The Autobat

Overall View at full extension

The assignment was to build a device to swing a bat and hit a ball off a tee as far as possible while being as cheap and light as

possible. Total materials were $49.63 and it weighed 24 lbs.

I needed to replicate human motion as much as possible. A single stiff arm with a bat would not generate much bat speed, so an arm and wrist design was devised. The main arm was drilled every 2 inches for various pivot and spring attachment points. The whole arm was inclined at 45° for maximum distance. The large sprocket on the base was fixed and the arm rotated on top of it. The small sprocket formed the wrist and it was attached to the bat. So, the arm rotated around the base, and the bat rotated around the arm. It’s a bit hard to visualize, but the picture at the right is the final position. The arm would rotate clockwise about 45° in cocked position, and the bat would rotate clockwise 180° until it was touching the arm. This system resulted in a very fast whip action of 889°/sec at impact. Four trampoline style springs provided about 230 lbs of force, but cocking only required a few pounds of force on the bat. This was due to the extreme mechanical advantage provided by the lever/sprocket system. Average distance on the fly was 140′ with a max roll of 268′. More than enough to win!

Wrist: Large concave diagonal piece cradles bat handle. This is welded to the sprocket, and it all pivots around the bolt.

The sprocket is fixed to the base, and the drilled arm spins on top. The springs are attached to the base through an I-beam and hook over large pins. There is an adjustable pin that attaches them to the arm, just outside the picture.


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