Put baffles in your mix tank. Then you can use a blade with vortex
overkill. The baffles keep the vortex from getting out of hand and
slopping. It will give you a lot more shearing action too. Faster
mixing/pulping.
(unless you're filling the tank to the edge.)
Put a hatch in your tank cover. Just the right size to inspect and
add paper through. Then you still get protection while fiddling.
Just make sure the hatch is not near the edge where slopping is most
likely. Think doughnut for a tank cover.
--- In papercreters@yahoogroups.com, Eric Randall <eric@...> wrote:
>
>
> 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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