Discussion in 'Bicycle Mechanics and Repairs' started by chriswoody, 12 Oct 2017.
Thanks for the best thread ever! Can't wait to see more!
looks awesome, would love to see the finished bike
At the rate I'm going it's going to be a little while I'm afraid, but stick around and I will finish it someday.
So this last week has seen me working on this tiny piece of Bamboo, (Apologies for the poor out of focus photo, it was a little hard to focus on it!)
Not only is it tiny and a pain to work with, but it has quite a complex shape. It's the brake bridge that the rear brake mounts to. It sits high up between the Seat stays, so the ends are not parallel. To add to the fun it also has to sit forward in the Seat stays so that the brake calliper will mount properly.
After a lot of whittling and sanding and measuring I had it sat in the right place and fitting like a glove. So I need to drill a hole through it now for the Brake Calliper mounting bolt, that should be fun!
After this, the main construction is finished and it's just a matter of binding it all together once and for all.
Don't know whats keeping you their Website says you can go on a course and build one in a weekend ..
Even worse, they say the homebuild kit should only take 3 days or 6 evenings.
Amazing thread. Not something I would have the patience to even contemplate, let alone actually undertake!
Bravo, say I!
So in the last update I said that all I needed to do was drill through the brake bridge, I mean how hard can it be? Looking at the brake callipers and an old frame I could see that one side of the hole is 6mm and the other is 8mm. Now the brake bridge is quite tiny and not easy to hold, so this was a bit of a challenge. Unfortunately I charged into the problem without really thinking it through. I drilled a 6mm hole through it, then turned it around and attempted to enlarge the back hole with an 8mm drill bit. Everything went well until I test fitted the calliper and the mounting bolt. The 8mm hole wasn't quite square enough and the mounting bolt didn't quite line up with the calliper bolt. No problem I think, a little pressure will line it up....
Yep, that's knackered then, so back to the drawing board!
It took a little while, but I made another brake bridge and this time had a good think about how to go about creating the holes. Firstly I wrapped the bridge in tape then taped it firmly into place in the frame. Then I drilled a 3mm pilot hole straight through the bridge, using the lines of the frame and the good old, mark 1 eyeball, to line everything up. Then I drilled the 6mm hole first using the tip of the drill bit in the pilot hole. The 8mm hole was the key one though and it took a bit of head scratching to come up with a solution. Drilling through from the back was not possible because the seat post was in the way of the drill.
So I had the genius idea of flipping the bridge around to the back of the Seat stays and taping it into place there. I could then drill the 8mm hole easily, again using the pilot hole to line up the drill bit.
Afterwards it was a tense moment to see if the brake mounted through it and to my great relief it did.
So thats all done now which is a relief and I was feeling really satisfied with solving another problem. So I can move ahead with the last preparations before I glue the rear triangle together. After that, it's full steam ahead with the lugs.
I think i would have filled the bridge with some resin and sawdust mixed together, just a thought. Great thread. thinking about doing one myself.
Loving this thread. I think the things that hold the brakes in place would be the most worrying part of the whole frame to me. I can't even begin to imagine how the front brake will be placed, look forward to seeing though.
It's not a bad thought and at the moment the bridge is unattached so it's still a possibility, however, I'll be wrapping the entire bridge in hemp and resin which will give it a lot of strength. In an ideal world I'd have waited to drill the holes until then, but I'm unable to drill the 8mm hole in the back because of the seat post so I'll need to keep the hole clear when I wrap it.
The front forks are actually not made from Bamboo, their just standard, off the shelf, forks. In my case I've gone for a set of steel forks so the front brake won't be a concern.
Resist the temptation. Adding more material like that (filling up the middle of a tube) does not add appreciably to the static strength, and the extra mass can even, in certain circumstances, lead to a reduction in resistance to fatigue.
Not that you need it now, but there is kind of controlled-feed drill (IIRC made by Quackenbush in the USA) where you can pass the shaft of the bit through the hole and attach a reversed cutter so as to increase the diameter of the back hole. I quoted one to a potential customer once. Only about US$ 12 000 !
There is actually a way to use a 6mm through bolt caliper with a concave washer and nut. Use a front caliper on the back, they are identical apart from a longer bolt.
Just thought I’d let you know you can buy bamboo bikes ready made if you don’t fancy the build. A company here in Ghana offer them, frame only or fully built:
Thanks for the information, I have resisted the temptation, but interesting to know. That drill bit sounds useful, but wow, what an eye watering price.
Now you tell me! I'd not thought to look at front brakes, but it's a good idea now you mention it.
Sacrilege! buy an off the peg frame when you can build your own? I'm having far to much fun, but they are a good idea and a nice initiative.
So the work continues on the bike.
I've finished preparing all of the stays, scraping back the outer layer of Bamboo and masking the centre sections. All complete and ready for bonding to the front of the frame.
One extra job I've been doing is filling the front of the frame. The instructions recommend filling any gaps you have with filler just before you start to create the lugs. However I decided that the top tube/ seat post join would be easier to fill and sand before the stays were bonded to it. So I've been building up layers of filler and sanding between. I'm almost there, what you see here, should be the last layer. The hardest bit is on the right side of the frame, i:e underneath, it's a right pig to see and sand properly!
Come off it, we wouldn't have got this brilliant thread if he'd bought a ready built.
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