TFT (formally FOE) Timing Lights

A Brief History

Following a conversation with Ted Reading of the National Sprint Association, it was decided it would be useful for me to provide a technical description of how TFT/FOE timing light and drag/sprint systems work, especially for competitors new to the sport.

Back in 1985, we were approached by Performance Bikes magazine, who were then having difficulty in measuring the top speed of motorcycles. They did have a Radar system, but it frequently missed bikes completely, especially above 150mph. Eventually after about 2 years of development, we produced a speed trap system consisting of 2 modulated infra red light beams and a control box. The system was designed to measure speed to an accuracy of 0.5mph at 200mph.

Several of these systems were made and sold to motorcycle magazines and proving grounds. In 1988 we were contacted by the NSA to make a sprint system, consisting of a start beam a stop beam and a speed start beam. Two of these systems were purchased by the NSA to replace white light equipment. Over the following years these basic sprint systems were developed into twin lane systems with a complete drag racing start line system (Straightliners) and a simplified drag racing start line system (NSA South).

Straightliners System Technical Description (updated July 2007)

For each lane, three start line beams, a 60ft beam, a speed start and an et/speed stop beam is employed, plus an additional set of beams (split) that can be placed to give a slit time and speed at typically 1/8 mile. A drag race start line tree is used with two white (stage & pre-stage), 3 amber (get ready), green (go) and red (false start) lights for each lane. Now completed for the 2007 season is a new clock that can measure 60ft times, split (1/8 mile) times and speeds, and terminal (1/4 mile) times and speeds.

The start line system consists of three beams, but only two are normally used for motorcycle events. The third is a guard beam for use in car events to prevent a low skirt or spoiler from staging deep. The first beam is a pre stage beam and the second is a stage/start beam. Once the timekeeper has reset the clock from the previous run, the pre-stage light (the smaller of the two white lights) flashes as a “call up” indication to the riders. As the rider moves forward and blocks the pre-stage beam the pre stage light stops flashing and remains on. As the rider then edges further forward he will eventually block the stage/start beam and the stage light will come on (the larger of the two white lights). Once both bikes are staged the start line marshal presses the start switch and the tree will then illuminate all 6 amber lights after 0.5 seconds. These amber lights stay on for 0.5 seconds then go out and the green lights are illuminated. A fraction of a second (<0.001mS) before the Green is illuminated, the control box logic checks that each rider is still staged, if he (or she) still is, then the Green is switched on, if not a Red is displayed. Once a Green light is illuminated, the elapsed time clocks are enabled, but will not start until the rider comes out of stage, which effectively means the start line beam is no longer broken. Note that if a Red is illuminated the elapsed time clock will not be enabled, as it means the rider was not in stage at the correct time. If the rider was not in stage, he (or she) cannot come out of stage to trigger the elapsed time counter, therefore no time will be recorded. However for the 2007 season, the clock has been modified so if a rider gets a red he will still get a time as long as he/she went on the Amber. If he the third guard beam is used this will also trigger the clock when broken if the clock has not been already started by the start/stage beam being made. This is only really likely to happen for cars will low skirts to prevent them gaining an advantage. Note the guard beam is the start of the quarter mile, not the stage/start beam.

The control box also measures reaction time to within 1/1000^th of a second. Reaction time is the time taken from the Amber being illuminated to the stage beam being “made”. In other words, the time from the Amber until the rider moves enough to start the et clocks. As time starts when the Amber is displayed, reaction times of less than 0.5 seconds are a disqualification. 0.500 would be the best reaction time you could get without being disqualified, whereas 0.499 would be a disqualification.

At 60ft the 60Ft beam is broken which stops the 60Ft clock to display the time to 1/1000^th of a second.

At the split, typically 1/8 mile on ¼ mile tracks, two sets of beams are used, 32Ft apart, a speed start beam and an et/speed stop. On breaking the speed start beam a second (speed) timer is started. On crossing the split finish and breaking the speed et stop beam both speed and elapsed time (et) timers are stopped. The et timer can measure to within 1/100^th or 1/1000^th of a second. The mph timer measures the time taken to cover the last 32ft to 1/10000 of a second. The logic in the control box converts this time into a mph reading and displays it on the front panel to within 0.1mph.

At the end of the track, normally a quarter of a mile from the start, a speed start beam is placed 32ft in front of the speed et stop beam which is at the quarter mile mark. On breaking the speed start beam a second (speed) timer is started. On crossing the finish and breaking the speed et stop beam both speed and elapsed time (et) timers are stopped. The et timer can measure to within 1/100^th or 1/1000^th of a second. The mph timer measures the time taken to cover the last 32ft to 1/10000 of a second. The logic in the control box converts this time into a mph reading and displays it on the front panel to within 0.1mph.

The control box also identifies which rider crosses the finish line first and displays a win light on the front panel. The appropriate Amber lights on the tree are then flashed to denote the winning lane. Once the timekeeper has recorded the times the reset switch is depressed which resets all clocks and allows the next two riders to stage. This win indication on the tree can be switched off for qualifying runs.

All times are recorded onto a computer database programmed by Martyn Greathead. The database has many features enabling the race data to be sorted and displayed in a variety of ways, with options to print individual time tickets after each run. Currently under development is a serial data link to connect the control box to the computer to automatically download times and speeds after each run. As well as reducing timekeeper fatigue and errors, this data link also will have the advantage of reducing the time between runs.