Build your own 35mm Follow Focus Gear
 

Quick and painless way to build a 35mm Follow focus gear.

Step #1
go to your local hobby shop and buy a 70mm Helicoptor gear.

Step #2

Clip to fit.

Step #3

Place it on your 35mm lens!

Also, i'm using the Chrosziel 202-16 Focus Gear Drive - Canon 16x Manual Lens.

The gear is available online for purchase here:
http://www2.towerhobbies.com/cgi-bin...&I=LXLBN7&P=FR

I just ordered three. I will post if this is cine-pitch gearing. If it is, I plan on keeping mine. If they aren't, I'll probably sell them.

Where's a good place to buy the gear drive and what is the cost? I searched for Chrosziel 202-16, seems to be 64 euros, is that item number all you need? The full unit was over $1000.

That's the main problem - once you get the gear to go on the lens, you need the gear to turn the lens. Like a chicken in the egg I suppose. Dan was selling one, IndiFocus has one, they just aren't cheap.

Sorry the link was removed, here is the new link:

http://www.dvinfo.net/gallery/browse...3&userid=13126

No, the IndiFocus is cheap, at $299. Dan's follow focus is an entirely different product, and almost twice as much, IIRC.

I don't know what your reasons are for wanting cine-pitch (e.g., maybe you already have a FF with gears that are cine-pitch), but pitch is irrelevant if one uses the same tooth profile on all gears. It won't matter whether your gears are helicopter, cine-pitch, or otherwise. (assuming there's no lash!)

Also, you can simply find out what the pitch is without buying any gears. For that gear for example, you could call or email Helimax.

Im not sure if anybody ever thought of this.. but remember when everyone was trying to find good metal 90 degree gear box. you know, one shaft is 90 degree to the other and they both turn inside a gear box. very important peice for follow focus unit. well the problem was they are made, but they are always really expenisive for a metal one and not plastic.

well...how many people use a drill press in here? then youve probally used a chuck key alot also. and did you know that that key is a 90 degree gear also? and what happens if you take 2 chuck keys, and fit them in a little box holder? you get a 90 degree gear box. and it will cost you about 3 bucks
http://www.lowes.com/lowes/lkn?actio...95302-70-U1533

i thouhght of this a week ago as i was working with my drill press. How easy is this!??

eh, eh? do i get a kiss?

Wow, I wish I'd been following the threads about that because I could have helped give something back to the forums. I know a lot more about mechanical stuff than I do cameras.

Those sorts of gears are called miter gears.

http://www.mcmaster.com/catalog/112/...e/6529kp1l.gif

They are available in plastic (molded nylon usually) for about $2-3 a piece in a variety of shaft diameters, tooth counts, diameters, and so on.

Check out mcmaster.com. You could build everything from a follow focus to a space shuttle from that place. Super inexpensively, too. McMaster Carr is heaven on earth.

Have fun!

thanx Bill that will help people find alot of gear parts.

The problem with the miter gears on their site is that the nylon ones are cheap. but their steel ones are over 20 and going up. that price sucks, and is not as nearly as cheap as the lowes replacement chuck keys. nylon could be fine, but isnt as durable as steel.

I also have a question. its something that i cant seem figure out.

from what i see on most follow focus's is the handle/wheel, (the wheel with the whiteboard attached) that is linked by a shaft which goes into a 90 degree gear box. The shaft that comes out of the box is attached to a smaller sized toothed gear (usually plastic) which interlocks to the SLR lens plastic toothed gear which is about as big as the diametter of the lens. and then you turn your wheel as it simultaniously turns the 35mm lens. since the slr lens gear(helicopter gear in this case) is large compared the the smaller gear that is on the 90 degree box shaft. How is the gear ratio still 1:1. wouldnt you need 2 gears the same size to get a 1:1 ratio.

or is there another gear involved somewhere that i missed. (note, i know that on professional FF's they have an adjustable extension peice that is pulley driven, that way you can swivel your gear back and forth for differnt size lenses. But i assume that pulley driven extender is 1:1 in itself. so i left it out of my question. to keep things simple)

Nylon isn't as durable as steel, nor does it need to be in this application. You won't ever wear out a Nylon gear in a follow focus since Nylon is a hell of a lot stronger than you even need. In a follow focus it will go through a very low number of rotations in its lifetime, at very low pressure, and very low speed.

Nylon is cheaper, lighter, and easier to work with (in case you want to drill a set screw hole, etc) than steel, and these are things you do want in this application.

You are right Bill, that makes alot of sense since steel is a pain to drill or dremel and work with for that matter. thanks

Happy to help!

This place rocks

How's this for a remote-controlled follow focus:

http://www.cameraturret.com/focus.htm

I don't want to put off anyone building a 90 bevel gearbox, but it is tough work. You need to have a way of stabilizing the gears (usually bearings), then you need a pillowblock for the bearings - onto of that, you need to make everything small enough that it is about 1.5 inchs length and width. I did it, and it wasn't worth it after seeing the purchased ones (gear boxes) which are of better strength and alot less time. But if you want to tinker, tinker away, just the product of my experience with trying to build one of these darn thing cheaply, in the end, it wasn't worth it to me.

Oh, by the way, the chuck doesn't have the correct pitch for use in a bevel 90 degree gearing system.

For anyone with cine-pitch follow focus already and doesn't want to shell out 80+ for lens gears, search "32 pitch gear" on ebay. You'll get black plastic hobby gears that fit nicely around lenses.

