Some of the boys have been kicking around a Focus Wheel concept for the HV20 elsewhere on the web. I picked up on it and while perusing through Toy R Us found a K'nex building kit that had a promising wheel in it. (K'Nex 4x speeders #3)

This prototype is just attached with velcro, and the rubber wheel lays right on the tine focusing roller. You can actually use your finger on the wheel just like it is a 35mm lens and it I am surprised how easy it works-- even with this rigged system. With just a little work, it could even look professional. See photos below, but forgive focus issues...

i had been thinking about doing something kind of like this and you just proved it's feasibility. this looks brilliant. 4 bucks gets you a completely usable focus wheel, and i already have probably around 5 kajillion knex pieces from many, many moons ago tucked in a closet somewhere... time to start searching.

does it grip the little focus-cylinder well enough, like, is there any slipping?

i had been thinking about doing something kind of like this and you just proved it's feasibility. this looks brilliant. 4 bucks gets you a completely usable focus wheel, and i already have probably around 5 kajillion knex pieces from many, many moons ago tucked in a closet somewhere... time to start searching.

does it grip the little focus-cylinder well enough, like, is there any slipping?

THe serrations on the focus wheel and nobby tires actually fibrated a bit, so I since reversed the tire giving it a smoother surface, and it worked fine.

/!\ OT Alert: Chris, what's that mean-looking lens-and-ring-thing you got attached there? A wide-angle setup? (looking for something with not too much barrel distortion). Thanks, Pieter

Pieter, just a $5.00 collapsable rubber lens shade I got of Ebay....