This past summer a number of slope fanatics successfully recreated the famous "Mad" elevator setup popularized a decade ago by Benoit Paysant-Le Roux (AKA BPLR) one of the world’s greatest R/C pilots and progenitor of the Madslide 3D glider. (see video below).

BPLR Madslide 3Dglider (1 min 53 sec)

The most obvious element of a Mad elevator is the extreme throw: 75° to 90° each way... and you need all of that if you want to do flips. BPLR used full-flying stab with a pull-pull system, similar to what is used on powered 3D craft, to get the large elevator throws. Others, myself included, have experimented with push-pull setups, similar to what we see on indoor 3D planes. Both these systems work well; but have their problems as you reach 180° of total throw (you want to do flips upright and inverted... right?). Geometry starts to work against you at the extreme ends of the throw.

I recently started experimenting with pulleys to see if I could get the full 180° of rotation (or more )... without any binding or slack issues. The pulleys have an even pull at any rotation AND it doesn't matter that one pulley is larger than the other. This second point is important since most servos only rotate 90° to 120°.

I started out by computing the size of the pulleys. I wanted 180° or elevator rotation from my 120° of servo rotation. A little geometry helped be figure that the servo pulley radius had to be 1.5 times the size of the elevator pulley. (180°/120°=1.5)...Continue Reading