René Hubris Treat-a-Trek
 

One night last month, I was up late at the biochem lab where I work, working occasionally in between bouts of bikeforums browsing and lurking. It is at these moments of weakness that I succumb to the siren song of the classifieds. A thread caught my eye: Frames and Forks for the Frugal by @Insidious C. The frame at the top of the thread stood out to me: a Trek 610 (probably?), from the early '80s. I'd heard whispers on the internet insinuating the mythical mystique of the early Treks with low trail, Treks that really beg to be kitted out with 650b wheels and a handlebar bag, Treks that even Bicycle Quarterly would deign to write about.
https://cimg3.ibsrv.net/gimg/bikefor...f92ba820de.jpg

Could this be one of them? It had horrible paint, that I wouldn't mind destroying with a torch! It had dents and the fork was bent, so I wouldn't feel too bad if I broke it while modifying it for the conversion! Its owner was _giving_ it away. I would have no remorse doing a nice restomod and ruining the originality of such a bike...

I quickly closed the Firefox tab and took a cold shower.

Then I commuted home. My Claud Butler Dalesman (I think that's what it is, but it's mystery meat with modifications and paint by Joe Bell) was making a really bad creaking noise. I have a janky Jandd front rack and VO front fender setup. Perhaps that was cracked? When I got home, even carrying it up the stairs to my apartment was enough to make it creak. This was new. Come to think of it, the bike had felt kinda weird the past few days.
https://cimg1.ibsrv.net/gimg/bikefor...2076c1678f.jpg

I was so sad. Devastated doesn't begin to describe it. This bike and I had been everywhere together, commuting through eastern slush, ice, and snow throughout my research career. That crack, to pre-empt any questions, does not go through the hole I drilled to install internal light wiring.

I re-opened the tab and as quick as I could sent a message to @Insidious C. He graciously replied the next morning. I would be commuting on a Trek.

So I received it a few days later and set about messing with the frame. I was kinda torn. I thought at first that I'd just replace my commuter's frame and call it good, staying with 700c wheels. But the bike seemed to be asking for more than that. About 20 firefox tabs later, I had a pretty good idea that this was, indeed, a low-trail Trek. The seat and head angle are 73 degrees, and the fork has a 55mm rake. Going to the calculator, that makes for 46mm trail with 650x42 tires or 50mm trail with 700x38 tires.

https://cimg9.ibsrv.net/gimg/bikefor...2495c5e800.png

I'd already built a 650b wheelset with dynamo, and it had just been collecting dust in my basement. I'd gotten some cheap old '70s aluminum 650b fenders from France, through Dr. Wagner, my German friend from work. I had been saving up parts, waiting for some free time to make a whole frame out of tubing from René Herse/Compass, to fit 650x48 tires, but right now I have the ability and I have the parts, so even though it won't be perfect, I should do the thing. Then this bike will be the one I ride on every day. So, here goes.

Rear Triangle **trigger warning to snobs**
 

First I filed some wooden frame blocks and squashed the chainstays a little bit in a vise. No pictures of this, but you all would probably cringe. It's fine. I know where the limits are, having seen an old frenemy/Vermont framebuilder exceed them in the past. It fits a 650x42 tire now.

Next spreading the frame. Why do Americans call it cold-setting? So pretentious and exclusive sounding. I dunno about you, but I spread things. I don't cold set them like some kind of materials scientist. It is 135mm now. I aligned the dropouts with an adjustable wrench.

Now onto the most controversial thing.

Some folks like to spread rumors on the internet. Some of these folks think they know what they're talking about, think they're telling the truth. But they don't get out enough. And it's bad for the community. Bike guys say it's not possible to bronze braze without oxy. Tractor guys say it is possible. Who is right? The temps look hot enough. The question is not of peak temperature but of how much heat can you dump into the part before it gets dissipated. Only one way to find out.

So I tried it. I'm using MAPP/air, in a turbo torch from Amazon that I normally use for HVAC stuff. I have oxy acetylene and I have oxy propane (just hook up your oxy acetylene torch to your BBQ tank, the pressures are a lil hard to balance but you can do it). I like oxy/pro for cutting. I like oxy/ace for gas welding (but TIG and even stick are way easier) and flame-hardening. But I also unfortunately have terrible neighbors. Neighbor Gilles told me I was abusing him because I fixed a hole in a kevlar canoe in the backyard which also contained his tomato plants (how does he think kevlar will get into his tomatoes? Does he really think my canoe is water soluble?), so I'm trying to do this stuff at the machine shop at work where people don't care how abusive my hobbies are. Unfortunately, oxy isn't allowed in the machine shop. So turbotorch it is.

