A word on safety:
This is the world's only chain and sprocket drive designed to safely
"interact" with fingers. The drive moves at a brisk pace, but the motor
is current limited so it stops very easily. In fact, putting one's
finger in this chain drive while it's running doesn't even hurt. Much.
Chain drives and pulley drives should always be handled with caution to
avoid being pinched, or worse. Belt drives on power tools and other
machines are completely capable of amputating errant fingers unlucky
enough to get caught between the belt and the wheel. If a chain or belt
drive is capable of injuring you, unplug its power supply from the wall
before handling the drive mechanism.
Chain and Sprocket drives have dimensional parameters similar
to timing
belts and pulleys. The pitch of the chain, the number of teeth on
the sprocket (closely related to sprocket diameter), and the bore of
the sprocket serve to identify the part. The sprockets in the demo are
1/4" pitch with a 1/4" bore. In between the sprocket and the bearing
shown in the right-hand photo above is an example of
another motion component, the shaft collar. The bore of the
shaft collar fits the axle, and is held in place on the axle by a set
screw. The shaft collar holds the axle against end-to-end motion in the
bearing.
The axle material is 1/4" drill rod, item #U-CGDR-4 from Small Parts,
Inc. and other sources.
Chain for chain drives may be bought by the foot and cut to length. The
ends are then joined by a master link, which should be purchased along
with the chain. If the chain is bent while cutting it, a permanent kink
will be forced into the damaged links. If this happens the chain will
not run smoothly. There is a tool for cutting small chain called
a "chain breaker", but a Dremel tool with a cutoff wheel often gives a
superior cut.
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Small Chain and Sprocket drive components
are available from Small Parts, Inc., and SDP-SI. See the sources
page .
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