Wednesday, October 17, 2007

New Rule!

New Rule: Never say you're getting into a rhythm. It's only tempting fate.

Since the last posting, work's dumped on me. That said, I did a little more work last night.

The front and back dropouts on the Surprise Bike are traditional Campy forged. No fancy stainless steel, just good strong dropouts. Because of the
horizontal slot on the rear, the bike will be a good candidate for a fixed conversion - which is another factor in choosing these DOs. Also, they are very classic and this will be a classic looking frame. So Campy it is.

Last night I brazed the rear DOs to the chain stays. I wan
ted to do these with brass filler. 1) there is a lot of space to fill and brass is way cheaper than silver; 2) when the seat stays are mounted, the temperature will be too low to bother the filler in the chain stay joint. The latter is important because with a high-mass DO like the Campy, much of the heat gets directed to it rather than the stay. If you over do it (without burning flux or anything) it carries this heat some distance and can cause silly problems. Therefore, it's brass on the first joint with the DO and Silver on the second.

I was low on flux and tried to pick some up at the local welding supply. I asked for Gasflux blue paste, but they didn't have any. Instead they offered me another brand, saying that all blue fluxes are the same. I should have just ordered some more from Henry James.

So, i
t turns out the new flux isn't paste. Its a dry powder. Powder may be an exaggeration. The grains are about like course sand. Anyhow, I tried mixing some with water. Nope, its just like wet sand in a bucket of water. It doesn't absorb the water no matter how much I mix it. Adding more flux doesn't help. So I set this aside. Fifteen minutes later, it was one solid mass. Hmmm??? Maybe with some heat it will melt and can be applied like paste flux.

can says to dip a heated stick of filler into the can and then braze with the fluxed filler. That doesn't sound good enough for me. So, I dipped the parts into some degreaser and then dipped them in the can. This seems to work to get a decent coating on everything.

So, the parts go together and the chain stay gets mounted DO-end up in the
vice. Then I heat the filler and dip it in flux and get to work.

ne thing I'll say about this flux, it covers the work pretty well. Sometimes, a flux can drip off of a small area of the parts being heated and that area gets a burn mark. Not so for this stuff.

Moreover, the dipping process makes it pretty easy to add flux as desired to
the hot parts. Adding a paste flux to hot parts is a no-no. As the water boils off, the temperature of the parts plummets which can affect their temper.

From here, the brazing went pretty well: plenty of penetration in the joint,
not too much excess brass for later clean up. The same went for the second chain stay. I let things cool, and over dinner the stays went into the washtub with hot (too hot for me to put my hands in) water. Usually, if no flux is burned, this (about 45 mins) is plenty of time for the flux to wash off. Not so with this stuff.

After another 30 mins of soaking, there was still a lot of excess flux hardened onto the parts. Maybe an overnight soaking would have worked better. Anyhow, I tried taking them back into the shop and chipping the flux off with a welders hammer. This often works easily after the flux has soaked for a while. Not with this stuff. It's tenacious. They should probably use it to coat the ceramic tiles on the Space Shuttle.

Using a combination of a sanding drum, the welders hammer, and an old bastard file got most of the remnants off. Then it was off to clean up brass.

been working on some ideas for a signature style for finishing off the ends of stays. I haven't seen any examples that I can remember of the style that most appeals to me - perhaps because it's a lot of work.

After slotting the stays, I file the ends in a semicircle with the slot being the equator of the semicircle. This differs from a traditional bullet end, where the profile as seen from the side & the top is similar. With my style, the tubing is not bent inwards on the end. When viewed from above, the surface of the tube forms a straight line all the way to it's end. Whereas on the bullet style, the end of the tube is hammered inward, so that even from above it looks like a semi-circle.

nce this is brazed up, I file off the excess so that this semicircle presents a square face to the world. Pictures will be clearer, so here they are (Click to Enlarge):

The reason that these are time consuming is that the further the edge of the tube is from the dropout, the more slumping/lumping the final filler will do in that space. With this style, there is a large open area between end of the stay and the DO. So, there is lots of post braze filing.

Next I have to prep the BB Shell so we can start to assemble the main triangle.

By the way, I hope everyone loves this little composition of pictures. Formating pix to page is a real PIA with blogger!

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