Background

General-purpose focus gears sold for photographic lenses are not so good, assuming that they will be used in the actual field, because the gears slip and the remaining parts are caught on the rig.

On the other hand, the fully customizable and already-built gears such as  https://followfocusgears.com/ are very expensive.

So, I tried to make it myself using https://github.com/jaymis/lens-gear-follow-focus, but this time the Leica R lens that I am going to use is made of a metal focus ring When I tried to fix it firmly, I had to make it quite tight, but while I made several prototypes, I felt like I was damaging the lens.

So I decided to design a customizable gear that could be tightened with screws.

Parameters

Because I wanted to be able to fully customize it, the number of parameters becomes relatively large. Therefore, it is not necessary to read the generated STL again with DesignSpark Mechanical, fine-tune it, and follow it.

In fact, it may be easier to see the figure.

NUMBER_OF_TEETH

The number of gear teeth for one lap. Note that the number of teeth is actually increased because a cut is made to tighten the screw.

GEAR_OUTER_THICKNESS

Outer gear thickness (axial length).

GEAR_INNER_THICKNESS

Inner gear thickness (axial length).

INNER_DIAMETER

The diameter of the inner hole. The outer diameter of the lens.

GEAR_RADIAL_THICKNESS

The radial thickness of the gear part. If it is thinned, the entire gear is easily bent when tightened with screws. When it is thick, it becomes difficult to bend.

SPRING_THICKNESS

The thickness of the spring mechanism on the inner plane. It should be a multiple of the nozzle diameter of the printer used.

SCREW_TIP_LENGTH

The length of the tab protruding for the screw hole.

SCREW_TIP_THICKNESS

The thickness of the tab that protrudes for the screw hole.

SCREW_HOLE_DIAMETER

Screw hole diameter.

SCREW_HOLE_OFFSET

Screw hole location. Distance from the outermost edge of the tab that popped out.

SCREW_TIP_GAP

The distance between the tab protruding from the screw hole and the gap between the tabs.

Thingiverse Customizer

https://www.thingiverse.com/thing:3926801

For the old lenses such as the anamorphic lenses, it’s hard to find the lens cap with exact size. But for now, with this customizer thing, the problem was solved.

Parameters

INNER_DIAMETER

The outer diameter of the lens. Consider the torelance of the 3d printer you use.

INNER_HEIGHT

Height to slip-on against the lens.

THICKNESS

Thickness of this cap. Same value for all part. This value becomes the radius for rounding the internal wings.

INNER_OFFSET

The length of the internal six wings. Must be larger than THICKNESS

Thingiverse Customizer

https://www.thingiverse.com/thing:3924676

Click ‘Open in Customizer’ on the right side, then enter the parameters.

Example

A real-world example is here:

• Rapido V3 Clamp Rear Cap

If the taking lens go wider, the vignette becomes serious issue. To solve this issue, we must place the anamorphic lens as close as possible to taking lens.

Parts list

Rapido V3 Clamp

• https://www.rapidotechnology.com/

Redstan Classic Original Custom Anamorphic Lens Clamp

EDIT: This is not the “Classic Original Anamorphic Lens Clamp”. Thanks to stan for pointing out on this blog. And thanks to Mikkel Bøje for pointing out on youtube.

I asked the original owner of this clamp about the exact name, and he said: “I sent him(Redstan) pictures of the Kowa and he simply said he had what I needed and referenced it as a ‘2 part adaptor in black'”. So if the others like me try to buy the same thing, it’s better to tell Redstan our requirements first before buying.
It should have

• The 52mm inner thread for Kowa 8z/16h.
• The 55mm outer thread.

But as commented below, Redstan makes different and better clamps these days. I just want to share the idea.

Stepdown ring: 67mm to 55mm

3d printed shim ring (detailed below)

Structure of the Rapido V3 Clamp

Confirm the structure of the Rapido V3 Clamp, the gap between Inner Ring and Rear 77mm Adapter is narrow enough. The paper cannot slip into the gap.

Combine the Rapido V3 Clamp and the Redstan

Combining the Rapido V3 Clamp and the Redstan’s inner part (M55 threaded) with a step-down ring, the anamorphic lens could not be tightened.

Tightened with 3d printed shim ring

To be tightened securely, I need to insert something like a shim ring between the Redstan’s inner part and the step-down ring.

The measured size is the following:

• thickness: 10.5ｍｍ
• Inner diameter: 55.5ｍｍ

There’s no size in the market, so I designed the 3d model and printed by 3d printer.

Rapido V3 Clamp Shim Ring

3d model on Thingiverse.

How to Assemble the Rapido V3 Clamp Shim Ring

Final Shape

Rapid Technology V3 Clamp could be found here:
https://www.rapidotechnology.com

Customizable Slip-On Lens Cap

Here is the Thingiverse customizer based on this model.
Fully Customizable Slip-On Lens Cap