How Tennis Ball Machines Work

A tennis ball machine might seem simple. After all, all that it does is to lob tennis balls at you. While the principle is simple, the actual mechanics of the machine are a little more involved than that.

The machine needs to be perfectly calibrated so that it sends off each shot at the same speed and at the exact right time.

So if you have read our reviews, decided which one you want and now want to know how it works, this article is for you.

It Needs a Power Supply

It’s air pressure that propels the balls, and for the machine to create the air pressure necessary, it needs to have a power supply. As long as it has power and tennis balls, unlike a human partner, a tennis ball machine can play indefinitely.

In general, there are two power supply options: a battery or a wall plug.

Using a Power Cord

The obvious benefit of having a machine with a power cord is that you can play as long as you want. The downside is that you’ll need to have a set power supply to the court, and you’ll need to be able to plug the machine in.

Using a Battery

The benefit of having a battery is that you don’t need to worry about finding a power supply. The better-quality machines will work for around six to eight hours on a single charge.

This is a convenient option if you’re not sure that the court you’re playing on has a power supply. It also solves the problem of having to run a power cord from the main building to the court.

The downside is that you’ll need to keep an eye on how much charge is left.

Having Both

Many of the better machines will allow you to use either option. That makes it easier for you – plug it in if you have the facilities or use the battery if you don’t.

Getting the Right Air Pressure

The underlying mechanism is pretty simple. The balls are loaded, and a fan sucks in the air. The air is filtered through a protective screen to prevent debris from getting into the motor. This filter will need to be replaced at regular intervals to prevent it from getting clogged.

If you don’t clear the filter regularly, the machine will have to work harder to draw in air. If the filter becomes completely clogged, the machine won’t be able to draw in air at all and it will stop working.

Back to the actual motor again. The motor powers an electric fan that sucks the air into the machine. The air is directed into the canister of the machine. The balls are loaded into a hopper, and it is this that positions each ball correctly.

The balls are rotated into place using a set of wheels. In more advanced machines, the speed of these wheels can be adjusted to change the spin of the ball. Where a topspin is required, the upper wheel spins faster than the lower one.

They are then pushed into a smaller tube by the air. The ball will rest in a slight depression on the side of the tube. The narrowing of the tube from the canister causes an increase in pressure on the balls. The other end of the tube is closed off with a plastic flap to increase the pressure further.

The Pressure Propels the Balls Forward

Eventually, the pressure builds up enough that the ball shoots out of the barrel of the machine so that you can take a whack at it. Once the first ball has been released, the flap lifts and lets the next ball fall into place. This process is repeated until all the balls are finished.

It’s All About Timing

This process is carefully timed out, and the machine will repeat the actions at the specified intervals.

Adjusting the Shots

How fast the ball comes out depends on how quickly the pressure builds and how much pressure is allowed to build. If you set the machine at a slower setting, it will reduce the amount of pressure placed on the balls.

They’ll still be under high pressure, but this pressure setting will be lower than it would be at a higher setting, and the ball comes out slower.

Depending on how advanced the machine is, several alterations may come into play. These include, as mentioned above, changing the speed at which the wheels inside rotate. Creating a backspin or topspin is as simple as altering the rate at which each wheel turns. This is one of the main reasons why they are worth investing in.

If the top wheel spins faster than the bottom wheel, the ball gets some topspin. If it’s the other way around, it will have a backspin.

Adjusting the Height of the Shots

This is a pretty straight forward process. The tube that the balls are released from is raised or lowered to help change the angle of the shot. The more intense the angle upwards, the higher the shot will end up being.

Maintenance of the Machine

These machines are relatively low maintenance. Over time, the filter will become clogged and will need to be cleaned out or replaced. This process is usually simply a matter of replacing the foam piece.

The motor itself should be serviced from time to time to ensure that it’s running at optimal strength. This will usually be a simple matter of cleaning out any gunk that has accumulated and reoiling the moving parts.

Final Notes

The mechanics of the mechanism are actually pretty simple when you look at them. As long as the machine can draw power, there’s not a whole lot that can go wrong. It’s the calibration of the machine that might prove to be more of an issue.

The good news is that because these machines are so simple, they’re also easy to maintain. It is crucial to do adequate maintenance, however, or you risk damaging the machine or suboptimal performance.

If you decide to buy a machine, check what the manufacturer’s instructions regarding care and maintenance are.

How to Build a Tennis Ball Machine

There’s no denying the best tennis ball machines are quite pricey to buy ready-made. If you’re handy with electronics, you can build your own. In this post, we’ll go through how to do this. Ready to get started?

