Having acquired some tatty KOK carcasses, I suddenly started to wonder if I could find a way to fit a rewind. The originals are nearly always non-functional, even if they are present – the rewind gear with internal teeth is Mazac and distorts. Oddly, however, the similar arrangement on my 17.5 rewinder seems fine. I have heard that someone in France had a batch of these wheels made up years ago; even then, they were £50 or similar – it must be quite difficult to make internal teeth. So I decided to see what I could do, with the usual proviso that nothing I did should make holes or whatever in the projector and it should be possible to undo it all without harming the machine and restore the status quo ante.

This is what I came up with. It’s quite complicated, and I have thought of several other ways of doing it as I’ve gone along. For instance, if one could acquire a toothed belt of exactly the right length and tooth spacing, it might be possible to glue this to the inside of a part made up to look like the original rewind. Or maybe a toothed wheel in the rewind pivot hole and a toothed belt to another on the spool spindle, tho’ it would be difficult to get a very high gear ratio. No doubt there are other possibilities.

The heart of the new rewind is the cross with two arms, centre bottom of first pic. This is made up from a piece of steel about 8mm thick, partly cut away at each end to accept the cross pieces, which are screwed to the upright. This assembly is held to the back of the steel plate, top, with a couple of countersunk screws thru holes A in the plate into threaded holes AT. The plate has two large, over-lapping  cut-outs B for the spool spindle bearing and the rewind pivot on the KOK. You may by now have noticed that the location of holes in the plate is not all that precise, partly because I was making it up as I went along and not always getting it quite right. A particular problem was to ensure that there was sufficient range of adjustment to allow the belt to be tensioned correctly (we come to the belt later). For the same reason, holes B are oversize. Note also the bent-up tabs E; these are to locate and fix the cover for the new mechanism.

 The main job of holding all this together is done by the four bolts shown, which pass thru holes C in the plate and the cross arms and into threaded holes in the round bars. The plate goes at the back of the machine, the round bars at the front. These bars have cut-outs to fit over the edge ribs of the casting of the back upright of the KOK. Tightening these screws grips the upright between the plate and the bars, with the main rewind upright fitting between the raised ribs on the rear of the KOK casting. It’s easier with pictures. I opted for round bars rather than square bars or plate for appearance and minimising the cutting needed to fit around the ribs on the KOK casting (the ribs are best seen in third pic from last). I wanted a snug fit here to ensure the fitting would not foul the projector reels.

The rewind upright has a threaded hole. This takes a fixed shaft on which fits a large toothed wheel (pic 2). This is free to rotate on the shaft, held in the right location by a pin riding in a groove in the shaft (see pic 4). The pin is spring-loaded, the spring being held in place by a grub-screw. The pulley wheel has a sort of one-way dog clutch, which engages the winding handle (a fugitive from a defunct 9.5 rewinder) only for rewinding. At other times, the handle is pushed back out of engagement by a spring (pic 5). A smaller toothed wheel fits on a replica spool spindle. Just to show the sort of thing that goes on in one's head, I realised a spring was needed to ensure the handle got pushed back out of engagement, then realised that I would no longer need the spring-loaded pin, as the job of keeping the pulley in place would be done by the same spring that pushed the handle back. You can see in pic 5 the washer and screw for the end of the shaft that would stop the handle coming off. Then I thought, why not make the handle loose/removable? In which case I needed the spring-loaded pin again.

 I can’t see a way of removing the original gear on the spool spindle, so just made a new one, modified to suit my needs. I have shown in pic 3 a comparison between mine and an original, tho' I think this one has been tampered with - I don't think the screw thread on the end next to the gear is original. I did however borrow the original spool retaining spring and the collar/dog that engages the spool. I have to confess that I made a small tapped hole in this for a grub screw. A toothed belt then links the two gears.

The remaining pics show the rewind in various stages of fitting to the projector. This is a decided weakness of this design - the rewind has to be built up actually on the machine. Two of the main securing bolts are behind the large pulley, which therefore cannot be assembled in advance. Finally, a cover to (possibly) make it look a bit less makeshift. Note the riveted construction; I can remember as a teenager using one of these snap rivet tools which fix rivets from one side only, and the same tool is obviously still in demand 40 years on, as I only recently bought it and used it on this just to try it out.

Now I suppose it will all have to be removed and painted.........   but first, measure and record, as much for my benefit as anyone else's as I am sure that 2 years from now I shall have forgotten what and how I did. because of the make-it-up-as-I-go-along approach, the measurements are a bit approximate, but should give enuff detail for you (or me) to replicate the thing, should anyone indeed ever wish to do so.

In pic 1 above, I have not measured the two holes used to fix the two-armed cross to the plate - they are there just to hold the cross in place during assembly really. In pic 2, the thru hole near the LH end is for a tommy bar to tighten the shaft firmly into the cross. There is another thru hole right at the opposite end, which was part of a rejected approach to fixing the winding handle in place; the shaft could probably be a bit shorter. Three and 4 now complete all that's needed for me to be able to make another when I've forgotten what I did. (One other thing; the big toothed pulley is 56.5 diameter, 60 teeth, the smaller one has 16 teeth. The belt is 9mm wide, 240 circumference, with 80 teeth @ 3mm spacing.).