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Been messing with this project on and off for a few years now.  Finally got it where it was ready to be tested this past weekend.  

Was originally a keene 3 inch with 4 hp motor and p160 pump i believe.  I sold off most of the 3 inch parts and started building the components need to turn it into a 4 inch.  From the 3 inch all that remains is the frame, floats and motor and pump combo.  I bought a 4 inch flare from keene, since i have no good way to fabricate a lightweight flare.  Everything else i have been working on fabricating, primarily being the sluice (16x40), riffle trays, and the power jet.  

The power jet is were i diverged from most of the current designs that are widely used.  I wanted to build a 4 inch as light as possible while still using the 4hp motor and pump combo, as most the streams i work are shallow and dont require huge amounts of suction for dredging at great depth.  The problem was that the 4hp motor and p160 pump struggled in my mind to provide adequate suction to the 3 inch even when near full throttle. Based on this i decided to build a copy of a dahlke tri-jet which should allow a 4 inch to be run off of a smaller motor and pump when compared to a normal 4 inch, due to increased efficiency over a standard style of power-jet.  

Pictures of the tri-jet in various stages of completion:

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Picture of the sluice and riffle tray, first iteration with woven wire:

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Testing day!  Couple of issues were noticed while testing.  There were a few leaks in the power jet, the woven wire was too open and large rocks would get stuck on it, the high pressure hose was way too long and since it was inch and quarter and so is the pump output , it was constricted to less than inch and quarter at the coupling areas, and the long high pressure hose probably caused a loss in pressure due to friction.  The power jet should also be mounted not right at the flare but a few feet from it, so that the hose acts as a longer jet tube and helps increase suction, a 20 ft suction hose also didnt help.  

But regardless i was able to dredge with moderate suction, with it.  So the test was a success, and with the various refinements it should have greater suction and water flow.  

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Then the next day, the various refinements and fixes from the problems noted during testing.  Replaced the woven wire with 3/8 inch 40% open punch plate, moved the jet so it is mounted about 3 feet from the flare, shortened the high pressure line and increased it to 1.5 inch so there are no restrictions, patched the holes in the power jet, and painted it.  I do have a question or everyone, would increasing the size of the footvalve and intake hose from 2 inch to 2.5 inch help increase the gpm of the pump at all?  The footvalve cage that came with the keene pump seems small to me.  I have some pictures below showing the difference.  

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I look forward to hearing from everyone!  It was a fun project!

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Thanks guys!  It adds another one to my arsenal which already consists of a 2.5 inch, a proline 4 inch and homemade/keene parts 5 inch.  I like building things and still have enough parts to more or less build another 4 inch and another 5 inch.  

Steve - 

What are you thought on increasing the size of the intake line from 2 inches to 2.5 inches, as well as having a larger footvalve.  The intake on the pump still constricts to 2 inches, but i wasnt sure if an increase in line and footvalve size would help or hinder the gpm.  

Thanks again!

Next project is a 5 inch ultralight mini, using a derivation of Dave McCrakens double screen classification system.  

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One day i want to use something like that.i know one for sale in the uk cheap but can't really use it here....

 

 

RR

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Good job on the dredge build! Bet it took a bit to fab up the Tri Jet. LOL.

It would be easy to add the 2 inch foot valve on to check but I don’t think it will make a difference in GPM. I do think it will make it harder to prime though.

I would put on a Honda Gx200/P180 pump and see if that dose it. If not check to make sure the jet and connections are fully submerged, if they suck air the loss is huge. 

I think all dredged need air. Where’s the T80?

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Hello PG, 

    I don't know anything about your equipment or gold mining and sluicing in general! But i am pretty familiar with water hydraulic's!  I will spare you the long winded explanation, and direct your search for answers to the internet! Search Suction and Discharge tables based on type of hoses, length, pressure etc... There are tons of sites where you can plug in your numbers and find the information you seek for just about any configuration you can dream up! I've attached a few screenshot examples! Good luck, and keep on innovating!

Also, other than motor horsepower, and intake hose diameter and length! The type and size of intake fitting's can also limit the amount of water you are able to get to your pump, which may limit its full capacity!👍

 

 

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Wow Joe gave a lot more deluxe answer than I was going to offer. Which is even with the choke point enlarging the hose size etc. will reduce friction, but in this case I doubt there would be any gain you would actually notice. But I like it, can’t hurt.

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Steve,

I'm sure your answer would fit the skillset⛏ much better than mine!!! My skillset is not much use since i retired!👨‍🚒  Hence, why I'm here, trying to pick up where i left off years ago and learn from you all!! 👍👍

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SJM - I will eventually throw on 5.5hp with proline p350 pump to see how much suction the powerjet can generate, but for the purposes of this dredge im hoping to mainly use the 4hp motor.  I removed the air compressor just due to the fact of wanting this one to be as light as possible and will mainly be in creeks that i can snorkle in.  If i hit deeper areas i just bring the proline 4 inch or my 5 inch.  This one will also serve as a lightweight sampling rig.  

 

Joe D - Thanks for that info!  Ill have to play around with those websites and see what i can learn!  I also plan to increase the hp of the motor by adding a performance exhaust and carburetor, go-cart guys do this all the time with their honda motors and simply putting on a race exhaust and re-jetted carb with race air filter should increase the hp of the motor by 1 or 2 hp.  

Joe D with your background you should get up with someone who has a dredge and go over it with them and work on figuring out all the areas where the flow dynamics could be improved.  While the components of dredges all work im not sure how much has been gone over by someone with a back ground like yours.  I mean in comparison performance exhaust systems on air planes are polished and meticulously gone over just to pull a few more hp of out say a 200 hp piper supercub.  Then i go an look at the inside of a keene pump and see how rough it is and cant help but think that if it were polished and gone over carefully that a few extra gpm couldnt be had.  Especially since the friction of water is far greater than the friction of hot exhaust. 

 

Steve -  Thanks!  Im of the same mind that less friction of a larger intake would help a tiny bit.  Im always of the philosophy that ounces make pounds and pounds = pain.  Using the same thought process with gpm and efficiency of the power jet.  All those little not noticeable gains/losses add up to a noticeable amount.  Larger intake hose and foot-valve coupled with a larger and shorter high pressure line, coupled with shorter suction hose and better placement of the power jet.  While each single thing wont make a noticeable increase in suction, all of them combined should.  Well at least thats what im going with lol.  

 

Sorry rambled a bit in there, with my thoughts and observations, but im just a geologist that tinkers, definitely not an engineer lol  

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