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Crawler II (1968-1971)

During the latter stages of CRAWLER I development, I began experimenting with some miniature hydraulic cylinders fashioned by encapsulating 30- and 50-cc irrigation syringes inside copper-tubing sheaths with epoxy glue. Considerable force could be generated with one of these devices when operated at about 100 psi; solenoid valves from discarded washing machines were modified to provide control. The homemade hydraulic system shown below provided valuable experimental feedback that influenced subsequent designs, but was way too big and bulky for practical consideration.

Homemade experimental hydraulic system (right) and temporary test gripper (left), circa 1968.
Homemade experimental hydraulic system (right) and temporary test gripper (left), circa 1968.

Instead, a small surplus chemical-injection pump was used to pressurize an accumulator made from a 4-inch length of 3-inch-diameter copper pipe capped on both ends. I also fabricated and tested a number of improved manipulator and 2-DOF arm designs my senior year in high school, to include a 2-to-1 inline pressure booster, which was pretty compact and efficient.  One of the biggest problems I encountered was leaky improvised hydraulic-line fittings.

Original sketch of an improved manipulator design, drawn on what later became a punched card for the collision-avoidance system of CRAWLER I (circa 1968).
Original sketch of an improved manipulator design, drawn on what later became a punched card for the collision-avoidance system of CRAWLER I (circa 1968).

CRAWLER II was eventually modified and equipped with an even smaller and more sophisticated hydraulic arm and gripper configuration, the latter based upon a commercial off-the-shelf ViseGrip. The gripper force was quite powerful. While attempting to explore the limits of remote-operator dexterity, I once squeezed the locomotive of my brother’s train set just a wee bit too hard, rendering it no longer compatible with H-O gauge track.  This final version also saw considerable well received service crushing beer cans at Georgia Tech.

CRAWLER II (shown here without the circular disk reader) was a teleoperated platform equipped with a 2-DOF hydraulic gripper (circa 1970).
CRAWLER II (shown here without the circular disk reader) was a teleoperated platform equipped with a 2-DOF hydraulic gripper (circa 1970).

Unfortunately, the bulky collision-avoidance disk reader and the manipulator would not both fit on the platform at the same time, and the modified hydraulic components were all rated for 117 volts AC. In addition, there was essentially no way to control the new manipulator in an autonomous fashion, so CRAWLER II had to revert back to tethered control. The few photographs I have of CRAWLER I were taken by one of my highschool buddies who owned a Polaroid camera.  Since most of the CRAWLER II development was performed while I was away at college, I regrettably don’t have any pictures of the final configuration. Work on CRAWLER II ceased my junior year, when I “borrowed” the onboard logic control unit to automate our (very) mechanized homecoming display at Georgia Tech.

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