June 23, 2012

Bar and stem

Once the brazing was done I started the finish sanding on the stainless steel lugged stem for the new build.  I have several minor blobs of silver to clean up at the shorelines.  Things did not go as smoothly as I would have liked.  This was my first attempt at brazing in a number of years, with the exception of brazing some copper plumbing pipe.  I was able to get enough heat into the lugs and tubing with a MAP torch as well as a propane torch.  I used the system 48 flux for the stainless lugs and tubing as recommended but found it much more challenging to get the silver to flow.  I didn't find it as hard to get things flowing with non stainless.

The shore lines were not as clean as I was hoping for, but on the positive side I was able to keep my alignment of the bar lug perpendicular to the steerer tube lug.  I mitred the tubing for an overall stem length of 105mm centre to centre.  The mitres were cut using the templates I had made earlier by hand.  I was careful to be as detailed as possible.  This step helped keep the two lugs from drifting from the desired alignment.  I tweaked the the lugs to sit snugly on the teardrop tubing with a few delicate taps of a ball peen hammer on the vice surface.  Once I was sure I had the correct angles I pulled the lugs off and applied a very liberal amount of flux (too much I think).

I will need to stock up on a few extra Oxygen cylinders for the MAP system as I ran out before finishing the bar lug.  I hope I don't have this problem with the steerer tube joint as it is going to take a considerable amount more heat the penetrate the thick walls of the steerer tube and fork crown.  I was able to finish up using the propane torch.  One thing I found different with brazing silver was you need to actually melt the silver in the flame as opposed to letting it melt on the hot metal as with copper tubing and lead-less solder.  I almost felt as if I didn't have enough heat in the tubes, however, if I kept the torch in one spot for too long I quickly saw the metal start to glow past a dull red.

Overall I think its an okay job for the first attempt at the torch.  If at some point in the future I want to replace the stem I can whip up another one as the kits are readily accessible.  I would consider the possibility of practicing fillet brazing on a stem for a future project before committing to a full fillet brazed frame.  In doing so I could use one of the two lugs supplied in the kit and fillet braze on the other end.  But for now it's on with the rest of the build.

On another note my headset I ordered last month arrived at Hoopdriver this week.  I took the opportunity to take advantage of the hot summer weather and rode down to the store to pick it up.  I can now do the layout of the frame and fork as I was not sure what the lower stack height of the  headset was.  The internet is a great thing but not all product information is available.  All that was listed in the on-line specs was the overall build height not the upper and lower stack heights.  12 mm was not what I had assumed for the lower stack height.

I have determined I have just enough clearance for Velo Orange 35 mm hammered fenders with the Grand Cru long reach brakes.  There will be enough for a 10 mm gap between the tire and the fender.  An interesting note, the Continental Gatorskin 28 mm tires are not actually 28 mm in width on the PBP rims, they are just under.  I will have more clearance between the tire and the bottom lip of the fender.  Even more room for a piece of gravel to clear without binding between the rim and the tire.  I am eagerly awaiting the completion of this build so I can venture out in search of southern Ontario's strada bianca.