Slurryguy,
I guess great minds think alike! My final seal, to keep water from
sneaking down into the gear box is a piece of rubber captured between
a flange and the tank bottom. Actually, I drilled and tapped through
the tank bottom and into the plate that supports the gear box:
http://ph.groups.yahoo.com/group/papercreters/photos/browse/ab7c?c=
(you can't see the rubber, as it snugs up against the drive shaft.)
So far I haven't seen any indication of water getting to the gearbox.
Note: before bolting the gear box to the support plate, my friend
cut to close tolerance a piece of nylon or teflon sheet (about 1/8"
thick). We sandwiched this between the gear box and support
plate. This is defense #1 against water. Defense #2 is the rubber
seal under flange, shown in the photo link above. Defense #3 is to
drain the tank when not in use!
Also in the photo section is the latest blade design, revision
#4. Revision 1 was a standard 21 lawnmower blade. A radius bend in
the blade designed to suck air up in a lawnmower application caused
paper pult to fly out and up. I cut down the radius in Rev. #2,
and it was better, but still pushing things out and up. Rev #3 was a
squarish Stihl 9" edge trimmer sharpened on four corners -- cut fine,
but no vortex action to pull material into blade's path. The blade
shown is now about 15", with the radiused sections cut off. This is
my best blade yet, as it tends to suck material down in a vortex, and
push material out at the bottom. It works pretty well, but I would
like to see a more aggressive vortex -- some of the material furthest
away from the blade moved too slowly, increasing mix time. Speeding
up helped, but still not quite right. I've also just been testing
with paper pulp, and once I add in portland cement it will slow the
vortex down even more.
When I cut off the ends of the blade, I was intending to sharpen the
curved side and mount the blade upside down. The curve would prevent
material from getting hung up on the blade, and mounting the blade
upside down will hopefully change the vortex direction. This will be
my next revision blade, #5. But being curious, I just had to see how
it would perform with the airfoils gone.
Fluid dynamics by experimentation. You need to create enough motion
to keep your material moving in to the blade's path, but not so much
that most of your material goes flying out the edge. If you suck
material into the blade going down, you miss the fun of seeing your
papercrete flying through the air. My tank cover works great, but
what I see from blade Rev #4 it is possible to get the blade geometry
such that you can actually mix with the cover off. And it is useful
to be able to closely monitor pulping and mixing.
Incidentally, I picked up a usedand broken lab-size high shear mixer
(1/2 hp). I put it in 5 gallon bucket with some soaked paper. Once
it got going it was amazing to watch how the material flowed and how
emulsified (smooth texture) the mix got. High shear mixers and
emulsifiers clearly will produce the best papercrete, but the
equipment costs are sky high. I think the high speed mixers (like
3450 rpm), like Eli Sutton uses come close yet are within reach. But
then you're also making the process two step: one to create
emulsified pulp, and one to mix portland cement, sand, etc. I like
this two step process, but it is more work than just throwing
everything into a tow or PTO mixer as a one-step process. I think it
all just depends upon what you want your end product to look like, or
if you even care. After all, once it is stuccoed over, only you and
your crew will know what your papercrete looked like. Perhaps the
more emulsified colloidal paper will create a higher R-value...
Best,
Eric Randall
Fairfield, Iowa
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