Check this one:
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=6054876251

hey , about the gear ratio, you do not need to worry if you think twice.
The size of gear between the knob and the gear on the lens is almost irrelevant, if the gear on the lens is same diameter as the knob. All the rest in between is just direct drive with no speed reduction.

I don;t know if that is entirely true. I was looking a couple of the ones that are for sale, and the gear that touches the lens is never that big...

Giroud, that's actually incorrect. The size of the bevel gears, if they are 1:1, is irrelevant. The drive gear (the smaller one that drives the gear on the lens) absolutely affects the ratio of how much knob rotation equates to lens rotation. The diameter of the knob only affects how much effort you have to exert.

I don't think so.
if you have only gear that act by there external diameter on all the transmission line (how it must be the case on an amateur project) you can not have any reduction.
To have a reduction, you need a double gear (one that has teeth close to the axis and teeth on the external diameter), but in that case only the speed change will require a proportional force change too (energy is conserved)
If you have simple gear all touching only by external diameter and both ends finish with approximately the same diameter, the ratio will be anyway close to 1:1

Giroud, you are incorrect. bill is correct.

imagine it like this. take the diameter of the drive gear (the gear that touches with the lens gear) and take the diameter of the lens gear.
NOW, turn the drive one full rotation. (covering the entire diatmer of the drive gear). Is the lens gear going to turn gear one full rotation? no. Only the Knob and driver gear will turn one full rotation. the lens gear will only turn as much as the diameter of the small drive gear is equal to. The size of the knob has NOTHING to do with it. If you turn the knob one full turn, the drive gear does one full turn also with it. But the lense gear (being much larger) will only do a fraction of that turn because of gear reduction.
lets say one full turn of the drive gear causes all 40 teeth to interlock during the process. That means that only 40 teeth of the lens gear will interlock also. But the lens gear might have lets say 100 teeth. That means the drive gear cannot be in a 1:1 ratio with the lens gear. Unless you build some sort of gearbox to correct the difference.

Ok so you just need to mount the knob on the same gear that the lens and the axis that will drive these two gear should have the same small gear at bothe end. Seems easy, but i am not sur that is usefull since you could loose some precision in focusing. (you rarely need to focus from one extrem of the lens to the other, but more often need to slightly adjust on a small range.)

Giroud, I am not sure what you are trying to achieve but the goal of the usual person's follow focus is to allow them good fine-tuning focus adjustment via a reasonable number of knob rotations, without high manual effort.

The way to achieve this is by using a large enough knob, and a low enough gear reduction at the lens.

I tried the helicopter gear but unfortunately it wasn't the right pitch. It still rotates the focus ring but it rattles fairly loud. I strapped a rubberband around it and that helps but I still think it can be better. Does anyone know the pitch for the cavision follow focus? Or is there a way I can measure it?

I am not sure if people know that when I speak of PITCH I am referring to the gears in the 90 degree gear box. Pitch does not refer to the lens gear or the gear that touches the lens. The Pitch is the angle that one gear meshes with the other gear. I don't know if that is clear or not...

David, you might be right
 

I have noticed there is considerable confusion/discrepancy in the ways people discuss gearing. If you have any insights, people would love to hear them. Would you be interested in posting a tutorial? You wouldn't even have to show your follow-focus unit, just indicate how a gear with 12 notches can mate with one of, say 1200. (I don't even know the terms of discussion here, other than pitch.) And what those pertinent dimensions are in terms of pitch, size or other. If this is information already available (and it probably is), perhaps you could point us to it with a few notes.

I appreciate and respect your expertise on this subject.

Shane, where to get the helicopter gear with large enough inner diameter?

The one in Ben Winter's post barely made it onto the 60mm-diameter SLR lens's focus ring.

However my lenses go up to 72mm. This is larger than the *outer* diameter of Ben's heli gear.

Where do I find a large helicopter gear that would allow me to grind it for up to 72mm inside, without coming too close to stripping the gear itself?

If you look back a few messages in this thread you'll see I recommended mcmaster.com. I went on there and found a nylon gear with a 77mm i.d. Sounds perfect to me, but I ain't gonna say it again! :-)

Bill, where the devil did you find that? :) the biggest 32 pitch gear I can find on that site is a little more than 2 inches OD, and it's steel!

Search for gears with a bore of 3.06". It's categorized into a goofy location as I recall.

Hey, you also owe me an email! :)

Follow Focus Gear
 

Hi All

I found this gearbox in the Maplin catalogue here in the UK and I think it may be what you are all looking for:

www.maplin.co.uk

Bevelled Gear Box, Part No. N16BQ @ £16.99 GBP

Hope this helps

Henry, I inquired with that company some time ago, asking what would it cost to deliver that gearbox to the US, but received no reply.

hello there,
i was reading your posts, but not absolutelly in detail. maybe this is already mentioned, but maybe not.
some time ago i discovered that gears from sewing machine can be used for building FF. you can find it easily in most shops/services with sewing machines. and its cheap. different sizes from different models and they are durable and precise enough for FF.

filip

Follow Focus Gear
 

Hi Alex

Here is another company which sells angle gear boxes and gears.

http://rswww.com part no. 748-443 in Power Transmission Components

They also sell a huge range of gears,tubes,bar,nuts and bolts and all the
bits you may require.
If they do not have depots in the US they will export from the UK.

They also have their catalogue on CD at http://rswww.com/newcd It makes
great reading for DIYers.

Hope this helps

Thanks Henry!

I would strongly suggest buying whole gearbox from experience. I have tried building my own, and to some degree had success, but the time and effort it took would have been better spent buying the $40.00 gearbox, stronger and precisely put together. Just my 2 cents...