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Rockers are widely used for washing placer samples and under most conditions they are well suited to the needs of the field engineer. It should be noted that since its inception, the American gold dredging industry has, for the most part, used rockers in preference to other types of sample washing equipment. The fact that the rocker has survived in direct competition with a variety of more "modern" or "improved" machines which have been introduced over the years attests to the reliability of results which can be obtained.
Rockers are usually homemade and are built in a variety of sizes and designs depending on the ideas and experience of the builder. The how-to page shows a lightweight rocker which is easily built and is suitable for general use. Click here or on the picture to be taken to a printable diagramed blueprint.
Individual components are a screen-bottomed hopper for receiving and sizing the feed material, a canvas apron for deflecting the feed to the head-end of the rocker, the rocker body which is equivalent to a sluice, and a bed plate or frame upon which the entire assembly is mounted. A rocker may be made any convenient size because within limits, its size will determine throughput capacity rather than its efficiency as a gold saver. Although there are no fixed size criteria, a rocker one foot wide by three feet long would generally be referred to as "small" and one more than 18 inches wide or 5 feet long as "large." When made of wood (which is usually the case) clear lumber without cracks or flaws must be used and the bottom should be made of vertical-grained stock which will not shred or rough-up when scraped. Heavy-duty rockers and those which are in continuous use are preferably made of sugar pine reinforced with suitable metal fittings. Where sugar pine is not available, redwood makes a fair substitute. Rockers made of exterior grade plywood have the advantage of lighter weight and they are strong and durable if the joints are sealed with waterproof glue. The exposed surfaces of a plywood rocker should be protected with marine varnish or spar.