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René Hubris Treat-a-Trek

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René Hubris Treat-a-Trek

Old 06-15-19, 07:39 AM
  #26  
unterhausen
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looks good. Good penetration where it matters, got a little cold around the edges. Smooth and no pinholes. The gasflux bronze is really nice to work with. A lot of people suffer with lfb they get from the local welding supply, who knows what is in that stuff, lots of pinholes. My first canti boss fixture was a flat piece of metal that I cut a slot in by hand. Worked pretty well.

I'm pretty sure I have told people they could use something like the turbo torch, air/propane. People usually want to use a regular old plumbing torch, which doesn't get as hot. But the issue is that the less heat you have, the more likely you are to overheat things, which seems counter intuitive. It sounds like you have a lot of brazing experience, so that's not as much of an issue. I'm pretty sure you can drive a rosebud with a 5l/min oxygen concentrator. Doug Fattic talks about rosebuds, there is a oxy/propane thread near the top of the framebuilding forum right now.

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Old 06-15-19, 11:55 AM
  #27  
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Originally Posted by unterhausen View Post
looks good. Good penetration where it matters, got a little cold around the edges. Smooth and no pinholes. The gasflux bronze is really nice to work with. A lot of people suffer with lfb they get from the local welding supply, who knows what is in that stuff, lots of pinholes.
When I did my first frame work, for my buddy Chip up in Vermont, he got me some lfb (low fuming bronze) from his Harris guy. I told him to get me the same spec as the Gasflux C-04 but he returned with something different so I had to buy the Gasflux rod from Framebuilder Supply. The commonly-sold lfb is RBCuZn-C, which is all the Harris guy could get. The Gasflux C-04 is RBCuZn-B. The difference between these specs is that -B has nickel and -C doesn't. In addition the Harris RBCuZn-C doesn't list lead or manganese in the composition either. I've never tried to do bike stuff with the RBCuZn-C.
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Old 06-17-19, 03:59 PM
  #28  
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Quick question about Mapp gas Turbo Torches. Would a bigger "Tip" burning more gas be better for doing brass brazing jobs like cantilevers?

Victor Turbo Torches have interchangeable tips. The largest is a 1" T-6. The specs are here:
  • T-6 tip pipe sizes (Soft Solders): 1-1/2" - 4" (38 - 102 mm) for Propane
  • 1-1/2 to 6" (38-152 mm) for MAP-Pro
  • T-6 Pipe sizes (Silver Brazes): 3/4" to 2" (19 - 50 mm) for Propane
  • 3/4" to 4" (19-102 mm) for MAP-Pro
  • T-6 tip gas flow: 2.10 scfh @ 24 psi (Propane)
  • 2.5 scfh @ 42 psi (MAP-Pro)
The 1/2" T-4 looks to closer to a standard torch tip specs:
  • T-4 tip pipe sizes (Soft Solders): 1/4" to 1-1/2" (6.4 - 38 mm) for Propane
  • 1/4" to 2-1/2" (6.4-64 mm) for MAP-Pro
  • T-4 tip pipe sizes (Silver Brazes): 1/4" to 3/4" (6.4-19 mm) for Propane
  • 1/4" to 1-1/4" (6.4-32 mm) for MAP-Pro
  • T-4 tip gas flow: 0.39 scfh @ 24 psi (Propane)
  • 0.48 scfh @ 42 psi (MAP-Pro)
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Old 06-17-19, 10:42 PM
  #29  
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Originally Posted by bark_eater View Post
Quick question about Mapp gas Turbo Torches. Would a bigger "Tip" burning more gas be better for doing brass brazing jobs like cantilevers?

Victor Turbo Torches have interchangeable tips. The largest is a 1" T-6. The specs are here:
  • T-6 tip pipe sizes (Soft Solders): 1-1/2" - 4" (38 - 102 mm) for Propane
  • 1-1/2 to 6" (38-152 mm) for MAP-Pro
  • T-6 Pipe sizes (Silver Brazes): 3/4" to 2" (19 - 50 mm) for Propane
  • 3/4" to 4" (19-102 mm) for MAP-Pro
  • T-6 tip gas flow: 2.10 scfh @ 24 psi (Propane)
  • 2.5 scfh @ 42 psi (MAP-Pro)
The 1/2" T-4 looks to closer to a standard torch tip specs:
  • T-4 tip pipe sizes (Soft Solders): 1/4" to 1-1/2" (6.4 - 38 mm) for Propane
  • 1/4" to 2-1/2" (6.4-64 mm) for MAP-Pro
  • T-4 tip pipe sizes (Silver Brazes): 1/4" to 3/4" (6.4-19 mm) for Propane
  • 1/4" to 1-1/4" (6.4-32 mm) for MAP-Pro
  • T-4 tip gas flow: 0.39 scfh @ 24 psi (Propane)
  • 0.48 scfh @ 42 psi (MAP-Pro)
I'm not an expert on tip variation, but for brass on cantilevers, I was taught that you want a tight flame and get it in close - I think a smaller tip keeps the meat just where you want it without overheating the rest of the tube. But note that I'm basing this on an OA setup.
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Old 06-18-19, 06:04 AM
  #30  
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Poking around I found a BTU calculator that gives the following with Propylene and the different flow rates.

T-6 5,927.5 BTU

T-4 1,138.08 BTU

I'm still not sure what it all means, but I've read about "hearth brazing" with propane which seems to be a lower temperature, high BTU process.
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Old 06-18-19, 07:57 PM
  #31  
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Originally Posted by bark_eater View Post
Poking around I found a BTU calculator that gives the following with Propylene and the different flow rates.

