Doug Fattic 

Since my classes were mentioned, I thought I better comment. My wife is going to retire this year so that means I will need to cut back on my teaching schedule. I'm way past the time when I could have retired. I usually do 5 three-week classes a year with one or two students in each class. I squeeze a painting class or two in there as well. I feel some obligation to continue teaching so the craft can maintain a high standard. I was very fortunate to go to Ellis Briggs in Yorkshire in 1975 to learn. Jack Briggs had plenty of time to show me and I worked along side Andrew the journeyman builder that allowed me to get my own experiences. I was a high school teacher at the time and my purpose for going was to bring the secrets back to the States to share them here. I taught my 1st class in a college setting in 1976 and have done it steadily since then. Over the years I've been able to refine the process. I expect every student to leave class with a professional quality frame. Sometimes I have to make up the difference for the less talented. I get a lot of students that have already taken another class somewhere else. I make zero effort to advertise and that weeds out the casuals. The most motivated seekers find me.

As a college and university trained teacher, I know what it takes for someone to catch on. Trying to cram everything into 2 weeks is usually too much. There is a huge amount of material to absorb. For example when students have come from 2-week classes, sometimes their former instructor(s) had to do some of the work to get them done on time. This can sometimes show in their lack of preparation to do it again. The most serious of my students go to the college campus in Ukraine where they stay 2 or 3 months making frames that we turn into bicycles for pastors. They are needed on the eastern front now. The 10 or so that have done that in the last 20 years have come back with some serious skills. My reason for mentioning all of this is that those that really want to get solid training should make plans before it is too late. I've got many that have expressed interest than I'll ever be able to teach. I don't know when I am going to stop but sundown is on the horizon. Probably before I want it to but it won't be immediately.

scarlson 

@Doug Fattic , I am sad to hear that. I probably won't make it, given what my next few years of career as a new PhD look like. But, equally likely to only build for myself and close friends, anyway. You were very helpful in your advice to get away from the Harris white flux.

Do you have any pointers for me based on the photos? Is no unsolicited advice from you a good sign or a bad sign? I will re-iterate that I appreciate all your advice. Here's a close-up of what I did. Unfortunately it's a little blurry, but you can at least see the flux and the coloring of the steel. The flux is Gasflux type H "Black Flux." You can see how much I applied, looking at the previous photo of the headtube with only the top lug brazed. Not enough?

Too much heat, again? By accident, I got some metal to dull red. Never bright cherry.
I did feel around inside the vent-holes with a soldering pick and could feel an internal shoreline. I used about 3/4 troy ounce of silver on the two lugs together.

Doug Fattic 

By coincidence, the student in my class that started this week has already earned his PhD + more. It is always difficult to analyze the quality of a braze from just a picture. I can see you got it a bit too hot and didn't use enough flux. Why you got it so hot can't be known without seeing you braze in person. Were you using the same Mapp Turbo torch like you did a couple of years ago to put on cantilever bosses? That provides a kind of broad soaking heat pattern. You have to control heat with it like an on off switch. Flick on flick off. A very common student error is that their torch hand freezes when applying silver because they have not yet leaned to operate both hands independently. The problem is that it is easy enough to bring a joint up to brazing temperature but then when they start to add silver, it is very hard to keep that temperature window without going over some. Another way to control heat without flicking the flame on/off is to pull back with the flame so it is cooler farther away. The reason this is difficult for students is because in it normal that both of their hands want to go in as the silver holding hand moves closer as the silver melts. It isn't natural they can operate them independently enough at first so one hand is moving in while the other is moving back. That hakes practice.

3/4 of an once sounds like more than enough silver for 2 luged joints.

I'm not familiar with Gasflux's type H. I use Gasflux type G. It operates at 100º higher temperature than their more common type U. Burning off the flux is a very common rookie error. I have students apply it way further up the tube then I need so they won't run out because it takes them much longer to braze a joint than me. Oops I have to go and get ready for another day of class. When I get a chance I can explain more about flux.

scarlson 

Thank you for your comments!! Yeah, the turbo torch is what I'm using for this. Aside from the fork crown, these are my first two lugged joints. I do a lot of flicking the heat away as you say. I took much less time on the bottom lug (my second one) than I did on the top, and you can sorta see that in how far the heat got down the tubes, turning them blue. I'm somewhat better with the oxy-fuel, it's quicker. I was practicing your "back-the-flame-up-while-adding-filler" technique with oxy-fuel (and got some great results doing that with bronze!) but oxygen isn't allowed at the Harvard machine shop where I've been doing my work. Working in the shop is much easier - no passive-aggressive massachusetts neighbors calling the fire department on me!

Good to know! Like I said, I could feel an internal shoreline when I ran a soldering pick inside the tubes. I could also feel a blob or two on the inside in at least one place. Better overdo the filler than leave a void, I figure!

OK, thanks. I am interested! The black flux type H is advertised as being able to reheat multiple times. This is true in practice, and helps with sketchy torches like the one I'm using here. Also if I take a look at the joint and decide I don't like something, I can go back over an area. I also bought a tub of type G but I haven't used it yet.

I'll re-iterate, I really appreciate your advice. I'm doing this whole thing as a learning exercise. This is how I have fun: learning new things when the stakes are relatively low.

Doug Fattic 

You can reuse Type G too. If you have let the joint cool you can always add more. What you want to look out for and avoid is surface oxidation caused by heating when there is not enough flux left. Or getting the joint too hot. That ugly black surface. Type G flux seems to clean better than type U. When the surface goes black silver won't stick to it. Getting more flux over that area can sometimes cleanse the surface some.

Does your lab prohibit any kind of oxygen assist or just pressured tanks? I ask because using an oxygen concentrator is an excellent option. Over on Velocipede Salon my subject thread on oxygen concentrators has over 30.000 views. The one on using propane instead of acetylene has over 180,000. Obviously more people are interested in an alternative to oxyacetylene units than amateur frame builders. It is the way home hobbyists in jewelry and lamp making (working with melting glass) can use oxypropane in a home setting. It isn't jut about heat volume or BTUs but the fine flame point that allows me to pinpoint my heat to get clean shorelines.