Hey, I love it when it works.

bgi, You planning on going to Perry in March?

Robert,

Thanks for the info on the bellcrank. I have two problems:
1) When I invert the outer arms so that they're opposite the inner arm, they don't line up perfectly. One will be vertical while the other one is a few degress off from vertical. Swapping them out left/right changes the amount they mis-match. It's not bad, but at extreme throws, it puts the elevator halves off a bit. I may put the center arm down. It looks like it would work OK.
2) The holes in the bellcrank arms are too large for a standard clevis. The DuBro clevises I used jiggle a bit when they're on the MK arms. I'll look for some MK clevices or extend the arms like you did.

You have to be sure your servo throw dosn't go too far with one of these or your bellcrank will go past 90 degrees. Then you have a toasted plane.

Yes, I plan to go to the Perry swap meet. I may bring a Cub to sell. It's being a PITA - doesn't want to take off. It prefers to do a right ground loop. I'll work on it a bit to see if I can get it to behave. I'm running out of room...

On an off-topic note, someone trashed the grass at the GMA field last night. I spent 30 minutes this morning dragging a chain link fence section around smoothing it up. They made a real mess slinging grass and mud all over the place.

-brad

bgi,
I 'll try to address your concerns with what I have learned doing my setup.

1. Mis-alignment - The socket and shaft for the two outer arms are square. You can orientate them at any of the 90 degree positions relative to the center arm. With them being square I don't see how they can mis-align unless one is defective. You may want to swap your Bell Crank for a replacement. You will notice some loose play in the opposite arms until you tighten the long screw that holds them together. If the center arm being down does not interfere with your Rudder cables, then go for it.

2. Holes and Clevis. At the Bell crank end I used 4-40 rods with Z bend. I drilled the holes out just enough for a VERY snug fit on the rod. ZERO play, and one less piece of hardware to adjust.

3. Over-throw. - With the short standard arms you have to move the end point further to get sufficient elevator movement. That is why I extended the arms. I used a heavy duty Dubro arm on the servo. I also used a heavy duty Dubro control horn on the elevator with clevis in the bottom hole. I cut the rest of the horn off. Look very closely at the end point travel marks in my picture referenced in the thread above. Arms only travel 30 degrees from center, do not even approach over-throw. With this setup my servo is set for 100% end point, and I still get 65 degrees elevator deflection. I use an HS 5945 servo at 133 oz torque which is more than enough.

Sorry to hear about the GMA field. I have never flown there, but have it on my list of places to visit. I hear there are some really good Aerobatic pilots there. I'll take all the advice and help I can get.

I plan to be at Perry also. Maybe we'll see each other.

Robert,

1) This MK bellcrank is different. The arms have round posts which have two flat spots ground on them. So they only fit one way or turned 180 degress. Hmmm...

2) I've tried my Z-bend pliers on a 4-40 rods before and didn't get good results. The wire is so thick it doesn't leave much room for the arm. DuBro Ball Links fit very snugly. I'll just use those.

3) Not having the extensions to the bellcrank arms (concious decision so far) and not sure I want to setup for 3D yet, I was playing around with it on the bench to see how the 5245 centers at extreme throws. That's when I noticed the way you could get into real trouble with overthrow.

I got the DuBro dual elevator arms and drilled some new holes for the 4-40 screw much closer to the hinge line. It's a lot better than Lanier's pre-installed hardwood hole which was a good 1" back from the hinge line.

I'll post some pics.

Anyhoo, I'll get it right soon. Thanks for the help!