Elevator trim mechanism

[pantherpilot]

Can you send me the drawings of yours? I would also like to see how that is accomplished, Thanks

 

[Chopndrag]

With mine? It's just the aeroconversion trim

 

[Elviar]

I used a 90 degree drill adapter to turn a screw that moves the front of the horizontal stabilizer. A small crank at the pilot seat also indicates position. After flight, the labels will indicate takeoff and cruise positions.

 

[Chopndrag]

Did just a regular trim tab. 5 inches x 18 inches works pretty **** good

 

[Bil4381]

Congrats it looks great to me
BilE

 

[Chopndrag]

Congrats it looks great to me
BilE

Thanks, still have to do some adjustments but works good. The video was my daughter and I doing a run spreading my dad's ashes. Tab adjustments were pretty decent keeping both of us level.

 

[Val_895]

I used a 90 degree drill adapter to turn a screw that moves the front of the horizontal stabilizer. A small crank at the pilot seat also indicates position. After flight, the labels will indicate takeoff and cruise positions.

Ok you have my attention. This looks light and elegant. I was starting to assemble an electric trim but I like this. Do you have photos of the rest? Thx

 

[Elviar]

There are a number of ways you can go with this. Your design may vary. I removed the extension on the DeWalt drill adapter and installed the gear mechanism in a housing that bolts to the rear fuselage structure. The front tube of the horizontal stabilizer passes through the tube assembly at the top, which contains a threaded insert. Max travel of the horizontal stabilizer is less than one inch, and pilot reports say very little of the travel is used in actual practice. I used a 5/16 tube to extend from the crank at the pilot seat to the trim mechanism, with a nylon support bushing mid way. It hasn't flown yet, and It takes a little welding and a bit of machining, but it works great in the garage!

 

[Elviar]

More on my horizontal stabilizer trim.... There are a number of 90 degree and 110 degree drive adapters on the market. You may find one that is more appropriate for your installation. I'll attach an exploded view of my mechanism, and a shot of what you'll find inside a typical 90 degree drive adapter. I bought several to check them out, and decided on the DeWalt for my project. (This shot is not the DeWalt design. but typical)

 

[Val_895]

More on my horizontal stabilizer trim.... There are a number of 90 degree and 110 degree drive adapters on the market. You may find one that is more appropriate for your installation. I'll attach an exploded view of my mechanism, and a shot of what you'll find inside a typical 90 degree drive adapter. I bought several to check them out, and decided on the DeWalt for my project. (This shot is not the DeWalt design. but typical)

Thank you for the response! I love the idea here. It is definitely lighter than what I had in mind. The electronic trim is a bit tail heavy as the actuator is in the back but doable I think with out removing fabric. But this gives me ideas that a mechanical maybe still a possibility as well. Thanks!

 

[Val_895]

Thank you for the response! I love the idea here. It is definitely lighter than what I had in mind. The electronic trim is a bit tail heavy as the actuator is in the back but doable I think with out removing fabric. But this gives me ideas that a mechanical maybe still a possibility as well. Thanks!

And brilliant using the 90’. I’ve used them for work and have pounded on them for years with only occasionally breaking one under unreasonable loads far excessive for what we would be using.

 

[Chopndrag]

I went with the kiss theory. Less weight and less to go wrong. One lever cable and hinge. Done

 

[Bil4381]

I went with the kiss theory. Less weight and less to go wrong. One lever cable and hinge. Done

My S2 came with that. The tab was say 3" x 12". i did it (stab trim)and its flying.

 

[Elviar]

My only issue with trim tabs is that they add drag by compensating for the less than optimum angle of attack of the horizontal stabilizer. The external linkage in the slipstream also adds drag. But for some builders this is not a big concern. It a matter of personal preference.

 

[Chucker]

I used a jackscrew system. The screw has left and right threads and mounts between the horizontal stab and the leading edge of the vertical stab. It is driven by a pulley with a beaded cable. The beads provide positive engagement and trim indications in the cockpit.

This system weighs less than the original solid stab adjustment system.

If I had it to do over, I would allow the upper attach point to pivot. As is, it took a little work to get the jackscrew to run as smoothly as I liked.

https://www.sonerai.net/media/albums/trim-system.569/

 

[Wayne Byal]

what size beaded cable and where do you get pullys

 

[Chopndrag]

Yeah I would've done the jack screw set up but I do not have the stuff to do it with at all. I am limited on everything and being that I'm a welder it was easier to just make the tab for me.

 

[Chucker]

what size beaded cable and where do you get pullys

My beads are 4.5mm. The size is not as important as the ultimate strength. I believe mine had a 60 pound breaking strength. I am confident that I can not break the cord using my thumb and forefinger.

The cords come as corded plastic beads as well as stainless steel linked beads. Shop around for the breaking strength you desire/require. There is very little stress on the cord (less than raising my household blinds) but you obviously want a large margin of safety.

The pulley was a simple phenolic version from Aircraft Spruce. I laid out a pattern and drilled indentations around the circumference. The cockpit pulley has no indentations...I adjust the trim by grasping the beaded cord and moving it in one direction or another. My intention is to paint a section of the cord to indicate a safe takeoff trim range. I don't see a need for any more precision than that.