Friday, May 16, 2014

How to Restore a Shaker Table

There are different sizes and shapes of shaker tables. There are at least two basic types and they are Finishing Tables and Roughing Tables. The roughing tables are much larger than the finishing tables, at least 6’ X 14’ and finishing tables much smaller. This shaker table is presently on display at the Cave Creek Museum in Cave Creek, AZ.

The style shaker table that I’m going to be discussing is the finishing table. This table was originally used at the Golden Reef Mine millsite, 10-stamp mill on Continental Mountain. It was in bad shape with all of the major timbers on its undercarriage rotted and the table top totally rotted away. The restoration was a total rebuild.

The table top was originally a wood deck that was covered with linoleum. Linoleum was discovered in 1855 in England and was brought to the US in 1872. Linoleum flooring is made from natural materials like linseed oil, recycled wood flour, cork dust and limestone. This material was used on kitchen floors in the 1950’s because it was very water resistant, very resilient and provides a slick and durable surface.  
Basic Shaker Tables The two basic deck types are rectangular and diagonal. Rectangular decks are roughly rectangle shaped with riffles parallel to the long dimension. Diagonal decks are irregular rectangles with riffles at an angle (nearly diagonal). In both types, the shaking motion is parallel to the riffle pattern. The diagonal decks generally have a higher capacity, produce cleaner concentrates, and recover finer sized particles. The decks are usually constructed of wood and linoleum, rubber or plastics usually cover the top of the deck. These materials have a high coefficient of friction, which aids mineral recovery. Expensive, hard wearing decks are made from fiberglass. Both the deck surface and riffles on these units are formed as part of the mold. In operation, slurry consisting of about 25% solids by weight and is fed with wash water along the top of the table.

Dis-assembly of the original Table The first thing that needs to be done is to determine what parts need to be replaced. The table frame can be made from metal or wood. In our case the frame was wood and needed to be totally replaced. We made sure that we had several pictures of the frame below.
 Large Components You should lay out the major beams below to show the orientation of the beams. The picture below shows the orientation of the timbers and the size of timbers needed for the frame. It is important that these beams are structurally sound, since the shaker table vibrates at about 200 shakes per minute.
Drawings of the lower frame: You should make a drawing of the frame to mimic the original layout of the base for easier fabrication of the new beams.
Start assembling the new parts installing the shaker boxes on the lower frame and the shaker box tops on the upper frame as shown below:
 Once the two pieces have been assembled they should be put together to verify that the two pieces match and will actually allow movement back and forth. After this is completed the upper frame will be removed for the installation of the shaker mechanism.
The timbers must be bolted to the lower frame, this includes the center timber
The shaker table needs to be placed back on the lower frame and the driver mechanism needs to be repositioned and connected to the upper frame. This requires that you bolt the mechanism on the two timbers and then slide it into the lower frame as sown below:
A fiberglass shaker table top was donated to the museum and that was fastened to the upper frame.  This had to be fastened with elevator bolt with flat tops. The table had to be countersunk to insure that the table surface was flat without any high spots.
The table had to be re-epoxy with a gray color epoxy and then several coats of clear epoxy was applied to make the surface smooth and free from bumps, with exception of the riffles.

No comments:

Post a Comment