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Author Topic: Hand Dredge Check Valve Size and Orientation  (Read 3677 times)

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Offline DharmaSoldat

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Hand Dredge Check Valve Size and Orientation
« on: June 11, 2018, 08:03:06 AM »
Hi all,

I have built a 3" diameter hand dredge body but have not yet decided on an arrangement or size of valve system.

I wanted to poll you guys to see what you have found success or not success with.

I was initially considering an arrangement like the gold recovery pump with two non-spring-loaded 2" backwater valves, 1.5" hose and 1" nozzle with a tee connecting  everything.

Thanks!


NOTE: I am fully aware of the legalities of hand dreging in BC, for all who are concerned.

Offline JOE S (INDY)

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Re: Hand Dredge Check Valve Size and Orientation
« Reply #1 on: June 11, 2018, 10:50:46 AM »
Say there, Dharma,

You accidentally called those hand operated suction devices a "Dredge".  Some folks do, in fact, call them that but they are NOT a dredge of any sort or description.

There are two general types of "Dredges" - the first is a "Bucket Line Dredge" which is sort of like a chainsaw on massive amounts of steroids.  It scoops dirt from the streambed (and like sawdust) it carries that removed streambed material internally to process it for gravity removal of Gold.

The other type of dredge is a "Suction Dredge" which uses pressurized water to create a vacuum and that vacuum is used to draw up material from a streambed source and then transport that material through a delivery hose to a waiting sluice box.

What you have is a "non mechanized hand tool", an underwater, hand operated, material extractor using hand generated suction.  The device was originally called a "Yabi Pump" and it was specifically designed and used for shellfish harvesting on beaches in Australia.  There have been other names attached to it from time to time, but - and this is important - it s not a dredge of any sort.   <-NO_> <-NO_> <-NO_>  People who make them for sale have, occasionally, and often intentionally, jacked up the buyer's perception of their use by creatively misnaming them a "Dredge".  Nothing could be further from the truth.

Aside from the sometimes intentional misnaming of the tool (usually by those who should know better) the concept works well.  A bit slow in use, but in some cases it is a wonderful tool that is just what is needed.

One problem with their use is the loss (falling out) of the captured stream bed material.  The intake brings material in but as soon as the intake rush stops gravity takes over and the "stuff" falls back out through the intake tube and is lost back into the stream bed.  Two simple 90 degree bends in the suction line allows the barrel to be rotated at the end of the intake stroke, rotating the tip of the intake upwards and stopping slide-out of "Good Stuff".

One way valves have been used in the past but traditionally suffer from ingested objects fouling the sealing surfaces.   <-shock_>  Give it a try and let us know how you do.

So, since you do not have a "dredge" but rather a "Yabi Pump" I wonder if that changes things a bit as to the BC regulations.  I don't know but, well,  maybe .....................................

Joe

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Offline mcbain

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Re: Hand Dredge Check Valve Size and Orientation
« Reply #2 on: June 11, 2018, 07:39:20 PM »
Hi.Joe nailed it. It is simply a hand operated straw.Check out My Gold Panning.I Have not been in contact with him for 2 years but he was building some very nice units.Randy at * in penticton.bc.Luck Mcbain.

* Mark,  May I suggest the phone number be sent via a PM - a public forum is a scary place to post it.  Moderator
I started out with nothing Istill have most of it.

Offline DharmaSoldat

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Re: Hand Dredge Check Valve Size and Orientation
« Reply #3 on: July 15, 2018, 03:47:09 PM »
So as it turns out, I ended up building the one-way valved unit at an overall 2" size.

I based it on a 45-degree wye fitting with the 45 degree part facing forward and down. I attached a 90 degree street elbow on the 45 degree part with the end pointing off to the right side and used 2" ABS backwater valves with flappers as the one way valves. The unit attaches to the main suction body with a 3"->2" reducing adapter. The inflow, outflow and suction body reducing adapter are all fitted with threaded adapters.

The design process is a fickle thing.

Some problems and solutions:

The suction nozzle
This is a threaded adapter attached to a 6" piece of pipe, and a coupling at the other end with a 2" drain-screen like thingy. No matter how many holes I drilled into it, it still did not get a lot of suction and was generally easier to get clogged. Instead of this, I settled for a 1/4" head bolt across the suction end with locknuts holding it in place and it works much better.

The goldsucker to bucket hose
I settled on a 1.5" diameter vinyl braided hose with poly adapters with a 2" male thread -> 1.5" hose barb. Suffice to say, it got WAY clogged and just generally was a PITA to clean out as this happened all the frickin' time. If I can fix the valve problems (see below) I will get a 2" PVC thread adapter and bond it to some flex PVC pipe I sourced with the standard cement/primer combo.

The valves
Oh god, the valves. They're the Bow Plastics one you can get at home depot and a number of other places. So they work great except for the fact that the valves stick. Initially I thought I could cure this with a 1/4" bolt and bunch of nuts on the other end to provide some weight, however that still did not prevent the hinge from gumming up with fine sand. I am going to try to put a cap of foam rubber over the hinge and clamp it down with the screw on cleanout lid. Still need to test this out, but it should solve my woes if it works.

