The
Challenge
By
the conclusion of the show it becomes quite clear that killing
someone with a playing card is really far fetched, but it
was just enough to self-challenge ourselves. The goal was
to hurl playing cards 45feet into a small trashcan flipped
on its side. I won’t get into the details of the bet
but one part of being the loser is taking A FULL 52 card
deck in the back from the winner’s machine!
The Feasibility Test
| Test
1
Dremel at high speed,
center positioned wheel. This is all handheld.
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| Test
3
Dremel at high speed,
off- center positioned wheel. Straight shot into
the dirt against the wall, note the straight lined
shadow. All other cards (not in line) are
in a location after the impact, bouncing back to the
camera.
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With the Dremel running at fulll speed - a full deck of
52 cards was shot from my hand in less than 2 seconds! Trust
me, 2 seconds is a generous estimate. Ok, from the initail
test it seems like it should be really easy to build a monster
card throwing machine!
Theres
a little physics to it....
Four
factors influence the flight of the playing card, speed,
rotation, gravity and air. Just for laziness sake - I'll
 only
write about the crutial factors...
A playing card is practically a slower flying model of a
bullet.
By spinning a bullet while it travels down a gun barrel
stabilizes its path after if leaves the barrel. Spinning
is intended to stabilize it through the air to the intended
target. The weight and length of a bullet factor into the
stability of the bullet and thus will affect a spinning
card similarly. The accuracy of the bullet would be affected
by different spinning rates of the bullet.
Since
the bullet spins when it leaves the barrel because of the
rifling, it has angular momentum.
Angular momentum stays almost constant throughout the flight
of the bullet, unlike the speed which obviously slows. This
is the same but much more significant with the playing card.
The angular momentum can be determined by the rate of twist
and velocity of the either the playing card or the bullet.
A playing card, like a bullet can spin too slow or too fast.
Bullets not spinning fast enough will “yaw”
or turn sideways in the air. By  “yawing”
the bullet will tumble and fail to connect with its intended
target. If a bullet spins too fast, it causes the irregularities
of the weight distribution of the bullet to be exaggerated.
Rotation is crucial. Without it a throw on playing card
would flutter and tumble like a falling leaf, because the
aerodynamic forces aren't perfectly centered. The lift is
often slightly stronger on the forward half of the card,
and so that half usually rises/falls causing it to flip
over.
When
these irregularities are started the bullet will start to
wobble and will cause the bullet/card to vary from its intended
course.When the bullet or a plying card is affected by air
resistance its linear momentum will also be  affected.
Linear momentum of is measured by the cards/bullets velocity
and the mass of the projective. The velocity will decrease
as the distance traveled increases. Air resistance and drag,
created by a playing card contribute to a decrease in linear
velocity of the bullet. You can see that while linear momentum
decreases and the angular momentum stays constant, a target
farther away will become harder to hit.
When
the linear momentum decreases with constant angular momentum
the card will yaw which causes the bullet to become unstable
and not fly to the intended target. These factors contribute
to the how the bullet will fly through the air to the intended
target. Recent tests with the last version of the card shooter
proves that these factors become significant at 40+ feet.
Prototype Testing
In Progress Development
3D Studio Comps of a Dremel based card thrower
Development
of Machine #1
Play
the first test shot video
Synopsis - Didnt work! Machine #1 was the loudest confetti
blowing machine on the planet!!! Ok, lets start Machine
#2....
Click to see the April 20th Competition!
On
to the Contest Day
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