Does it have a serial#? I have a Dyno Moto 7 from 1997, it's serial# is WYO7I0106, I believe the number letter combination following the first three letters "7I" is the date code year 7 or 97 and month I (ninth letter ninth month) or September, the last four digits are the serial build number...
The double straightbars or twin bars come in 2 styles. The early where the bars stand alone and attach at the seat tube and down tube side, and the later where the seat stays pass the seat tube and continue straight to the front downtube. These are early sixties (I believe) and both middleweights.
An additional note: these are all heavyweight frames. Schwinn introduced the Corvette middleweight 54-55 and the straightbars also became middleweights. So approximately 56-59 there are middleweight striaghtbars that match the late post-war description but are narrower.
Again if you have better info please correct me.
These are approximate guesses. If you look on the CABE they talk about overlap of production years.
1) 34 - 37
2) 37 - 41
3) 46 only
4) 46 - 56
It was the classic Schwinn straight bar Klunker that caught my eye and got me reinterested in bicycles as I neared retirement age. In my search for a Straightbar I found out that there was more than one style. I'll share what I think I know and hope for some input/insight from some of the sages...
Sorry about your bottoming rat trap fork. I had the same problem with balloon tires on a middleweight fork. I extended the spring to rocker struts about an inch and solved the problem. Just a thought if you still wanted to use the springer.