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that is amazing and all credit to you for having the patience to detail your build, writing it up must have taken an age.
Cannot wait to see the finished bike.
will you need to use a reamer to get a consistent diameter in the seat tube or does that not matter? -
Thanks for your kind words, guys :) I've been feeling a bit down about the whole thing for the last day or so because I totally cocked up skinning the headtube with carbon cloth (mainly cosmetic) and ended up wasting quite a lot of epoxy and cloth, but I'll give it another go in a few days. I can't wait to see it finished either!
There are a few different ways to get the seat tube to work, none of them quite ideal. Most people try one way or another to recreate what you get on a metal-framed bike - either the bamboo seat tube or a metal insert has a slot cut in it, and a normal separate seat clamp tightens it. The downside is that the bamboo is prone to cracking if you clamp it directly, and the metal insert is both difficult to glue in securely and a little ugly in my opinion. On my first bike I kind of did this, but using a clamp like this - the bottom clamp held the (unslotted and hence still strong) bamboo, and the upper clamp held the seatpost. Worked alright, but it's difficult to get an exactly round clamping area the right size on a bit of bamboo, and it came loose occasionally from expansion and contraction due to humidity.
Another option is to do a fully integrated seatpost. This is a pretty cool idea if you know exactly how long you need it, and (vitally) don't plan to change saddle, cranks, pedals, shoes or height for the lifetime of the bike.
I'm going for a middle route which I'm not entirely convinced about, but I think it's a good principle at least. The first option is out because the thinner bamboo I'm using is only ~22mm internal diameter, which no good seatposts are made in. It is, however, the size of some old stubby BMX posts, and the diameter of the thinner part on the top of those shitty plain-top seatposts. So my plan is to have the bamboo going most of the way up to the saddle (as can be seen in the pics), with a very short 22.2mm seatpost glued in the top for the last couple of inches, onto which a Brompton Pentaclip is attached to hold the saddle rails. I'm hoping that with the Brooks saddle I plan to use the metal part should be mostly hidden anyway. The Pentaclip is not a pretty bit of technology but it's nicer and works better than these horrid things. At some point I'll find someone who can CNC me a nicer one.
Like I said, all these ideas have downsides. The downside of this is that I have to have a stubby cromo seatpost from the 80s glued into my lightweight bamboo and CF frame. There are a few aluminium ones about, but I'd rather carry the extra 50g or so and not have to worry about it bending (very unlikely for such a short bit, but it would be terminal for the bike).
It is quite time consuming to write up, but I really regretted not doing it properly the first time around. Now I'm regretting not taking very good photos, but I'll want to build another one to test out my prototype jig anyway ... it's a terrible addiction!
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Fuck. I had an enormous post all written out, and then I pressed submit and it disappeared like it hasn't done for ages. Of course this time I neglected to copy like I normally do. So this will be a bit briefer than it was beforehand.
ANYWAY. Update time...
SHINY BITS ARRIVE
Shiny bits by comatus1649, on FlickrI've fallen for the whole disk brake fad. Got a TRP Spyre on eBay for less than the price of a BB5, and it should be a little better than a BB7 so I'm pretty pleased with that. Looks ace too. The hub is a pretty unexciting Shimano M756, which I chose because I like matching hubs and it can easily be converted into a pretty ace rear hub with a six-bolt sprocket. Rims will be Halo Aerotrack; spokes will be DT Swiss Revolution because I've never laced a wheel with very light spokes and it will be a good experience one way or another ...
More of what I wrote and lost tomorrow.
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Next update. This is brief because I can't be bothered to type it all out again. Look at my Flickr for more notes and process photographs.
MORE CF
Finishing the tape layup
Last on my hit list was the BB. I chose an aluminium one because it's much lighter than the steel equivalent I used before; however it's best to isolate carbon fibre from aluminium due to the potential for galvanic corrosion. So I skinned it with a thin layer of fibreglass first, then built it up with the carbon fibre as before. I took my lead from the wrapping guide already mentioned but had to change it quite a bit because my 25mm tape is much wider than tow. After the peel ply (hard to wrap tight around this complex shape) came off, this is what I had:
After curing by comatus1649, on FlickrLooks pretty neat and strong. But if you look at my other pictures on Flickr you'll see that there are voids in the layup on top of the chainstays. These could have been avoided by building the fillets up more, or possibly by thinking about my wraps a bit more carefully. I'll have to fill these later, but I don't think they'll affect the strength too much.
