Tennis Ball Pickup/Feeder

As tennis captain, I noticed my team waste ~20 minutes every practice picking up balls by hand. We didn't have a ball machine, so feeding drills meant someone had to stand and feed balls instead of practicing. Commercial ball mowers run $850+, and reliable entry level ball machines start around $1,000. Buying both would cost $2,000+ and still leave us with two separate pieces of equipment to store and maintain.

I designed a dual-purpose machine that does both jobs: picks up balls when you push it across the court, and feeds them back during drills. In testing, it cut our daily pickup time significantly and gave us a ball machine we otherwise wouldn't have had.

My initial design used a drum with divots cut into it, so that balls would nestle into the cups and get carried up into the hopper. It worked sometimes, but jammed constantly when balls didn't seat properly.

The current design compresses balls between two surfaces, a fixed rear wall and a rotating drum at the front. As you push the cart forward, the drum spins and squeezes balls up and over into the hopper using the forward motion provided. This approach handles misaligned balls much better and eliminated the jamming problem.

I reverse engineered a commercial ball machine to understand the ejection mechanism, where motor driven wheels grip and launch balls at adjustable intervals. I implemented this in my design, along with a 3D printed funnel that channels balls from the 350 ball hopper down to a central feed slot. The funnel had to be split up due to available printer bed sizes. I also planned to build a web interface to control feed rate and oscillation patterns, so the user can set it and step onto the court without needing someone at the controls.

The hopper itself is a repurposed team cart from our high school tennis equipment, with welded sheet metal panels added for weather resistance. Reusing the cart saved significant cost and gave me a proven frame to build on.

I estimate the bill of materials would come to roughly $500, with $250 for bent sheet metal, $80 for the repurposed cart, $70 for motors and electronics, $50 for batteries, $20 for 3D-printed parts, and $30 in hardware. Since I made this at my high school, I had a lot of parts that I got for free. $500 is about a quarter of what commercial alternatives would cost, and this would be with having two machines instead of one.

The design is cost effective enough to sell to other programs and local clubs, saving them hundreds per unit compared to buying separate commercial products.