smontanaro 

This turned up on the C&V forum. Probably more relevant here...

https://madison.craigslist.org/zip/d...626288484.html

Andrew R Stewart 

Someone needs to scoop this jig up and save some history while progressing their own path. Andy

bulgie 

On the other hand it might be an absolutely terrible jig, not worth the effort to haul it to the recycler. I am very curious to find out, hope someone gets it and reports what they find.

unterhausen

I don't think I would like to use it, but I am very curious where it came from. Don't think I have ever seen a downtube attachment scheme like that. I wonder if it's only good for standard tubes.

Andrew R Stewart 

I see that the listing has been deleted. I hope this means that someone took up the offer. Perhaps this person will find us here and give us more story

I had hoped to get a better look at the DT clamping too. It almost looks like there is a second HT pilot shaft being only held by the DT clamp... Andy

Doug Fattic 

This kind of big flat plate fixture was popular back in the early days of frame building (after the bike boom in 1970/71) before decent commercially available fixtures were available in the US. My worry about any semi-home made fixture is that the chances it can reliably do a rear triangle accurately (so the wheel is centered at the chain and seat stays) is very small. Even expensive fixtures can likely have that problem. This is the main reason I teach how to build the rear triangle using a true wheel and straight edges. That way insures more accurate results.

My philosophy of building is to only use a fixture to tack the frame tubes together and then braze free. There are good reasons for this. 1st a fixture can get in the way of your flame and probably inhibits or actually prevents moving the frame to be in the best brazing position. 2nd a frame needs to be able to expand freely when heated. A fixture doesn't insure alignment accuracy if brazed in it anyway. Your heating pattern keeps things aligned. Most fixtures are a bit out of spec. It can be really expensive to get everything machined so all the holding mechanisms are perfectly aligned. This is why the fixtures I have laser cut and etched in Ukraine sit on a flat tale so the table provides the accuracy.

There are 2 things that are important to me that some fixtures lack. 1st is the ease of setup. I don't want to struggle to get the angles and lengths precisely set. And I don't want to work much if something needs to be reset (like a tube is mitered 1mm short). And I use my fixture to design the frame based on the rider's bicycle position. I know some of my colleagues enjoy the drawing process but I let my fixture do that work.

In other words the kind of fixture one chooses determines the process used to make the frame. It is an important choice and I would choose carefully. I think before one gets a fixture, one should get an alignment table. Or have a good system to align a frame while it is being made.