Do o2 concentrators really affect frame building cost or is simply a matter of being able to produce the o2 needed at a super low cost after the machine has been paid off via cost savings?
I ask because I built 5 frames, replaced 1 down tube, two drop outs, brazed up a fork, and cut down a square tubed basketball pole all on a single tank of o2. Tank size is 80 cubic feet. Just recently had it filled as it was about 80% empty. The acetylene tank of the same size needs a refill as it is empty.