T-6 5,927.5 BTU

T-4 1,138.08 BTU

I'm still not sure what it all means, but I've read about "hearth brazing" with propane which seems to be a lower temperature, high BTU process.
Hearth brazing uses a brick enclosure to reduce thermal conduction to the air and keep the work piece temperature up for faster and smoother brazing. It's essentially a cross between furnace brazing and torch brazing.
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Old 06-19-19, 03:18 PM
  #32  
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Mine's got about a half inch nozzle, so probably similar to the T-4 tip. It seems like it consumes more gas than half a pound per hour, but I have no idea what pressure the regulator (and yes, the shutoff of the cheap turbotorch I have does have a regulator, not just a needle valve) is putting out.

I got the canti posts pretty hot for a longer time and kept the heat on the frame to a minimum, just drawing it over until the bronze flowed well and I achieved proper penetration. I used this technique because I knew the posts had the most thermal mass, so they'd require more time to get up to temp, and it's less critical if you overheat whatever mild steel they are made of. I'd think you wouldn't want a tip that's larger than the posts, if you wanted to use this technique.

Ron Cooper has spoken about his time at Gillot's and mentions that the old guard learned to braze on a coal-fired forge. Oven brazing was also used by Rudge in Nottingham (see video, about 5:00). These were thicker walled tubings no doubt.


I am trying to do things similar to what I've seen framebuilders do with oxy-fuel. With a little adaptations in technique, it seems acceptable. I see a similar heat-affected area to what I've seen from professionals.
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Old 06-25-19, 08:01 PM
  #33  
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I raked out the fork using a hastily-made plywood tool I created with a jigsaw. It went ok. Offset (rake) is now 70mm. I overshot my goal a little, but it should be similar to the Soma Grand Randonneur, with about 30mm trail.

Then I did the braze-ons. First, canti posts.



Then, the low rider eyelets.


Now I am on to little bits and bobs. I have cable stops and bottle bosses and fender mounts and other stuff that I've done but haven't photographed yet, plus a little surprise that is NOT finished yet; I will post about that later after I've done it!
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Old 06-25-19, 08:04 PM
  #34  
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Originally Posted by jeirvine View Post
Could you post pictures of the blocks and results? I'd be interested in doing this on a bike or two.
Thanks,
-J
Here at long last, I have not forgotten about you

Chainstay squeezing blocks, I filed them with the raspy part of a cheap 4-way file, which is a little domed so it helped to make a round divot. I made the inner one flatter because, well, I wanted the inside of the chainstays flatter.



And here's the resultant squashed chainstays. I probably could have taken better care of the outside to not indent it so much, but I think it will be just fine. My Colin Laing tandem is the same way from-factory and it looks fine.
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Old 06-27-19, 11:10 PM
  #35  
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Little bits and bobs

Cable housing stops, I brazed with a nice low-buck jig. Basically it is a 1/4-20 socket head cap screw (For those continental types, an M6x1 would also work) stuck into the housing stop and then clamped to the frame with a hose clamp. This allows for good view when positioning and easy brazing without things moving around. These cable stops were put on top tube and downtube with Harris Safety-Silv 56. I also removed the original housing guides and saved them for another build. Hey, they're nice looking. Just not the direction I'd like to go with this one.



I went kind of crazy with the rear fender mounts. First here is the upper mount on the brake bridge. I wanted to preserve the cool Trek brake bridge, which looks to be brazed out of several pieces with a through-tube. I used too much silver and I disgust myself but it is well stuck on there. Basically it's just a stainless donut with m6 threads. I tore the donut out of a clamp for high-performance liquid chromatography (HPLC) valving. Again, science junk is the best junk. Again this is silver brazed with Harris Safety-Silv 56. None of the original brazing filler is melting when I do silver temps. I think I read somewhere that old Treks are made with either silver or nickel-bronze, which basically are the two I'm using here. It looks like mostly bronze, in the work I've uncovered.



The chainstay bridge had no hole and no tube. I put a nice non-threaded tube in. This will allow me to do some experimentation with fender mounting, where a threaded mount would restrict me more. I want to try a wingnut and bolt to perform the same role as the Velo Orange Spring Thing, allowing me to remove the rear wheel without deflating the tire. Or maybe an entire fender that removes with wingnuts for rinko. The concept is not fully thought out, but a smooth hole with built-in washers should be future-proof. All the washers and tubing I used were stainless, so I brazed with Harris Safety-Silv 56. It was a fun exercise.


I had bought some rear brake cable housing stops (to go between-chainstays above rear canti) from Framebuilder Supply, so I brazed one of them on using bronze. These are really hard to braze with the turbotorch, as it turns out. I did OK but this is one of those things for which I'd really have preferred oxy/fuel. It's on there solidly but it ain't pretty. Luckily for the hobbyist on a budget, this is also easily supplanted by a cheap thing from Surly or an expensive thing from René Herse, that hangs on the seat binder bolt.


Finally waterbottle cage mounts. These are easy!! No jig, just drill a 1/4" hole, flux up the mount, tap it in with a hammer and a block of wood, square it with its mate and the frame so the cage isn't lopsided, heat it up until the flux looks good, dab in silver, and you're done.

Last edited by scarlson; 06-27-19 at 11:19 PM.
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