Bamboo bike - finally doing it
 

I'm finally started on my dream to build something...

Getting a kit (Hero Bike) made it a little easier to get started.

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where did u get the geometry layout from?

The Hero Bike kit (click on the OP's link) includes the full size drawing.

That kit looks like a great way to go. It looks like you could buy it without the bamboo and substitute routed out and laminated hardwood a la Renovo. Cool.

http://www.renovobikes.com/storage/f...ts-487x261.jpg

The drawing comes with the kit.

My plan is to be able re-use all these jig parts to do other things. Maybe a carbon tube bike or even steel.

The kit creators even have a series of 'how to' videos to ensure you get a good result (i.e. safe).

http://bikeforums.net/attachment.php...hmentid=384006

I have begun the shape the balsa lug cores. The seat stays were not glued in place yet, so instead of doing that right away and having to wait for them to set I did all the shaping I could do and only then glued them on. When it is dry I will complete the shaping.

http://bikeforums.net/attachment.php...hmentid=384385

Getting there.

Lots of aesthetic decisions to make with the shaping of the lugs and care needs to be taken not to remove too much material too quickly. It is difficult to see if the back side (i.e. facing downwards to the board) is matching as I've only got 6" to play with.

Next step is a light fibreglass strapping to 'tack' it together a bit more robustly so that it can then be removed from the jig for the carbon wrapping. You need a lot more room to move your hands when trying to wrap carbon tow ribbon from a small spool.

Looks great! I'm impressed with both the kit and your skills in assembling it.

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Next step is some basic fibreglass to be a more solid 'tacking' together. All major lugs done, but I'm just showing you the head tube here. Four long strips with an over lapping X pattern, then two simple rings around the balsa-tube join.

http://bikeforums.net/attachment.php...hmentid=385273

Wrap in electrical tape to compress.

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Tape off, but lots of little ridges to remove. Air powered sanding tools are your friend to do the bulk of this, then finish by hand.

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The frame is strong enough to take of the flat jigged position. Also handy to help with the sanding of the lugs.

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First carbon. A little spool spread between the two stays. I've put tape down to mark the ends and on the chain stay I've already laid some peel ply on top.

http://bikeforums.net/attachment.php...hmentid=385270

After the peel ply came the bleeder/breather cloth then the sealed bag.

This is my first ever solo vacuum bagging effort and it wasn't easy (I've only assisted with simpler set ups before). Needed to re-do it to get it all on and sealed, but learned a few tricks to make the other areas easier.

Next up will be the other stays, then on to the main lugs.

Nice 'how to' photo sequences. Thanks for posting them.

I'm an ex-high school design and technology teacher, so it is a habit! There are more, so I might stick up a full gallery somewhere and link to it.

https://plus.google.com/photos/10246...MTd9uC9kMfNwwE

Full album of photos.

Today's highlights:
http://bikeforums.net/attachment.php...hmentid=385443
Head tube wrapped in carbon tow (initially following a set pattern to ensure strength, then just filling the gaps)
http://bikeforums.net/attachment.php...hmentid=385444
Then wrapped for compression.
http://bikeforums.net/attachment.php...hmentid=385445
Bottom bracket in progress. You can see the first pattern here - basically tying the bottom bracket shell to the seat tube with figure of 8s on both sides. I'm just starting the next wrap pattern, tying the down tube to the chain stays.

Some updates:

https://plus.google.com/photos/10246...29594896357441

http://bikeforums.net/attachment.php...hmentid=385812http://bikeforums.net/attachment.php...hmentid=385813

Unwrapped these two lugs. Quite a few lumps, ridges and ripples to sand out. Electrical tape compresses well and leaves a good finish, but only if it is laid down well. I suspect that a wider tape might be more effective.


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Did the last lugs. Carbon laid up then later wrapped.

Frame is fully out of the jig now. Needs lots of sanding to get rid of the deeper ripples - then a clear coat the finish.

http://bikeforums.net/attachment.php...hmentid=386048

Shaped and mounted a rear brake bridge today. This will need to be wrapped more firmly in place with some additional carbon ribbon.

http://bikeforums.net/attachment.php...hmentid=386050http://bikeforums.net/attachment.php...hmentid=386051

Might use the same off-cut carbon block to create the two 'braze ons' for the rear brake cable. This stuff is about half an inch thick and I think it is part of a busted racing yacht boom.

http://bikeforums.net/attachment.php...hmentid=386310

Cable stops for the rear brake.

