Rev rate and ball speed from an AirPod in your ball

Introduction

Rev rate is the number every bowler wants and almost nobody measures: dedicated sensor balls cost several hundred dollars. Kinapod reads it from an AirPod riding in the ball: drop the pod into the thumb hole, plug the hole with a piece of sponge, and bowl.

Every roll is detected automatically. The app knows the difference between your ball going down the lane and the return machine sending it back, so there is nothing to tap between shots. When you stop, the session is saved with a per-roll breakdown: rev rate, ball speed, axis tilt and roll time, plus totals, averages and bests.

What it measures

• Rev rate, the rotation speed of the ball at release, in rpm, read straight from the AirPod gyroscope.
• Ball speed, from how long the ball takes to travel the lane.
• Axis tilt, how far the rotation axis leans away from a straight roll, in degrees. Straight-ball rolls sit near 0°; more tilt means more hook potential.
• Roll time, how long the ball spends on the lane from release to the pins.
• Rolls and session stats, totals, averages and bests, per player when you play with friends. The CSV export also carries full revolution counts for each roll.

Kinapod is a practice and training aid. Metrics are estimates derived from motion sensors and are not a certified measurement instrument.

How to use

• Mount the AirPod
  • Drop one AirPod into the thumb hole.
  • Plug the hole with a piece of firm, springy dish sponge so it sits flush with the ball's surface and holds the pod snug. The sponge cushions the pin impact and keeps the pod from popping out. Give the ball a gentle shake: nothing should rattle.
  • Keep the second AirPod out of its case, near the phone, so the ball pod reconnects quickly after each roll.
• One-time AirPods setup
  • In iOS Settings, Bluetooth, tap the info button next to your AirPods and turn off Automatic Ear Detection, so motion keeps streaming while the pod is out of your ear.
• Record a session
  • Open Kinapod, pick Bowling, choose who is bowling, and bowl.
  • Rolls are detected automatically, and the return machine is recognized and ignored.

A pod in the ball may not be legal for sanctioned competition. Kinapod is built for practice: check your league or governing body's equipment rules before using it in play.