Hand Crank Drum Machine
After a long “battle” with Hobby King, the motors and propellers that Neil Hickey and I ordered for our blimp never showed. We went our separate ways in our mechanisms finals. After some thinking and due to the influence of my past as well as seeing EJ Park’s Mechanical Storytelling, I came up with the idea of a hand cranked drum machine.
Looking around on the Internet for inspiration, I found this:
I thought this was a great project, but I really wanted to stick with real drum sticks. To start out, I went with the best prototyping tool I know for building…LEGOs. You can see a very basic version of what’s to come. There’s a hand crank, a gear system and the “sticks”, represented by the long red pieces.
After this prototype, I decided to just dive right in. After the major failure with Hobby King, I wanted to make sure I got all the parts as soon as possible for my drum machine, so I went with the quickest manufacture I could think of…me. I made the entire thing out of scrap wood and parts I could get at local hardware stores. I started out debating between a gear system and a belt-drive system. A gear system, while it would look nice, seemed far more complex than necessary. I decided to make the belt-drive system, beginning with the pulleys. The pulleys were cut out of wood that was over an inch thick with a jigsaw and then the grooves were cut out with a Dremel tool. That alone took most of a working day to do.
From this point it was really just a matter of making a somewhat symmetrical system. Here’s some in progress photos, showing the belt-drive system using nylon rope and the entire mechanism, loosely put together.
An issue I ran into with using nylon rope as the belt was that it would constantly slip, especially since I had to knot the rope together and the knot wouldn’t fit into the pulley grooves.
At this point I came to a mechanical realization. I needed to change the direction of one of the dowels in order to have both drum sticks pushed downward. At first I thought…”hey…I just need to add another pulley…like gears.” Then I tested and I saw that pulleys in a belt-drive system do not work how gears work. Simple solution, twist the “belt.”
I added another pulley to the left dowel and twisted a belt, then wrapped it around my right pulley. Done and done…except that the rope still kept slipping. Next solution…elastic. Where to get elastic? Kmart XXXL sweatpants, $10 a piece, gives you lots of elastic to experiment with. After cutting up some elastic, I realized again, that a knot just wouldn’t work. This required a new skill. I learned how to use a sewing machine. It worked out quite well.
Next part was actually getting the sticks to hit the drums. I had a spring attached to each stick and then to the base of the drum machine, pulling the stick downward onto the drums. My idea was to use PVC pipe, drill holes in each one and have metal rods sticking out of each hole to push down the stick as the crank is turned. After some bending of metal and smoothing of edges, this worked out well.
And here’s a video of it in action:
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