cyclotoine

If you're wondering why there is no hole on Gugie's test joint it's probably because the short pieces of scrap tube don't need the hole to vent, but when you close up the frame with lugs on either end of the tube, then yes there should be a hole there.

cyclotoine

just a small hole, not the same size as the tube, the hole is necessary for venting. Check your frames, they should all have holes in the head tube.

TenGrainBread 

That's awesome!

I'm doing a full-time, 1 year metal fab program in August with the intention of going into frame building eventually. Let us know if you like the UBI course as I'm considering it post-metal fab program. This is really inspiring!

Drillium Dude 

Nice! I'd like to do this one day, too. And I'm jumping on the hole bandwagon; IIRC, Confente used to drill four small holes (maybe 1/16" in diameter?) and you can see that when you remove the seatpost. @gugie: given any consideration yet to some sort of "signture" for your frame?

Btw, why isn't building a fork a part of the curriculum?

DD

fender1

I wonder if many folks just use standard carbon forks with steel frames? I think forks may take a bit more skill with raking, prepping crowns etc.

crank_addict

This gugie guy is on the gas!

I really enjoy his threads and the DIY approach. JYL's project and now this.
Thanks for sharing-

noglider 

I like the way you sawed your result in half to see how good your brass/silver penetration is. How do you know when to stop doing that and trust penetration is good enough?

I suspect there are a few reasons many of these courses don't have you build a fork.

Ready made forks are good these days, and it's harder to justify building one than to justify building a frame.

Alignment on a fork is tricky, and bending a fork to correct your mistakes is not always possible. Frames are forgiving this way.

Integrity of a fork is so much more important than of a frame. A frame that fails during a ride isn't that likely to cause a disaster, but a fork that fails during a ride is a thought that's painful to even think about.

Drillium Dude 

Sure, I could see that - happens in the real world all the time. I just figgered that either way would be an option in the course as it is in the real world, too.

Maybe the fork can be done in an advanced course?

DD

Bikerider007

Gugie has fork experience already as well, I had a cracked end and he reset fork and brazed and cleaned it all up. Gave me great advice on touch up paint from auto place to match and it came out fantastic. Can't even tell in before and after pics. Expect he will be valedictorian.

Wilfred Laurier

I read through the UBI webpage, and the reason they don't generally build a fork is lack of time. They say a fork can be included in the course if you are building a brazed lugged frame, but it is completely out of the question if fillet brazing or TIG welding, because those techniques require much more practice time with the torch.

TenGrainBread 

The frame building/vintage collector community is a bit of a stubborn anomaly in that respect. While TIG is looked down upon as cheap, easy, and brutish by many in these forums, the consensus in the metal fab industry is almost exactly the opposite. Ask any veteran welder and they will tell you that TIG is the process that requires the most skill, forms the strongest joint, and can be used more precisely than any other process and on more materials. When I mentioned brazing to my last welding instructor, he made a face and explained that brazing is seen as a messy and antiquated hobbyist's process by most professionals.

fender1

Sounds about right for this group.....!

jyl

Gugie has the tools and experience to precisely rake and align forks. I imagine he can build a fork at home . . . But might be expedient to start with a ready made steel fork and rake to his specs.

gugie 

The answer is...

Yes. Well, the lug doesn't "cover" it, it hides it. Without that small hole, the top tube would be sealed. You can braze one end, no problem, but once you try to braze (and seal) the other end, hot gasses will build up and blow out the braze. To give the gasses somewhere to go, you could drill a hole in the seat tube but that's where the seat post goes, giving one more place to scratch up the post during installation. Do it on the head tube, and there's no downside. I learned that awhile ago when making racks and forgetting to put a vent hole in a closed piece. Damn thing wouldn't seal no matter how much silver I pushed into it!

You typically don't see one on the seat tube/head tube intersection , since it's already open at the bottom bracket. One rare, very rare exception for the the downtube would be if you wanted a rotary contact for internal wiring to the rear light. That would require an opening in the headtube and a spring loaded contact. One of these days I'm going to figure out that one out and implement it.

gugie 

There's only one guy in the class doing a classic lugged bike, he gets to do a fork. Fillet brazing requires a lot more practice, so no fork for us!

Hey, how about a pic? Would love to see your matching paint job!

Everyone's a winner in our class, good energy, helpful to each other, makes it conducive to learning. The teachers are really top notch and hands on.

Yep, you beat me to it. Can't even start making a bike until you do at least 10 practice fillets. I've done a lot of fillet brazing for racks, but they're tiny compared to frame tubing, and heat control is critical. Building up nice fillets is more of a challenge. For 3/8" tubing, 50% silver gives a nice, tiny fillet with hardly any effort.

Tony Pereira (Breadwinner Cycles) is the guest instructor this week. He started out doing lugged, then fillet brazed custom frames. Almost all of his bikes are now TIG, the metal fab industry is correct. The problem is investment cost - a good TIG setup is several thousands of dollars. A decent torch can be bought at a garage sale for a couple hundred. Many (most?) frame builders start with torch and move to TIG later on. The other "drawback" is aesthetics. Some people don't even like fillet brazing, and have to have lugs. The problem with lugs is they're only made in a few different angle combos. My bike will be fillet brazed due to deviation from a horizontal top tube, "classic" design. I have plenty of those. Well made TIG, lugged, and fillet brazed steel bikes are roughly equivalent in strength, durability, and rideability. -

I could, but I'll be making it over at Norther Cycles - nothing on the market quite matches what I want. My buddy StarMichael (Velocult's owner's name is Sky, I suppose there's a Moon running one of the 70 shops here in Portland) has a real nice jig. I just laid out all of the fork dimensions with him today so I can design the frame to match.

