The SW1 allows you to quickly and accurately measure the swingweight of racquets.
- Oscillates about a vertical axis to determine swingweight independent of racquet mass and balance.
- Uses your iPhone gyroscope sensor to measure with high precision. The companion app is available free in the Apple App Store.
- More compact and portable than any comparable device.
- Group measurements and see summary statistics. Displays the difference between groups to determine twistweight easily.
- Adjusts to your work area: configure it for left or right racquet release, and place your iPhone on either side.
- Scan the NFC tag on the SW1 with your iPhone to open the app. If you use more than one SW1, it selects the scanned device. (This features requires iPhone XS or later.)
- Calibration object included. It consists of a squarely cut and precisely measured black PVC pipe and a weight that can be installed onto the end of the pipe. Swingweights with and without the added weight are marked on a wrap-around label.
To use the SW1, you will need:
- An iPhone 7 or later. (Android app in open beta)
- Approximately 4,000 4.5 mm (.177 cal) steel BBs to fill the device. In the US, a package of 6,000 BBs is available from many retailers for ~$10. The SW1 is much easier to package for damage-free shipping when unfilled and can be filled easily without tools.
The plastic components of the SW1 are 3D-printed in PETG, which is tough, durable, chemical-resistant, and heat-resistant.
Video: Briffidi SW1 Introduction
Video: Briffidi SW1 Getting Started
Blog Post: Briffidi SW1 Linearity Testing
Questions & Answers
Q: Why is the SW1 not available pre-filled with BBs?
A: A filled device would sell for ~$70 USD extra, to cover the cost of BBs, protection parts, packaging, and time resolving shipping damage. Shipping would also cost more. BBs are widely available in the United States for ~$10 USD, and filling the SW1 is easy to do with no tools.
Q: BBs are difficult to get in my country. Can I use something else?
A: Yes. The BBs are used as ballast, so something similarly small and dense should work. The BBs required to fill an SW1 have a mass of ~1.35 kg, so that should be your target. One customer used small screws. That mass of lead fishing weights may work. Sand or common pebbles will not work, as they’re much less dense than steel.
Q: What happens if Briffidi ceases to exist?
A: The SW1 will still work. The app will continue to function; it does not contact a backend server. If the SW1 will no longer be supported, I will publish the app source code and the hardware design.
Q: How accurate is the calibration object?
A: I estimate that the marked calibration values are within ±0.3 and ±0.6 kg·cm² of actual for the bare pipe and the pipe with end weight, respectively. Each component is individually measured to determine the calibration values, and those estimates are based on a 3-sigma (99.7% within) error analysis of the process. I also measure the swingweights of each one to guard against measurement and data entry errors, and those measurements support the estimates.
Q: How often should I recalibrate the SW1?
A: If you move the SW1 to a new location, you should re-level and recalibrate it. I have marked the spot where I use mine, so I can place it back in the same spot and avoid re-leveling. You should recalibrate if the temperature changes significantly. For a typical racket, the measured swingweight increases by ~0.09 kg·cm² per °F (~0.16 kg·cm² per °C). Otherwise, it’s not necessary to re-calibrate except occasionally to verify that nothing has changed. When measuring racquets, I typically only take a quick measurement of the calibration rod with weight to make sure it’s close.
Q: Why does SW1 calibration require measurement of two known swingweights?
A: Two calibration measurements are required to subtract out the moment of inertia of the iPhone. It allows you to use any iPhone in whatever case you want (as long as it fits in the cradle securely). Of course, that means you should recalibrate if you add/remove a case or other mass to/from your iPhone.
Q: I broke something, can I get replacement parts?
A: Yes. I haven’t had to replace much, so I don’t have published spare parts. Please send a message to email@example.com, and I will work with you to get your SW1 back in service.