Building a 4" Dredging Machine

-Gold Duster Dave

-Gold Duster Dave

Jr. Member
Nov 5, 2011
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S.W. Michigan
Primary Interest:
Prospecting
Building a 4" Dredging Machine

Have been researching a lot of discussion on this site, plus on many others for purposes of obtaining info on the many different systems that have evolved in dredging systems. Seems like most everyone is struggling to make one riffle box perform highly in all areas. I believe I am going to attempt to design and build an over/under two riffle box dredger. The upper riffle box will be faster flow for large nuggets, pickers and the like. The lower riffle box will be slower, wider, for better recovery of fine gold. Have been researching various discussions on riffle box design and wow, are there varying opinions. From what I understand the design/layout of both types of riffle box and angles are quite a bit different. Am bowing to experience here, so any constructive comments to the design, measurements as in width of riffle boxes, placement of riffles , riffle size/design, materials, that would help me build this dredger design would be greatly appreciated. First, I want to build the two riffle boxes, the top riffle box will be 4 feet in length, the lower will be 3 feet, 10 inches. I have decided on having the engine separate from the main unit to eliminate excess vibration which would cut down efficiency of in recovery of fine gold. The angle of both riffle boxes will be adjustable, and I will be able to move whole unit forward/backward to maintain balance. I have a little while to plan this out, so welcome any constructive help. Also am planning on incorporating a strong magnet for black sand removal at the head of the bottom riffle box. -Gold Duster, Dave :coffee2:
 

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Re: Building a 4" Dredging Machine

Am planning the design and size of two separate riffle boxes for a over/under 4" suction dredge. The two riffle boxes will be separate from each other so that I may dial in the most effective angle needed for each riffle box. The first/top sluice I am planning will be 4'L x 12"W x 4"High for recovery of nuggets, most pickers, flakes. The second/bottom riffle box I am planning will be 3'-8"L x 16" x 4"H. Am planning on bottom sluice set-up to be slow flow, shallow angle for maximum recovery of Gold Dust, Gold Flour. Trying to build set-up that will restrict chances of blowing Gold fines back into the river. My question is: Will Honda 6.5hp with HP400 Pump be enough to efficiently handle the flow needs for both riffle boxes? Comments would be greatly appreciated. Trying to do this right from the ground up. -Gold Duster, Dave. :coffee2:
 

Re: Building a 4" Dredging Machine

Over/under setups are notoriously hard to "dial in", let alone a homebuilt one..... Just an idea, but you may want to go with a flared sluice with a screen up top. Say from 16" to 24" flare on the sluice with 3/8" screen.

This will give you the best of both worlds with your larger pieces dropping out up top and your fines settling in down lower as the water slows down.
 

Re: Building a 4" Dredging Machine

Thanx for the input, I appreciate the advice. The dual riffle box design that I am thinking about is not within one large riffle box. 2nd riffle box is 4"-6" below top riffle box. Material suctioned from river will be classified through expanded screen to 1/2" size. It drops down to riffle box #1 where slurry flows across 12"-14" of sieve plate that will further grade material down to 3/16" size. The riffle box in upper I believe will use Hungarian riffle design starting from a nugget trap downward. The bottom riffle box design I believe will utilize a design perfected by popsandson fine gold sluice, design, and operating guidelines. Both riffle boxes will use expanded aluminum, miners moss, and ribbed black mat. Both riffle boxes will be adjustable as to each ones angle of operation. The bottom riffle box will have adjustable gate plate to maintain even flow across head of riffle box. Will have to build, then use rules of thumb for each type of riffle box as beginning points to experiment on what is ideal set-up for each riffle box. Anyt questions, advice on this build I would greatly appreciate. -Gold Duster, Dave. :coffee2:
 

Re: Building a 4" Dredging Machine

YES that eng/pump combo will work fine for a over/under box. and yours will putout more water than my 6.5/P180 and mine works just fine!
 

Re: Building a 4" Dredging Machine

Overall I agree with Russ, it'll work for what you are doing. Keep in mind that your pump is a low-pressure, high volume pump which works just fine for sump pumping and such. The GPM will drop accordingly as your feet of head increases, which your jets will do....increase the pressure. I can't find a real good chart for your pump, but it should be comparable. Keep your sluices as close to the water as you can get, without to much lift out of the water, especially if you plan on flaring your jet before it enters the head of your sluice.
 

Re: Building a 4" Dredging Machine

i think he can either contact proline or go to their website to info on this pump. this is the pump they use on their dredges.
 

Re: Building a 4" Dredging Machine

OPPS! that nomenclature of HP400 is used by Proline for their pumps. your pump is also using this nomenclature for theirs............i recant my statement of if itll work on a 4 inch dredge.although, some trashpumps will work on smaller dredges 3 inch and smaller. but then the venturi needs tobe designed to work with that pump to work properly! missmatching pumps/venturis will develop some suction,but not their best results. ive read this from many people that are in the know of whats needed.
 

Re: Building a 4" Dredging Machine

Thx, for the inputs. I welcome any and all comments. The maximum height from water should be 16", according to my calculations. I want to make sure that both riffle boxes are independently adjustable as to pitch angle. Will also install level indicators for side to side and end to end adjustments. Want the right marriage of slow, even flow, steady rate for max. fine gold recovery on bottom riffle box. Am working on sort of modified flared version to help eliminate trapped air that would interfere with recovering fine gold. -Gold Duster, Dave.
 

Re: Building a 4" Dredging Machine

-Gold Duster said:
Thx, for the inputs. I welcome any and all comments. The maximum height from water should be 16", according to my calculations. I want to make sure that both riffle boxes are independently adjustable as to pitch angle. Will also install level indicators for side to side and end to end adjustments. Want the right marriage of slow, even flow, steady rate for max. fine gold recovery on bottom riffle box. Am working on sort of modified flared version to help eliminate trapped air that would interfere with recovering fine gold. -Gold Duster, Dave.
Click to expand...

Fine gold recovery is the weakest link in dredging due to the gpm that has to be implemented, especially on the dredges over 4" and it gets worse with every inch diameter. Of course wider sluices with taller riffles spaced closer together helps but like you said it's a balancing act.

Sounds to me like you are on the right track :icon_thumleft:
I really like your idea and can hardly wait to see how it pans out.

GG~
 

Re: Building a 4" Dredging Machine

You might want to rethink your mounting the engine and pump on a different float. The harmonics or vibrations of the engine help settle the find gold to the bottom of the surface is lying on be it miners moss or vortex mating.
Here is a cross section of the 4” that I am building now.


Here are some views of the 4" I am currently building.

PRO-HMR4-2.JPG

GP-193-2.JPG

GP-193.JPG
 

Re: Building a 4" Dredging Machine

Rebel.....Dude..........That is saaweeet! :notworthy:
Heck the nuggets will be fighting over which one can get in there first :tongue3:

The cad work ain't bad either :icon_thumleft:
GG~
 

Re: Building a 4" Dredging Machine

Very cool stuff guys -that 1 looks a little like a gold vac.
 

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Re: Building a 4" Dredging Machine

Thanks,
Yes I'm using solidworks, Switching from Solid Edge and still trying to get the hang of it.
 

Re: Building a 4" Dredging Machine

rebel003 said:
Thanks,
Yes I'm using solidworks, Switching from Solid Edge and still trying to get the hang of it.
Click to expand...

What a coincidence, me too LOL- Switched from AutoCad. Looks like you're getting the hang just fine so far ;)
 

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