We began today with a lecture on dropout installation. After the lecture we returned to our work benches and began preparation on the lower head tube joint. There is probably about an hour of hand filing of the lug. We've been told that the cheap Chinese lugs are finished poorly and require a lot more filing than the finely crafted California born Henry James lugs. I can't wait to get my hands on those. I had this joint brazed well before lunch.
After lunch I prepared and brazed my first mock dropout. This is a very difficult joint. First, the materials are very different in thickness. The name of the game is heat control. You want to heat the materials to the same temperature. The fact that the brass has a higher melting temperature than silver only complicates things. You put the torch on the thick dropout material exclusively at first. When it gets up to the proper temperature the tube is just about the same temperature through conduction. At this point you tack it.
After it's tacked you continue heating the dropout and begin to add brass; lots of it. After you fill the top of the gap you heat just below the filled area on the tube and draw the filler down into the tube creating a gap again. Fill it and draw it down and repeat. You do this on both sides until you've used up about 18 inches of brass. If you don't draw the brass in properly it will spill over the top and end up on the outside of the tube. You can see this on mine. The first one I did was bad. The second one (in the photo) wasn't so bad. It's not the ind of the world; it can be filed later. The less filing the better.
Gotta go watch the all star game now! More tomorrow.
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