Filed In: Process

Father/Daughter Project - Part 8

December 11, 2019   |   Chris Blandford

Moving forward. Steps for today:


12. Check Frame Alignment
13. (Align Frame if Necessary)


I only recently purchased my little alignment table. Up until my last couple frames, I’d been relying on my fixtures and the various string/straightedge/frame-alignment-gauge methods to check alignment. The classroom at UBI housed a full-size BB-tower style alignment table; in both of my courses it served as a very heavy coffee table.

I think the attitude there is that if you use good fixturing and processes, an alignment table isn’t really necessary. I think I understand the wisdom in that. One of my favorite walk-around-town activities is one-eyed-squinting at the rear ends of production bikes that I see locked up to racks. Yikes. At least in terms of alignment, the bar isn’t set very high. And really, I don’t know enough about bikes to know whether any of it matters or not. Especially for the types of bikes that I build and ride.

So, I “align” my frames to a level that my perfectionism will accept. Which--given that I’m new to making bicycles--is a pretty loose tolerance. I’ve put a couple of my scrapped frames on my little table and felt the amount of force that it takes to move a head tube even a half-millimeter. A triangle made out of tubular steel is shockingly strong. In essence, I’ve quasi-decided that: A. if something needs mild correction, it isn’t worth me yanking the hell out of my frame to correct it; and B. if something needs major correction, I should probably just start over. So--as of right now--“aligning” my frames is really just a way to gain a little feedback as I go along. I'll nudge dropouts, but that's about it. I use the alignment process as a tool for improving the work on my next frame, not as a way to correct my current incompetencies. I hope that makes sense.

With that said, here’s what I check and how I check it. (Note: I didn’t take photos of this until after I’d finished the fillets, but I checked the frame before I started filing. Nevermind the shine for now!)

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Father/Daughter Project - Part 7

December 09, 2019   |   Chris Blandford

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 chain stays, 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.)

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Filed In: Process

Father/Daughter Project - Part 6

December 04, 2019   |   Chris Blandford

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 also really loves squishing stuff in my vise. I keep having to tell her that 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
9. 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.

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