The servo is dismounted as for a full rotation pan servo. It is possible to remove the potentiometer outside and set it on the tilt pivot.
On a normal 35x40x20mm servo, next to the motor, there is enough space to drill a hole Ø2mm. It must be exactly perpendicular. Then, insert a Ø2mm rod, 25mm long, screwed at each end, and fix it on the cradle.
On the outside spindle of the servo the hole for the screw is re-tapped for a normal Ø3mm screw. It will maintain the worm.
On the tilt pivot, fix a cog-wheel. Donít forget the spiral spring between the servo and the rig, which holds tight the worm to the cog-wheel.
Iím using cog-wheels Ø32mm with 30 cogs or Ø40mm with 40 cogs, both 6mm width. The worm screw is Ø12mm with archimedean shape, 4mm step.


  Old facts

Having rigs with video control (even if it usually donít work well), I was not satisfied with the tilt movement. It was set as direct drive on the tilt servo, and I found it was too sudden and not enough precise.
Since years I had the idea to change it for a worm system. On my portrait-frame rig I have experienced a cog-wheel with a 1:2 ratio which I found as short  improvement.
End of 1998, after some unsatisfying sessions of KAP, I was determined to action and to mount the worm screw that I had purchased years ago. So I designed and re-designed until I got a simple and easy installation giving the efficiency I was expecting.
I have now mounted about a dozen on different rigs, including frame change and with mini-servos. After so many seasons using them I can guarantee it is the best tilt system I ever used.

This is gear-wheels Ø32 with 30 teeth, and Ø40 with 40 teeth, both 6mm thick. the cog-wheel is Ø12mm with a 4mm step.
With longer cog-wheel, enlarge the hole at one end to fit tight over the servo gear.