The Grand Slam pitching machine from PIK Products appears to be a pretty solid piece of training equipment for you or your child. It is small, portable, and appears to be very affordable, as it sells for just under $200. It pitches golf ball sized wiffle balls out of a tube to the batter. It doesn't require any intervention by anyone except the person using it, so you can take batting practice by yourself.
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It
does require AC electricity, so you will need an extension
cord to use it. It uses a 4.0 horsepower shop-vac motor to power the
machine and propel the wiffle balls out of the tube to the hitter.
The speed of the pitches can be adjusted by opening or closing a small valve (called the "gate valve") on the side of the motor. By moving close enough to the machine, pitches up to 100 mph can be simulated, but
The machine comes with 48 wiffle balls, but the reservoir that holds the balls on top of the machine can hold as many as 100. It delivers a pitch to the hitter every 6 seconds. The thing I like the most about this pitching machine is that before the ball is pitched, it is dropped down a see thru tube into the motor and then fired out toward the batter. The fact that this tube is see thru means that you have somewhat of a warning before the ball is pitched and you can time the pitch a little better than most machines.
It doesn't appear that the Grand Slam pitching machine has the ability to throw curveballs due to the way it's constructed. However, it does come with a 45� extension that you can add to throw fly balls and grounders for fielding practice. It also includes the stand that it sits on unlike some of the other wiffle ball pitching machines.
Here is a video that gives a good overview of the Grand Slam.