I'm using Gasflux type B flux and Gasflux C-04 nickel bronze rod from Framebuilder Supply. The jig is made from science scrap, but any scrap will do, really. My buddy Will way overbuilt it, but we had fun and it was nice to use and maybe I'll keep it.

https://cimg3.ibsrv.net/gimg/bikefor...1237efe4eb.jpg


Clearly it works. I had the torch just roaring, all the way on, to dump a lot of heat into the cantilever post (why do they call them bosses? Again, too fancy. My boss tells me what to do, she has nothing to do with stopping my bike, I hope). Add filler, then just drew the flame ever so slightly onto the tube, to get it to wet. Add more filler and done quickly. I probably could have tig welded them, but I didn't want to tig 531 and tig is not C&V (wait for me to contradict myself when making decaleurs). Call me superstitious, but it felt weird to think about welding things to a brazed bike.

The posts are like 84mm apart, which I know is a smidge wide. What can ya do. That's where the frame was, and I wasn't about to do some custom cantilever posts. It's a rear brake so I'm not worried about it.

Next week I'll do the fork.

Good to know that MAPP can do brass (bronze).

One good data point is worth a thousand expert opinions...

Nice work! Like @gugie, making it all look as simple as creme brulee!

Fire.
Heh. Heh.
Let's burn something.

Keep the info and pic's going. I already learned a bunch. Sorry about the Claude Butler though.

Fab work. Before you know it, you'll be replacing the cracked lug on the Butler.

Exactly! My point I'm trying to make is that anybody can do this, because there's far too much negativity and "ordinary-Joe-can't-do" among framebuilders. I wasn't even going to try until a tractor enthusiast literally talked me into it after hearing me complain. First thing I did was an old Tubus Duo rack, which had cracked at a tig welded joint. That was surprisingly easy. Also Tubus has terrible quality control. Part of the joint wasn't even welded.

My experience brazing with oxy/pro is that I need a bigger tip. Always need a bigger tip. And always waving and dancing the torch all around to avoid cooking things. This was actually kinda nice because I could heat a large area and keep the flame on it rather than waving the torch in the air a bunch.

HVAC guys also have opinions. I had some telling me I couldn't do refrigerant lines without some special thing, and I bought that turbotorch to prove them wrong. The first fridge compressor I did, in 2015, is still working today.

I must have sensitive eyes or something, but I need to use #3 or #4 green goggles to braze -
I have a really hard time seeing the bronze flow without them.
Do others use them, or am I just odd?
I usually braze with OA - Maybe that's why? The OP is just using safety glasses, so maybe the flare from MAPP brazing isn't as bright.

I've used #3 lens with oxy/ace and oxy/pro (I've also not and it's definitely harder), but you're correct in surmising the oxy/fuel operation is a LOT brighter. Curt Goodrich, who used to do frames for Rivendell, told me that the occasional user wouldn't risk eye damage, but it was essential for the professional who does it every day. The flux doesn't light up so much with mapp so you can see the puddle and the flux pretty well. Alex Wetmore likes a didymium lens - says he can read the color temperature of the metal better - but those are expensive. Then there's those old pictures of Ernest Csuka, of Alex Singer, brazing in nothing but a sweater and slacks, and he built amazing frames without going blind. To each his own, that's what I say.

@mixteup, I use didymium glasses, which block "sodium flare" - let's you see through the flame. (edit: scarlson beat me to it! I got them on Alex's recommendation) I use traditional Oxy-Acetylene. I know a guy (Jim G., the guy that made the trail calculator shown above) that has an oxy-propane set up using a refurbished medical oxygenator he got for about $300. Now his oxygen is essentially free, propane is cheap and easy to get. The flame's not as hot as OA, but "hot enough" for brass even by conventional standards.

For bike frames, I find that a smaller tip is desired for doing just about any add-on bit, a larger one is for fork crowns, lugs, and bottom brackets. Keep that collection of tips! For racks with .028/.035 thinwall tubing I'm using tiny flames.

Whenever I think of 650B Trek conversions- I always think of @lonesomesteve 's FREKs. Cool, cool bikes.

https://cimg5.ibsrv.net/gimg/bikefor...2273c97d08.jpg

OP, this is a cool project, but the attitude about people trying to tell you things can't be done is a little unwarranted. You can make a lot of things work with subpar methods and tools, but it inserts risk into your final product.

People who cut corners with cleaning base metal before welding or brazing risk joint contamination.

People who cut corners with heat input and fit-up risk annealing and cold joints.

People who cut corners with fixtures and safety equipment risk personal injury.

When a professional tells you you shouldn't do something, they're not saying it's impossible. They're saying it's risky. It's not a challenge but a warning.

Ah shucks... Thanks, I'm glad you like them! The original Frek pictured above has been going strong for three years and over ten thousand rough and rocky miles without incident and it's by far my favorite bike.

@scarlson, I like your project. You're going about it in pretty much the same way I did when I first started resurrecting old Treks. Similar equipment/tools and similar attitude. Although I have to say, your canti post jig is waaay better than what I cobbled together.

Keep it up. I can't wait to see how it turns out.

@lonesomesteve Your Frek in Bicycle Quarterly is the chief source of inspiration for this whole thing! Hearing you had a similar experience means a lot to me. One question: does it plane?