List of Supplies

In our example, we used components from MakeBlock. Here’s a list of the supplies that we used:

  • 3 x Beam 0824-144
  • 2 x Beam 2424-312
  • 4 x U Bracket-C
  • 4 x Flange Bearing F688ZZ
  • 4 x 125 PU Wheel
  • 4 x Wheel Hub 3
  • 2 x D8x96mm D Shaft
  • 2 x 62T Timing Pulley
  • 4 x 62T Timing Pulley Slice
  • 4 x 4060 Plastic Rivet
  • 4 x 4120 Plastic Rivet
  • 24 x Type 7 GB Socket M4x14C
  • 4 X M5x5 Jbckscrew
  • 2 x 8×1.6 Washer
  • 4 x 0824-320 Beam
  • 4 x Rubber Foot
  • 2 x CNC Motor Case
  • 2 x CNC Motor
  • 24 x Timing Pulley
  • 2 x 56mm D Shaft
  • 4 x 90T Timing Pulley Slice
  • 2 x 4mm Shaft Connector V2.0
  • 14 x M3x-C Jbckscrew
  • 2 x 4x8x3 Flange Bearing
  • 2 x P3 Bracket
  • 1 x 0808-136 Beam
  • 10 x 4mm Shaft Collar
  • 2 x 3×3 Bracket
  • 1 x Acrylic Sheet
  • 2 x 1-direction motor driver
  • 2 x D4x160mm Shaft
  • 2 x 0808-312 Beam
  • 3 x 45° Plate
  • 6 x P1 Bracket
  • 24 x M4x22 Screws – Socket Hexagon Button Head
  • 8 x M4x35 Screws – Socket Hexagon Button Head
  • 28 x M4 Lock Nut
  • 6 x M4x30 Screws – Socket Hexagon Button Head
  • 12 x M4x16 Screws – Socket Hexagon Button Head

Step 1

Create the frame using an L-Shaped configuration.

Step 2

Install two right-angle connectors on the end of the base. You’ll be left with a triangular structure with the point facing forward.

Step 3

When you’re putting together the mainframe, leave the four corner screws alone. You’ll need these to attach the foot pads. Only use lock nuts on the frame because the vibrations that the machine will put out while in use will be powerful.

Step 4

Attach the foot pads to the screws in the corners, and the frame is complete.

Step 5

Now it’s time to put your friction wheel module in place.

Step 6

Now connect everything to the shaft. Tighten the screws.

Step 7

Process the rivets and then attach them to the friction wheel. It’s now time to glue on the timing belt. At this point, you want to leave the headless screw in place but not completely tightened. You’ll do that once you’ve finished with the whole assembly.

Step 8

Repeat with the other module to create the second friction wheel.

Step 9

Now that that’s done get the part you’ll be using in the bracket for the friction wheel ready, and then you can attach the friction wheels to the frame.

Next, after you prepare the part used in friction wheel bracket, you can install the friction wheels. Don’t forget to set the timing belts beforehand. You’ll use the longer belt at the top and the shorter one at the bottom.

Back to the friction wheels, one should be installed at the bottom of the frame so that it’s leading the frame. The other should be placed higher up, with the frame in front of it.

Overall, it should look something like an S-Shape. Make sure that there’s enough space between the two so that a tennis ball can fit.

Step 10

You’re ready to install the motor module now.

Step 11

Start with the synchronous belt wheels.

Step 12

The timing belt wheel can now be installed onto the shaft and linked up to the motor.

Step 13

Follow the same steps with the second motor module.

Step 14

When that’s done, the motors can be attached to the main frame. You’ll need to secure it with the motor brackets. Link the timing belts to the synchronous belt wheel before you screw the motors into place.

Each belt should be attached to a different motor, and the belts must be tight.

Step 15

It’s a good idea to secure the end of your motor output shaft. This step lends extra stability and ensures that it won’t shake loose easily.

Step 16

If necessary, adjust the timing belt’s tension by moving the bearing. It can now be fixed in place.

Step 17

To further stabilize the structure, run two support beams along the sides of the frame. These beams should be attached at an angle so that triangular shapes are formed between the original frames and these beams (get someone to hold the frame steady while you to do this).

Step 18

That concludes the construction of the support structure. Now it’s time to install the circuits. Start by welding the wires for the motor. Use a higher gauge wire and make sure to place a protective tube over the welds so that they don’t short circuit.

Step 19

The boards controlling the motor speed can now be installed. These boards will allow you to control up to a 10A current. For added stability, secure the circuit to some scrap wood or the acrylic board.

Step 20

You can now secure the sheet or scrap wood and the circuit board to the frame. Using the acrylic board is easier here because you just fit it into the threads of the two diagonal support beams that we used to reinforce the frame in Step 17.

Step 21

You’ll then need to splice together your power cord and attach it and the battery. Use a secure T-joint and make sure that the cord is connected to both edges of the circuit board. Check that all the connections between the circuit board and motor board are secure.

Step 22

You’re done. It’s time to test out your creation.

Final Notes

Building a tennis ball machine does require some expertise in electronics, but it’s not impossible. It could be a fun project to do with your kids. Or, if you’re not all that familiar with electronics, perhaps get the kids to lob the ball for you instead.