Haha Lesgold, did you not see those soft pink fingers in the pics? I grew up on 3000 acres, but we left the land when I was 15 and moved several states south to just 10 :scared-eek: I could see neighbours houses from our letter box, damn it! That took some adjusting. Worn several hats in my time since. All but this current one where hands on gigs.
A point to note while trueing up the risers on the belt sander. I wanted these parts to be (within reason) identical. So made sure the shoulder to mouth and shoulder to base dimensions where all within 0.5mm of each other. The reason being the bubble caps are assembled from 3 components. Random parts too long or too short would mean the cap either wouldn’t clamp up against the plate properly, or the downcomer would sit too high in the bottom of the riser cup, requiring mixing and matching parts for best fit. Just easier to get it right from the start.
Next step after that was to clean up the risers and get rid of those scratches. For this I dug out a 1/2” square to 1/4” hex adapter. The kind you can put in an impact driver to rattle up bolts with sockets. So spinning the risers on a 14mm socket in a drill made this painless. It was time to mark out for the vapour/reflux slots. First mark the upper and lower limits of the slots. This was done consistently and quickly by holding the marker fixed on some packers, and turning the part by hand.
An example of the same technique on a different part;
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As far as making the slots evenly spaced, the simplest way to do that is to take a neat strip of paper. Wrap it once around the riser. Mark the point where it overlaps. That is your circumference. Lay the paper flat and measure it. Add up the total width of all the slots combined. Subtract that from the circumference. Divide that answer by the number of slots. That figure is the distance between slots. Along the edge of your strip of circumference paper, mark one slot width, one space distance, slot with etc until you get to the end mark. (If I’ve stuffed up this description, sort it out for yourself :teasing-neener: )
Wrap the paper back around your riser and transfer the marks.
From here I put the socket in the vice, slid the risers back on for support and gently center punched the approximate centre of each slot. Drill those holes and then you can start the most painstaking part. Filing the rectangular slots.
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I did the first riser or two entirely with files. Customised a triangular file to fit the slots and get into the corners, but is was a bit tedious. Had a dremel siting idle in its box under the bench, so bugger it, went and bought a small carbide burr to hog out most of the slots, leaving minimal file work to tidy up the corners. Much quicker, left about 15min of file work on each riser.
All slots done and deburred, it was time to solder on the bases.
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Had fun with the four I soldered too close together, but the 4” grinder did it. Then chomped off most of the excess bases with a pair of snips, working around the curve. Onto the belt sander to round off the points left on the base plates, then back to the socket in the drill trick for a final emery cloth cleanup. Which nicely marked the centre of the bases;
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Last step was to drill the hole for the bolts and that was the most technical part of this cap finished. Next time the bubble cap and downcomer.
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