Discussion in 'Bicycle Mechanics and Repairs' started by chriswoody, 12 Oct 2017.
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.
That’s true, and very interesting it has been but if you bought the ready built one I suggested you’d be helping a local industry which provides much needed jobs for local people.
You could make up for his oversight by buying one yourself.
As we approach Christmas I find the amount of time I have has diminished even more and when I do have time I'm pretty knackered.
However, I have found some time to work on the bike, so here we go.
Last time I decided to fill and sand the toptube/seatpost junction before the rear triangle was glued together. It's not completely smooth, but it doesn't need to be, it's just a foundation for the hemp lugs.
With that finished it was time to look at the rest of the rear triangle. I spent a little bit of time adjusting and re-sanding the ends of the stays, making sure they sat flush. Then I looked at the brake bridge again. With the dropouts they are quite long and because it's a single speed, the wheel will be mounted at various points along it in order to maintain chain tension. So given that, the bridge needs to be mounted so that the pads will always be able to hit the rim. Looking again at the Bridge I decided it was too short and hence to far up the seatstays, so I decided to make another one.
Yep three of the bloomin things! no wonder this build is taking so long. So with that out of the way I made the final preparations for gluing and then it was all go.
So thats it, the frames all glued together.
Now it's a matter of checking it all for alignment and then filling and sanding any gaps I can find. Once all the preparation has been done I need to find five hours to go ahead with the lug creation. I need to sit down though and plan it all carefully, it's a big step and I need to be sure I get it right.
If it was easy it wouldn't be nearly as satisfying. Well done so far, I'm looking forward to seeing the finished bike and I bet you get more satisfaction out of it than if you'd spent 10K on some pro ready megabike.
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