[Rockhounds] Elutriation

[Flint Smith]

I would be surprised if it worked as described.  My initial concern was turbulence in the u-shaped areas.  Not a big deal, I guess, but fine materials might settle there with the coarser material.

This though sounds just wrong:
"Each glass tube had a smaller inside diameter than the one upstream, and they were connected in series with a rubber tube"

Smaller diameter would give a higher flow rate but later stages have to have lower flow rates to allow the coarsest grains from the previous stage to settle.

I propose the following design: 

mixed grit in sealed bucket
          
_____________
          
|                     ======= water inlet with regulated flow

          
|                     |

          
|                     |

          
|                     |
          
|  ___________|
          
| |

          
| |  

          
| | 

          
| |

          
| |            |            ====  rock dust overflows to waste


          
| |            |            |



          
| |            |            |



          
| |            |            |



          
| |            |            |



          
| |            \           ==== valve/outlet (fine)



          
| |             \         /




          
| |              |       |





          
| |              |       |





          
| |              |       |





          
| |              |       |





          
| |              \      ==== valve/outlet  (medium)




          
| |               \    /





          
| |                |   |







          
| |                |   |








          
| |                |   |








          
| |                |   |








          
| |                |   |








          
| |                |   |


          
| |                \   ====valve/outlet (coarse)






          
| |                 | |
          







L=========J

First open the upper valve and drain out the fine grit.  Then you drain out the medium grit, and finally, you drain out the coarse grit.




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