Page 119 - The Unofficial Guide to Lego Mindstorms Robots
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Figure 5-3.
Cutaway view of a swing-arm directional transmission
W orm Gear Design
Minerva's drivetrain is based on a worm gear directional transmission. The basic design of the worm gear directional
transmission is quite simple. A cutaway view is shown in Figure 5-4.
Figure 5-4.
Cutaway view of a worm gear directional transmission
The input shaft drives the worm gear, which slides freely along the shaft. In fact, it's easier for the worm gear to slide on its
shaft than to turn one of the output shafts. Depending on which way the input shaft turns, the worm gear slides as far as it can
in one direction or the other. When it can't slide any more (because it's hit a beam), the worm gear will turn one of the output
shafts.
Minerva actually uses a modified version of this design with four outputs. The worm gear engages two outputs at a time, as
shown in Figure 5-5.
