In using two servo's for split elevators, does it make any difference if the pushrod's cross each other or does each need to remain on it's own side of the fuse? Bud...

makes no diffrence as long as you dont confuse your self on seting up which servo does which, just make sure the rods dont wobble and knock each other and that your throws are exact on each side, or you'll roll on pitch slightly.

If using metal pushrods, try to avoid contact between the two rods!

Wouldn't you have to keep the rods the same length in order to have a linear movement on the controls?

It's not the length of the rods that matters. It is the angles formed by the clevis and horn (and the servo wheel at the other end) Have a look at some of these and instead of wheels think control surfaces.

http://users.ids.net/~bdfelice/ackerman.html

http://www.muller.net/mullermachine/docs/ackerman.html

http://www.rctek.com/handling/ackerm...principle.html

Interesting articles Flatfour.
Mike

The main reason people cross over the pushrods or pull-pull cables going to the tail is so that the pushrods exit the fuse at a steeper angle. If you don't do this, you have to either cut an extremely long slot in the fuse where the rod exits, or you have to put an offset bend in the pushrod, which weakens it. The slight increase away from perpendicular between the pushrod and control surface is insignificant.

Mk also makes a very nice gadget for pattern people. It attaches to the rear fuselage, with the single pushrod mounted internally, and eliminates all elevator differential. (ball bearings, too.) Here's a photo. You can get 'em at Central Hobbies or Falcon Hobbies.

I have recently been the culprit of ackerman. When setting up my rudder pull/pull I could not get my control horns right on center of the hinge line due to some interference on the end of my fuse. I overcame this setback by compensating at the servo wheel. Measure how far your control horn hookup is set back from the center of the hinge. Then measure back that same distance fromt the center of your servo wheel and drill holes for the hookups at the servo negating the Ackerman effect. Saved me a big headache in hooking up my rudder.