Model 5 Fluid Bed...Its Alive!!!

Capt Nemo

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Apr 11, 2015
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Oshkosh, WI
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Model 5 Fluid Bed...It's Alive!!!

My model 5 recirc fluid bed sluice is alive but with a few bugs to work out. It's kinda expected when engineering a new toy.

I started with a 27 gallon water trough. A neat feature is it has pockets on both sides at the ends for staking it down. I'm thinking of using those to build a future cart or wheelbarrow type contraption for hauling it to the dig site. This trough is USA made at Portage, WI by Freeland Industries.

I then set about with building the fluid bed. I used 1/2" acrylic from a hockey dasher panel broken during a game. 1/4" was getting a little strained with the water/slurry weight on the model 4, so it needed to be thicker. I cut the bed 27 x 8" allowing for 45 degree mitered edges. The plumbing holes allow 1/4" above the bottom of the bed. I left a space at the head of 5" unplumbed as flow from the header box would help keep things fluid in that area. The biggest problem in plumbing is making 10 solvent welds at once! Before attaching the jet tubes to the manifolds, check the fit!!! The manifold with the most fit problems is the one that gets assembled first! Then the easy manifold will weld into place with few problems. I had to run 2 feed manifolds due to using bilge pumps for supply. Both are valved, so if you have a higher pressure pump, you can feed one side and shut off the other. All the jets are angled toward the head of the bed, so in theory, will push any heavies toward the head of the sluice and not the tail.

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I then set to work on the frame. The frame holds the sluice about 2" above a 6 gal bucket, and works with the spout of the bed for cleanout. The bed just tips and pours once the header frame is removed. The only problem is that you can't adjust the header box angle without building another header frame. The feet are 1 1/4" x 1/2" tees that were slit and then bent open with a heat gun. I used 1/2" PVC electrical conduit for all the tubing and plumbing fittings for the joints. The electrical conduit seems to be a little tougher than pipe, and is also UV resistant. The pic is showing cleanout with the header removed. (the yellow is a broom handle to hold it up)

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The header box is acrylic with a 3/4" UHMW PE floor. For a grizzly I made saw cuts like a featherboard. It does work fast at 15 degrees and should work good at 10 degrees. It has it's own 800 GPH bilge pump. While sawing the heat would warp the plastic, and I had to add a spreader bar and 1/8" silicone washers to keep them straight. When water testing today, I found a major problem. The water likes to flow along the cuts and not through them. I think I'll have to route a couple of slots across it to make the water drop before the end of the grizzly and not at it. Otherwise, it works well, just not where I want things to go.

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The only other thing I'm considering is a flow diverter for the buckets. The water going over the rim of 6 gal buckets can fall on the rim of the trough and cause water loss. It might be the height of the bucket that's the problem here, and 5 gal buckets might solve it. But all I really need to do is divert the flow so that it doesn't fall towards the walls of the trough. A cut bucket lid might work for this.

But other than that, we're ready to go get some gold!
 

To fix the water problem, I cut a hollow out of the bottom of the grizzly. I also ran an X-acto knife over the corners to remove the burr that might have also contributed to keeping the flow running down the slots.

Got a pretty good bath from the garden sprayer while getting the pic and testing. Another week or two of these warm temps, and I might be able to run her for real!

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Just added Model 6!

Model 6 is a 3" x 5 1/4" x 3/4" cleanup bed. I built this one with a perforated floor. Holes are drilled with a #80 bit. (~0.013") Ran it last night with a 180 GPH fountain pump, and will probably want to valve it down some. I may add a Y so that I can run it alongside the miller table off the same pump. I'd love to find a 12 VDC version of the pump for concentrating and cleanup at the dig site. It does make a 6" fountain before enough water collects in the bed to calm it down.

It would also make a good pack sluice for preclassified material.

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I estimate that a cleanout for the model 5 will be about 2-2 1/2 gallons. With what I saw on Superior, I'll have to clean out every 2-3 hours to change water. So I could be looking at 10 gal of cons from 8 hours of running material. Having a mini bed to take it down to snuffer bottle amount is needed.

