Race Car


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  1. The operation of the unit should be checked as soon as you receive it and before mounting the Start Sensor and Finish Sensor(s) onto the track.   For this purpose, the supplied metal starting Flag, which serves as an optical blocking device for the Start Sensor, can be manually positioned within the slot of the Start Sensor (see Figure 2B below), and manually removed (see Figure 4B) to simulate starting of a race.   In a similar manner, any thin and opaque object, such as the flag of a collision block or a corner of a card, can be inserted into and removed from the slot in each of the Finish Sensors when simulating events at the finish line.  The operation of the timing unit can then be tested by manually simulating a race and verifying the timing and display steps described separately in the section on DETAILED OPERATING PROCEDURES.   In your simulation, be sure to remove the flag or card blocking the slot of each Finish Sensor within 10 seconds of having removed the Start Flag from the Start Sensor; otherwise the results displayed will not be fully useful in assuring that the unit is working properly.

  2. Mount the metal Start Flag (see Figures 1 through 4) to the track Start Bar using one No. 6 x1/2" long, oval-head, self-tapping screw as supplied.   Mount this metal Start Flag in such a way that its Flag part moves cleanly and fully into the slot of the Start Sensor when the Start Bar is in the "Ready" or cocked position.   This positioning is best done in conjunction with the mounting step of the Start Sensor itself, given in the next step.

  3. Mount the Start Sensor (see Figures 2A&B and 4A&B) to the underside of the track such that the metal Start Flag can be repeatably positioned within the slot of the Start Sensor when the Start Bar is in the Ready or cocked position.   This slot is in the black plastic part of the Start Sensor assembly.   Use two of the No. 4 x3/4" long oval head self-tapping screws as supplied for this purpose.   In preparation for mounting the Start Sensor, make a shallow groove about 1/2" to 1" long in the bottom of the track (and clear of the holes used for the mounting screws) to allow cable clearance under the Start Sensor assembly.   Alternatively to providing a cable-clearance groove, space the Start Sensor off from the bottom surface of the track by using washers or other suitable spacers.   Before a race starts, the metal Start Flag blocks the invisible infrared light beam that otherwise crosses the width of the slot of the photosensor which is inside the Start Sensor.   Rotating the Start Bar swings the metal Starting Flag out of the slot of the photo-sensor and thereby starts the timing of a race.   The alignment of the metal Start Flag in relation to the slot of the Start Sensor should be performed carefully so that the metal Start Flag will not crash against the body of the Start Sensor when the Start Bar is rotated into the Ready position.   In other words, the metal Start Flag should be made to swing smoothly into and out of the slot in the Start Sensor without interference.

  4. Attach a rubber band (see Figure 2) between the Start Bar and the underside of the track to enable the Start Bar to be automatically rotated by the force of the rubber band when opening the gate to release the cars in starting a race.   This will help assure that the track operator will not affect the race times by lowering the Start Bar at a different rate with each race.   It is recommended that each end of the rubber band be anchored to a nail or eyelet as illustrated (see Figures 1A, 2A, 3A, and 4a).   [Also, it is suggested for your convenience, and for race-time repeatability, that you install a simple Trigger/Release mechanism on the track Start Bar to hold the start gate closed until an operator triggers it, or otherwise releases it, to start a race.   The recommended mechanism for this purpose is the Start Handle illustrated in Figures 1A&B, 2A, 3A&B, and 4A.   An alternative Trigger/Release mechanism can be made from a strip of 3/32" thick aluminum, and then attached to the underside of the track with a screw.   Another alternative is a piece of heavy-gauge coat-hanger wire bent-to-suit for this same purpose.]

