Adapting a Patterson-type reel for large-format films

by Don Day (donday at bga dot com)

You can adapt a standard Patterson-type reel (the white plastic reels that slide onto a "bouncing" center post) for films larger than the standard 120 size. The secret: a cheap and lowly 1 1/4" plastic drain pipe adapter from your hardware store!

This project assumes that you have a two-reel version of the tank, since we are making up a larger reel and will need the extra capacity of the two-reel tank for processing larger rolls.

Here is what to shop for--a standard bathroom sink drain pipe extension (1 1/4" marked diameter) that should cost no more than a couple dollars.

This is a tube about 6" long with a small reducing section about 2" from one end, and usually comes with plastic compression rings and a threaded coupler. Buy several so that you can make spares for other film sizes. These also make great telescope eyepiece adapters, but THAT project is for another forum, another community.

You will also need a "nibbling tool." Radio Shack sells these for trimming metal project boxes to mount meters or cut holes larger than your drill bits can handle. Each pinch of this tool removes a small rectangle of material about 3/16" wide and 1/8" long at a time. We'll use this to dig out the channels for the adapter to interlock with the reels. There is no better tool for the job. I got frustrated trying to use hacksaws, coping saws, Dremel bits, metal shears, you name it. This tool does the job so fast that you can easily overdo it!

122 adapter

First, let's make the easy one--an adapter for 122-size film. This was the size used for the very common Kodak 3A cameras, therefore there is a chance that you might use this adapter once in a while.

Use a hacksaw to cut off the threaded end at about 1 1/4" from the reducing section of the pipe. Sand off any plastic burrs.

From the reducer, measure out about 1 1/8" or 1 1/4" onto the narrow part of the tube, and again cut and deburr that edge.

The big end of the adapter should just slide over the narrow half of the film spool. You guessed it--the narrow end of the adapter will go into the larger film spool hole.

Place 3 equally-spaced guide marks around the narrow part of the adapter. From the edge of the reducer, measure back 1/2" at each guide mark. Now, at each guide mark, use the nibbling tool to cut a channel from the end of the narrow tube up to the 1/2" mark. Fit the channels to the matching reel to test the fit as you go.

You can now assemble the pieces, slide the assembly onto the black central tube, and use the snap ring to keep the assembly together. Done!

For extra credit, there is ample room around the narrow end of the tube to put two more sets of channels. In this photo, you can see one set that I added for 130 film, with space left for another format that I'll dig out once I know which film it is! Three for one, not bad for a 3 dollar adapter.

70mm (116/616) adapter

This adapter involves modifying the end of one of your reel halves.

Trim off the large end of the drain pipe as before. Trim off the narrow end at 1/2" from the reducing section. On the narrow end, mark off and even up the equidistant thirds as before. Use the nibbling tool to cut the channels up to the reducer. If you wish, you can also nibble in some catch bays to lock the reducer onto it matching reel half, although this is not necessary.

Now for the modification to your other reel half. If you have the two-reel tank, you can dedicate one reel for the 70mm adapter and leave the other reel to handle any other size. The part that you trim off for the 70mm conversion will throw off the adapter used for 122 or any other large film.

This modification is straightforward. You need to cut off the end of the center post down to the depth of the alignment notch on the reel.

____ ____
 |__| <- trim down to this point 

Before you trim, mark the location of the notch with a permanent marker so that you can continue to align the reel parts for your other film processing. This cut determines how closely the reels fit together--without it, the gap is too wide for 70mm film, too much taken off and the film might become hard to load due to binding along the edges.

At this point, once you reassemble the reel parts on the adapter and secure them on the black central tube with the pinch ring, the new spacing should be very close to the 70mm needed for 116/616 films.

In that last photo, you can see that I added nylon screws to give this adapter the same "snap on" behavior as the reels. After all that work, I decided it was not worth it since the basic problem of spacing has already been solved, and the plastic pinch ring is enough to keep the assembly together.