Dear papercrete friends and patient advisors:
I just posted some pictures on the papercreter's yahoogroup site of my
new 55 gallon drum based papercrete mixer powered by a 2 horsepower
electric motor. The mixer and I were recently the object of a local
green newsmagazine article (not online, unfortunately).
http://ph.groups.yahoo.com/group/papercreters/photos/browse/6495
The mixer is capable of shredding heavy duty cardboard up to 4 layers,
at least. I have stuffed in boxes that are as big as I can fit with no
trouble. It takes whole phone books, but only one at a time. It mixes
any junk paper, including packing tape and windowed envelopes. It will
not shred Tyvek DVD envelopes.
When I first started, I used the blades that were on the plaster mixer
that forms the skeleton of the mixer. The plaster mixer was designed to
be bolted onto the top of a 55 gallon drum. The blades were two twisted
6" bars welded to the end of the shaft in an x pattern. That simple
blade design overloaded the circuit breaker and finally the motor
overheat protector many times before I cut them off. This makes it
clear to me that straight blades are terribly inefficient, which
explains tow mixer are driven by 100+ horsepower trucks. As an aside,
my next mixer will be based on a 5 foot diameter stock tank with self
cleaning blade design.
Much of my design work has been on self-cleaning blades. There are two
pictures of the current blades, with two, three and four tips. The
blades are cut from cheap steel circular saw blades. More expensive
ones are hardened and will not allow the tips to bend enough to create a
good vortex without snapping. It doesn't really seem to matter how many
tips there are, as long as they spiral backwards enough.
I recently mixed an old hardbound textbook, the binding strings got
wrapped around the shaft, causing the only overload I have had with the
three blade design. The blade designs are adapted from Eric Patterson's
self-cleaning blade design described in Gordon Solberg's Building with
Papercrete and Paper Adobe book.
The mixer blades are a vast improvement over the original 6" straight
cross blade originally on the plaster mixer shaft. I replaced it with a
self cleaning blade designed after a food processor blade. Later, I
added more blades with a lower angle to decrease mixing time and even
the vortex. They also allow me to make a very thick mix that settles
less when poured. I typically mix 20 pounds of paper, then add up to 5
pounds more until the pulp is thick enough to form a heavy ball in my hand.
The blades are only bent less than 1/4 inch at the ends, I have found
that anymore produces more vortex motion than shredding. With too much
vortex, pieces tend to circle up and down for too long without shredding
much wasting power. Too little and the vortex disappears when the paper
turns totally to pulp resulting in insufficient mixing of the Portland
cement.
I've been improving the design and making blocks for about 30-40 loads.
The design has been stable for about the past eight loads. The next
change I anticipate are adding a spiral folding bar. I now use a 2x3
stick attached to the inside of the barrel to fold in the vortex, it
catches too many small pieces of paper.
The mixer shaft and mount came from the plaster mixer ($35) which I
found at a local used tool shop where I also bought the 2 HP 110/220 V
motor ($80). The belt, pulley and metal shield around the motor came
from an old laboratory shaker/bath that I got from a university surplus
property auction for $5 - just the bearings are worth more than that!
Most of the rest of the parts came from a local used lumber/construction
materials company. I have two sets of forms, one 8 foot long, built
from 2x4's (pictured), the other from 6 foot long 2x6's (pix coming).
The first form has an expanded metal grate ($8) for a drainage base, the
second uses a sheet of steel with 1/16" holes punched in it ($27). It
is a standard part that I have seen somewhere before.
The new second form has two levels. The inside dividers are 1x6's
ripped down to 4 1/2". That allows me to overfill the whole form, then
trowel off the excess on top of the dividers. My blocks are coming out
really square and neat! More pictures then they dry.
The wooden parts for the platform and forms are scrounged from the
neighborhood for nada ($15 for deck screws).
The platform design includes a water recycling system that is still
going together. More on that later. At the moment, it recycles about
15 gallons of water from a 45 gallon load. I found a used submersible
pump for $20 that will pump the drainage water back into the next
batch. It has been very handy to pump harvested rainwater into the barrel.
Now that I have a reliable mixer that my wife, Terry, can operate, I can
get back to my other responsibilities!
Any questions?
Thanks,
Vince
P.S. more pictures to come...
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