Parts List for 4" Subsurface Dredge

[Steve Herschbach]

Hi,

You can no longer buy a subsurface dredge off the shelf. However, Keene still makes a 4", 5", 6", and 8" subsurface dredge riffle tube that you can use to make your own dredge out of off the shelf parts.

Here is the parts list for a 4" subsurface dredge I built:

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4” SUBSURFACE DREDGE ( SUCTION NOZZLE )

PART # ITEM
KESS4 4” SUBSURFACE TUBE
KEPF25 2 – 2½” FLOATS
KESN42 4” X 2” SUCTION NOZZLE
KEP103BH 4HP HONDA PUMP W/BASE PLATE
OPTION - KEP103BCH 4HP PUMP W/T80 AIR COMPRESSOR
KESH4 15ft. 4” SUCTION HOSE
KEPH2 16ft. 2” PRESSURE HOSE
KESS72 4 – 4” HOSE CLAMPS
BJRB200125 2” X 1¼” REDUCER
KUPHC2F 2” PRESSURE HOSE COUPLER
KUSH15 4ft. 1½” SUCTION HOSE
KESS24 4 – 1½” HOSE CLAMPS
KESS32 4 – 2” HOSE CLAMPS
PANMM 6” MINERS MOSS
KEFV20 2” FOOTVALVE

NOTE: Frame is not included in this price because you will need to build your own. Tubing can be bought from Greer Tank. You will need 20ft. of 1” square aluminum tubing. See picture for simple frame assembly.

Two items of importance. First, I opted for a suction nozzle design as I wanted to allow the gold to settle before it gets to the box and to reduce the chance of the riffles being "blown out" should the prime be lost in the main suction hose. An alternative would be to use a 4" power jet mounted directly to the tube, which is how Keene normally did it.

Second, since I used a suction nozzle, I cut the tube opening into the box back far enough to insert the 4" hose into the tube and clamped it down. This shortened the overall length and eliminated a clog point.

Thye entire unit weighs and costs about the same as a 2.5" surface dredge. It burns the amount of gas a 2.5" dredge would, saving more costs and weight.

Recovery issues with a subsurface are simple. The riffle is small, and must be open to capture gold. If you hog material, you will bury the riffle, and lose more gold. If you are getting into gold, check the riffles to make sure they are clearing properly, and then slow up on cramming material through the unit.

These are great unit for hit and run operations where you have coarse gold. If all you have is fine, flaky gold losses may be prohibitive. The longer term the operation, the more gold will be lost over time. For longer term, relatively stationary dredging operations, use a surface type dredge instead.

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[Brian Berkhahn]

Hey Steve,
If you don't mind me chiming in here I found on the smaller subsurface dredges (my 2", 4" and 6") that the hose length shouldn't be anymore then 13ft otherwise you'll lose to much suction which will end up clogging the hose and rifles, now on my 8" subsurface having twin 9hps Honda's 20ft was pushing it.. probably should've gone to a max of 18ft.
Having had many of these subsurface dredges I found the suction nozzle to be the best vs. an inline powerjet.
1 thing I didn't see mentioned is the changing of the carpet to just miners moss.. since it sits in the tray the moss would protect the gold so it wouldn't get washed out.

Brian

[Steve Herschbach]

Hi Brian,

Maybe that is why I was losing all that gold!

Miners moss is listed in the parts list - second to the last item. And a critical one for sure.

I do like subbies - all this posting is making me want to build another one. Got most of the parts in my garage so maybe time to get to it.

[Brian Berkhahn]

Oops.. sorry Steve, didn't see the miners moss in there.
This is making me want to build another one.. maybe another 4" just for pulling around and testing areas..hmmm... got me thinking now.

Brian

[kiwijw]

Hi guys, Would fine gold recovery be improved if you made a double decker over under tray & classifyer in the sluice catchment tray for the finer gold to drop into with a large expanded mesh as a riffle system in the lower compartment. Or lengthen the box or even made the box flare out wider at it exit so the water velocity is dropping & so help the fines settle out.

Large expanded mesh as a riffle system. Notice the black sands behind the mesh


JW

[Jeff in ME]

kiwijw,

What you're describing sounds something like a three stage system. Isn't this similar to how the modern dredges are set up? It might be interesting to see something like this in a high banker.

Edit: Although it's presently listed as, 'currently out of stock', you could try using something like this in your sluicebox, http://www.akmining.com/cart/kehbcs.htm.

Jeff

[kiwijw]

Hi Jeff, I was just throwing some ideas at improving the recovery of fine gold in a sub surface dredge as they are usualy fast & aggresive & only good for sizeable gold as there recovery tray & system is pretty short & narrow. I was just showing the large expanded mesh in my highbanker as an example. I have a classifyer screen in the top hopper of the highbanker but you could add one to a subbies tray system like in a dredge set up to help the fines. Also fishing for replies to anybody who may have tried ways to improve fine gold recovery in a subby.

Happy hunting

JW

[Jeff in ME]

Hi kiwijw,

I'm thinking it would be difficult to improve the fine gold recovery of a sub surface dredge because of the high rate that the water flows through it, and the fact that the material, being submerged, is lighter in weight than it would be above the surface. Any improvements would have to be elaborate and would probably add to the weight of the overall unit It's kind of difficult to say without seeing the inside of the tube and tray of a subsurface dredge..

The idea of one sluicebox above another would be difficult to make work because the material being lighter and the water velocity would prevent material from dropping to a lower tray any more than it does with the present design.

Jeff