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Building Binbike

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21 July 2006: Spent much of the weekend getting back into building bikes! Hooray! After a 6 month hiatus (broke my collarbone) we can make the transition from "bought the steel" to "real progress". Megan is much happier.

Anyway, this is the second weekend back into it and we finally started brazing so there's actual shapes to show for all the work to date (3 or 4 weekends of cutting and filing).

The rough schedule:

  • October we built a prototype, then bought the steel and got Ben at Trisled to get dropouts laser- cut and send us up a big box of bike bits. He bent up a bit of 16mm tube for the racks (nice, round bends coz he has the gear) and turned some oversize head tubes (he has a lathe too).
  • November... broke my collarbone
  • July: decided I'm healed enough to work on the bike.
  • Spend a weekend filing and cutting to get everything ready. Realise that the plan we have is not the plan we bought steel for. Fake it.
  • this weekend: a little more filing, lots of brazing.

Back again (29 July) the next weekend... more building, but also some riding!

Binbike laid out on our first jig - the main triangle held in place with blocks of wood naile din place, holes drilled in main tube, rear wheel supports cut and more or less in the right place. Binbike laid out on our first jig - the main triangle held in place with blocks of wood naile din place, holes drilled in main tube, rear wheel supports cut and more or less in the right place. Detail of the head tube - this one is megan's, I can tell from how the down tube is mitred. That "tab" will get hammered around the head tube once things are hot and tacked so we get a really solid attachment. note that there's room to add a reinforcing ring to the bottom of the head tube if we get really serious (it's more than 2mm thick tube anyway, but this is where the Filibus bikes often break)). Uses for a crappy sopke tool #20: it's just the right size to cap a bottom bracket and hold it in place for brazing. More filing is needed on those mitres.. The Shed. Well, ok, "Megan's Shed". I get to play here sometimes. Megan. That's more like it - lots of flux, lots of heat. Brazing in the jig. Note that this risk here is that the down tube will pull up as it cools. I had to re-set mine after the first attempt pulled a long way out of line. Eventually this will look like a bike. We really, really need a proper bottom bracket jig.Doing it this way is tedious and often we don't get it quite right, and that really matters. So it takes a long time to do a mediocre job. Megan checkjs her filing for square. Then tacks it up. Then checks it again. Then bends it a bit. It breaks off. She tacks it agin. She bends it again. She breaks it again. She tacks it, bends it, bends it. Brazes it up. Whew! We didn't have quite the right size holesaw for the seat tubes. So we used the next size up. Then brazing it in place to complete the main triangle. I think this is the first bike I've built that actually *has* a main triangle. Filling in the gap from the oversize hole with scrap steel.. Cover it all in bronze, no-one will ever know. Bronze and a bit of wire. High-tech bending gear for the chainstays. Agricultural? You reckon? But it should clear a 4" tyre. Whizzy dropouts. Laser cut 6mm mild steel, built to let us slide the disk brake caliper with the wheel as the chain wears. We really are Rohloff users, not fixie riders (a fixed load bike... now *that* would be pushing it). It's all in the hands. I'm a computer programmer... does it show? They call it "getting your hands dirty". We work mostly outside because the shed has no ventilation so it gets pretty bad if we braze inside. And there's not much space in there, so we take over the back yard too. Megan heating and bending her chainstays. Brazing in action! Note the glowing brass and a bit of glow on the smallre steel tube. This is why working with steel is easier than aluminium - aluminium doesn't change colour when it melts. My chainstays are built to give lots of crank clearance because I like a small Q factor and will be getting straight cranks if I can. The back brace will hold a mudguard, the front on is more there to hold stuff while I file it to fit the BB. We made a rear dropout jig to assemble the bits above. Having a decent jig makes life a lot easier. Especially a fairly solid one like this - we can lean on it a bit if we need to (bending chainstays) as ewll as assemble the bike on it later. Here we're brazing in a pivot for a section to locate the main tube with. Yes, I got the alignment wrong and had to redo it. Then I checked the jig... and it was the jig that was crooked. So I had to re-redo this section back to the way it was. Bah! Ready to braze the bottom bracket to the chainstays.\nNote how the jig holds it all together? People who build diamond frame bikes can have whizz-bang jigs that hold everything just so, but those only work if you're making minor variations on a theme, even the good ones. They don't work for us. So we get stuff like this that holds bits of a bike in place at low cost (and low precision). Such is life.\nAnyway, the chainstays are bolted into the jig, there's a bar holding the main tube at the right height and another one holding the bottom backet likewise. The chainstays don't fit around the bar they're sitting on any more, they're slightly too wide (so we can over-bend them in and they don't hit each other. Once we let them go they spring back a little, and they're nearly touching... Brazing the seatstays to the top tube (frame is upside down). Two frames ready to have the threads in the bottom brackets cleaned up. The tool for this is expensive so we pay a bike shop to do it for us. But not just any bike shop, we use the best bike shop in town. The Monkey have a transport shop... that's us to a T. Even better, Dave is learning to build frames (from a professional, not from us) so he's all keen and interested and stuff. We hope.