Twin-loop timing line for race and lap timing: two steady tones, read by a single vertical coil on the vehicle

Inventor(s)

• River JamesFollow

Abstract

A timing line for race and lap timing made from two flat wire loops laid across the track side by side, sharing one conductor on the line. A trackside driver puts one steady tone on each loop, at two different frequencies, both always on, with nothing modulated onto either and no command, clock or wake-up sent through the field. Each vehicle carries a single receiving coil with its axis vertical, a linear amplifier and ADC, and a digital lock-in on each tone. Directly above the shared conductor the two vertical fields are equal at any height, so the vehicle is on the line where the amplitude ratio is one, whatever the coil's height, position, lean or gain. The vehicle's clock is set by radio or satellite time, never through the loops; the vehicle works out its crossing on that clock, and the trackside unit can recompute it. In simulation at 25 m/s the full fit of a pass finds the crossing to a few hundredths of a millisecond or better, and the ratio zero, which needs no model, is noisier but stays put when the gain steps or the coil's height changes during a pass. A gain mismatch between the two tones, and unequal coupling of each tone into the other loop, are the new sensitivities; the drive and calibration that remove them are described. An overhead version, a painted-line installation, a field model, a Monte Carlo and the code are included.

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.

Recommended Citation

James, River, "Twin-loop timing line for race and lap timing: two steady tones, read by a single vertical coil on the vehicle", Technical Disclosure Commons, (October 20, 2026)
https://www.tdcommons.org/dpubs_series/12333