These are fairly chunky, but I can sand them down a bit later. I drilled them out to locate a cable ferrule in one end, but I did not cut a slot for quick insertion of the cable. This was going to be a bit fiddly with my tools and I thought I'd probably make a mess of it.

http://bikeforums.net/attachment.php...hmentid=386538

Pretty much done.

A light flow coat of epoxy has just been applied (frame is actually hanging to dry upside down - flipped image) to the carbon. I could have spent many hours more sanding and so on, but this is fine for a first effort. I will do a few things differently next time to ensure a better finish.

I'm just trying to chase up some more reasonably priced second hand parts (fork in particular) for the bike so that I can assemble it.

Looks damn good for a first effort. Congrats.

You can cut slots for your cable with a fine toothed hacksaw blade. A bit more surface area could have been useful if the stops are being held in place by epoxy alone. Probably wouldn't hurt to use a couple of countersunk stainless screws for insurance.
It is very important to coat the whole frame if you want it to last. Over time with moisture cycling the bamboo will shrink and separate from the carbon if your local temperature and humidity levels fluctuate.

Thank you. We'll see if it rides properly before passing final judgement!


In hindsight I think I should have cut the slots earlier when I had more material to work with. There is quite a lot of surface area (half a square inch), so unless I give these a very direct solid knock they are not coming off with general use.


Not sure that a clear coat on the frame will stick. The epoxy drips and so on have so far been very easy to flake off the bamboo surface. I'm reluctant to give the surface even the lightest of sanding to help a coat of something key to the surface more securely.

What has been your experience with longevity and method for a clear coat?

You definitely have to sand the outer surface off to get a coating to stick. I always sand it off completely so that the power fibers are visible and then give an epoxy coating followed by a light sanding with synthetic steel wool and a coat of UV resistant clearcoat.
Just a coat of Epoxy will last for years if the bike is kept out of sunshine except when in use.
I have several bikes that have looked the same for years after being coated.

Not so sure I want to sand so much off. Can you send me a link to some photos of your bikes?

Perhaps a VERY light sand that won't change the outside look too much might be just enough to help a clear coat stick (OK, any sanding will make the surface change to a matt finish, but the application of the clear will 'restore' the look a bit).

You can see several pics in the "Show us your builds" thread at the top of this page.
You can just knock the gloss off the bamboo with a scotch-brite pad and replace the natural coating with a more durable waterproof layer while retaining the appearance of the raw bamboo.

The Gougeon Brothers, developers of the WEST (wood epoxy saturation technique) System for boatbuilding using thin wood veneers, devote a lot of print in their book The Gougeon Brothers on Boat Construction to stabilizing the moisture content of wood by completely encapsulating the wooden structure with epoxy resin. This maximizes the strength of the structure and minimizes shrinkage and swelling. While bamboo is technically a tropical grass, the hollow stem is woody and hygroscopic (moisture content varies with ambient humidity) like woods.

I would strongly recommend taking Canaboo's advice about sealing the bamboo with an saturating epoxy resin moisture barrier.

I'll hit the tubes gently with a very fine paper to see how it turns out. I am liking the finish of Canaboo's bikes, but had initially thought that it was a bit 'too much' with the node rings and all the original finish taken off.

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I took to the tubes with some 300 grit wet/dry paper and it produced this matt finish. The painters in the workshop agreed it was enough to help the clear coat key in. I think I could have easily hit it with 120 and not over done it since the bamboo still looks quite original after the clear is applied.

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2 pack polyurethane clear coat applied by brush. A thinned out epoxy ('everdure' style) probably wouldn't penetrate this unless I took a lot more off the bamboo surface, so this is more an outer layer than anything else.

If anything the bamboo has 'warmed' in colour a bit with the clear coat.

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Looks good. I was worried about screwing up the look of the bamboo, but Canaboo's experience has been shown to be right.

I'm sure that I'll get better after 2-3 more frames. A couple of friends want one and I want to do another more road oriented one.

Disn't calfee have to stop using carbon wrap because the frame joints fell apart due to the differences in response to atmospheric conditions between the materials?