I'm looking for folks who worked for the old school brands back in the day and can share some info on the construction... and I'd especially like to see pics of the inner workings of the factories.

I'm a custom framebuilder and I generally build mountain bike frames, BUT many of my fondest days were aboard 20" wheels. I've got pages and pages of retro designs I'd like to build, but I have a few questions:

Wall thicknesses of main tubes. I assume they ran between .035 and .049 for a race frame, no?

Wall thicknesses and diameters for seatstay and chainstays.

How did they bend looptails, especially the one-piece rear ends? Were they heat-bent? What did the fixtures look like?

How did they taper the box-section crankarms, like the old (now reissued) profile box cranks? I'd love to build some retro-modern cranks.

How do you pronounce Breithaupt? I've gone 27 years NOT knowing how to say it.

Any help you could give would be very cool.

I can answer some.....: .035 tubing were on many oldschool frames, and many broke. .049 is much more common. 7/8" was a common chain/seat stay diameter.
"Bright" "hopt" (at least that' how I've pronounced it all these years, haven't been corrected yet!)

Actual annunciation is: Scot or OM! (HA!HA!)

What frames did they use 7/8" on the chain stay and seat stays. All the ones I have had over the years were 5/8" and smaller on the old bikes.

How can you tell if a frame is .035 or .049?

And isn't it Birdtrap?

Yeah, my mistake, it was 5/8" ...I just typed it wrong....

Hey bystickel, what kind of frame jig do you use? I would like to see pics of it.

There's some good stuff at the link below about how they used to build mongoose frames and motomags bitd. It's an awesome read if you haven't seen it.

http://www.vintagemongoose.com/company/factory.php

Mr Garn over at BREW bikes isn't too far from you, he has been building frames since the early days. You should hook up w/ him.