Cosmetic skinning
So the tape laid up already is structural, and the bike is finished in that respect. However, I wanted to put a layer of carbon fibre cloth over the top to really finish it off - UD tape just looks black and uninteresting, and you don't have the nice weave texture people associate with CF. I also chose a carbon/aramid blend which will add a degree of crash protection.This is a totally different process to the wet layup already shown. The skinning technique is generally used to cover car parts or things like that, and it's much much trickier on complex parts like the joints on a bike. It is also a tiny subset of the tiny community of bamboo bike builders who use carbon cloth, so this is rather undocumented territory. I was helped enormously by this guide, but I have a few tips of my own. First, use a thicker epoxy like the one CarbonMods / Easy Composites sell in their kits. West Systems is a bit thin really. And really do let the epoxy go off until it doesn't come off on your finger when you poke it - only then will it properly stick to the fabric. Otherwise it will drive you mad by coming off, plus the epoxy may soak through the fabric and spoil the look of the weave. You may need to use tape to hold it down while it cures, especially on the smaller tubes (you could alternatively use a very lightweight cloth (90gsm is available), but it's very very expensive).
Working with woven CF cloth is not very easy. It frays easily, is expensive, and the weave distorts if you look at it funny. Easy Composites will sell you 'ProFinish' cloth for £5 more per metre; it's just been sprayed on the back side with spray mount. I used the cheapest stuff I could find on eBay and it clogged endlessly. Post 3M stuff might be better. You want to slowly build up a thin layer on the back. If you're buying from Easy Composites you can cheaply buy a sample of their ProFinish cloth to see how much you need to apply. This makes the fabric a little stiffer but much easier to handle, cut and look after - no longer does it instantly fray wildly.
You need black epoxy for this so that bamboo can't show through the weave of the cloth. I used graphite powder because it's cheaper than pigment and has other uses. You want a smooth, very dark black mixture - mix the graphite into the epoxy before adding the hardener, mix, then transfer to another pot to avoid lumps of unhardened epoxy or graphite. Paint it on everywhere you want the fabric to stick:
Black base coat on dropouts by comatus1649, on FlickrWhen it is tacky, you can then apply the cloth which you have already cut to shape, and hold it in place while it cures. At first I had it overlapping, and I then cut back the excess. For larger parts or those where you need a very neat symmetrical seam, I pinched it like this:
New improved skinning technique by comatus1649, on FlickrWhen it is almost cured I trimmed back the flap and pressed what little excess there was left into the tacky epoxy. This gives you joins as neat as you are ever going to get. They will never ever be as good as the seamless appearance on moulded carbon frames, but they will look alright once the clear coats of epoxy have gone on.
Another note on complex shapes - I tried cutting the fabric into a shape that would let me do the joints with one bit of cloth, but it was a disaster. The best way, as it seems to me, is to do it in parts - first do the bits that could be considered not the end of a piece of bamboo, then when they're done, neatly do the bits that are the ends of the lugs. That sounds confusing, but the pictures may help. This is the second (and final) lot of black epoxy being put on the HT/DT joint:
Second application of cloth to the HT joint by comatus1649, on FlickrThat's all for now. At time of writing I'm just letting the epoxy cure for the last few bits of cloth to go on around the BB. I've fucked up a couple of bits but it's surprising how well the clear coats of epoxy cover it up (or that's the hope anyway). I will update with that whenever I manage to do it!
Thanks for reading, and for being patient!
Ben
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FINALLY FINISHING THE CARBON
After many weeks of doing the carbon fibre, I was getting pretty bored. I feel like this reader's wife and I are celebrating our diamond anniversary. It was nice to finally get it done. After all the carbon fabric is on, it's time to put on (at least) two thick coats of epoxy to create a surface that you can sand down to be fairly flat. As I said before you'll never get the finish you might see on a moulded CF bike, but you can get a pretty nice result. At this stage you'll start to see how all the little defects and imperfections don't look so obvious now it's all shiny, and how the weave of the carbon comes out. However, the surface will still be a bit rough:
2 thick coats of epoxy later... by comatus1649, on FlickrYou can also see little bubbles left in the resin. These can be greatly reduced by a combination of heating the two resin parts before mixing, stirring very gently (definitely transfer it into a second pot if you're being very gentle as you'll otherwise have a bit of unmixed resin at the bottom), hairdrying the resin in the pot (this shortens pot life a bit - a roller tray is best to stop it curing very quickly) and then again when it's on the bike. The foam brushes also tend to froth up the resin so you can either change to normal brushes, or as I did, just go very gently. Beware of cheapo paintbrushes which dispense bristles everywhere.
