Date: Sun, 12 May 2002 09:55:37 -0500
Author: "Paul O. Johnson"
Subject: Re: Installing Baseball Battery
Our baseball doesn't measure or announce its speed but it has a slick
way of maintaining its battery. We have a Doppler effect hands-on
exhibit that features a beep baseball. The softball-size ball emits a
loud steady shrill beep and is normally used in beep baseball for the blind.
The ball has a fully stitched traditional baseball seam, a series of
small holes on one side with a speaker inside them, and a 1/4-inch hole
on the other side with a small plastic rod projecting from it. You
switch the beeper on and off by pulling the rod out of the hole and
inserting it back into the hole.
The ball comes with a Radio Shack 9-volt charger and a unique coax plug
that connects the charger to the rechargable battery inside the ball
when you insert the plug into the switch hole (which, of course, also
switches the beeper off).
For our exhibit, the ball is encased in a nylon mesh bag whose top is
twisted and secured to one end of a 6-foot length of twine. The explorer
stands at the center of an 8-foot circular barricade and twirls the
beeping ball horizontally around his head. The twirler hears
constant-frequency beeping but his audience standing around the
barricade hears the beeping tone shift frequency as the ball approaches
and recedes from them.
We have plans to make the exhibit more maintenance and accident free by
(1) attaching a small solenoid to the ball to pull and push the switch
rod when voltage is applied by means of a pushbutton switch at the
center of the circle, and (2) attaching the free end of the twine to the
top of an 8-foot-high free-standing pole that is, in effect, a
crankshaft. The explorer twirls the ball by cranking the pole while
pressing the pushbutton..
The excellent design of the ball avoids having to open it to change
Paul O. Johnson
The Science Place
>I just saw dozens of these "radar" baseballs in Fry's electronics for 19.95
>The batteries were in the package uninstalled so I assume there is an easy way to
>>I was in a gift shop today.
>>Someone came in looking for a "radar baseball".
>>The store had one. It measures the speed at which it is thrown.
>>The package says "displays speed on impact" -- certainly not radar. It was
>>priced at $22.95.
>>Have any of you seen one of these? Have you ever used one in an experiment