The Potato Launcher will use a
frozen mixture of sawdust and water, called Pykrete, as an alternate
projectile. Pykrete offers the same environmentally friendly
attributes of potatoes with the additional benefit of uniformity,
added mass, superior shape, and coloration.
Pykrete was
developed by an English mad scientist named
Geoffrey Pyke
around 1942. Pyke found that by freezing a mixture of sawdust and
water, a super-hard, slow-melting substance could be created. Plans
were made during World War II to build naval carriers out of Pykrete
that would dwarf anything available at the time. Due to lack of
funding, a ship was never fielded (a prototype was built, though) ... but today we can benefit from the
discoveries of that time.
The launcher was originally meant to use the standard, small, red
potato as a projectile. With a 2" diameter barrel, the potato could
be forcefully loaded into the launcher to ensure a tight fit
with few air gaps. Potatoes have the following benefits:
- Cheap
- Biodegradable
They are the traditional, number one choice because of their low
cost and natural composition. If a potato is not found after
launcher it's not littering... it's fertilizing. This second reason
is of utmost importance for legal and ethical reasons.
The potato, however, has a number of shortcomings.
- No regular size
- No regular shape
- No aerodynamic shape (causes the potato to flip end over
end)
- Light weight
- Earthy color hard to see in the grass
To create a more regular round, we began experimenting with ice
rounds. By creating a two inch PVC mold, we were able to make "ice
bullets". These bullets had several disadvantages. Most of all, they
would melt extremely quickly. They lost a considerable amount of
volume while extracting each round from the mold. Also, they were
fragile and would shatter fairly easily. They were also clear,
making them extremely difficult to see.
Pykrete enabled us to improve on the ice round. By adding wood
pulp / sawdust, we significantly increased the durability, weight,
and visibility while decreasing its susceptibility to melting. When
complete, the Pykrete rounds appeared satisfactory:
Molds were created to pour Pykrete into for freezing. The molds
were formed from 2" PVC pipe and a 2" PVC end-cap.
The outside of the tube was ground down using a grinding wheel to
prevent a lip forming at the end of the pykrete round:
 |
 |
|
Before
filing, a lip formed
in the mold, above. |
After
filing, the pipe the pykrete could no longer form
a lip inside the mold. |
The end cap was not glued down, but could be
removed to make extracting the frozen round much easier.
References