Bike #3! The Flying Curmudgeon

[veryredbike]

tubes.jpg

Alright, the tubes have arrived for bike 3! I'm using Pego-Richie with some Manorina lugs. Going to do some test-riding of similar bikes this weekend and get things sketched out. Quick question: I haven't used double-taper seat stays before, does it matter if the short taper or the long taper goes up?

Thanks,
Jim

[Eric Estlund]

The tube itself doesn't care, but the bike might. Drop out type/ size, relative trim length/ distribution, seat stay upper attachment, brake/ bridge placement etc. will all play into how that little tube sits. Juggle the variables, do a little eyeballing, and check out what's been done before and you'll start to get a feel on how to make it work for your bike.

[Curt Goodrich]

Most builders put the short taper on the top. Still every Serotta Csi put the long taper on the top. I prefer the short taper on top but there is no right or wrong answer here. Just make sure both stays are oriented the same way.

[e-RICHIE]

does it matter if the short taper or the long taper goes up?

It does matter atmo. The part is designed so that a brake bridge is the correct place and fully supported. That is why the stay is supplied in three lengths.

[Eric Estlund]

Yes, no and maybe. That should cover your bases. To top it all off, I'm pretty sure Richard, Curt and I are all actually agreeing, too.

[veryredbike]

Yes, no and maybe. That should cover your bases. To top it all off, I'm pretty sure Richard, Curt and I are all actually agreeing, too.

HA! Fair enough! Richard, when you say the brake bridge needs to be properly supported, that means the brake bridge should sit on the fatter portion? Other than that, are there any things I should look for that aren't part of the eyeballing process (gets too thin to attach to the seat lug at some point along the tube, etc)?

[e-RICHIE]

I didn't read the other posts when I replied above. The stays have a parallel section that, when correctly used, allows a bridge to be in the center. So, using the bridge dim as a guide, remove length from either end/both ends of the stay so that this happens atmo.

[veryredbike]

PROGRESS! A few days ago I dropped the braze-ons on the seat tube. Took me a minute to remember how to do things, but it came back pretty quick.

Today I put together my LCMPFJ (low cost medium precision fork jig) and used it to hold a fork blade at the right angle to put one of the dropouts on.

There was a bit more slop than I liked, so I used 45% instead of 56. The cycledesign stuff. I put a nice coil inside the blade and sweated it out. Had to keep it at a dull red glow for a little bit to get the coil to melt, but once it went, it jumped like lightning.

Two little glitches: I the silver didn't want to jump to the very tip of the dropout and a little pinhole on the shoreline. I think both were the result of me burning little bits of flux, and not serious issues.

Pictures tomorrow!

[veryredbike]

Examining the second dropout and blade fit... I'm not happy, and it's identical to the first one. So... I'm going to work on it a bit more. For the second one I'll just trim the blade a quarter inch higher.

How do the pro's feel about the one I've already brazed on? Specifically: if I de-brazify (tm) the dropout carefully and use a fresh fork blade, should I worry about the extra heat cycles on the dropout if I reuse it? It seems like it'd be able to take it, since it's a decent lump of stainless and it hasn't been up to brass brazing temps, even if it did go a bit above normal silver temps. This is one of Dazza's socketed drops, in stainless.

Thanks guys!

p.s. Here's a pic of the LCMPFJ, set up without adjustment for rake since the blades aren't bent yet.

https://plus.google.com/u/0/photos/1...57729632562609

[Willie1]

Any idea what type of stainless it is? Different steels have different heat treat normalizing, and tempering practices. On a small part such as a dropout, errors can be corrected, but it may be cheaper to just get a new dropout. One way to evaluate if its worth it is to think about what will happen IF the part fails. Now think of whether the wait for a new dropout is worth it.

[Mark Kelly]

The dropouts are austenitic and therefore not capable of heat treatment. Austenitic steels can be hardened by cold work (eg forging or rolling) but this is a cast part so that doesn't apply either. I'm struggling to see a mechanism whereby a second brazing operation would cause any weakening of the cast structure.

[veryredbike]

Ok, first finished, bent, brazed fork blade done. Stainless, so I cleaned and brazed quickly. Used a #3 on my oxy/pro rig this time. FANTASTIC. Feels a lot more like the #2 I was using with acetylene. Lights easier for some reason too, less detachment issues getting started.

The bad: Couldn't get the silver to sweat through without holding it red for a minute. Might have actually gone through earlier but was masked by TONS of flux and dark conditions, not sure.

The good: Flux (stainless pro) didn't burn except the very little tip of the lug point. Silver did sweat up from the bottom all the way through. Practice piece done in a similar way showed a ridiculous internal fillet, and the blade on this one is about 1.7 mm thick on the end. I was also using system 48 for added strength. Not ideal, but I'm pretty confident (for a newb) that it'll work.

For the other blade I'm going to have a giant flashlight and a spoke for scraping on hand to verify before going to overkill.

Jim

[veryredbike]

Actually just thought of something it was dumb not to ask earlier... does system 48 require a higher brazing temp than 56%?

EDIT:

Answer: No it does not.

[veryredbike]

After some fumbling and practice, got it pretty well down. This time it went nice and fast; silver seemed to flow where I wanted it, fed primarily from one spot on the exposed stump of the stearer and it dropped right through to the bottom, and through the brake holes on both sides and around the pin. The burnt flux was all from checking and double checking stuff... except for the bit at the blade sockets, where there was just hardly any flux at all so it went up fast.

Going to get the blades in there tomorrow and then spend some quality time with the die grinder removing that excess steerer tube. Probably didn't need that much sticking up, but I wanted to make sure that I got 100% of available contact area, and that I had some material to work with when it came to getting the unexposed bits of the steerer nice and hot.

[NBC]

hi jim,

i'm pretty much in the same boat as you in terms of experience,

but with the couple of forks i've built so far, i've used a nail to hold the crown in place with the steerer, i've then drawn a line around the exposed section of steerer below the crown with a sharpie marker, then roughed it out on the bench grinder leaving about 2mm exposed, made life alot easier filing it back afterwards !

hope this helps for attempt #4 !

keep the good work up

nathan

[veryredbike]

Thanks! Good point, even if I want a lip, doesn't have to be on the whole piece.

[NBC]

not to mention that die grinder tools are more expensive than a hacksaw and a couple of files !!

if i'm correct, is that a long shen LC16 crown ?

could you please post a pic post soak and filing ?

thanks

nathan

[veryredbike]

LC16, yep! And yeah, I'll put up more pics when I'm a bit farther. Going to a family reunion, so it could be end of next week.

[NBC]

any new happenings ?

nathan

[veryredbike]

Yep. Finished the fork... going to call it practice. It ended up a bit crooked. Usable, yes... but more dropout filing than I like. Also, the llewellyn drops require a fair amount of trimming on the small end. Once that's done, with the nova forks and the crown I was using, it JUST fits the longer reach brakes I want for potential fender clearance. Would be totally functional (can get it adjusted perfectly), but it looks a bit odd with the pads slammed to the top. I ordered enough parts for 2 more forks and am going to try to make another this weekend.

Follow up question on the fork:

Because the dropouts are a blind-braze, I don't have as much experience with stainless, and I'm hopelessly paranoid, I've been drilling a tiny hole on the inside of the dropout at the bottom of the socket and feeding silver from the opposite side. That way I get an extra indicator of a complete fill... but with a little dot of silver left.

How does 56% tarnish over time once it's polished? When folks do stainless water bottle reinforcement diamonds / bosses... do they have to pick one or another to prevent visible silver, or clear coat, or does it tend to hold up once it's polished?