Making a Cleated Belt

francist

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Not sure if this will fit into one post or not but we’ll see.

A couple months ago I spied another interesting machine on our local used marketplace and of course dragged it home. It’s a Swiss-made “Turissa” which I’m not going say is super-rare but it’s definitely uncommon. At least in North America anyway.

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When I got it home and started going over it I suddenly realized it was missing its timing belt. This is pretty important — it links the main driving shaft on top to the lower bobbin and feed mechanisms down below. — and without it the machine can’t sew. And then I realized something even more weird — the belt was still there, just in a much-altered state.

This is what’s left of the original cogged belt: just a few wraps of the fine reinforcement wire that formed the inner core of whatever synthetic they had made the rest of the belt from. That material had bizarrely degraded into small pockets of granular dust down the bottom of the chassis leaving only the wires grinning like the Cheshire Cat smile over the pulleys.

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So what to do? Parts as might be imagined are few and far between (early 1950’s machine) and even then why would I want an original belt if it was going to turn to dust too? To make matters more complicated, the pitch or spacing of the cogs on the pulleys didn’t match up with any of the standard belt sizes I could find today. I don’t know if it pre-dated the standardization of belts or whether it was just one of those proprietary things, but regardless there was not one to be had that was going to fit. As a bit of a sidebar here, I did find one later in my salvage drawer that belonged to an old IBM electric typewriter of about the same vintage and it had the same pitch, so I’m guessing at one time it may have been a common belt pattern but not so now.

So after much head scratching and napkin designing I came up with a list of options on how I might make one. I have a couple of other machines that use a belt made from cord wraps held together with wire cleats (this was a very common method) and that’s the option I chose as my first attempt.
The string or cord was easy enough: some nylon builder’s line from the local Canadian Tire seemed about the right weight to me so I went with that. For the cleats themselves I worked through a number of material choices and techniques to ultimately settle on 6061 aluminum. More experimenting to get the right amount of stiffness and still be bendable enough for me to crimp in place but eventually I had what looked promising. Here’s a test fit with some sample string in place but cleat length not quite nailed down yet.

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Once I had my sizes figured I just had to come up with about sixty-five of the little suckers so I decided to run them in two cards that would give me consistent sizing but be easy to separate. Here’s a photo of milling the crossways lengths using an 0.028” slitting saw. The blade is shy of the platen by about ten-thousandths so that the card stayed in one piece for all the cuts.

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And here’s what happens when you think you have enough hold-down points but really don’t…

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Once the aluminum was all scored I could break off the individual cleats for filing and finishing. I wanted them accurate and fairly close fitting as they would provide my register to get the spacing right. I could file five in the space of fifteen minutes, so after a few hours I was done. They are slightly trapezoidal in cross-section to slip in and out of the pulley slots nicely.

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Assembling the test belt was definitely easier if the cleats were somewhat formed in advance so I made a little setup to get a decent pre-crimp starter shape. It’s just a slip of metal filed to the right width and held vertical in the vise so that the blank can be bent around it. I used the two hardwood sticks for that — worked great.

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Part 2 to follow….
 
Part 2 — Building the Belt

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Armed with my little tub of tiny aluminum cleats it was time to wind the belt for real. My theory was that if I could wind the cord on the pulleys in situ I would be assured of the proper length for the finished belt (there is no adjustment on the pulley spacing, they’re a fixed distance apart, period). And, if I could work the positioning and crimping of the cleats sequentially along the belt but always leave at least two previously crimped cleats engaged in the grooves, I should (in theory) arrive at the proper spacing. I won’t say how many sleepless nights went by trying to work through that process but there were a few!

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This is one of those three-handed jobs so to make things a little less fussy I loaded the free ends of the cord with a couple of light springs just to keep some tension on while I wound.

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With the first few cleats installed and crimped I clipped the spring tethers and proceeded to slip in two or three cleats at a time as I gently advanced to the next open groove, always keeping at least two of the previously crimped cleats engaged in the pulley. For crimping I just used a similar hardwood rod to gently tap the cleat closed against the pulley. The top shaft runs in solid bushings and I wasn’t tapping anywhere near hard enough to be worried about deforming anything. Still, it was a bit nervous-making and I worked carefully.

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Coming around the home stretch, will the spacing work out? Yup, the last cleat fit right in as if it was planned that way. Actually I was really relieved — the thought of making a new batch of cleats was not inspiring!

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With all the cleats tapped into place I ran over the entire length again with the offset pliers just to give a final tweak to the crimps.

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And that’s all she wrote for this episode! I still need to do a bunch more work on the machine before it’s up and running, and I also have to verify that I have the timing right and it will actually stitch as I envision, but that’s for another day. Thanks for tagging along.

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-frank
 
awesome work Frank. that was really well done. Is it noisy due to the aluminum, or does the casting keep the ticking inside?
 
Thanks for the kind words, Jeff. I don’t notice any clicking but I’ve only turned it over by hand so far, I still need to work on getting the motor re-established to try under power. One my other cleated belt machines though there is no audible noise or roughness because of the belt — they run as quietly and smoothly as anything else as far as I can tell. It was a pretty common way to make timing belts and a number of the major manufacturers used them.
 
Great work! That is an awesome machine. I wonder if you sprayed the belt with some Flex Seal or rubber paint to quiet it down.
Martin
 
This is nothing short of amazing! Well done!!
 
Very impressive Frank. Obviously your experience with other vintage machines gave you a place to go to. Having never run across those kinds of belts I would have been stumped and figured foiled again by the proprietary demons. Thanks for sharing.
 
Thats certainly thinking outside the box Frank. The majority would have junked the machine when an off the shelf belt wasn't available. Kudos to you !!!

Greg
 
Very creative Frank, well done!
 
The machining of 1950s and 1960s of Swiss made products is just amazing. A few years ago, my wife bought her second Passap knitting machine. In this case, this was the model Duomatic 80. Both she and I tore it down, cleaned it, and put it back together. After a couple of test socks, she made me a pair of the best fitting and most comfortable socks that I ever worn.
Frank, did you ever considered to check out the belts on the old 1950s Elna Supermatic sewing machines. I Believe that they use the same type of belt, not sure that they would fit. However, I'm impressed of what you have done.
 
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