max fork brazing - YouTube
Perhaps a different technique than one is taught at UBI? Rosebud! Nicely done Brent.
Andy's comment reminds me of a story that Eisentraut told us during one of his long ago classes. He visited a number of Italian frame building outfits and saw in one (think of Breaking Away and orange) that they were heating up the entire head, top and down tube area to a bright orange temt level. Al was taken at this having thought that low temp Silver was THE WAY. He knew that this brand did not have rep for frame breakage. He explaned that the eveness of the heat was a s important as the ultimate level of the heat (within some range). A spot of too much heat was worse then an over all high level.
Watching Brent's video i see a high heat level, when compared to Silver, but not excessive heat and importantly an eveness of the heat. I wish to have that control myself some day. Andy.
There is a spirited discussion on the google group about metallurgy wrt silver vs brass. Is anyone aware of a silver or brass joint failing when all of the variables like interference fits, full penetration, cleanliness, no blunt force impacts etc were not part of the equation? I've seen lots of failed frames, but never a properly brazed joint fail because the filler was pushed beyond its spec. It's always something else. The joint is almost always stronger than the frame.
That's a great video.
These Silver vs Brass debates pop up periodically and while there are points on either side, I always end up scratching my head a little as to what the fuss is all about, because the fact of the matter is that, when done correctly, both of these methods of brazing are perfectly fine for building a sound bike frame.....
Dave is the one that brought this video to my attention. My reason for posting the video isn't about brass vs. silver. Especially in the US, there's a misguided view that somehow a use of a particular filler (in this case silver) creates a superior product. I get the theoretical argument but IMO it falls short. What makes a superior product is the builder. Not the this filler or that tubing or the latest fixture. My reason for posting the video was to show there's many ways to do this and Brent was showing his way with a great deal of skill and experience. It's up to the builder to decide if there's something of value there to take away and use or not use in the never ending attempt to make a better bike.
I agree...sorry Curt...my comment was in response to Jonathan's and some of these ancillary conversations that go on...not about this video or why it was posted.
Frankly, this video and Brent's way of doing it backs up what Curt has said over the years and on another recent thread about brazing the crown/steerer/blades at the same time, rather than in sub assemblies. Note that at the beginning of the video Brent talks about how straight the forks end up. I have always brazed my forks in stages...ie steeer to crown and then blades to crown, which works, but I have always pinned the blades to the crown in order to keep the blades from moving around and etc. A couple of years ago, upon Curt's recommendation, I started brazing these parts all at the same time and was amazed at the time I saved and how straight the fork ended up right out of the jig.....no pinning required.
I don't have an ulterior motive for asking, I just thought it was a good place and ultimately my point is the same as yours Curt, it's not the filler but the knowledge you bring to bear with it that matters and the video is awesome for showing that.
People are too tenetive about heat - the duration of the heat cycle kills steel too - get that shit up to heat and do your job quickly & get out of there.
I love my rosebud.
Great vid, great builder.
I won't contribute to the filler discussion other then to say that there are no shortage (ie- millions) of brass brazed forks and bikes that are going strong after many years on the road.
only thing I have to add about rosebuds is just make sure your acetylene tank can flow enough gas to feed the thing. I have the biggest tank my LWS sells (they didn't want to rent one to me) and it will not flow enough gas for the smallest rosebud that fits a Smith AW1A. I found that an AW209 tip provides enough heat for bronze and that's the biggest size tip I could safely feed with my tank. The rule of thumb is 1/7 of the tank volume per hour.
Eric, can you tell me the method involved in making the calculation regarding tip flow? Do manufacturers have charts relating tip size to pressure and flow, or is it calculated some other way?
I ask because it's not information I've come across before (for my Victor tips), and I'm wondering if I can drive a rosebud tip from my smaller (80cu ft) acetylene tank.
I've also wondered if the light weight hoses (eg. Smith and Tinman Tech) might set some upper limit on gas flow rates to the torch? Anyone got any thoughts on that?
Fuel Gas Cylinder Tip Capacity | Baker's Gas + Welding Supplies here is a link to a flow chart, 1/7 is the standard . We have all seen the problems with this, maybe you just did not know that was the reason. But if you are brazing, etc. and your tank is getting a little low, your flame is getting a little inconsistant, and you look at your tank and it says 25psi. The next day you turn on your tank and it says 50 psi, and it burns good for a while then the same problems show up and tank reads 20 psi, next day it shows back at 50 psi. You have drained the tank to low to handle your flow and it is not converting fast enough. Every safety thing always talks about this, I was kinda suprised some people did not know about flow rates versus tank size, but im paranoid about gas so maybe I over reaserch this kinda thing