  5. Figure 5 shows how Finish Sensors (with Collision Blocks) operate, whereby each car crossing the finish line collides with a Collision Block located on the finish line in the middle of that car's lane.   Figure 6 identifies the features of a Collision Block, in particular showing the optically opaque Flag that extend below the bottom front portion of the block.   Each Finish Sensor has a slot across which an infrared beam of light passes, the beam of which can be interrupted by insertion of the Flag of a Collision Block.   Figures 7, 8, and 9 show more clearly how the Flag of a Collision Block is to be positioned within the slot of a Finish Sensor before a race begins.   Figure 7 shows the sensor and tube assembly pushed up through the track from below and to a position higher than normal for illustration purposes to show that the tube does not cover the end of the PCB that has the actual slotted photosensor device.   Figure 8 shows the sensor and tube assembly back down into its required position with its top edge flush with the upper surface of a lane's guiderail.   Figure 8 also shows a short tapered groove made into the top surface of the track's guiderail.   This groove should be shaped to facilitate clearance of the Flag of a Collision Block when it is knocked out of the slot of the sensor and down the track (see Figure 12 and the comments above Figure 8 below for recommended dimensions and placement of this groove).   Figure 9 shows a Collision Block in place over the sensor ready for sensing the arrival of a car at the finish line.   Figures 8 and 9 also show that the solder-side of the PCB should face up the track, and the slot should face down the track.   Figure 10 shows a car racing toward a finish line, whereas Figure 11 shows the car as it arrives at the finish line and just before it knocks the Collision Block off of the finish line to end the timed duration of that car's racing performance.   Figure 12 shows, from a top view, the dimensions and placements required for a Finish Sensor Installation Hole in each lane of the track.

  6. Be careful to mount the Finish Sensors in each lane along a common finish line.   First draw a straight reference line perpendicular to the lanes at the finish line.   Drill the Finish Sensor mounting holes along this line, but centered about 1/8" closer to the starting line.   After mounting the sensors into the track, carefully position the flags of the collision blocks into the slots of respective slotted photosensors.   Once all blocks are equally positioned in respective sensor slots and along a common imaginary finish line, draw (or score, or paint, or tape) an official finish line such that it lies directly under the collision surfaces of the collision blocks.   Thereafter, from race to race, always replace the collision blocks in their positions on this finish line to an accuracy of at least better than 1/16".

  7. Before mounting the Finish Sensors on the track, choose them to correctly correspond to which lane numbers are associated with each lane.   It is advisable to mark the track lanes with their desired lane numbers.

IMPORTANT: To protect each sensor from potential damage caused by excessive pull on its cable, clamp (or duct-tape) each cable securely to the bottom surface of the track within 4" to 6" of the respective sensor, leaving some slack between the clamp (or tape) and the sensor.   At the end of a derby, before taking your track down for transportation and/or storage, remove the sensors and cables for their protection.   Do not store the collision blocks in a compressed shape as that may deform them permanently.

start-gate views from above when ready to race

start-gate view from below when ready to race

start-gate views from above after finish of a race

start-gate views from below after finish of a race

View of Installation and Operation of a Finish Sensor

View of Collision Block showing its flag

Figure 7 shows the upper portion of an assembly of a finish sensor in its mounting tube pushed from below the track up into its mounting hole at the finish line, but pushed further up than normal justfor illustration purposes.   Note that the proper assembly of a sensor in its mounting tube does not position the actual slotted sensor device inside of the tube:

finish-line photosensor pushed up for viewing

Figure 8 shows the sensor assembly pulled back down to its proper location with the top of the sensor aligned flush with the upper surface of the track.   Note that the slot of the sensor faces down the track and that there is a short tapered groove that should be made into the track in order to facilitate clearance of the flag as it leaves the slot of the sensor when the block is struck by a moving car.   And note that the collision surface of the block is that surface above the flag.   The groove can be made with a knife, chisel, or file, and should begin at the mounting hole where it should be at least as deep (About 3/16" deep) as the height of the slotted photosensor to provide sufficient room for the flag to block the slot of the photosensor.   The groove should taper and become more shallow as it runs away from the hole over a distance of at least 1/2" down the track.   Note that masking tape can be used to cover over the sensor's mounting hole leaving exposed only the slot of the sensor and the groove in the track, as this will facilitate guiding the flag into the slot when placing a collision block properly over the sensor:

finish-line photosensor in place and collision block tilted up for viewing its flag

Figure 9 shows the collision block and flag in proper placement over the sensor, with the flag inserted within the slot of the sensor, and with the front collision-surface of the block consequently lined up with the finish line:

collision block positioned correctly over finish-line photosensor

Figure 10 shows a car racing toward the finish line:

image of sensor on PCB

Figure 11 show the car at the moment it reaches the finish line and is about to knock the collision block off of the finish line to stop the timing of the race:

image of sensor on PCB

Figure 12 is a drawing of the guide rail for one lane at the finish line of a track and shows a mounting hole for a finish sensor and a short and shallow tapered groove that should extend a short way down the track from this mounting hole: