A Father-Daughter Build Thread

[cblandford]

I am about to start on a new project, and thought I would try something a little different. I hope this thread proves enjoyable for you and informative for me.

To date, I’ve built five or six keeper-bicycles. Three or six garbage-bicycles. The numbers depend on who’s counting. In any case, I feel like I’m at a point in my hobby-ism where I’ve established a beginner’s routine. The last couple bikes I built went (oddly) according to plan, which was not the case for the first four-or-eight that I built. At the least, I’m no longer (grossly) intimidated by the idea of building a simple bicycle. Learning-curve progress, I think.













And so, I figured it was time for a little reflection; I think I need to really check-in on my budding processes.

I’m going to document a project here in this thread. Start to finish. With photos and explanations. To this point I’ve taken photos and made notes as I’ve gone along, but not in a real, comprehensive way. I think it’ll be interesting to get it all down in one spot, here. To the pros and more experienced hobbyists: I’d love your thoughts and feedback as I go along if you’re willing to share them. To those (like myself, previously) who are just trying to figure out how to slap a frame together: please note that is not meant to be any sort of hack’s how-to. I’m doing this to open myself up to criticism in an effort to improve upon an activity that I’m finding I truly enjoy. I don’t know anything. Take this for what it’s worth, which is very little.











So here we go.

The project, briefly: I’m going to build a pair of kinda-matching bicycles, for my daughter and myself. Mathilda turns four in February and is ready for her first pedal bike. Her only request is that her new bike be “pink... like a giraffe”. I like the sounds of a pink-life-a-giraffe bike, too, so I thought I’d build both of us new rides. I’m looking forward to cruising alongside her, each atop our own single-speed giraffe. As I type this I’ve little idea what these bikes are going to look like outside of a few key details. So--come along--we’ll find out together.







If nothing else, enjoy the show-and-tell. I owe this forum more enjoyment than I can repay, but perhaps this will relieve some of my debt.

Back with more soon.

-Chris



PS. I’ve started this thread in The Path because I think it’ll be more fun if I open up the heckling to everyone. That said, if--as I go along--certain things warrant their own Mentor thread, I may start new ones over there, too. We’ll see how it goes. I personally know which voices carry what weight in this place, but I’ll try and make things useful for those reading this ten years out.

[cblandford]

Before I dive in, a couple notes:

I took the UBI framebuilding course in the summer of 2015, and then again--because I’m a terrible student--in the spring of 2017. Tony Pereira (of Breadwinner) and Dan Harrison (now of Vanilla) were the instructors the first time around. Ron Sutphin and Rich Bernouli taught the second course. So hey, if I show something here that indicates bad habits, blame the four of them! Ha. (Anything of apparent quality, though, is completely my doing. Obviously.)

I currently build my bicycles in a small studio that sits above our home's detached garage. I also actual-work from that same space, and try to steal an hour or two each afternoon for the bicycle stuff. At the very least I’m down in my “shop” most evenings, after the dog has been fed and Mathilda is asleep. Sports talk radio during the day, music at night. Picture painted, I hope.

My space is mostly machine-less. I own a drill press, belt sander, and a cordless drill. That’s about it. For fixtures, I have an Anvil frame jig and an Anvil fork jig. A Sputnik braze-on kit. Some other little things. Various bending... devices. We’ll get to all of that stuff, I’m sure.







Finally, I have no supervised fabrication/metalworking experience (outside of my time at UBI), nor do I have any real bicycle experience. (I’ve certainly never worked in a bike shop. Or raced. Or even ridden with a group, actually.) A perfect recipe for bicycle-making success, yes? I’m just a lifelong commuter/get-arounder/tinkerer/self-maintenance-er. Feel free to judge accordingly. Given my experience and intentions, I’m quite unoffendable in this realm.

Anyway, that's the context. I thought it was important.

Phew. Now then...



Here’s what we’re building.

A FATHER/DAUGHTER PAIR OF BICYCLES

For the Father (me, 34 years young):
700c x 35mm-ish Singlespeed Cruiser

For the Daughter (Mathilda, 3 years old):
16” x 1.75” Singlespeed Pedal Bike

Both bikes will feature fillet-brazed frames and (most likely) lugged forks. My bike might also get a fillet-brazed stem. Mathilda’s bike will likely not. Both bikes will get hand-operated V-brakes--number and locations to be determined.







My tentative plan is to build both bikes as quasi-mixtes, with curvy twin top-tubes that extend from the headtube to the rear dropouts (Retrotec inspired/shamelessly ripped off). This might change if I’m unable to execute them on the Daughter Bike for whatever reason. Clearances and such. We’ll find out. I’ve built one mixte previously, but it sucked... hard. It now hangs on my wall, unfinished, and mocks me daily. So this should be fun.







Neither bike will have fenders. No racks. Minimal braze-ons. Pretty simple, compared to my last couple projects. I may try my hand at internal-routing the rear brake cable on the Daughter Bike. I’m indifferent to internal cable routing in general, but in this case, it might be nice to keep the potential-flesh-wounders (braze-ons) to a minimum. A kid’s bike sounds challenging enough already, though, so we’ll see.

My goal is to have both bicycles ready for paint before the holidays. Fingers crossed. That should give Black Magic Paint enough time to get them painted by mid-February--Mathilda’s fourth birthday is on the 16th.

That’s the plan.



My first action when starting on a bicycle is to brainstorm a bit and visualize the bike as a whole. Do a little photo research. Make mental notes. So that’s what I did, for these bikes, last night. Ironically, this is the same way I begin a new professional project, too. I find photos of better work than I’m capable of, print them, and hang them on the wall. A target at which to aim, I suppose.







Tonight I’ll put together an actual design and a list of needed materials. I'm excited to get started and find out what I'm completely overlooking, this time.

Back tomorrow-ish.

-Chris

[Bill Bryant]

Looks like a fun project, Chris. I'm a former elementary school teacher and have done quite a lot of cycling with young kids of various ages. Have you seen your daughter on a bike yet with handbrakes? My experience is that the kids around 5-6 tend not to do so well with them and often prefer bikes with coaster brakes. Hand braking involves multi-tasking (balancing, judging traffic conditions and safety, and pulling on the brake levers to various amounts of hand strength.) As they get older, around age 7-8 they get better judging how much brake to use, and by age 10 they are proficient. My suggestion is that when you first put her on the new bike, try to do some braking drills in a safe area with no distractions. With some practice braking while pedaling or coasting, she'll get it-- but don't assume she has it already. Safety first!
Have fun on your rides!

[claritycycler]

Very cool project, I'm really looking forward to following as it progresses.

regards, Brian

[Mark Walberg]

Cool. My advice is to include your daughter in every step of the build. The entire thing.
It will be good for her, and it will be good for you.
Cool.

[cblandford]

...Have you seen your daughter on a bike yet with handbrakes? My experience is that the kids around 5-6 tend not to do so well with them and often prefer bikes with coaster brakes...

Bill - Yah, I've been snooping around the local shops for a couple of weeks, eyeing details like this. I really thought I'd see more 12 & 16" pedal bikes with coaster brakes. I've been surprised that many (most?) these days feature little Tektro mini V's instead. I have distinct memories of being 4/5 years old and skidding my coaster-braked bike down my old driveway. Doesn't everyone?

Anyway, I figure I'll design the frame to accept the little V brakes. I can always default to a coaster hub if the hand brake gives Mathilda trouble. She's tearing around on her brakeless balance bike pretty good these days. My plan is to let her get used to this new bike as merely a "big" balance bike--with brakes--first, then add the drivetrain bits and teach her to pedal. One piece at a time, as your comments suggest. Thanks for the input. We'll see how it goes.

Very cool project, I'm really looking forward to following as it progresses.

regards, Brian

Sweet - thanks!

...My advice is to include your daughter in every step of the build. The entire thing.
It will be good for her, and it will be good for you...

I've been going back and forth--whether to include her or make it a surprise. I think you're right, though; we'll both be better for it (in many ways) if she can "help" along the way. The final product can be a surprise... The building of the thing shouldn't be. Thanks for mentioning that.


-Chris

[rwsaunders]

Great story and photos and I’m looking forward to following.

[claritycycler]

"...My advice is to include your daughter in every step of the build. The entire thing.
It will be good for her, and it will be good for you..."

I strongly second this method! Lots of kids remember most of their bikes for a lifetime(I do), but making one with dad? Never to be forgotten(for both of you).

[cblandford]

Time to play connect the dots.

To this point, I’ve been designing my bicycles based--largely--on the published geometry charts of brands and builders that I respect. I don’t have the riding experience to have justifiable opinions about much of anything. So, I build to match models that look interesting to me, adjusting here-or-there for fit and whatnot.

Given that a kid's bike has all sorts of odd things going on (and given that nobody publishes dimensions for these little bikes) I decided that--for the Daughter Bike--I’d just go ahead and pick up a stock model to have on hand. (Sorry if that’s cheating.) On Wednesday I purchased a 16” Cleary Hedgehog from Clever Cycles here in Portland. This would’ve been the model I’d bought if I wasn’t planning to build Mathilda a bike. Yesterday I stripped the frame (see Nerdnote A) and took measurements, plugging them into BikeCAD as I went along.







This is how I usually “design” a bike. I find something to reference, and then enter those dimensions into BikeCAD. Then I iterate/adjust quickly in the computer and, once satisfied, I translate the design into a final full-scale drawing. This is probably (at least) double the necessary work, but I like idiot-checking myself on paper at this stage. And I enjoy the drafting.

Here’s where Mathilda’s bike ended up:







This design matches the Cleary, except in two ways. First, I’m allowing for a lower minimum saddle height and more standover than the Cleary. Mathilda has short little legs for her age. Second, I increased the fork length about 10mm compared to the Cleary (see Nerdnote B).

Once satisfied, I drafted up the frame and fork, full-scale. As I do this I start pulling parts, too. I tend to over-order when I buy frame bits. As such, I have a small-but-ever-growing collection of dropouts and fork crowns lying around. Helpful here. I'll likely order a few additional pieces this time around, too.

Having completed The Daughter bike drawing, I moved on to The Father bike drawing.









Little to see here, I think. When I was in college, I lusted after another student’s Gunnar Streetdog. Figured I’d take the chance to make myself one, now, with a couple slight modifications. Next, I drafted the full-scale version just as before (see Nerdnote C).

Now that these are done, I have enough info to order parts. I’ll do that tonight.

-Chris





Nerdnote A:

I’m actually really impressed by the Cleary, and surprised at how much of a “real” bike it is. 68mm BB; square taper cartridge; regular 1” threadless steerer and headset; 28.6 down, top, and seat tubes; 25.4 seat post; 100mm front spacing; 110mm rear (that'll be interesting); 305 BSD (that’ll be interesting, too); little Tektro brakes; on and on. Unfortunately, though, this thing is HEAVY. Holy hell. I wish I owned a scale. I definitely don’t trust the published weight! It’s a tank. I think I can cut down on the weight significantly, both in the frame/fork and in the components. I'll give this bike away when I'm done with this project. If you'd like it, call dibs.


Nerdnote B:

I had a feeling I’d be testing the lower-limits on my Anvil jig for this project, and this indeed turned out to be the case. It was oh-so-close, though. Increasing the fork length 10mm moved the headtube bottom (the Anvil’s primary setup point) in-bounds. (I designed this bike with the jig setup dimensions displayed… shown above highlighted in orange.) That’s a slight concession, but it’s better than having to build a one-off jig for this little bike.


Nerdnote C:

Axle Line > Bottom bracket drop/rise and diameter > Seat tube angle > Effective seat tube length > Effective top tube length > Headtube angle > Fork rake > Front BSD > Front tire > Front fender > Clearance > Crown width > Lower headset stack > Headtube diameter and length > Down tube diameter > Seat tube diameter > Top tube location, angle and diameter > Rear wheel BSD > Rear tire. Chainstay length > Chain/seat stay top view (I usually do this later, though).

[cblandford]

Quick update:

I ordered materials for both bikes on Friday. I’m going to swing by Framebuilder Supply and pick up the bike-specific tubing from Tony tomorrow. Dropouts and a few other bits are on their way from Paragon. And a bunch of straight gauge steel is en route from Aircraft Spruce.

I over-ordered, as usual. Adding to my collection. I’ll find a use for everything at some point.

One thing that did come up while I was ordering was figuring out chainstays for The Daughter bike. I was planning on using straight gauge 4130, and bending it to suit. As I was sorting through my pile of tubes, however, I started eyeing some seatstays. I went back to the drawing board (literally) and quickly completed a chainstay top view. And yes, the shape of a pair of (previously “ruined”) 16mm s-bend seatstays would work perfectly on Mathilda’s bike. But I wondered about the strength. Then I started thinking about where else I might use lighter weight, bike-specific tubes on this little frame...







So I posed the question over in the Mentor forum. I normally wouldn’t ask wall-thickness questions about something I’m making (because I’d simply err on the side of way-overbuilt), but in this case I figured it was worth an ask. Anything I can do to keep the weight down seems worthwhile.

That’s it for now. While I wait for parts, my next couple evenings will be spent practicing my brazing.

-Chris

[cblandford]

Ok, enough of the planning and ordering. Off we go. I’m going to start with the Daughter bike, and--as such--have set aside the Father bike’s materials for now.

To this point, I’ve always started with my bicycles’ frames. So, same here.

Steps for today:

1. Clean and Inspect Main Tubes
2. Miter Front Triangle
...

First, I clean the head, seat, top (though not in this case), and down tubes, inside and out. For this, I use 80 grit emery cloth (shoe shine style) and 91% isopropyl alcohol.







Next, I mark the tubes for orientation. I have one of the small Bringheli surface plates. I roll each tube across this plate--sighting between the tube and the surface--to find its bow. I mark the “top” of the bow. I’ll orient the bows in the vertical plane (? sorry, I should’ve paid more attention in Geometry) of the bike/jig.









Next I Sharpie and scribe a line along the “top” of the tubes. I do this by holding the tube against a piece of U-channel aluminum. I like the Sharpie for visibility, but the scribe carries through the build process better. So I do both.

At the same time, I cut the head tube to length (based on the full-scale drawing) and square off its ends on the disk-side of my belt sander. I also mark the center of the bottom bracket, using my calipers as a scribe. If any of the tubes I’m using are butted, this is also where I’ll mark the butts. I do this by referencing the spec sheets (found on the supplier’s website). I also confirm the specs by holding the tube up to my skylight and sighting the internal butts. The main tubes of this bike, however, are straight gauge, so I skipped that step here.









Next, I move on to mitering.

I hand-miter everything. First, I print the little paper templates from BikeCAD, cut them out, and tape them to the tubes. The templates have indicator lines that I line up with my scribed “top” line. I get the distance between miters from my full-scale drawing. Then I trace the templates with a sharpie and slide the templates off of the tubes.

The miters are first cut out (within a few mm’s) with hardware store-bought tin snips. Then they’re shaped with half-round files (the size of which matches the mating tube’s diameter). Finally, I hone them in with the mating tube wrapped in a piece of 80-grit emery cloth. I load the tubes into the jig as I go (which is now set, I should have mentioned, based on my drawing/BikeCAD).









If there’s one tip I could give someone new to hand mitering, it would be this: act like a machine! I treat my file strokes like a machinist trams the head of mill (I think). I always try to file horizontal to the ground, and either parallel or 90-degrees to the edge of my workbench. If a tube requires an angled cope, I adjust the angle of the tube in the vise, not the angle of my file stroke. If a tube requires an actually-angled miter (like a unicrown fork blade with rake built-in), I adjust the angle of the vise in relation to my bench; I don’t change where I stand or the direction of my filing. In addition, I affix two Paragon tubing blocks to each tube (using the surface table to keep them in phase), and I keep these blocks on the tubes until all the mitering is done, just like a machinist would. I do this so that as I go back and forth between vise and jig, I’m not having to re-orient the tube in a block, potentially messing with the phase. Finally, I use a digital angle finder and my eyes (sighting along the vise or bench top) to check the miters.









All of that, above, was an epiphany I had a couple frames ago. Act like a machine. (I realize that these types of things are probably very obvious to someone with fabrication experience.) As a result, my mitering has gotten much more accurate as of late. This time around, I only had to check the downtube in the jig a couple times before it fit nicely. On my first couple frames I chased my tail for hours. Maybe days. It’s really satisfying to improve at something like that, even if just a bit. I wish I’d had this epiphany earlier… My files would be much sharper than they are now!







The front triangle is now mitered up. Chainstays are next.

That’s it for now. I apologize for the garbage photos... Dark, winter evenings here in Oregon.

-Chris

[shirk]

Great project. Thanks for sharing the details. Looking forward to following the progress.

[suzyj]

Best of luck! One of my more enjoyable builds was a bike for my daughter.

[cblandford]

Best of luck! One of my more enjoyable builds was a bike for my daughter.

Thanks Suzy! Also, I should mention that I've (retroactively) enjoyed your blog tremendously over the past couple years. One of those places on the internet I reference often. Very inspiring!

-Chris

[cblandford]

Moving on to the chainstays.

Steps for today:

…
3. Tab Dropouts; Slot Chainstays
4. Braze Dropouts to Chainstays
5. Finish Chainstay Ends
...

Before I dive in, one thing to note. For the first couple frames I made I did things one step at a time, with a sort of process tunnel vision. Now, however, I tend to do things whenever it makes most sense in the overall build. An example of this is with the chainstays. Previously, I would’ve brazed the front triangle together before even touching a chainstay or dropout. Now, however, I work on these as separate sub-assemblies of a larger whole, prepping everything in anticipation of finally joining stuff together.

Anyway. I begin by laying my chainstays on top of my overview drawing. I include the tire, chainring(s), and crankarm in these drawings, and check that the chainstay will clear all three. I also check that the outer diameter of the dropout end isn’t wider than the tab on the dropout. It’s a bit of a balancing act to choose the most appropriate chainstay (to this point I’ve only bought pre-formed stays--I haven’t bent my own) and get it ideally positioned. Once satisfied, I trim the dropout end of the stay to length and rough-cut the BB ends to length. Then I lay the chainstays on my surface plate and run a straightedge across their tops, scribing a “top” line onto both.







Tool note: I use my Anvil fork jig as a makeshift chainstay jig. A while back, I made a crude little adapter that fits in the steerer tube holder of this jig. It holds the BB ends of the chainstays in place while I work on them, kinda like a crappy chainstay mitering fixture. (I miter out of the fixture, but the jig is helpful for getting everything in its place.) I use the fork rake measurement and a little math as a makeshift BB drop/rise indicator.

Next, I put a tab on the dropout. For chainstays, I’ve been making these 8-10mm deep. I check the internal diameter of the small end of the trimmed chainstay, and take off an equal amount of material from each side of the dropout (hacksaw first, then files), so that the tab fits into the stay.









Now tabbed, I can place the dropouts onto their dummy axle and load them into the jig. I return the chainstays to my drawing, and trace their shape onto the paper. From this, I make note of the chainstay-to-tab angle. I also note the length of the stays (to the back of the BB) and distance between one another at the BB. I slide the chainstays into the jig and onto the tabbed dropouts, and then move the axle holder assembly back and forth until the spacing (on the BB side) is as measured. I use a straightedge held against the dropout face to double-check my slot angle.

Next, I slot the chainstay ends. Using a hacksaw, I cut a slot the width of the dropout, 8-10mm deep (for 16-20mm total overlap), at the angle measured and confirmed previously. I then finish the slot with a slotting file (?... the flat one!). Finally, I spearpoint the end of the stays using a large round file.













To prep for brazing, I first dry fit everything. My goal is a tight-fitting tab/slot along with an assembly that is held in the fixture without having to apply any force to the tubes. Sometimes, my slot angle will end up a touch off. If this is the case, I’ll nudge the dropout tab in/out a smidge, using my vise and a large wrench. This time around, though, everything played nicely.

I use the usual 80-grit emery and 91% isopropyl to clean the chainstay ends and dropouts. Then I flux everything inside and out, and load the chainstays back into the jig. I braze these vertically--in the jig--as I was shown at UBI. (I know some braze these out of any jig, horizontally, or on a flat surface. I haven’t tried that.)









Now might be a good time to show my brazing setup. I’m using Oxy/Acetylene, with a Smith A1WA torch, the little Kevlar hoses, and a few different tips. For bronze, I use Gasflux brand rods and type B flux. For silver, I use Harris brand silver rods with Gasflux type U flux. I’ve also used CycleDesign stainless flux/rods on occasion. I run my O/A tanks at 7 and 6 psi, respectively.

For tab-style dropouts, I use a Smith 203 tip, a neutral soft-rumbling flame, and 1/16th inch bronze rod. For each dropout, the brazing goes something like this:

1. Tack all four “points” of the chainstay to the dropout
2. Get the entire joint up to brazing temperature
3. Sweat the tacks down into and around the slots
4. Fill each side with bronze (hopefully to the bottom of the tab).

I try to shove 14-16”+ of bronze rod into each stay, depending on the volume of the joint (more for a large chainstay end, less here because the end was small).








After brazing, I let the chainstay assemblies cool in the jig, then give them a soak in my heated ultrasonic cleaner (water only). Once clean of flux, I finish the ends. (This is another thing I previously did what-now-seems-out-of-order. I used to wait and do all of a frame’s finishing work at the end of the build. It’s much, much easier to do this type of work, though, while the chainstays are loose from the rest of the frame. So, I now finish these before attaching them to the frame.) I worked on these with a little Dremel drum sander and some needle files. At the same time, I also dressed up the tab. These bikes are (hopefully) going to end up very swoopy/curvy, so I thought rounding off the tabs would look complimentary. This was done with small files.











That’s it for now. Next I’ll miter the chainstays, connect the seat tube to the BB, and get all those sub-assemblies prepped for the fillet brazing.

Back soon,
Chris

[cblandford]

Some days I end up with a few minutes to spend on bike stuff, but not enough time to really get into a task. So, that's when I do this.

There's this thread over in the General Discussion forum; it has me a little bummed out. I'm not sure why though, as I have zero interest in "framebuilding" professionally. That thread, however, reminded me that I needed to post photos of my most recent batch of practice fillets. So, here you go:











For about a year after I completed my second UBI course, I tried to braze one practice fillet joint per day. I definitely fell short, but probably averaged 3 per week. (I do wish I'd kept that pile of metal, though. It would've made a much more interesting photo than these, the past few month's worth.) They were mostly ugly as hell, however, so I chucked them as I went along. In denial. Almost as soon as they were cool enough to touch. Ha.

More recently, I haven't been keeping up with that pace. Now I just try to braze a handful of joints right before I put a frame together. This time around, I brazed five fillets. I love the practice brazing. It's the practice hand-mitering that isn't nearly as on-going-fun. So hey, if you're reading this and you'd like to punch out a few hundred little .035 miters for me on your milling machine, I would pay handsomely-per-unit for them! Just sayin.

Anyway, that's that. Back with the actual build soon.

-Chris

[cblandford]

Over the long holiday weekend, I had Mathilda down in the studio with me a bit. She’s a wiggly almost-four-year-old, so the patience for my show-and-tell is a little short. That said, she’s been enjoying seeing the progress made on her bike, and asks to see the little frame each time we head through my space down to the garage. She’s always loved squishing stuff in my vise, too. I keep having to tell her we will not be squishing her frame. She only seems mildly disappointed.

Onward:

…
6. Miter Chainstays
7. Drill Vent Holes
8. Tin Seat Tube to Bottom Bracket
8. Final Fit & Prep for Brazing
…

I miter my chainstays in the same way as my main tubes. However, there’s one extra (semi-backwards step) that I take here. Back in BikeCAD, I now retroactively make the computer drawing match my chainstay hand drawing. All I care about here is the miter template. So, now that I have a chainstay miter angle (from my hand drawing), I can make the BikeCAD version match. It takes 30 seconds--and I don’t care about the overall shape of the chainstays in BikeCAD, just the diameter and angle. Once done, I print the templates, tape them onto the tubes, and set their distance from the rear axle (which is taken from my hand drawing). Trace, hacksaw to rough length, tin snip, and file.







These used to give me fits. I’ve found, however, that thinking of the chainstays as a single unit--instead of individual tubes--has helped me with their mitering quite a bit. Once I get the individual chainstays mitered, I place them onto their dummy axle--together--and lightly clamp them in my vise. Just a light swipe or two with the file--across both tube ends at once--saves a lot of tail-chasing in the jig.











Next I drill all of the vent holes. I first trace the joining tubes’ copes with a Sharpie, then drill the holes on my drill press. I start with a combination center drill/countersink bit, then move to a regular drill bit for each hole. Usually ½ inch for the main tube holes; smaller for the chainstay holes. I also drill vent holes at the dropout end of the chainstays, facing down (obviously) and about 10-20mm from the dropout tab. After drilling the holes, I clean everything up with 80-grit and a swipe of isopropyl.









Next I tin the seat tube to the bottom bracket. I load up the inside of the seat tube with blue flux, give the BB a light coat, and load the tubes into the jig. I center the seat tube on the BB by checking either side (between the seat tube and BB edge) with calipers. Here, I use the same Smith 203 tip and 1/16th bronze rod as was used on the dropout brazing. I start at the front of the frame, and braze from centerline to 90-degrees in both directions. Then I move around to the back of the frame, and braze from centerline to 90-degrees again, to meet. The goal is a small fillet with full internal penetration the entire circumference of the joint. I let the assembly cool in the jig, then it goes into the soak tank.











The little fillet now gets in the way of the downtube/BB miter. I take a couple swipes at the fillet, and round off the points of the downtube to return the fit to how it was prior to tinning. Again, this is another advantage to working in larger, more cohesive steps. The first couple frames I made, I mitered the downtube after tinning the seat tube to the BB. Getting good fit up was tricky, though, because I wasn’t sure if the miter was as it should be if the little fillet wasn’t there. Much easier now that I have a (slightly) better grasp of the overall process and can avoid this type of thing.











The frame bits are now ready for fillet brazing. Time to have some fun. Hope you're enjoying the show-and-tell as much as Mathilda has been!

-Chris

[cblandford]

All right, time to tack and braze this little frame together.

For today:

…
9. Tack Frame in Jig
10. Quick Alignment Check
11. Braze Frame Free of Jig
…

To tack the frame together, I begin by applying blue flux to the tubes and loading them into the jig. I apply a full coat of flux--enough to last through the tacking and the brazing. I also flux about an inch up into the ends of the mitered tubes. Using the same 203 tip, a neutral & rumbling flame, and 1/16th bronze rod, I tack the tubes together along the frame’s centerline. Here’s my tacking sequence:







In short: obtuse angles first--from the BB up and around to the seat tube, and then acute angles--back down and around. The general thinking here is that tacking the obtuse angles first will minimize any pull-apart on the opposing side of the miter, as the bronze will pull the tubes more “into” one another. For chainstays, however, I tack the outside (acute) sides first, then the obtuse sides. This is done to minimize suck-in at the rear dropouts and to keep the rear spacing as designed. (For this little bike, I’m waiting to connect the top tubes along with the seat stays, mixte-style. So, I skipped tacks #3-6.)









I let the tacks cool in the jig, then pull the frame. At this point, I haven’t touched the BB with a facer but I go ahead and throw the frame onto my small alignment surface anyway. This is mostly just to check that nothing went super awry during tacking and--less importantly at this point in my learning, I think--to inform the brazing. I use a handy little alignment gauge (available from Compass) to quickly check the head tube and dropouts against the centerline of the frame. (I’ll go over how I check alignment more thoroughly in my next post.) In this instance I found that the headtube and the dropouts both sucked ~1mm toward the non-drive side of the frame’s centerline. This has been a trend with my frames. I think it has to do with the fact that access to the non-drive side of my jig is limited, and it takes me a few seconds longer to get those chainstay tacks in place compared to the drive-side ones. I’m also right-handed and tend to tack looking “over” the headtube of the frame, so the heat is coming from the non-drive side of the frame. I’ve made a mental note to try and work quicker and direct my heat more uniformly into the centerline of the frame. Small progress with each frame, I think.









Thankfully, the headtube itself showed no twist at this point. I was very pleased about that. Given that this frame--in its current state--only has the down tube to support the head tube during tacking/brazing, I was a little worried things wouldn’t work out so great. So far, so good.

Next, I make a Sharpie mark on the outside of the drive side chainstay as well as on the drive side of the down tube, near the BB. When I go to fillet, I’ll start with these sides of the frame, hopefully sucking things back to center along the way. I’m still learning how to inform my brazing via this alignment check, but I think that’s the idea. I’ll make notes when I’m done and try to improve on the next frame.

Finally, I pull the frame from the table, throw it into a Park stand, and fillet braze all the joints.











For the main fillets, I use the same 203 (sometimes a 205) tip, but use the larger (3/32nd) diameter Gasflux bronze rod. I definitely prefer the larger rod for these joints. As mentioned, I don’t apply any additional flux; I just reheat the flux that was there during tacking. I'd love to try a Gasfluxer, but that'd probably be a silly purchase for someone who brazes a few times a year!

I know there are many schools-of-thought when it comes to fillet brazing. No pre-heat vs. pre-heat. Small and tidy ala tig welding vs. broad and entire-joint-focused. One pass vs. multiple passes. Etc, etc, etc. I’ve read everything I can get my eyes on, and have (mostly) settled on a process. I like to pre-heat my entire joints (including the “back” sides of the tubes) to temperature and then lay down as broad and even a fillet as I can manage, in a single as-fast-as-I-can pass. I’ll scrounge together--and post later--a few links to the writings of Dave Kirk, Steve Garro, etc. that describe this method. Super insightful. This was also how I was shown to fillet braze by Tony Pereira in UBI course #1, so it’s how I started out in my practice and how I’m most comfortable. (Interestingly, Ron Sutphin showed a no-preheat method in UBI course #2. Just different strokes, I think.)

A couple beginner’s insights. First, I braze the harder joints up front! I used to start with the “easy” head tube joints, but have since moved to beginning with the bottom bracket and chainstays, then moving to the head tube and finally finishing with the seat tube. Second, I like to take a quick break between joints. Set the torch down, take a swig of beer, change the album that’s playing, stretch. I try to remember that I don’t need to sweat and stress while I braze. And finally, I try to figure out how I’m going to clamp and move the frame--for each joint--before I light the torch. Gameplan it a bit.









For what it’s worth, I’m completely in awe of the professionals’ fillet brazing, as shown in this forum and elsewhere. Garro, Kirk, Estlund, Bilenky, Steve Rex, on and on. Pretty ridiculous. What a gulf between those that actually know what they’re doing and someone just learning. I can’t imagine how long it would take me to get to that point. A lifetime. Maybe next time.

That’s it for now. Back to work. More soon.

-Chris

[shirk]

Appreciate the detailed work your are putting into your write up.

I got lucky and picked up a used Gasfluxer when a frame builder was moving across the country and he wasn't sure it would integrate into his new set up. I've only used it on a couple frames but I like it. At this point I only have 7 frames under my belt and I am more the type to leave it raw and rough and ride it till it brakes and move on to the next one, no patience for soaking flux and hand filling the fillets. I love the idea of practicing a joint a day I need to do it.

[claritycycler]

Appreciate the detailed work your are putting into your write up....

Myself as well, thanks a lot for taking the time to share your process.

regards, Brian