Rich posted some great stuff about follow focus ring gears for those who have a 3D printer or access to a 3D printer. But for those like me who don’t have either, I found another less elegant but functional solution to making your own follow focus ring gears.
All that you need to make your own ring gears is to buy some cheap follow focus ring gears like this (I got several of these last year for around AU$2 each, delivered), some gimbals etc also come with suitable ring gears to do this mod:
You cut off the handle and then place the ring gear on the lens, holding it tightly and noting where the teeth match up. Using a very sharp knife, my Buck knife works a treat, cut the ring so that when joined, they make up a proper ring. Then get some plastic glue, the two part type that has a tube of primer and a tube of superglue (cyanoacrylate), prime both ends and with a dob of superglue applied, lay the ring gear flat on a flat surface and bring the ends together. Hold tightly for a few seconds and you have a perfect ring gear to put over the lens. Any excess glue can be scraped off (don’t apply on a surface that you don’t want superglue leftovers).
It’s important that you stretch the ring gear when measuring, as it’s easy to make it too loose, but if you do, there’s a good chance that all you will need to do is break the join, cut off a little more and re-glue. The join is very strong and will not break when on the lens and, even if you need to force it over the lens, it’s unlikely to break the join. I’ve made a number of these after I bought a coupe of 3D printed ones off eBay and they have worked perfectly. It’s just a pity that they don’t come in a slightly wider aspect, as then they would be absolutely perfect.
I made one for my zoom lens after buying a 3D printed one (the 3D printed one is on the right) and I’ve used the follow focus motor with both gears and they work fine. If I could get another follow focus motor, I’d have one for focus and one for zoom, but with all things Tilta, finding parts is often not an option.
The other use I found for this method was to make the Tilta follow focus control a bit more manageable. I found the wooden hand control to be less than precise for fine movement and would have much preferred a rubber surface that allowed finger tip control. So I decided to make a ring gear for the control wheel and it works a treat.
My concern with the 3D printed ones is whether they are a good fit, mine luckily were and it helped that one lens had an all metal barrel. With the one that had a rubber focus/zoom ring, it was a lot harder to put into place as the rubber wanted to move as well. if it were possible to buy this 0.8 mod gear ring material in long strips and slightly thinner material, like you can with 3D printer belts, I’d get a couple of metres and redo some of the rings.