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Serena's New Thing

SEPTEMBER -- Clockwork Mechanism

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My "Clockwork and Clockwork Mechanisms" project was slow to get off the ground, mostly because I wasn't sure what I wanted to make. For a time I was determined to make an actual working clock, but I reluctantly gave up on that idea due to complexity and time constraints.

I was fortunate in that Baron Conal O'hAirt contacted me soon after the monthly survey was over. When he saw that Clockwork had been the chosen category he wanted to know what I was going to make. Since I really had no idea, I asked him if he could give me any advice. He said that he'd made a waterclock, (pictures can be found here) so he could help me with that. He sent me links to pages of information and some great pictures. Finally I decided that I'd like to try to make a silk spooling machine. There is a complex Japanese silk reeling machine called a zakuri. The machines I had seen are out of period, but I'm convinced that versions existed in period, perhaps with less gears or simplified gearing.

Some time later, I got a chance to sit down with Conal at an event and talk about machines. He suggested using a different gearing system, one that didn't involve toothed gears. He sent me a picture of a three-speed hoist, designed and built by Filippo Brunelleschi in 1420 and sketched by an engineer named Francesco di Giorgio.

From the online exhibit -- Museo Galileo - Institute and Museum of the History of Science, Florence, Italy.

Conal directed me to the gearing mechanism shown on the right; a toothed spoke-type gear and a cage gear. I thought that would look really interesting, and could work out very well. I consulted with Ser Farthegn Rinkson, who's my go-to guy for any woodworking questions. He steered me away from trying to use all hand tools in the construction of this project. While it was possible to get the needed level of precision from hand tools, he reminded me that I wasn't setting out to master hand-crafting technically difficult pieces out of wood. He suggested I use a modern drill press, and even lent me one! Farthegn was also was very helpful in assisting me in figuring out things like an ideal size and how to design the gears.

I made some initial drawings of the gears. I was limited by a major factor: the drill press I was using would only accept a piece of wood 6 inches or less in height. So I had to design my spoke gear to be six inches or less in diameter, since I would be drilling into the side of it. I made some sketches, and then I contacted Captain Crispin dela Rochefoucauld who, though his work, has access to some very impressive woodworking machines. He agreed to convert my drawings into CAD drawings that he could use on the CNC machine he had at work. That would make things considerably more precise and easier!

Sure, I could have cut the circles myself. However, Farthegn, who is a master woodworker mundanely, told me that it's very difficult to cut an exact circle with hand tools. Better to save myself the aggravation and have a machine do it. Remember, it's about the clockwork, not about how well I can cut circles!

Once all the pieces were cut out (plus an extra set in case I made mistakes) I got to work drilling holes in the spoke gear. Since Crispin made the document to scale, I was able to print it out and use it as a template to make marks on the outside of the spoke gear so I knew where each of the 36 spokes needed to be placed.

I made a jig to hold the gear in the drill press that allowed me to set the drill to make the hole in the center of the width of the gear. Once each hole was drilled the jig enabled me to simply turn the gear to the next mark and drill the next hole.

Once all the holes were drilled, I needed to cut spokes. I made the spokes long enough that they would engage the rods on the cage gear, but short enough that they would be strong and not apt to bend or break. I wanted the ends of the spokes to be rounded, but the prospect of sanding each by hand was a little daunting, so I used a pencil sharpener. It worked surprisingly well! I glued the spokes into the gear with wood glue.

Then it was time for the cage gear. Since Crispin's CNC machine also tooled the inset holes in the face of the gears, all I needed to do was cut the rods and glue them into place.

I made the first cage gear, but once I started to put the two gears together I realized I had made the cage gear too tall, which is to say, the rods were too long. So I made a second gear with shorter rods that worked out nicely.

Next it was time to assemble the frame, which was simply two sides with holes in them for the axles, screwed to a base. The two axles on the machine are just metal rods. After drilling a few holes in them for cotter pins to hold them into place, the gears were ready to be put on. They meshed together surprisingly well on the first go!

I fashioned a handle out of a scrap piece of wood and a drawer knob, stuck it on the axle of the spoke gear and the machine was completed.

I chose an axle size that would fit my existing silk spools--you can see one in the machine. I have tried it out and it works very well. It's not as quiet as my modern spooler, but it's certainly much cooler looking!


Next up For Serena's New Thing #4: Lapidary!

Want to get involved? Vote every month in the Serena's New Thing survey. Join the Midrealm Arts and Sciences Group on Facebook, where I will be posting a link to the voting page, as well as pictures and videos of the projects. Or just keep up with everything here.

-- SK