FIGURE 15. The newer head mechanism with properly
designed bevel gears to enable 3DOF for a camera
mounted at the front output shaft.
more. This continues all the way for the entire length of the
line. This is similarly done for the top disc, and since the
discs are of the same radius they generate an identical
62 SERVO 01.2012
curve. The other way to think about the shape is by
unwinding the string from the disc. This unwinding is shown
in Figure 12.
Using the shape, the full tooth can be made. Figure 13
shows a set of spur gears made using this method with
various numbers of teeth and therefore, different diameters.
Also using this shape, a slightly more complex cut can
be implemented to design bevel gears as in Figure 14. With
the use of bevel and spur gears, I am now designing a
proper head mechanism which will be smoother, and may
not require any break-in time. Figure 15 shows the usage of
various bevel gears in a differential type mechanism to get
3DOF with a camera mounted on the front output shaft.
When designing these gears, I followed a large part of
the tutorial on the cartertools.com website. Please see the
Links sidebar to get a full understanding of the gear design
process.
Next Month
Now with properly designed gears, I can begin working
on building parts out of aluminum. I will show some of the
complications of going to aluminum and discuss part of the
leg redesign needed to assemble all the components. I will
also be getting new computer hardware to make the system
more capable of advanced behavior. Finally, I will be
assembling the complete system and will discuss my
thoughts on the components as a whole. SV
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