Thursday, February 11, 2010

Reinforcing a Stamped Seat Lug

Last year, in a fit of madness, I ordered five sets of Reynolds 531 tubing from Bicycle Classics. I had nowhere to build and no equipment, and very few prospects for finding either in the immediate future.

Luckily, when I ordered the tubing, Greg at Bicycle Classics had no way of knowing this. He was very slightly late shipping the order out, and went to the extraordinary length of throwing in as compensation an extra set of 531 as well as a fork crown and two sets of Prugnat "Type S" lugs.

Things have changed somewhat, and now I have a place to build, so I am finally able to put Greg's stuff to use. Including the lugs! The problem with stamped lugs is the binder: it's hollow and weak and needs to be reinforced. Since I was interested in using these lugs as a "learning experience" (lots of carving and shaping!) I was actually looking forward to this process.

I took my steps from Mitch Pryor's (MAP Cycles) sequence on his Flickr page. First I got my friend Olivier to machine a steel tube in the correct size (as it turned out, I provided the incorrect dimensions, but he faithfully followed them!) to fit inside the binder. You can see it in the image above. Then I went wild with brass and filled up everything in sight. Then I filed away all that extra brass into something resembling the desired shape. There are some gaps in there still, but they should fill in during the silver-brazing process of attaching the ST and the TT. It's a much sturdier lug now!

Here you can see where the reinforcement went, and how useful it will be! The little hole in the middle opened up when I reamed out the binder slot to the correct size. The gaps in the brass are my own fault!

Still some cleanup work to be done, but I'll do it once it's been brazed together...

What came out of the reinforced seat lug!

1 comment:

AH said...

I've turned on comment moderation for the time being, since some imaginative person has started leaving comments reading "you're a homo" on all my posts!