Fluid Bed Sluice 36

This site shows how to build a 36" fluid bed sluice.

Field Test
Click any of the pics to enlarge. The slide show works or press > for advance. Roughed in size 6" x 36" x 16" tapered to 9". The acrylic landing surface is 1" above the slide plate surface. Manifold holes drilled with 1" bore and filed to fit threaded 3/4" pvc nipples. Outside tubes drilled @ 45 degrees downward @ half inch intervals. Middle has staggered centered downward and at half inch intervals.
Inside view of middle tube. Holes are 1/8" on 1/2" intervals. Inside view of outer tubes. Holes are also 1/8" on 1/2" intervals. Fluid box is approximately 2.5" h x 5.5" l x 9" w inside measurements tapered to 7.5". Dado with chisel work on inside end for 1/4" acrylic. Threaded cap for easy hole cleanout.
The acrylic is put in place at the same time as side thwart screws tighten and hold it permanently in place. This is done after glassing the fluid bed and sluice. Sanding, sealing with wood filler, and more sanding. Careful cutting and sizing, sanding and fitting until perfect. Careful measurements. Twenty drops catalyst to 2 oz of resin. The plastic white cap to the resin is a great mixing container. Just enough to do about 12 minutes worth of fiber glassing. Acetone on hand and cheap rubber gloves are in order. I also use cheap throw away brushes but fight loose bristles.
Light sanding between coats. Personal preference dictated resin over epoxy. Either will work fine. I've just had a lot of experience with resin, sealing and glassing. Give a couple hours of drying time between coats. I also use steel wool and a lightly acetone soaked cleaning rag for dust and chips. Adhesive caulk for all screws to help prevent water damage to wood. Pre-drilled holes keep wood from splitting and leaving areas for water entry.
I used adhesive caulk to secure the acrylic and seal the joint and then tightened all the screws. I used the adhesive on a small piece of 1/4" aluminum edging to protect the leading edge of the acrylic. More sanding and glassing. t
u I know ...... I know........ the acrylic will get scratched. I like the idea of seeing the boil in the fluid bed .... besides, acrylics can be buffed out. I would have used polycarbonate but already had the acrylic. Resin flows smooth on a horizontal surface. Much easier to work but takes more time. I'm retired and not in a hurry to do anything but find more gold. x
y z I use a 1/2" piece of pvc to find the balance point for the handle. Mark the point on both width and length axis. I've decided to hang this beauty on the wall so it never gets dinged ........ not!
I used a heavy 1/4" expanded metal for the grizzly, letting an average size media of 1/4" through the openings. I use this same weave on my drywasher and it catches very fine gold but also allows pickers and nuggets into the box. I can always add a 1/4" woven hardware cloth to the grizzly if I think it is necessary but as stated, on a grizzly like this the larger gold will hang and the media pore is 1/4". SWO (short way of opening) is 1/4" @ 18 gauge. The expanded metal opening width pore size is > 1/4" diameter with the outlying possibility of some slightly larger pieces fitting the diamond tapered geometry remaining. A simple mounting angle with caulking screwed to each side for the grizzly attachment. Done! Let's find gold.
I'm always on the lookout for different grizzly material. Here is a swapmeet special ..... 1/4" heavy woven stainless used for food drying tray. In the event a hole gets plugged, it's easy to remove the nipple cap and clean out the hole with a bent brazing rod or piece of hanger. 1/2" aluminum angle protecting the side edges. The finished fluid bed sluice weighed in at exactly 13 lbs.
Hole Flow Pattern of fluid bed box. Orange represents current hole placement. The outside tubes have 1/8" holes at 45 degree downward angles. The middle tube has holes staggered along center line. The black represents potential angle change after testing of orange placement. After testing the sluice I found the upper corners were packing. To solve this problem I reduced the size of the trap by adding 1/2" wood spacers to the sides and adjusted the tubing to run parallel at 1/2" from sides. I also added adjustable tubes which spin and allow aiming of jets to fluidize better. There are added jets along the edges and corners. The jet pattern closely resembles the black angles in the previous slide (Proposed) and the jets are angled the same on all three tubes. The sluice worked great as it was but I'm a perfectionist so I took the time to change it. In the future I will build my fluid bed sluices with rectangular traps so the angle/packing problem is not an issue.