OK, I am building a racetrack for a local boys club for pine box derby. I have all the dimensions and such that I must adhere to, and I am trying to add a little local flavor to the deal by building a finish line that will register which lane won. Nothing electrical, just a trip of some kind that will throw up a flag (or even turn on a light, yeah, I know that's electrical) indicating which car crossed the finish line first.
Anyone ever done this and if so, how did you do it. I have my ideas, but would like to hear others before I start on that part. I have to have it done by the first week of May.
How about a "photo-finish" --connected to a "big screen", of course. A little "mood audio" (racing sounds) in the background shouldn't be too hard to locate (my dad took care of that part years ago, borrowing the audio from the library).
My first thought was to try to use the torsion spring from a mousetrap, but I couldn't decide how to fairly decide close calls. Have fun!
Robert, How many lanes? If there are only two, it should be pretty simple to make a flap for each lane, with the hinge for each flap flat to the bottom of the lane, but angled so that the outer end of the hinge is further down the track than the inner end. After the cars both pass the flaps, the flap for the first car will be under the flap for the second one. Kerry
If you mean Pine Wood Derby, them you must polish the axle / nails. It is best to have the most weight in the back. Another tip, is to only have 3 of the wheels touch the track.
If while runn> OK, I am building a racetrack for a local boys club for pine box derby.
I'm reluctant to add a berry to your apple pie but this is an idea that is cheap, simple and easy to reject, if, on hearing it, you say nay. With a bit of interpretation, it also skirts your ban on electricity as that means line power.
Walmart and other retailers sell a very, very cheap, portable, battery-powered photocell alarm. The configurations of features and modules vary. If any of them will function in the light levels you have, they could contribute sound effects as a car crosses the line. Features will dictate possible applications.
For just recognizing the winner, one unit would work. Should you prefer to cover the four cars, perhaps one alarm can be switched on and off fast enough to handle the field. Again, with the availability of operators, multiple units could be set up and each unshielded as successive cars crossed the line. Various photo/video notions worthily mentioned might add this audio component to further memorialize the event.
Structurally speaking, if you build your track with staggered start/finish positions, alongside the lessened possibility of race collisions (read "liability") at the cost of some drama, your variations on rigging chiming/alarming photocells would expand.
It later came that you could mount the above units under or over the track, obvious restrictions and considerations allowing. That would obviate much of the fiddling needed in a horizontal plane. The model I saw had two sound alerts. That gives you enables you to cover 2 lanes distinctively. Find offering with the same capacity and 4 lanes are now marked separately.
On the mechanical flag-drop, I thought. Without knowing the design constraints or your own formulation, pondering goes wide. If you can let us hear what your considerations are along with the ideas contending, that would likely be best.
I've had an idea, let's see if it would work. Just pased the finish line are a series of cross-linked levers going across each lane. The lever in each lane prortudes only about 1/2" or so into the lane. When the first car passes by the lever, it switches the position of all of the levers, for example from this position / to this position \ . All the successive cars would be caught by the switched lever. Obviously this isn't going to give you millisecond timing, and the clearances/tolorances will affect accuracy, but this is purely mechanical and uses no electronics. This is a mechanical "flip-flop" and something like this is used in marble machines.
My design is a simple trip lever that does two things; puts the flag up on the winning lane, stops the other flags from going up by dropping their trip levers out of the way (or prevents flags from going up when tripped).
That requires simply a trigger for each flag (flag goes up under counterweight assist when released) and the trigger releases a block that stops the other flags from going up. I will try to do a drawing and post it somewhere.
Let me recommend the book/download featured in this search to you:
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have the book and found it illuminating reading when considering fabricating mechanisms such as yours.
Probably the first thing you might do is find the established contenders for most reliable device in the Google search previously recommended. Then if you want to tweak, tweak.
In my thinking, one thing that recurred was a spring- mounted roller bar set fully across each lane as a trigger mechanism. Because it would cover the lane, contact would be reliable and less prone to "steer" a car. Depression of the roller would work to actuate your mechanism, the springs would both attenuate car impact and automatically reset. For safety purposes, you could also contain the axles of a roller in a box against failure. Working under the track may be more cumbesome, so that might be a consideration for you.
You might also try posing your notion here and on rec.crafts.metalworking when you get a tentative design viewable on the web.
I have several portholes, sliding pole and a submarine door here for an eventual "He-Man Boys Club", so I appreciate your work.
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