A note on masking techniques - wrap loads of tape around the end of the lugs. This means that you can take off one wrap after each coat, and not have a massive drippy buildup when you're finished. It's probably easier to take off the tape when it's stiff but not cured, but I always put epoxy on before I went to bed so I always had to do it when it was dry - bit more tricky.
The seams between bits of fabric now look much subtler, but it looks pretty homemade:
Built-up epoxy by comatus1649, on FlickrSo it's now time for more sanding.
I hate sanding.
You're taking off a lot of epoxy so begin with the rough stuff - I began with 80 grit aluminium oxide paper. Reading the Carbonmods skinning guide it tells you to use 240 wetndry, which is all very well if you're taking out little lumps and bumps on an otherwise flat surface, but you need to build up a lot more epoxy on these complicated joints, so you'll need to take it off more roughly. This is also your last chance to knock off the high points caused by loose fibres, rough joints and other mistakes. I started with 80, then 150, then 400 wetndry, then a quick go with 1200 to really smooth it out. This was slightly overkill - if you can't see scratches when it's wet, you won't see them when they're covered in epoxy.
This was the technique I mostly used:
Flatting round pieces by comatus1649, on Flickr
For flat bits you could use a block, but there aren't many flat bits on a bike (bottom of the BB shell is the only example really, unless you're doing some ambitious aero nonsense). Excuse the dodgy photo, I don't have three hands and had to wedge my phone between the chainstays ...It's ok if you get down to fabric in places, but that's a sign you need to back off because once you start damaging the fibres you'll change the final appearance. It's hard to describe what exactly it looks like when you go too deep, but you'll see when you do it - the white high points, instead of looking like random lumps and drips, will look like tiny rectangles at right angles to each other.
Once you've washed off all the dust (and seriously do wash it off, in the shower and everything, because otherwise those little bits of carbon and epoxy dust will fuck it up), it will all look kinda ruined:
After being flatted by comatus1649, on Flickr
But that's alright - it's much flatter now which will make for a good final result. The reason we have to put all that epoxy on and then take it all off again is that there will be some bits of fabric that are maybe 2 or 3mm below the general layer of the part, and you want the surface to be as free from pitting as possible.This is also a good opportunity for a few sanity checks - will the headset cups fit, for example, or is the joint overbuilt? Does the carbon extend over the edge of the BB shell, or too far onto the dropouts? You can fix all this later if you have to, but it would be nice not to have to.
Now for one final coat of epoxy. I applied this with paper towels to get a really smooth, thin, run-free surface. After this cured, I had a pretty good finish, dust nibs and the odd concealable pit aside:
After final very thin coat of epoxy by comatus1649, on FlickrNext step is to polish this up with 1200grit, and think about lacquer ... This is the third week in a row I've said this, but I really do think it'll be done this week.
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Echo David213's comment. Great read, it's basically a reference thread. Kudos for taking the effort for putting it all together
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VERY, VERY NEARLY FINISHED
So life has a way of filling up what you thought was free time, and I've not quite finished yet. But it's tantalisingly close, probably closer than you could easily tell from photos on the net and I'm going away tomorrow for three weeks, so here's the nearly finished product, and how I got there...
Polishing the CF, a dead end...
The CF was all in place and sealed, so I just had to get it to a finished state. I decided I would polish the epoxy - first I smoothed it off very lightly with wet 1200 grit wet and dry, and then I polished it with Autosol.
Polishing process by comatus1649, on FlickrAutosol is a metal polish, but it's pretty good at this as well. I used loads of it, but it came out nicely, better than I had expected in fact:
Polished CF by comatus1649, on FlickrAnd it looked better than that in really life. Unfortunately the finish didn't last very well - it seemed to be mostly down to the protective coat that Autosol deposits, and it dulled quite quickly. I also found that the bottom of the BB was getting scuffed pretty easy, so I decided that I wanted to put another protective coat on top. I was going to clear coat the epoxy, but decided not to because of its tendency to yellow, peel and generally be a bitch to get right in the first place. So as I was going to be using Gorilla Glue to seal the bamboo I decided to give that a go (cleaning off the polish residue and roughening it up with 150 grit first), and I was pretty pleased.
