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Elevator electric trim servo

Mick RV7

Member
I have a T3-12A electric trim servo and spent this afternoon installing it.All was good till I cycled the servo.When I retracted it the leadscrew didn't line up with the 5/8 hole in the E-702 spar.I was confused thinking I mounted it incorrectly so do I make a hole in the spar to accommodate the leadscrew?
 
Can you post a picture? I am not clear on your description but the only thing coming through the rear spar would be the wires to the trim servo.
 
I have a T3-12A electric trim servo and spent this afternoon installing it.All was good till I cycled the servo.When I retracted it the leadscrew didn't line up with the 5/8 hole in the E-702 spar.I was confused thinking I mounted it incorrectly so do I make a hole in the spar to accommodate the leadscrew?

Yes, the servo has a jack screw that extends out the back of the unit. It will extend and retract along with the actuator movement. You need to make sure there is a hole and sufficient clearance for this jack screw to go back and forth. I vaguely remember that the 7 has a hole pre-drilled for this, but I could be wrong. In any event, you want to make sure the hole is there and lines up.
 
Look at Drawing 4 in the lower right corner. You see a label ELECTRIC TRIM EXPLODED ISO VIEW, just to the left of that is a note. The note states "Route servo wires through snap bushing allowing travel for servo jack shaft."

When you mount the trim motor inside the elevator trim section that jack shaft should line up with the existing hole. If it doesn't something isn't quite right.
 
sometimes I would get confused with the drawings up and down ect, the wires go through the spar and the tinny threaded rod will go outside into the airstream pointed towards the trailing edge and attach to the trim tab.
 
Look at Drawing 4 in the lower right corner. You see a label ELECTRIC TRIM EXPLODED ISO VIEW, just to the left of that is a note. The note states "Route servo wires through snap bushing allowing travel for servo jack shaft."

When you mount the trim motor inside the elevator trim section that jack shaft should line up with the existing hole. If it doesn't something isn't quite right.

+1 on this. Look at the close up drawing and read the instruction and you should be fine. The jack screw has to have a place to go when fully retracted.

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Wire routing

I haven't finalized the route of the wiring yet, and instinctively don't like the suggested routing on the plans where the wires share the same hole as the jack screw. Has anyone else thought this and done something different or am I worrying about nothing as usual?
 
I haven't finalized the route of the wiring yet, and instinctively don't like the suggested routing on the plans where the wires share the same hole as the jack screw. Has anyone else thought this and done something different or am I worrying about nothing as usual?

Same here, I didn't like sharing the pass-through with the jack screw, so I put a new hole in the spar & snap bushing just inboard of existing jack screw hole. I centered it in the most outboard elevator horn "lightening hole", so I don't have any concerns personally with an additional hole since the horn acts as a big, strong doubler. This way my wiring is no where near the jack screw during any operation. I can dig up a picture when I get home if you like!
 
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Same here, I didn't like sharing the pass-through with the jack screw, so I put a new hole in the spar & snap bushing just inboard of existing jack screw hole. I centered it in the most outboard elevator horn "lightening hole", so I don't have any concerns personally with an additional hole since the horn acts as a big, strong doubler. This way my wiring is no where near the jack screw during any operation. I can dig up a picture when I get home if you like!
I did the same...I was worried that jack screw would chafe the wiring.
 
G'Day, Mick,
If you look closely at the drawing (Larco posted), the hole that the jackscrew is supposed to go through in the elevator spar is pre-punched and is in the lower half of the spar. It is possible to build the elevator skeleton using the spars with the hole in the upward half. I made this mistake and thankfully caught it before I riveted on the skins. I had to disassemble the skeletons and re-build them flipping the spars so they would be used in the opposite elevators. That caused the hole to be in the lower side, and the jackscrew goes right through the center. Best regards,
 
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