Your Most Reliable
Tennis Training Partner
Frustrated with $100+ per hour tennis lessons?
Hi, I'm Sophie Luo, creator of rallie
I'm a:
- UC Berkeley & UPenn-trained engineer and robotist
- Serial entrepreneur based in San Francisco
- Passionate tennis player
I've tried nearly all the tennis ball machines on the market but found none of them satisfactory, so I decided to build my own! Read more about my story here.
I aim to build the most COMPACT, DURABLE, and INTELLIGENT tennis ball machine ever.
My current design is:
- •80 MPH top speed
- •Topspin, backspin, volley, and even sidespin
- •Internal oscillation
- •30% smaller and 30% lighter than current models
- •Lots of AI functions to make your training really personalized (and interactive :D)
Join me in shaping the future of tennis training!!
Development Progress
Follow along as we build the most compact, durable, and intelligent tennis ball machine ever. I'll be posting regular updates about our development process, challenges, and milestones.
May Update: Draw Winner, Development Progress, and My Take on the New Kickstarter Campaigns (AceMate, Tenniix)
May Draw Winner Announcement
Congratulations to Delice for winning our May $100 Tennis Warehouse gift card draw!
Drawing results from May 9, 2025
$100 Tennis Warehouse Gift Card
Delice, I will reach out to you in a separate email and have this gift card sent to your email.
Thank you to everyone who participated in our survey and referred friends! Your feedback is invaluable as we continue to develop our tennis ball machine.
Development Progress
Hardware
We're making exciting progress on the hardware front!
We've successfully assembled our first prototype using RoboMaster motors and 3D printed parts to test our "dual flywheel launching" concept. The results are promising - we achieved launch speeds of ~75mph, confirming that our design direction is on the right track. For the pitch and oscillation mechanisms, we implemented custom-designed and 3D-printed gears, though we did identify some durability challenges that need to be addressed.
Based on these learnings, we're now advancing to the next development phase. Instead of continuing with off-the-shelf motors (like the RM 3508), we've designed custom motors and sent the specifications to a specialized manufacturer. On the mechanical side, one key improvement is the implementation of a worm gear shaft system, which should significantly enhance durability and control precision. Additionally, we're testing a new flywheel design that promises to further reduce the overall volume and weight of the machine - making it even more portable and user-friendly.
First prototype design with RoboMaster motors and custom gears
Close-up of the dual flywheel launching system
Software
On the software front, we've made significant progress! We've developed a functional app that can detect player position and poses in real-time, and through our custom reasoning module, determine the optimal ball placement for your practice session.
We've also started experimenting with training custom models to better adapt to various lighting conditions and camera positions, which will ensure consistent performance whether you're playing indoors, outdoors, or in changing weather conditions. If you have expertise in computer vision, I'd love to connect and discuss potential collaborations!
Now that the core functionalities of phase 1 are developed and being tested, our next focus is enhancing the user interface and experience. If you're interested in being an early tester, please reach out and I can add you to our TestFlight (sorry it has minimal UI for now).
I've been monitoring feedback from users of other ball machines, and features like offline editing mode and real-time ball speed and spin data displaying on app are often requested. Don't worry, these will all be standard features in our app - we are the only team on the market that understands both technology and tennis.
Other Updates
We expect to have several EVT (Engineering Verification Test) units ready by late July or early August. Once these are shipped to the States, we plan to host several user testing events in the Bay Area this summer. If you're local and interested in being among the first to try our prototype, please email us at hello@rallie.tennis. We're particularly looking for players across different skill levels (from beginners to advanced) to provide diverse feedback.
My Thoughts on Acemate and Tenniix
As some of you might have noticed, there are two projects that recently launched Kickstarter campaigns: AceMate and Tenniix. Both feature autonomous mobility for "rallying style" playing.
From what I'm seeing in the pictures, both products present significant risks in terms of durability, battery limitations, and potentially overadvertised capabilities. As someone who's been working on autonomous robotics, I don't see a real rallying robot that's durable on outdoor courts with compact design and 4+ hours of battery life coming in the next 2 years.
Development Update 3/22 - 3D printed parts, motors and other issues
The 3D printed parts have arrived! There's some issue with the precision of these components, particularly the section for ball ejection. We'll need to reprint these parts to ensure a proper fit and function.
Read more about our March updates →
Help Shape Our Product
Your feedback is invaluable as we develop our tennis ball machine. Take our survey to share your experiences and preferences - and you could win a $100 Tennis Warehouse gift card!
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