Idler Gear - DIY Project
How to make an idler gear for your follow focus.
Having worked with both cinema glass and SLR glass on the RED and getting great results from the SLR glass, I have decided to see if I can adapt the Redrock follow focus to work in a cine-standard with the Zeiss ZF SLR glass that I have. Currently, the Nikon SLRs rotate backwards from the cinema standard. If you do not know any different, then it is not a big deal. But if you have already trained with cinema lenses, or want to get used to using cinema lenses, then this is a big problem.
After doing some research on how to solve this problem I found two solutions: 1. Have the lenses rehoused to the cinema standard, costing thousands of dollars or 2. Add an idler gear to the follow focus, many idler gears sell for well below $200. If I was going to spend multiple thousands of dollars to have the SLR lenses rehoused, I’d rather just buy the cinema lenses. But as that is currently out of the question, I opted to look into the idler gear. As of this writing, Redrock does not offer an idler gear for their follow focus, and the other ones on the market are not compatible with their follow focus. so, I decided to build my own idler gear using some extra parts from Redrock, and some supplies from Home Depot. In the end the idler gear cost me $4.76, and an afternoon of my time. Which is a considerable savings in my opinion.
Before I get started explaining how to build your own idler gear for the Redrock Follow Focus, first off I thought I’d explain what an idler gear is and does for those of you who are wondering. An idler gear is an additional gear that sits in-between the follow focus gear and the lens gear. It is a free spinning gear that when introduced to the follow focus, reverses the direction of the rotation of the lens with the follow focus. The idler gear has to accomplish two things in order to work correctly: 1. It has to be free spinning, and 2. it has to introduce no additional play or slop into the system.
Now on to building the idler gear....
To build your own idler gear for the Redrock Micro Follow focus, you will need the following tools, and supplies.
Tools:
- Tin Snips
- Drill w/ Metal Drill Bits (At least one of the bits has to be able to drill a hole for a 6-32 screw)
Supplies:
From Home Depot-
-Post Base: $3.78 (Part# 707392228301)
-6-32 x 1.5" Screws & Nuts (6 pack): $0.98 (Part# 030699283514)
From Redrock-
Extra drive gear
Extra drive box
(You'll have to talk with Brian at RR to see about pricing on these)
To build the mount for the idler gear, see the schematic to see where you will be cutting, and what the final piece should look like. With each Post Base, you will be able to make two mounts, so if you mess up on the first, you have a back up to play with.
INSTRUCTIONS:
Disassemble the RR drive box, you will now have two shafts, each with a small black gear on the end.
Cut down the post base according to the schematic.
When cutting the post base, make sure to cut around the big hole in the plate, as this will be where you will mount the drive shaft & gear. If you mess up do not worry, you can use the other half of the plate, as there are two holes.
In the bottom of the plate drill two holes for the screw to fit through. It is VERY important to get these holes to line up correctly, as if they are off, it will cause wobble in the idler gear, which is a BIG NO-NO. I used the plate of the follow focus to mark exactly where I needed to drill. Before proceeding on, assemble the unit with the plate to see if you have any wobble once everything is attached. If you do, then you need to remake this plate. If not you can proceed to the next step.
Once you have verified that there is no wobble, mount the drive shaft in the big hole. It will be a VERY tight fit, but if you mount it with the small black gear end in, first, then it will fit. If you try the reverse, it will not work. When you are mounting the drive shaft, make sure to un-mount the extra drive gear. (The big black gear.) To get the drive shaft to snap into place, you may need to lightly tap it into place using a screw driver and a hammer. Make sure to tap on the outer casing of the shaft and not on any of the moving parts.
Once the gear is in the mount, reassemble everything in the following order. (Except use the 1.5" screws instead. the head of the screw will need to mount in the upwards direction.) Base plate - idler gear plate - extra nuts - original gearbox with plates & cover - final locking nuts. (The extra nuts are to raise the gear box into place so that the gears interlock securely with the idler gear. You may need to add one or more extra nuts depending on your setup.)
Lastly, attach the extra drive gear to the shaft and you are ready to go.
Cheers,
Ryan E. Walters, Cinematographer
FINAL - SIDE VIEW
FINAL - BOTTOM VIEW
FINAL - EXTRA NUT (In-between plate & gear box.)
FINAL - TOP VIEW