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296 Making Things Move
Recipe:
1. Order or make the gears, disks, and sail holders. See the Resources section at
www.makingthingsmove.com for templates and links to where you can order
these.
2. Put on your safety glasses and cut an 18 in length of the aluminum rod with a
hacksaw. Use a deburring tool or file on the inside and outside of the end of
the rod to smooth it and avoid cutting yourself.
3. Make sure your aluminum rod fits through the flanged sleeve bearings, thrust
bearing and washers, and the shaft collars. Remember that issue of tolerances
you learned about in Chapter 2? Look at the tolerances of all the parts:
• The aluminum rod has a ±.025 in outer diameter tolerance, which means it
can range from 0.475 to 0.525 in.
• The shaft collars don’t give a tolerance for their inner diameters.
• The flanged sleeve bearings say +.001 to +.002 in for the inner diameter.
This means they will be between 0.501 to 0.502 in.
• The thrust bearing says 1/2 in +0.002 to +0.007, which means the inner
diameter can range from 0.502 to 0.507 in.
• The thrust washers don’t give any tolerance for the inner diameter.
This means that the outer diameter of the aluminum rod needs to be smaller
than the smallest possible part it needs to fit into, which is the 0.501 in sleeve
bearing. As you can see here, we have a good possibility for overlap in an
inconvenient direction.
4. If your aluminum rod is too big for the sleeve bearing, put on your safety
glasses, dust mask, and gloves (aluminum dust is not good for you). Grab the
aluminum rod with the sandpaper and rotate it while you’re squeezing until
you see aluminum dust coming off. Continue this until the rod fits through all
the components.
NOTE If you’re lucky enough to have access to a lathe, it could be a big
time-saver when you have a lot of aluminum to shave off. A bench grinder
will work faster than sanding by hand, but it will be harder to maintain the
round shape of the rod.