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.
google is your friend
the first 2 returned are
there are only 23900 more links to investigate.
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!
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.
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 running you are not doing well in forward, turn the car around
and see if it runs better.
On 04/19/2011 02:48 PM, Robert Allison wrote:
I like the idea of a "photo finish".
A simple video camera hooked up to a lap-top which simultaneously feeds a
large screen monitor (donated for the event).
You could even jazz it up with a split-screen showing a wide angle view of
the entire race track. An elapsed timer in the corner.
If a dispute, think SLO-MO INSTANT-REPLAY.
Print each race to a CD to give to each contestant.
The mind reels.
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
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
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
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.
Good luck. Have fun.
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.
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
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:
I 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.
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.
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