Wednesday, November 25, 2009

Painting The Chassis and Other Parts

The projector had originally been painted in a mid-grey crackle finish paint. The main chassis, feed and take-up arms and lens holder all had this finish. However, as explained in earlier posts, the condition of the paintwork was very poor. Over fifty years of weathering plus the effects of ubiquitous lubricating oil had turned the paintwork a dirty grey-green.

After removing this old paint, the metal surfaces were scraped, filed and sanded back to a clean finish in preparation for painting.

I had decided to repaint the machine using a dark grey hammer-finish paint, readily available in a spray can. This spray-on finish can be applied directly to ferrous metal, but application to Aluminium requires an etch primer coat first. This is also available in the convenience of a spray can.

The first task was to spray the outside of the main Aluminium chassis with the etch primer. This was a light grey colour with a very smooth finish. Once that had dried, the finishing coat of hammer-finish could be applied.

above Here you can see the main chassis after spraying with a few coats of the dark grey hammer-finish paint. Note the masked areas which should not receive paint. Also the use of bamboo skewers to plug small holes to keep the paint out. The painted chassis looked very smart indeed.

The interior of the main chassis had originally been painted black. I wanted to re-coat this too, and for that purpose had purchased a spray can of matt black enamel.

above Here you can see the inside of the main cast Aluminium chassis after cleaning but before painting. Masking tape around the outer edges will keep overspray from the newly painted outside surface. I also masked the bearings for the main drive shaft and the claw mechanism to ensure no paint got into them.

above Spraying the black matt paint was straightforward and the extra effort paid off in a uniform and new looking finish. Here you can see the interior of the main chassis after spraying. The masking tape was carefully removed after the paint had dried.

above With the chassis painting completed, various smaller pieces needed preparation and painting. Here is the take up arm after removal of the original paint. When the projector had been modified in the 1950s, a full size take up spool would not clear the larger base which had been fitted. So my father cut the take up arm in half and extended it with a small brass plate and some one-eighth inch bolts and nuts.

Because I was removing this oversize base, the take up arm could be restored to its original length. The metal fabricators who made the new base for the projector (more on that later) were also able to weld the two halves of the take up arm together.

above Here is the welded take up arm sprayed with the dark grey hammer finish. You can see the weld and the filled bolt holes in the middle. Almost as good as a new one!

above The feed reel arm was also stripped and repainted. Here you can see it after painting. The spindles at each end were covered in masking tape, still visible in this photo. All these small pieces required building up a series of light coats of the hammer finish paint, both to prevent paint runs or sagging if too much is applied too quickly, and to achieve coverage from different spray directions so that all nooks and crannies are painted.

above Now it was the turn of the lens holder — a detailed casting perhaps in a zinc alloy, shown here after removal of the old paint. This was a precisely manufactured and put together piece. See the photo below of the lens holder before disassembly under the post “More Disassembly”. I carefully dismantled this piece and put the tiny screws and metal parts into labelled yoghurt containers. Only the spring ball which clips the lens holder firmly into position could not be removed. I opted to cover it in a small piece of carefully cut masking tape.

above How clean and new it looks with a fresh coat of paint. This being a non-ferrous metal, I opted first to use the same etch primer used on the main Aluminium chassis. Once that had dried, multiple coats of the dark grey hammer finish spray paint were then applied.

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