Saturday, December 5, 2009
The truck is coming along. Here, you see one motor tipped up and out of the way, to allow painting of both motor and truck. Since the traction motor is nose-hung (half hung on the axle and half tied to the truck), this is very easy to do. Both motors have been painted, and the truck is being painted too. This is slower than you'd think. Scraping is the hard part. Media (i.e. sand) blasting cannot be used, because sand and blasted bits go absolutely everywhere and into everything. (Dry ice blasting is often touted as a solution to this, as the dry ice evaporates. However those blasted bits are just as bad as sand. The beauty of dry-ice is when when sending shop sweepings to hazmat disposal at $500/barrel.)
Applying paint on the intricate surfaces is also slow. A truck has a lot of surface area. But it's not just about paint. A lot of electrical work has been done on one of the motors, and the other will get the same. The commutator was cleaned, and the micas were re-grooved. Then the commutator and other areas were masked for painting. The area on either side of the commutator needs painting. The paint must have a high insulating value.
Twin-Pack is a two-part silicone epoxy coating. It comes in a box with two packs. That may be why they call it Twin-Pack. Or maybe because each pack is a very heavy plastic bag, with a clip in the middle. The clip separates the two parts of the epoxy. Remove it and knead the two parts together, then clip a corner and pour.
Trouble is, our stock was old. When mixed, it resulted in a heavy paste. The company only sells it in a minimum quantity of ten, um, Twin-Packs, and we use about one box per motor. So we sacrificed a Twin-Pack to the altar of science. What might be a compatible thinner, a solvent/diluent to reduce Twin-Pack to paintable consistency? Paint thinner resulted in only an angry emulsion. The same for mineral spirits, toluene, Awlgrip T0031 epoxy reducer, nor Imron reducer. Until - YES! Denatured ethanol did the job. A test paint yielded a very durable dry coat. So one of us played bartender, mixing up packs of epoxy as the painter needed it. The truck had to be moved several times to expose the relevant parts of the commutator.