Groundhog knee deep in mine muck.2D mine map produced by Groundhog.3D mine map snapshot produced by Groundhog.Ferret1 deployed into the Mellon Institute void.Second generation Ferret with higher power laser range finder.Ferret2 scan of a limestone mine after a domeout, Kansas City, Kansas.Borehole deployable, inflatable mobile robot concept.
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Chassis-in-a-Day
Dave and Chris grinding on GroundhogGrinding & Cutting

The first step to reforming Groundhog into a useful machine was to remove all of the superfluous parts. This was accomplished in the course of a long weekend spent in a farm shop in Somerset, PA. Dave the welder helped us tear apart the original structure of Groundhog and replace it with big pieces of steel.

One of the trickest changes that was made was moving the steering column. The steering column was original designed for an ATV and therefore extended from the frame at a significant angle. The decision was made early on to link Groundhog's two steering columns in opposition so as to cut the turning radius in half while still only requiring a single steering actuator. However, with the steering columns angled towards each other this would be a very difficult linkage to construct. Therefore, the steering columns were rotated such that both shafts were perpindicular to the ground.

Dave welding on the base plateWelding

After grinding and cutting, the next step was welding. Dave MiG welded most of the initial structure of Groundhog. A large base plate was added to provide room for the payload and drive train of the robot. Smaller plates were welded above the steering columns to provide mounting points for the sensors. In addition to providing mounting for various other component, some structural modifications were made to the chassis.

The one foot high lip going into and coming out of the Quecreek-Saxman breach was often discussed. In order to make sure the vehicle maintained a sufficent ground clearance while traversing this obstacle, new mounts for the shocks were welded into place. Now instead of needing to lift up on the wheel to install the shocks, the shock had to be actively compressed before it could be installed. This proved to be a critical change as Groundhog continued to gain weight throughout its development.

With the addition of mount points for the drive train and bearing mounts for the spline shafts entering the ATV differentials, the robot was ready to be powered for the first time. Late on Sunday night after working nearly all day, Groundhog moved under its own power for the first time.

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