ZBSprint Free

Cadence baseado BMX Sprint timer. Non-logging versão gratuita.

Win the gate and win the moto.

ZBSprint aims to assist BMX racers in sprint training. Enter your bike data, sprint distance and target ET - get sprinting.

ZBSprint requires an Android device with built in compass (magnetometer) and accelerometer - which basically all have. Seems hard to find magnetometer information in smartphone specs, and the easiest way to know if it is supported on your device is probably by downloading any of the compass apps. You also need a powerful magnet. Pick the magnets out of an old spinny disk HDD :) Or buy one on ebay or at your hardware store. If you pick one from a HDD it will be glued to a bracket. Instead of hurting yourself trying to pry them off, follow the instructions on youtube (link below). We used HDD magnets wrapped in heat shrink tubing.

Setup is easy: magnet goes onto inside of pedal axle which should be steel. Android device goes onto top or down tube, close to where pedal axle will pass on crank revolution. The frame itself, and the seat rails (pretty much anything), can interfere with the magnetic field. We tested using a modified workout-phone-holder. If the phone hits the ground, it will probably break. Just so you know. Before strapping the android to frame, calibrate the compass by moving it in a figure-eight while rotating it in all three axis (link below). The magnetic force field reading should be somewhere around 40 - 60 uT (presented in app). When mounted onto bike this can reading drop quite a bit - everything disturbs the magnetic field. Test the magnet and handset by starting a sprint and moving the magnet close to the phone while looking at the crank rev counter. Result is depending on where in the phone the magnetic field sensor is mounted.

Initial tests were performed using an LG G3 which (probably) has its magnetic field sensor in the upper left. To have the sensor as close to the crank arm as possible, the phone was strapped to the top tube with the top of the phone facing the seat tube, and magnet mounted on inside of right pedal. Improvisation is key. Mount the phone in the way that works best, and keep doing it that way. The application also allows for magnets on both crank arms, whether this will work with your device is up to you to test.

More info, e.g. app preferences, are detailed on the app homepage. Follow the link.

By design, this app leaves much to be wished for in precision. However, if the application can provide consistent feedback on sprint training then it might just be worth the low ($0) investment. Final cadence and speed, and total elapsed time, of a sprint run can be just as important as the initial acceleration.

In the non-free version sessions are logged to comma-separated text files which easily are imported to spreadsheets and shared with your coach.

Don't hurt your self. Wear a helmet. Chains snap.

Yes, please email the measured circumferences (tyre + rim + circumference) and help us build a database.

Good luck!

knockesmockeathletic@gmail.com

youtube magnet brackets link - https://www.youtube.com/watch?v=GQhSy-Kz5DM

calibrate compass image link - https://lh3.googleusercontent.com/eloZBMBLQ9o8CC_84rfN-JedVCdzStQhhbs1FImcgOEmUYoeijg-tS4xNh6Kmd234n4=w350