Step 5: Making the Riffles
My biggest challenge on this build was making the riffles for the sluice out of steel angle stock. I am an old carpenter. I can make anything out of wood. Metalworking though is more of a challenge for me. So I hesitated for a while before taking the plunge and using steel. But I decided it was high time I learned how to weld anyway. So I bought some 1/2 x 1/2 angle stock and some 1/2 x 1/8 flat stock. My intent was to use the flat stock as rails on either side of the sluice and weld the angle stock between them to make riffles. The entire steel riffle assembly could then be lifted out of the sluice during cleanups.
I settled on 6 riffles, 4 inches apart and starting 4 inches from the bottom end of the sluice. I cut up the steel pieces without too much difficulty, even though I only had a hacksaw for the job. I don't have a lot of metal working tools.
I built a short section of sluice out of scrap lumber to serve as a jig for welding the pieces together. I used a borrowed welder to weld the pieces together. My welds are ugly (I need more practice) but they seem strong enough. I also welded on two angled pieces in the middle of the riffle assembly to serve as anchor points for holding it in the sluice. Not bad for a welding newbie.
The third photo shows the nearly finished riffle assembly, looking like a mini ladder. I still needed to trim the top hold-down ear back a little.
After early tests with the sluice, I found I needed to weld on another flat piece at the top end of the riffle assembly (4th photo) to hold down the mesh and ribbed matting that would go under the riffles. More about those later.
The last photo below shows how the riffle tray is held in the sluice. There are two right-angle "ears" welded onto the center of the riffle tray. They have passage holes drilled in them to fit over hanger bolts in the side walls of the sluice. Wing-nuts hold them in place. It's a good system. The only challenge is not losing the wing-nuts when disassembling the sluice for cleanups.