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I protoyped and made this device in 1983 at the Franklin Institiute  
for our Changing Earth Exhibit.  Hadn't seen it before then, but  
maybe it did exist before that.    There were three 3inch diameter  
plexiglass tubes  about 18 inches long, each on it's own vertically  
oriented turntable.   They had 1/4 thick walls.
Their ends were capped with plexiglass and Orings with threaded brass  
rods running the length of the tube holding the ends on.  Here's why  
to do three tubes on three turntables:  The first has as a label  
"Same size, different density"  and has about 30 steel and 30 nylon  
balls @ 3/8 diameter.  They are in Mineral oil bought at the drug  
store.  Turn the tube over and the steel balls fall much faster  
through the liquid.  The second tube has "Same density, Different  
size"  and has steel ball bearings 3//8, 3/16 and 1/16 of an inch  
diameter balls, also in mineral oil.  The small balls take quite some  
to get down to the bottom of the overturned tube.   The reason is  
that the surface area of a solid sphere goes up by the square, while  
it's volume and therefore mass goes up by the cube.  The third tube  
has real stones and sediment in it.   Experiment with what you use  
here; it was nice having some really fine sediment that would leave a  
layer on top if it was allowed to sit for ten minutes.   Big  
particles  lined the bottom, and by picking materials of different  
densities that had different colors, you could get some nice layering.

The overall text explained how the size and density of material in a  
stream decides how far downstream it gets carried.  Boulders don't go  
very far.  The finest silt can stay in suspension to make it all the  
way to the sea.

We did add a leather pad in the back to keep it from being spun at  
high speed.

I might be able to dig up a photo if it would help.

Clifford Wagner
On Aug 18, 2008, at 6:04 PM, Mike Levad wrote:

> ISEN-ASTC-L is a service of the Association of Science-Technology  
> Centers
> Incorporated, a worldwide network of science museums and related  
> institutions.
> ********************************************************************** 
> *******
>
> Hey Everybody,
>
> We are building a sediment model which consists of a tube with a  
> clear fluid
> in it and different sized particles. When you turn it over the  
> bigger stuff
> hits the bottom first and the little stuff stays on top.  I have  
> seen this
> in a few different places.  Is anybody willing to share what works  
> best for
> the clear fluid and the sediment particles?
>
> Thanks,
>
> Mike
>
>
>
>
> Mike Levad
> Lead Exhibit Developer
> 651-789-4735 (direct)
> 651-631-2211 xt.735
> 651-631-0707fax
> Toll free: 800-433-9599
> [log in to unmask]
> www.splitrockstudios.com
>
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