Pinewood Derby Track Timer and Lane Finisher. Need to build one for a six lane track, two sided display +- to a Computer


hoverbored5 years ago
Old school... I'm not qualified for computer interfaces, but this worked quite well 15yrs ago. Get a cheap stopwatch for each lane, all the same. Mount the watches with switches accessible, and first rig all stopwatch resets to one ground and one common reset switch (momentary) - resets all to zero in one move.

Now, for each lane, use router below lane to clear space for a microswitch with a long batton, clearing up THRU the track where the batton needs to interface the car. Do this very carefully, at the top (start - after starting gate, about 6inches) and bottom (end - before friction brake) of the track. Wire the switches in parallel, and then to the Start/Stop button for the lane.

Now for the really low-tech part: Cars can be hollow underneath! To avoid multiple start/stops - 1/2" above the beginning of the switch slots on the TOP, take a square and draw a line. Cut an index card just a hair's width narrower than the track, line it up short edge on the line, and tape it there. Tape will last for years if not abused. Same at bottom of the track. Card stock means car will only trip switch once per pass, not hitting once for the front of the car, popping up in the hollow, and hitting again at the back of the car (STOPPING the stopwatch!).

When cars are released, first switch starts timer, end switch stops timer. Read them off to someone on a spreadsheet. Start racing with one car, move the car one lane over, add a new car to the empty lane, and race again, till all lanes are in use, continue till last car goes down last lane. Have the spreadsheet (visible to the crowd via projector?) average the scores down each lane. NO QUESTIONS ABOUT FAIRNESS: Each car went down each lane, and their times were averaged to get their score... all the same for every car. No issues of how fast a lane might be, etc.

Switches on the watches need to be accessable, as on occasion, watches don't stop, switches bounce, etc. But 99% of the time, this was rock solid and unquestionably fair. If you use molex or DB-9 or DB-25 connectors, it makes track disassembly easy. Can rerun one car down one lane for any clock screwup, derailing, etc.

WARNING: Make your inter-lane space wide enough that wheel-to-wheel interference is almost impossible. Beef-up your track joints with VERY solid wood, almost 'shingling' (upper piece, a tiny bit higher than the lower piece) the lath material of the lane at the joint. Experience is the best teacher.

There are DEFINITELY more 'elegant' setups, but this worked great for a bunch of guys setting up their first track, the kids had a ball, and not a single parent said "That's not fair!"

Make 'official' certificates of participation for EVERY RACER - certificate paper and judges signatures are COOL!. The more racing and design judging categories means more ribbons, which means more excitement, which makes for a real 'hit' with everyone. Design categories: We did several [1st/2nd/3rd for all, of course!]::
  Best Design - most beautiful car on the table!, 
  Best Cooperation - You can tell the kid had a hand,
  Most Unusual - Well... Some cars don't come looking like CARS! How DO you judge a whale with wheels, or a conestoga wagon??

OH! And have the kids yell at their cars. Proven fact they run 3-5% faster!! <grins>