In the 50's, while living in Arizona I bult a rocker box exactly like the one in the prospectors handbook except I built it with a hopper with a spray bar and used 1/2 inch washplant screen for a classifier. I mechalnized it with a shaker arm and ran it with a one horse gas engine through an eccentric at about 160 shakes a minute. I used a separate 1 inch water pump for recirculation. I split a 55 gal metal drum lengthwise and laid them in the creek end to end joined with a plastic pipe. The suction hose was placed in the downside half. I also welded baffels in the barrel halves so most of the tailings had settled before the suction inlet. I Used canvas for the apron with a 2 inch pocket. I tested it by putting 25 #6 lead shot in a 5 gallon bucket of creek material and got 24 on the apron and one on the first riffle. In actual operation 99% of the gold was caught on the apron and none was found when I panned the tailings. The gold I recovered was coarse with some attached quartz along with fines. I could work all day with 4 barrels of water. I never measured how much dirt it could process but I do know that after a full day of picking and shoveling it never got overloaded and I was worn out. Weighing about 75 lb. it took two guys to get it around. Gold was $35 oz. so it was mostly a fun thing. I think one fabricated of aluminum would be more practical.