The nice thing is I don't have to spend any time with braze-ons. Those will all go on the frame at home.

gugie 

Day 2


Spent some time learning about geometry considerations. Most of it I already knew, which was good to hear from some professionals in a classroom setting. The remainder of the day was practicing fillet brazing. Those in the class making fillet brazed bikes need to complete 10 of these first:



Dropping overlapping dimes of brass all the way around takes practice. What you see above would be acceptable for strength reasons, but wouldn't file and sand out to the organic look you expect to see. Learning the proper order of tacking the tubes in place on a jig, then pulling the frame out to slowly work your way around the mitered tube, while managing heat and keeping the line you're working on parallel to the ground needs to become second nature. The small fillets on small rack tubing I've done is relatively easy and quick.

Velocivixen

For the reason no fork is included in the build read number 13 here:

Frame Building Class FAQ

qcpmsame 

Its strange that so many welders have abandoned brazing, our most skilled welder credits his father's insistence that he learn how to properly braze before moving on to stick welding, back in the early 60s, for his quality welds now. His dad taught him the details of properly brazing tubing, and had him master that art before moving on to elementary stick, and eventually TIG and MIG welding. Not to much call for brazing in industrial settings, and he cut his teeth in the nuclear components manufacturing sector. But, his brazed joints are something to behold, as are his TIG welded items. I imagine his knowledge of metallurgy plays a big part in how his welds come out, too

He wanted to start instruction for welders in a local welding class, with brazing but that was shot down in short order. I can only imagine how well he could do a bicycle frame in either brazed, lugged construction, or in a TIG manner. His welding beads are true examples of the classic, "row of dimes". When he brazes a connection, it looks like it was actually cast in the proper form, very little mess to clean up, he is meticulous about how he apples his flux, and on using the correct solder material for the application.

I agree with Gugie about the welded frames, and what you can accomplish with that method, but please give me a lugged frame for my steel bikes. Aluminum bikes, that is welded territory, the procedures for steel to aluminum that lugged would require are not cost effective, and probably not as strong,(I have absolutely no idea of the strength of those kinds of joints, between aluminum tubing and a steel lug, at all.) Cannondale's USA built frames had some of the nicest welds I have ever seen, not sure about how much clean up work after the welding was required, though.

Bill

JohnDThompson 

With experience, you can actually see how far the braze material has penetrated: if there's a gap between the lug and tube, that area heats faster and will be brighter than the surrounding area. Once there's braze material in there, heat gets conducted away more readily, so it's a little cooler and less bright.

crank_addict

Not my intention to derail gugie's thread but aesthetics and welding is partly the subject.
Fan of both lugged and fillet brazed.

Yet I really dig the modern technology in hydro-formed shaped tubes, aluminum and then smooth joints. Using Giant as an example. The top frames use a narrow double pass weld and then hand filing and sanding. Believe the jointed tube ends are also slimmed. They're sensational up close. The best I've seen.

The next tier down is like the above but without the extra hand filing and sanding.

TenGrainBread 

For me the aesthetic debate between fillet brazing and TIG is almost a moot point. They can be made to look basically identical if you apply the same amount of finishing work (grinding, filing, sanding, polishing) to the TIG joint as you do a brazed fillet. A good example is Cannondale's beautiful 90s track frames. This is TIG on polished aluminum:


Granted, with aluminum it helps that TIG beads are pretty large compared to steel beads (don't need to add more filler material during the welding), but it can be done either way.

So when people say they prefer fillet brazing to TIG, it's not because of any inherent property of the two processes, but rather that fillet always gets heavy finishing work because it looks like crap without it, and TIG doesn't always get such finishing work because it's pretty clean without it and many can appreciate the beauty and skill in an evenly-laid TIG bead.

Edit: by the way, if any one is interested in seeing the finest TIG welds in frame building out there, check out Steve Potts' instagram page. Yes, that Steve Potts. His titanium welds are insanely perfect.

cyclotoine

I don't recall them making us do 10, maybe that is a new thing (and a good idea! My clean up was done after the class and a big job). I had a local portland frame builder build me a fork. I'm not happy with it though and ended up buying different production fork, though I'd prefer one with the dimensions of the custom fork, it has flaws that make is unusable.

So, what sort of frame are you building? I wish I had sloped my top tube more and made it a cm or two longer.

Jseis 

Imagine if all space frame tube chassis were fillet brazed. Next time you see images of a rally car/NASCAR/dragster/formula 1 ...rolled at speed.....the strength of those chassis is phenomenal.

himespau 

Could someone dual-purpose that by using the same holes to attach a head badge or do they need to be up by the actual junction?

cyclotoine

yes the holes are at the junction and a head badge hole is too small. 1/4" or even a bit bigger.