Sunday, June 05, 2005

Preparing for the MS150

I've been trying to get caught up on many things. In three weeks I'll be riding the MS 150, which I usually turn into a 175. Right now my training is behind schedule, and though I got several rides in this week, they were too short.

Meanwhile, hope is still there to have a new frame prepared in time for the ride. It likely won't be more than primed, and perhaps this is a delusional fantasy. So, work started on my Alex Singer inspired frame. It will have a wheel-base of 1045mm with HT angle of 73 degrees with a 61mm fork rake, a seat-tube angle of 74 degrees, 570mm TT, 585mm ST, and 80mm BB drop. It will be shod with 28mm tires but have room for 32s with fenders. I may build a stainless front rack and permanently attach it to the fork.

With this as a goal, I haven't done much to get ready to post pictures of Sarah's bike. There will be more on that later. Meanwhile, yesterday, with help from my recently college graduated son, I drew up the full scale working drawing. The, I did my HT/DT joint. All told, this joint took about 6 hours. While this bike is planned as being sliver brazed, the first joint got brass - which may be a blessing.

To explain, the lug fit is fine to start with for silver. However, the lug angle was wrong for the low bottom bracket by about 1.5 degrees. The lug ordered had pretty good coverage of the tubes, but what they had and shipped is what I'd call a bikini lug - there isn't much to it. So, after studying how to reshape it, the decision was I didn't have black smithing skills to make that work. It was possible, however, to tip the lug slightly on the Head Tube and make the desired angle. However, the top of the HT socket was then a slight way off from the HT. The gap seemed too big to me for using silver, even thought the distance wasn't so great as to make the finished lug edge look unusual. Net, I decided on this course of action although I haven't heard of others doing this before. Naturally, pins were employed to hold the alignment.

Practice is beginning to show some good results. Working with the DT spigot upwards, brass was flowed from here to throughout the lug. That meant it had to be drawn past the miter and around the lug-ring surrounding the HT. Overall, it came out neatly. I consciously used too much brass as I wanted to make sure I was getting penetration and flow through the whole lower lug edge. There were several places where I thought the penetration was good, but I didn't see the flow. For these, I keep working (and feeding more brass from above) until I did see the flow.

The joint only ended up with one small spot where a brass booger marred the shoreline. There were a couple of places where there were slight irregularities to the brass surface away from the shoreline, and several boogers away from the shore line, but the net result was a clean joint by my standards.

I soaked the flux off, did a little bit of filing, and spent some time with a wire wheel polishing things up. The results look good if I say so my self.

By the way, I've been using Picklex on this effort. I hope to pickle the whole frame for rust protection.

Pictures will be up in a day or two because my son was photographing things as I went.


No comments: