Sunday, April 01, 2007

Lugs galore

Yeah, lots o lugs, and they're all on one frame. This tandem is coming along pretty well. These pictures aren't quite up to date, the frame is further along than this, but I haven't had time to take pictures today.

The third eccentric is in as well as all the couplers. There's a whole lot going on around the rear BB shell. The lateral tube now nestles down in right on top of the rear shell and passes right over the top of the thrid eccentric. Here's a shot of the rear BB lug all mitered up and ready to braze. I'm also adding a taller point on the seat-tube socket.

There's six couplers in this frame as I do with most tandems. Placing the couplers was a little tricky with the davinci drive, they needed to be immediately infront of the drive in order for all three sections to fit in the 26" x 26" case.

I have my own system for installing couplers in new tandem frames. Since I design the frames with tube butting to fit up to the couplers, I have to install the couplers into the tubes before building the frame. The jig shown in the photo is how I align the tube while installing the couplers. The jog holds the tubes in perfect alignment while I braze in the coupler.

This is my favorite part of most lugged tandems. The headlug. Yeah, singular, not plural. I combine all three lugs into one continuous shape. For this one I welded the three lugs together then fillet brazed on the port. I was able to start with Slant Six lugs for this one , cut them up a bit and work them into this design. I really like the look. Certainly a pile of work, but this whole frame is and it'll be worth is in the end.


Here's a quick shot of how I start off the other lugs. I miter up sleeves to fit around the tubes, then I jig up the frame to ensure the tubes are at the proper angles. Next I tack the sleeves together in my jog with a couple tiny welds then I remove the tacked lug from the frame and fillet braze it in the vise. Finally I finish file the whole thing and shape it up, then it's ready to be brazed into the frame.

Well, it's late and I'm tired, so the rest will have to wait till later.

bbbb

2 comments:

George said...

I saw your article in Bicycle Quarterly that featured your stainless frame.

Goof stuff.

Baba said...

How do you remember all the steps? I can't remember my middle name.