Quote Originally Posted by richard littlewood View Post
Had to reverse the helical inner part and make a new inner sliding 'keyway' arrangement, but on the whole it was pretty easy and works well.
I had to cut away the part which holds the slider tab which runs in the slide groove so to prevent it turning there will be a bracket which locates on an 1/8" steel pin at the bottom of the lens.

I will post some pictures when I get the helix back.