"The Avalanche" - Slingshot Of Mass Destruction

[MachineCrossbow]

the speed of rubber is limited - and so is the speed of the ammo

There is a workaround for this. I've been thinking about this, too. The problem is: the elastic energy of the rubber bands transforms into kinetic energy via acceleration. During this, the given energy gets distributed proportionally all over the moving parts of the launch mechanism, the proportionality factor being the mass. I mean, if the overall mass of the projectiles constitutes some 67% of the projectiles+rubber combined, then the projectiles
will have 67% of the given energy. This proportionality is valid, because of the presumption
that parts move at the same speed. In general sense, the energy distribution
is proportional to (velocity)*(velocity)*mass, which only differs by a 1/2 coefficient
from the E=0.5*v^2*m formula of kinetic energy. If your machine was made
such that the rubber bands launch the projectiles through a pulley system, the
balls would go faster, the rubber bands would go slower. According to the
v^2 part of the formula, the waste kinetic energy in the bands would be
"exponentially" less, and the kinetic energy in the balls would be more. In
other words, if launching through a pulley system, the mass of the projectiles
appears to be "bigger" to the bands. By the way, it's kinda reinventing the wheel,
because the compound bows and crossbows use the same principle (pulleys), to
achieve higher performance.

 

[JoergS]

Actually the pulleys in compound bows/crossbows allow a higher draw force as they have a "let off", which means that in drawn out position the draw weight is much lower than at the peak of the draw.

For slingshots, cams don't really work as the rubber stretches between pulley and pouch. If you use a string instead of rubber, then the contraption needs a bulky frame and the string acts like a lash, quite dangerous.

 

[MachineCrossbow]

That's true (let off allows for higher draw force), so I shouldn't have cited compound
bows for example, because it's ambigous if the higher performance is due to
the higher draw force or higher efficiency, evidently both.

Your objections against string is arguable, luckily, the draw distance of the rubber
would be [mechanical advantage of the pulley] times smaller. It requires shorter
structure to bear the load, and shorter elements are of course lighter, and less
susceptible to buckling. At the same time, there would be more rubber thread,
altough with less length (folded). With proper arrangement, the whole mechanics
would work like a spring-mass system, after firing, the mass (spring) just moves
through the 0 spring force point, and does an antisymmetric deceleration on the
other side. OK, it's complicated, just a thought experiment, right? Keeping
the whole thing simple also makes sense. Fabricating pulleys and such things,
after making an excel model or something, designing, I just like it.
I attach an image to show more details.
OMG, I'm lame at editing posts, I couldn't insert the image, I
just attached it, I hope it will show.
Anyway, the yellow is the rubber, the circles in the middle are the
pulleys, green arrows for speed, thickness for force.
There's a pouch equivalent whatever at the midpoint of the string.
Here the slingshot D) is not charged.
After launch, the pouch would oscillate around the resting point,
until all remaining energy has dissipated, so dangerous string
movement is controlled. The little complex two-way block-and-tackle
is for allowing the rubber to "bounce back", to oscillate.

By the way, I like your videos! I saw one where you shoot through
ballistic gel, it's surprising, how capable slingshots are.
I think firearm bullets waste too much of their energies
to speed up tissue, I mean wasting energy for the temporary
cavity, leaving less for damage. Of course, it's a question
of projectile, not firing device.

(Are slingshots illegal? No, they l e t h a l.)

 

[MachineCrossbow]

I forgot to mention that this thing (draft1) fires horizontally,
not vertically. One could get the wrong impression from
that sketch that it fires vertically.

I think I will build a working hardware just to show it's viability.
No quick results expected, however... I like more thinking
than DIY...That means, I may eventually come up with
another idea to achieve exceedingly high speeds, who knows,
I'm not stuck with rubber ropes. No explosives, of course. :banghead:

 

[MachineCrossbow]

...Yet another thing: I've seen more of your videos,
and noticed that you've already used pulleys, but
for directing the rubber band. In the draft and on
a compound bow, the pulleys make up a simple
machine, ein Flaschenzug. I mean that, instead
of single pulleys.