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Harry Lipke

Best Box Design For Gravel

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I acquired a trommel with no boxes. It runs about 4-5 yph 

 

There are two separation screens, one 1/4" minus and the other 3/4" minus to 1/4".

 

The box for the 1/4" is easy but I'm wondering about the 3/4" minus box.  What type of a setup do you need to keep basically coarse gravel moving and keep still the nuggets in that size range?.

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I would say that minus ¾ inch is still pretty easy to
handle. It’s the rocks bigger than about 4 inches that give real problems – if
your boxes are steep enough to wash out larger rocks like that, you will also
push out finer gold at the same time. Those bigger rocks are the ones to worry
about. To handle the gravel between three quarters and one quarter of an inch,
I would build a box with Hungarian style riffles about three quarters of an inch
high over miners moss on the bottom. You will have some fine gravel sizes that
do not separate perfectly into the minus quarter inch fraction, and this type
of a setup will give you reasonably good recovery for both the minus 3/4 and
any fines that happen to make their way into that sluice box.


 

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Taller riffles are probably not necessary, but I doubt they would hurt.

Is there any kind of nugget trap for larger pieces or are the bigger nuggets not really present in the district in which you plan to work?

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There are pieces larger than 3/4".  Not just a "possibility"... they are there.

 

The trommel has a 3" lip at the outlet but I'm not so sure a larger nugget might not crawl the wall with the oversize and drop right out!  Maybe weld a 1 1/2" piece of strap on the inside of that lip to keep a larger piece  in?  What else can be used for a trap?

 

It has a 3" grizzly at the feed.

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There are pieces larger than 3/4".  Not just a "possibility"... they are there.

 

 Sounds like some sort of "nugget trap" at the throat of the hopper, before entering the trommel

would be a better choice.

  Guess you would have to weigh the factors, how prevalent are larger nuggets. At 4-5 yph you might be better off just

metal detecting the coarse for nuggets.

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Thanks for the advice.

 

I don't think a trap at the inlet is possible as the material almost drops straight down into the trommel.

Maybe someday if we have a conveyor on the oversize, we could put a detector there with a "trap" door.

I hate to move the oversize too many times.......... move it from trommel, move it to an area to detect, spread it out, scoop it up again.

 

Scratching my head....

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