I couldn't believe that one team made a giant crossbow with strips of
plywood. Wondered if Brit plywood is made differently than the material
here
in the USA. Most of the plywood I've seen is a fairly coarse sandwich of
alternating grain direction and a better final layer. I would have thought
that there would be enough voids to substantially weaken the bow. The
first
shot was low with plenty of force though. Second shot hit the target but a
bit low. Third shot should have left the bow as before and just increased
the elevation. No, they had to pull it back so far that the bow snapped in
half. Glad that nobody got hurt.
Other team comes up with a spring driven swing arm that looked interesting
but literally fell short.
I sort of miss Geo from the NERDS with his calculator and analytical
approach to a build. I figured that the teams would build a projectile and
then figure its mass, and the amount of energy and at what angle to propel
it to target. No, none of that. Just the expert saying that this is what
we're going to do...
A few years back, the school kids here had a competition to make mouse
trap
powered model cars. The trick was to utilize the energy stored in the
spring
most efficiently. Cars had to travel a straight line course that had some
hills in it. Since the spring force decreases as it snaps shut, the idea
was
to use some variable ratio drive to keep the car moving at a fairly
constant
speed.
It was a good education in practical science,
Oppie
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