Ram Air Servo

Sometimes it's fun to overly complicate things just to have cool buttons to press!  This was the case with the actuating function of the Ram Air.  The kit comes with a bowden cable you can run to your panel.  I'm sure that works great but I felt I really needed more buttons to push in flight so I pushed forward looking for a solution.

The switch requirements are the same as my cowl flaps as it requires just swapping of polarity to extend and retract the actuator. The actuator itself is a L12 Linear Actuator 30mm 50:1 12v. 30mm is the throw and the lowest it can be.  I did some measuring and it seemed to me that would work fine. 50:1 is the gear ratio that is essentially the force to open and close.  I'm going with this one first and if in flight I find it needs more force for whatever reason I can replace with a 100:1 or more.  wiring that swaps polarity between the two switch positions.  Since I resolved that with the cowl flaps that was the easiest component to this.

My dilemma was trying to figure out how to work the actuator arm on the canister in a somewhat cramped space, which running the arm the full throw of the servo. I tried various things such as replacement arms, changed brackets and even remotely mounting the servo somewhere else.  The only other person I talked to who had done this mounted his servo in the tunnel and ran the bowden cable there.  If I end up with heat issues I may have to go back and do that.  But for now I tried to do a self contained unit.  I won't bore you with my trail and tribulations so here's what I ended up with.

Canister prep was basically attaching a small piece of bowden cable and adel clip.  I expieremented on different holes and in different orientations.  What I found worked the best and didn't interfere with anything was to position the arm for a downward movement, run the bowden cable down and to the side to allow me to mount the servo on the bottom of the unit.  Far from the engine, exhaust and other heat elements.

Then I made a bracket to mount onto the canister that would allow the actuator enough space to move a very small piece of bowden cable.  It's about 3 inches wide and hand formed to the curve of the radius of the canister.  I then drilled 2 holes down the center, with the mounted point to match an existing canister hole.  Then I spaced to additional holes an equal amount apart.  Lastly I put some foil tape on the back to help as much as I could with heat.

 I did a test run and found the actuator pushed up vs pushing the cable.  The actuator came with two little clamps, having no idea what they were used for I just ignored.  Then it occurred to me that these are to mount the actuator so it wouldn't move. Fortunately me I happened to space the two hole out in just the right spot that these could be attached to the bracket screws.

I re-purposed some connecting hardware meant for the carb heat (Which I don't have) as well as safety wired everything up.  I mounted the unit fairly painlessly and used a molex connector for the wiring.  Checked the cowl spacing and gave it a quick test. As you can see in the video it works well.  It doesn't close as much as I would like, however I'm not overly concerned with anything getting through that space.  If it poses a problem I can upgrade the servo to a 100:1 or more to get something with a bit more pull/push strength.  I'm going to wait though to see if heat becomes an issue as well before I do anything like that.