And re the canti jig, it's just built out of science junk, which is clearly the best junk. I am spoiled, working in a lab, with dumpsters full of science junk right outside the building.

Here are some photos of the unfinished, and then the finished, brake posts. I think I did a good thing.https://cimg5.ibsrv.net/gimg/bikefor...44b798060b.jpg
https://cimg4.ibsrv.net/gimg/bikefor...b3ebf67f50.jpg
https://cimg8.ibsrv.net/gimg/bikefor...e4028f41b2.jpg

And here's a little dent removal
 

I also made some frame blocks to take out the largest dent, which was in the top tube.
https://cimg1.ibsrv.net/gimg/bikefor...540287ae9c.jpg

Luckily it was easy - someone had a 1" drill bit. In retrospect I should have gone 1/64" undersize and then reamed it out, but oh well. They removed the dent pretty well, and then I filled it with bronze. I think I got the thing hot for maybe 30 seconds. Terrifying. My Ron Cooper has a couple spots like this that I found when I got the paint redone.
https://cimg6.ibsrv.net/gimg/bikefor...2900e1efbb.jpg

That's also what Alex Wetmore uses. I thought about it, but went for a tank only because I wanted to be able to use my torch to cut, because I work on cars and motorcycles and sometimes tractors as well. That and I figured I could do silver with mapp and small tubing with tig, so I'm not using as much oxygen. Can that oxygen concentrator blow hard enough to run a rosebud tip?

Yeah, it's true. Don't worry, my tiny tip collection is not going anywhere!

I’d think not, but I know you can use a compressor to fill up a tank at higher pressure, one more thing to buy...

Thanks :) That is low-key the plan. I'm building my skills doing this stuff before I dive into joints between main tubes. I have spread the crack enough to peek inside and it appears that the tube is not cracked. Just the lug. That along with the jagged zig-zag profile of the crack suggests that on original assembly the filler metal had not penetrated all the way into the joint and the crack formed where the filler metal ended. If this is the case, it's a fault in workmanship. I should call up Holdsworth and ask for my money back grind the cracked portion of the lug off to see. If the tube is intact all the way to the miter, and the miter is tight, I think I could get away without replacing the tube. If the tube is cracked, it's real iffy I think. One option is to just grind off the part of the lug that is not brazed to anything, build a filet up at the mitered joint, and call it good. The other option is to peel off the old lug and try to put on a new one. I don't know if that's possible, however. Either way, that lovely splatter paint job will be a little more gone.

Right, now it's coming back to me. I think I saw a German guy do that on youtube. An oilless compressor!! That is key!

Does it plane? Well, I can say that it performs well for me and it's a joy to ride. The old Treks seem like they were designed for 650b x fat tires. They're great bikes with their original 700c or 27" wheels, but they're even better when converted to 650b.

Yep, you did a good thing. That looks like a proper brazing job!

I have a friend who converted a 1983 610, and could not fit 42's. On my 1984 610 I can fit 700x31 (actual) with fenders, but I think it would be quite tight with 35's.

Mine is low trail (64 mm offset) based on a custom fork, giving about 36 mm trail. Jan might say it's too low but I like it (for 700c he recommended something like 40 mm as a preferred value). I do not think 50 mm trail or 46 mm is low trail. Mine will handle a Berthoud bag with a decent sized rear bag, pretty well.

One interesting about these Treks is that the 73/73 combination of angles, the 42 to 45 chainstays, and less-than-7 cm BB drop make the geo very similar to his beloved Herse (or was it the Singer?).

But in general there's no way I'd consider the original 55 mm (pre 1984) or 52 mm (1984) forks to provide low trail. My original 52 mm fork certainly did not feel like it, either.

@scarlson, frequent poster @nlerner is in Brookline and rides in the randonneur style. He's got a few bikes that could use some torchwork, shipping back and forth to Portland OR gets expensive...

@gugie Always happy to meet other like-minded people in the area! Thanks for connecting us.

You're correct, of course. As I said above, I squashed the chainstays a bit with some wooden blocks in a vise to get the required clearance. It wasn't pretty, but I have done it on other 531 frames that have held up fine, and while I wouldn't do it for a frame someone else rides, I'm happy to do it myself for my own frame. I once hired a guy to do it, and he waaaay overdid things trying to get '70s style dimpled tubes with some roller jigamathing and cracked a chainstay - for the life of me I can't really imagine how (crack went around the circumference of the tube). But it's put the fear of god in me about it. Ending the fender above the chainstay is always an option if need-be, also. I think I have about 48mm in there now where the tire is at its widest.

I agree. I guess I didn't mention, but I'm planning on building a fork raking tool (crudely, from science junk and maybe even hardwood scrap) and raking out the fork to get trail between 30 and 40mm.

Could you post pictures of the blocks and results? I'd be interested in doing this on a bike or two.
Thanks,
-J

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.

The problem with not using glasses is that you will get cataracts.

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.

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.

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.