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Chapter 7. iBlow > The Drive Train - Pg. 197

MAKE: PROJECTS Eccentric Cubicle ritually dismembered CDR spindle case. We'll need to make some crucial material choices to deal with potential rusting issues as well. If we design a mechanism that's simple and elegant from the ground up, we do an end-run around the need for a case to hide all the techy bits. Our mandate, therefore, is to do just that, and save ourselves the (in this case avoidable) pain in the ass of bodging together a housing for the machine. Do not be put off if this is starting to feel more like a pressure- filled product design course assignment than an entertaining DIY project. Stop for a moment and reflect on the fact that it's a bubble machine we're building here, and anything that involves a bubblemachine is inherently Fun. Get on with it. · A drinking straw · A playing card · Four 1½" #6 wood screws · A 1" 6-32 machine screw · Hookup wire and shrink tubing · A tube of "automotive sealant" 1 · A selection of rubber bands to use as drive belts · 6 large grapefruits · A volleyball net Just kidding about the last two. You may want to sacrifice a USB cord for testing purposes: Lop one end off and bare the ends of pins 1 and 4. Pin 1 is hot, pin 4 is ground. Cooking your own bubble juice? You already have the dish- washing liquid in the kitchen, so you just need to grab a pint of glycerin at the pharmacy. Resist the urge to restock the supply of nitric acid you use in your Champlevé enamelling projects at the same time: otherwise, alarm bells will likely go off, followed quickly by an indefinite vacation in Cuba cour- tesy of the United States government. What You'll Need There's not a lot of shopping to be undertaken. You might already have a 2" CPU fan stowed away in your "miscellaneous computer hardware" drawer, and the motor needed to drive the bubble wheel can come from a scrapped cassette recorder. We'll need: · 6" x 6" of 1 / 4 " clear acrylic sheet (if you're not feeling the need for transparency, substitute 1 / 4 " plywood) · A USB socket I used a type A PCB mount number harvested from a first-generation PCI add-on card. I learned (much) later that A-to-A USB cables are somewhat rare: a couple of years ago I picked up an intestine-poppingly heavy box of assorted new-in-bag PC cables at a yard sale that included half a dozen cables each of every conceivable USB terminator combination, a resource most people lack. When it came time to cable up this build, I just grabbed what I needed out of "The Box," not realizing how anomalous the A­A terminator combination actually is in the wild. · Adhesive-backed hook-and-loop fastener, like Velcro (a few inches) · 1" medium-density fiberboard (MDF) for the chassis · A subminiature SPST slider switch · A 10-ohm 1 / 4 watt resistor Other stuff you likely have squirreled away somewhere includes a few CD jewel cases, some uncoated CDR blanks that they top up spindle cases with, and an empty 25-disc spindle case. You'll also need: · Brass or galvanized steel 1 / 4 -20 threaded rod 3" worth · A cheap ballpoint pen The Drive Train The basic mechanism is shown in the illustration. There are three pulleys to turn. Mark the outlines (the dimensions cited in the cutting diagram will get you close, but you may need to do some tweezing, depending on the speed your motor runs at. Start out with the blanks on the large side and fine- tune the operational diameters when you're forming the belt groove), rough-cut them with a coping saw or scroll saw and sand them to a close approximation of round with the disk sander that I finally convinced you to buy. Drill out the centers with 3 / 32 " pilot holes, and (MA!!! He's doin' it again!!) tap the holes for 8-32 threads. [Figure 07.01, Figure 07.02] NOTE: Use the slowest speed possible when cutting acrylic with a powered saw to avoid the thoroughly annoying "melted acrylic re- sealed my damned kerf" effect. To finish the pulleys, chuck a length of 8-32 threaded rod into your drill or drill press, and thread on one of the blanks all the way up to the chuck jaws. Add a washer and nut as retain- 1 This stuff looks the same as, but is different from, silicon glazing compound. I used Automotive Goop, which is also popular in the Sk8tr community as a deck grip treatment. Comes in a purple tube resembling a toothpaste tube on steroids, smells horrid, sticks to world + dog. 186