Saturday, October 3, 2009

A previous post talked about the connecting air hoses and brackets. Significant work has gone into refurbishing those parts.

In most cases, the work needed is merely surface prep and paint. Last Saturday, the beadblast cabinet was in use continuously with people waiting for time on it.

In this particular case, three air pipes require three valves on each end, for six total. Every one needs "lapping". The valve is first pipe-plugged, then beadblasted with great care to keep beads out of the innards of the valve. Then the valve is disassembled and cleaned. Often, there are scratches on the surface of the valve, which will cause leaks.

The heart of the valve is this cone-shaped piece, which fits into a valve body of same proportions (below). Ignore the rod at the top, that's an improvised handle to make this job easier.

The cone is coated with lapping compound, which is an abrasive compound made into a slurry. Liquid sandpaper. The cone is then fitted into the valve body, rotated back and forth several times about 1/4 turn, lifted out, seated in a different place and rotated again. This constant reseating is necessary to avoid adding new scratches. Periodically the valve must be lifted out, washed off in solvent, and inspected. You only want to remove barely enough material to remove scratches. Finished, it looks like this.

Many other parts needed surface prep and painting. The primer used is Awlgrip 545 primer. This is a 2-part epoxy primer comparable to some of the best automotive finishes. Because it's designed for boats, it's designed to be brushed as well as sprayed. That's useful, because the safety precautions in spraying it are considerable, but with brushing it's mainly a matter of "don't get it on your skin". All the same can be said about Awlgrip Topcoat, the finish coat used on these parts.

The paint room was kept busy.

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