So far the suction body with just the bare 3" end has been the best performer so far for shallow water work where a shovel isn't as good, but the valved unit will be better for direct-to-bucket capture in hard-to-reach places.

If anyone has any questions, I'm happy to answer as this has been quite a process.

Offline DharmaSoldat

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Re: Hand Dredge Check Valve Size and Orientation
« Reply #4 on: July 17, 2018, 09:38:42 PM »
SOOOOOOooooooo.... an update.

Tonight I tried the foam cap idea and it did great for capturing the stuff going on top of the hinge, but there's still an uncovered gap up front and the fine grit cakes in there like nobody's business.

I have to go to plan B, which is to make a rubber flapper to replace the plastic hinged cover. This is made easier (I hope) by the fact that the opening into the valve has a ~1/4" 'gasket area' around the hole and up the side of the housing to where the plastic hinged cover would hook in.

We'll see. If it can continue without fouling it has potential to move a lot of gravel in a short amount of time.

Offline DharmaSoldat

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Re: Hand Dredge Check Valve Size and Orientation
« Reply #5 on: July 19, 2018, 04:51:57 PM »
Another update...

So with the failure of the original plastic hinged flappers that came with the backwater valve, I got to plan B finally.

After some measurement and materials sourcing - I engineered a foam rubber flapper out of a 1/8" Dollarama Off-brand My Little Pony™ placemat and some Off-brand 3M plastic furniture sliders. With a cap of sponge it holds it in place perfectly and passed the water test with 50 continuous strokes.

Next up: find a harder foam rubber 'cap' to hold the flapper in place, produce a more nicely cut and/or reinforced flapper, then test against them gravels.

Offline beav

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Re: Hand Dredge Check Valve Size and Orientation
« Reply #6 on: July 20, 2018, 03:13:26 AM »
Any chance of taking some pics of what you are talking about and post them on here?
Hard to visualize for us ole' fogeys.
Beav

Offline DharmaSoldat

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Re: Hand Dredge Check Valve Size and Orientation
« Reply #7 on: July 20, 2018, 10:16:01 PM »
Pictures? Sure!

Here's pictures of the:

- Whole unit assembled
IMG_1549.jpg

- Taken apart
IMG_1550.jpg

- One-way valve unit detail
IMG_1548.jpg

- Suction nozzle
IMG_1567.jpg

- Suction nozzle guard bolt
IMG_1566.jpg

- The new valve design and foam rubber cap
IMG_1565.jpg

Offline suburbanator

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Re: Hand Dredge Check Valve Size and Orientation
« Reply #8 on: July 21, 2018, 04:50:12 PM »
I Bought one of the commercially available hand dredges (Mother Sucker).
The one that can snipe or can convert to  pump to a bucket.   I can see its use in some areas,  however nowhere that I go is there really enough gold just sitting 2" down behind some rocks.   Most of the terrain I have experienced so far requires trenching or a fairly large hole to start recovering gold in any quantity.

once some bedrock becomes exposed in Late August,  perhaps this tool might be more effective for me.

Hopefully you didn't spend more than $180.00 building it,  because that's about what they cost online.  The guy has put a ton of time and effort into it and it works fairly well,  sometimes best to suck up the $$.   

When I started I tried to make everything myself... now I prefer just to modify.  Definitely not trying to discourage you however!

Improvements that could be made to the Mother Sucker that perhaps you could consider.

1.  Easier removal of tips for cleaning after sniping
2.  Easier swap from snipe to pumping
3.  Larger reservoir for the material captured when sniping as currently it holds maybe 2-3 cups of material before it needs dumping


Offline DharmaSoldat

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Re: Hand Dredge Check Valve Size and Orientation
« Reply #9 on: July 21, 2018, 06:48:30 PM »
Well Suburbanator, there's definitely no discouragement here :)

The goal for this project was to be able to suck up a lot of material behind rocks and such specifically those underwater or close enough to have shovel holes flood easily and deposit the gravels into a bucket, á la gold'n'sand but with a much larger intake valve, suction force and intake capacity.

I have found it difficult to extract decent gravel without disturbing much of the surrounding material when 8"-10" rocks appear after digging a few inches - especially when those bigger rocks are held tight to the boulder face or 1-2" away.

I tested out just the suction body with a 3"->2" reducing coupling (instead of the one-way valve system) against some gravels in a similar circumstance. The gravels moved really well and it was easier removing the large rocks because the surrounding fine sand was compacted whisked away easier whereas a shovel would be clangin' an' bangin' the face edge against the bigger rocks.

So far, all toll'd, I'm in for about $250, but that's because I also had to buy a lot of the tools and glues and whatnot that I did not have prior to starting.

I have other ideas that I want to do so I figure it's a good investment and building this thing has definitely given me more than $250 of enjoyment as a hobby so... it's all good.

 


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