PortaTree Accurate Drag Race Starting Line - Manual (Page 2)

Unblock the stage beam light source and make sure that there is no crosstalk between the pre-
stage and stage photo detectors. This is done by going over near the light sources or reflectors and
blocking each light source separately to make sure neither light source has an effect on the other. We
usually take a 4 inch square object and move it through the beams at the light sources or reflectors. This
will immediately tell if there is any crosstalk.
The rollout wheel should now be placed in the racing groove and should be rolled into the pre-
stage and stage beams. Each time a pre-stage light or stage light goes on or off on the Christmas tree,
make a mark on the track surface with chalk. Roll in - - pre-stage on - - mark track - - roll in - - stage
on - - mark track - - roll in - - pre-stage off - - mark track - - roll in - - stage off - - mark track. Take
your ruler and measure the distance between marks and you should have 7 inches - - 5 inches - - 7
inches. If you have done your previous work correctly, then these measurements should be obtained.
The layout of your entire track can now begin. The starting line is the most difficult to setup and must
be square and true with the rest of the track and photo cell layout. If you know where your stage beam
line is located due to past surveying, then the rest of your track can be measured per our track layout
drawing.