The Sandcrawler, a junk-collecting operation, is a very large and rustly old
vehicle containing many storage rooms. McQuarrie envisioned a toothy front
with a scoop that moved up and down like a present-day garbage truck. Lucas
later came up with a magnet arrangement by which R2-D2 is taken into the
behemoth vehicle.
McQuarrie depicted the Sandcrawler against the cliffs because the story, at
this stage of its development, called for it to be hit by falling rocks, which
knock it off track; during this commotion, the two robots were to have escaped.
(The control devices which, in the film, restrain the robots, had not yet been
conceived.)
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(Last updated at: 980414)