I got nothing like that with the unti when I bought it. I'm kinda wondering if there were stops for the unit when I bought it?

You around on Sunday? I gotta hoist the right wing up for fitting.
Click to expand...

They're optional on the Dynon, so I'd have to think they'd be optional on the TruTrak as well as Duane points out above.

I'll be out at the airport around from 1:30pm or so until around 7:30 - I'll stop by your hangar on the way in.
 
Cool. I'll be out for a little bit between 12 and 2. Son is bringing some friends over for a b-day party this afternoon (notthing like a party in the rain; maybe I should've suggested we move it to the hangar.)
 
Bob,

The TruTrak does not have stops like the pic of the Dynon.

It uses the control surface stops and the the TruTrak will
be "inside" of these limits.
Then you use the holes to make the travel right.

And you do have to have your
control surfaces mounted and hitting limits BEFORE you
try to hook up the servo arms. At least that is what I
did and seemed to work.

I hope this helps out.
 
Bruce said:
Bob,

The TruTrak does not have stops like the pic of the Dynon.

It uses the control surface stops and the the TruTrak will
be "inside" of these limits.
Then you use the holes to make the travel right.

And you do have to have your
control surfaces mounted and hitting limits BEFORE you
try to hook up the servo arms. At least that is what I
did and seemed to work.

I hope this helps out.
Click to expand...

And mine is the same. I wouldn't want stops on the TruTrak servo.

L.Adamson --- RV6A
 
Bruce said:
Bob,

The TruTrak does not have stops like the pic of the Dynon.

It uses the control surface stops and the the TruTrak will
be "inside" of these limits.
Then you use the holes to make the travel right.

And you do have to have your
control surfaces mounted and hitting limits BEFORE you
try to hook up the servo arms. At least that is what I
did and seemed to work.

I hope this helps out.
Click to expand...

The Dynon is the same way, actually - they provide the stops as optional insurance. I do not have the stops installed for my Dynon servos; they hit the control surface stops way before they get close to going over center and thus the supplied stops aren't needed.
 
Both of the TruTrak autopilots I've installed came with stops exactly like the one pictured (although not black). These are for safety.

If, for example, a builder attached the autopilot pushrod to the flight pushrod using an Adel clamp and the clamp were to slip a bit, then without the stops the AP could conceivably rotate to a position where movement of the control surface was impossible. If power were to then fail, the pilot would not be able to regain control surface deflection unless they had sufficient leverage to overcome the stuck Adel clamp.

If your servos did not come with the stops, TruTrak will send them to you. Installation is up to the builder; there are in fact circumstances where you might reasonably choose not to install them.
 
I find this thread interesting enough that I went back to the installation drawings and guides for the four TT servos I've installed - two in the -6, and two in the -8. None of the four servos (with install kits) came with stops. And none of the installation drawings for those four applications show stops.

But....lookign at the installation instructions for the Digitrack, I find:

It is important to note that at the neutral point of the control the SERVO ARM must be PERPENDICULAR to the push rod, and that the stop must be mounted so as to limit travel as near as possible to equal amounts in both directions. In certain factory-designed installations there may be well-proven exceptions.
There will be installations in which space does not permit the use of the stop. When this is done the aircraft’s primary control stops must be positive and care must be taken to be sure that at the neutral point the servo arm is perpendicular to the push rod, and that the travel limits of the servo arm are not exceeded.

So I have never been worried not to have stops on the servos - and I am somewhat surprised that I have never seen them - the picture in the earlier post of the Dynon stops is the first I've ever seen. Curious. (The travel on our servos is so small that the control surface stops are reached with pretty small arcs of the servo arm.)

This would be an interesting question to post on the Tru Trak forums Bob - I'd like to see Lucas' opinion/answer!

Paul
 
We supply servos stops with the kits that we feel REQUIRE them. Most of the RV install kits will hit the control surface stops long before the servo arm could get into an overcenter condition. However, I will be happy to send a stop kit to anyone who wants one for the simple cost of freight. Thanks!
 
Just to throw our comment in here, the stop bracket we sell is never meant, in any install, to be the normal stop that a control surface uses. In normal operation, it should never be touched. Positive stops at the control surfaces should always be the primary.

We include the stop with every servo because we feel it's an important safety item. If the pushrod going from the servo was to bend or slip, the stops will prevent the travel of the servo to an angle that can be over center.

It's very much a backup to a backup. Since our servos know their position, even a servo 100% disconnected from anything should not move to the stop. But it's not just the servo driving itself over center, it's possible to get a servo over center even if has no power at all. So the bracket is a light and simple safety item that we like to see them in all installs unless they cause an issue.
 
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