Now if I can find the time to get out and dig!
 

Picked up a 6 gallon sample and decided to run it through the model 5 to see what would happen. The sample was beach sand where I did hit a #100 in a test pan, and also had a bunch of small stones similar to Superior beach sand.

The header box did break things up but did so a little slower than I would have liked. Need a more water and pressure up there to speed things up. The small pea gravel gets stuck in the grizzly and backs up, causing sand and water to wash off the end. May have to go to a metal rod grizzly. Another thought would be a trommel, as I do have the room to do a small 6".

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Here's the mess that got rejected. Too much sand!

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On the fluid bed itself, the drop zone didn't fluidize the way I hoped it would, and just piled up. I expected the water drop to keep that area fluid. The fine gravel that did make it through the grizzly backed up the first few spraybars, and also caused a reduction of jet pressure at the head end. The tail had all the pressure, though there were a few weird dead spots of about 1-2 sq.in in size, but everything around them was fluid. I might have to block some of the jets at the tail to move more pressure to the head. Did find one suprize, in that throttling down to 1 pump will keep things slowly moving. Cleanout also works best on one pump. Cleanouts are about 2 gallons of cons. The water flow off the tail seems to be blowing the sand out of the tailings bucket. Looks like the model 5 wants to run open circuit rather than recirc.

Here's the full bed. The head is on the right. You can see the first four spraybars running subdued, then everything is madly boiling till you get to the tail. The black sand on the tail is a thin layer over blonde, and usually isn't very magnetic.

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So, I got a little work to do! Rod grizzly (worst case a trommel), slick plate for the head, possibly break up bed plumbing into 2 seperate throttlable sections. Oh well, these things happen when prototyping.
 

Finished the above sample and bagged 10 flakes out of the cons, nothing in the tailings, and 2 flakes in the grizzly rejects. So at least any gold that makes it into the bed stays there.
 

Just picked up a Coleman 55W solar panel system for battery charging. The charge controller in the kit can handle up to 105W, so I could expand another 2 18W panels. The three bilge pumps for the Model 5 are fused at 3A each, so I figure they're running about 2.5A each. That would be right about the amount that 5 panels could produce for no drain on the battery. The batteries I'm running are 575 CCA and can give 200 minutes at 23A. At 10 amps, it would give about 7.6 hours of run time. I may just buy a second kit and parallel the charge controllers.

The kit also comes with a 200W inverter that would be perfect for running the miller table or Model 6's AC pump.

I tested the kit today, and it recharged the battery from 11V to full, between 9 AM - 5 PM with overcast rainy skys. Not bad!

Will have to build a road case for the system.
 

If I build a machine can I also call mine the model five? It you say yes legal you have to let me ha ha ha nice work. I thought about building mine out of acrylic... Any reason you went so thick? Just curious.
 

I went with 1/2" due to the weight of the water in the bed. I've had 1/4" seams give out on an 8"x8"x12" tank filled with water. A small bed like my model 4 (6"x14"x3") can handle 1/4", but anything larger really needs the 1/2" for strength.

If only it was due to the weight of the gold in the machine!:laughing7:

I did seperate the spraybars into 2 groups of 5. Had the valve break on the head group, so it's no longer throttleable. It's not so bad, but I did have to add a check valve to prevent backflushing if the pump shuts down. Action now is the way I want it, wild at the head, and calm at the tail. I did rebuild the grizzly to a rod type, and it seems to work well! Also picked up a second set of solar panels, so I should be able to run fully on the panels with battery as backup. I wanted to get up to Superior, but had car troubles, so it will be at least 2 weeks before I can try running her for real.

The model 6, I found, requires REALLY clean water! Had to redrill the bed to #76 so I could clean the holes out when needed. I'm building a filter cage around the pump so that I can use a coffee filter to keep the junk out. Otherwise, it seems to work well when I ran some tailings through it. It pulled the brown/black garnet out of the quartz, so it should keep the iron and gold!
 

Model 5 Fluid Bed...It's Alive!!!

Hey there! decided to follow in your step and start my own acrylic sluice. Please drop by and give advice if you like.
 

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