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4 Masterpeice 1 • Stair-Climber

Figure 1.3 Climbing Mode

I came across this concept some years back on Cynde Callera’s LEGO Web page:
http://tyranny.egregious.net/~khrome/lego.The sketches and information there captured
my imagination, and I had soon built several tri-star variations.To review some of my
earlier designs, please take a look at: www.visi.com/~dc.
While experimenting with these variations, it became clear to me that for stair
climbing, as opposed to minor obstacle avoidance, it was necessary to provide separate
drive mechanisms for both the wheel assembly and the wheels.The Stair-Climber model
uses a differential to split the drive torque between the two separate drive modes. On a
flat surface, the model will roll along like any normal wheeled vehicle. However, as soon
as the model encounters enough resistance to start climbing, as when something blocks
the wheel from rolling, the drive torque is transferred in order to rotate the wheel
assembly that begins the climbing process. Each tri-star wheel has its own drive motor
and differential to enable independent wheel action, as well as enough torque to easily
climb a set of LEGO sized stairs at a reasonable speed.
Another way to accomplish stair climbing would be to use separate drive motors for
the climbing and rolling functions. Many sensors would be needed to determine the
vehicle’s position and attitude relative to stairs and other terrain. If you had enough com-
puting power and sensors you could possibly use only one pair of star-wheels, program