This year for Vacation Bible School at Church the theme is 'Maker Fun Factory'. All of the decorating ideas revolve around gears, and other industrial stuff. The ladies who are decorating asked if I could cut them some gears to go on one of the walls. That was their mistake...
I ended up using a gear generating program to make a bunch of large gears with the same pitch and gear angle, and laid them out on a sheet of plywood to fit the wall that they gave me. I made the axles a little smaller, to allow for some slop and misalignment as I mounted them to the board. The real challenge came when I moved the plywood from horizontal to vertical, and had to deal with gravity. Every bit of misalignment caused for binding in the gears, and I had to make a few adjustments.
I had a simple hand-wheel arrangement, using a clip art plaque that I adjusted until it looked like a hand-wheel. This worked great until my 16 year old stuck her finger in the gears... which required a re-design and adding a layer of Acetate to keep little fingers at bay. Best to find this out at home, than with a 3 year old! I didn't want to buy anything else, so I stood off the leftover trim I had milled on the left over dowels. It kind of adds an interesting look. I added a cross bar to support the longer shaft for the hand-wheel, I don't like how clunky it looks. I should have cut some curves on it. Maybe I will add some caution stickers or a nameplate to break it up.
The ladies still may want to add more decoration to it, so everything is removable.
The acetate is thin, and as hard as I try, I can't get every ripple out. But I got it for $20, so I can't complain. In all, the only thing I had to buy was the sheet of 3/4 ply, the Acetate, and a 1 inch and 7/8 inch dowel. Everything else came out of my scrap bin, or from the 'free stuff' section of craigslist. I did break one 1/4 inch end mill, but that was me being stupid.
When it was all laid out, there were some blank corners, so I cut an extra gear and tacked it in place.
there was a lot of learning opportunities on this build, one being the differences in thickness for MDF from one batch to the next, another being to set the Z zero from the BOTTOM of the stock when cutting all the way through, to make sure that any deflection from clamping the thinner MDF stock is eliminated. Fortunately these were all fixable with a flush trim bit on the router table. Another tip to remember, make sure you cut on the side of the line you are supposed to when profiling. When your center hole is a LOT sloppy, that is usually the culprit.
Fun project, way too much dust, glad it's almost over. Hopefully this weekend I will be able to take it over to it's final spot, fasten it to the wall so it can't tip over, and glue some carpet pieces to the base so it doesn't tear up the floor.