New! Twincam elliptical Madstab pulleys
Now this is exciting! Vincent “Prop-er” of RCPlans.nl has come up with a really innovative solution to the biggest problem facing the increasingly popular “Madstab” 180° rotation full flying elevator: resolution.
The typical Madstab uses a pushrod, pull-pull or pulley arrangement to translate 60° of servo movement into 180°+ of elevator travel. This “crazy” amount of elevator travel is absolutely mandatory for us to be able to successfully pull off tight Madflight flips in the style of Benoit Paysant-Le Roux.
The problem is that we give up a significant amount of elevator resolution for normal flight because of the mechanics of the system. It is a double edged sword and even though dual rates and exponential can help tame it, you still wind up with a fairly imprecise elevator response, making the planes very pitchy in normal flight and harder to fly smoothly.
Hopefully Vincent’s solution, incoporating elliptical pulleys, is the answer to our needs! Based on what I’m seeing above, we should be able to get the majority of exponential required from the mechanical arrangement of the pulleys. This will allow a significantly increased amount of elevator precision around “center stick”, where the vast majority of flying is done, while still giving us a huge rotation when desired.
Vincent has provided the following details:
Relative rotation
| servo | stab |
|---|---|
| 0° | 0° |
| 10° | 5° |
| 20° | 10° |
| 30° | 25° |
| 40° | 40° |
| 50° | 75° |
| 55° | 100° |
Notes:
- Servo cam: Ellipse height 20mm, ellipse width 4mm. (ellipse ratio 0.2)
- Stab cam: Ellipse height 10mm, ellipse width 3mm. (ellipse ratio 0.3)
- Both cams hinged right in the center
- The cam on the tail needs a rounded bottom, as shown in the pics.
I’m very excited by these prospects and can’t wait to test them! If it works out, it will mark a very significant turning point, and make this kind of flying even more accessible.