Sealing the bamboo
As mentioned before, bamboo has a naturally waxy finish which protects it for a while, but decays after about 6 months when it's dead, so I decided to take it all off (hell of a job) and replace it. I chose to use Gorilla Glue because I had it about, I knew it was very UV-resistant and tough, and because it's been used a little in bamboo rodmaking with good results. It is a bit finickety to use, and I'm not sure whether I'd be bothered with it again. I would probably just use spar varnish. However, it did come out well. You have to apply it very very thinly - I used a slice of washing up sponge to put it on very lightly. Put on too much, and this happens:
Ooops by comatus1649, on FlickrThe same foaming action that makes it great as a glue is not what you want for a finish. It's also worth adding that you don't wet the surface as you would if you were gluing it - the humidity in the air is enough to make it go off very slowly, leaving a nice smooth, glossy and hard finish.
Gorilla glue drying by comatus1649, on FlickrBottle bosses
To make this bike as much of a jack of all trades, I wanted to put bottle bosses on. I wish I had bought more, but ended up only putting enough for one cage on the downtube. I nearly just put one on the seat tube because I personally think that position has some advantages, but I didn't have a spare cage and bottle to test and I was worried about clearance with the sloping top tube. So one in a conventional location it is.I also put two other bosses in strange locations for other purposes - one is on the back of the seat stay wishbone - this will provide a very nice neat way of mounting a rear rack. Drilling a hole here was incredibly difficult but now it's in it actually looks quite neat. The second odd one was on the back of the seat tube, at the point where the wheel will be closest to it. My rationale - I want to run full mudguards because life's too short not to. But I didn't put a chainstay bridge in for cosmetic and ease of wrapping reasons; this boss here will allow me to bolt the mudguard to the seat stay about 5 inches above its end (I'll have to drill another hole unless I have the mudguard ending early). I will have to see how this works out - the rear wheel clearances are relatively tight so it should work alright, and look nice and clean. Of course, it might be a terrible idea. But there have been 6 or 7 things I've done on this bike for the sake of experimental innovation so that I will know not to do them again (or potentially know they're a good idea).
The holes for the bottle bosses were drilled with gimlets first and then with an awl. I thought this would be the most gentle way but still cracked the sodding downtube very slightly. Take it very easy, boys and girls. I don't think the crack will spread but I will add a little more glue to seal it.
So this is where the frame is, essentially finished:
Finished (nearly) by comatus1649, on FlickrWhen I get back, I'll finish it totally - one more go with 1200, then more Autosol, then beeswax or similar all over. That should give me the durable shiny finish I want... For now you'll have to be content with smartphone pics, but when I'm happy with it I'll get some proper arty ones. And then it's a matter of building it up (Christmas is on the way, thankfully...)!
Thanks for reading!
Ben -
Hi, my bamboo frame seems to be coming on OK if a little slowly.
Thanks for the blog it is ace.
I have a question though. I am now wondering the best way to get cable stops onto the bamboo frame and cable guides under the bottom bracket for gears cables.
Are you going to do this?
Do you have any advice?
Cheers,
Phil
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Hi, I guess I am going to answer my own question here.
I think I will probably try to do what this guy did and epoxy some thin bamboo to the frame like this:
http://1.bp.blogspot.com/-px8HdKT6g10/UEfxwhrovcI/AAAAAAAABto/uTGhPPtWYvM/s1600/DSCN1056.jpg
From:
http://build-its.blogspot.co.uk/2010/09/building-bamboo-bike-frame.html
I guess finding some decent bamboo with the right diameter might be the issue here?
A bit of cane might suffice?
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Wow, sorry it's taken me so long to do an update. It's been one thing after another stopping me doing the very last steps - first I didn't have a job and couldn't afford to work on it, then I had a job and had no time to work on it... but over the last couple of months I've been slowly acquiring the remaining parts and fitting them to the frame.
I'm a volunteer at the Broken Spoke Bike Co-op in Oxford which has meant that I've been able to use lots of pretty shop tools and do every bit of labour on the bike myself. I've also built the wheels: Shimano XT M756 hubs front and back (back respaced to 120mm with a solid axle and a Velosolo bolt on sprocket) laced to Halo Aerotrack rims with DT Swiss Competition spokes on the drive/disc sides and Revolutions on the other side. Saddle is a Brooks Team Pro Classic, handlebars are Profile OS Airwings with green and brown harlequin tape and twine. I've also fitted SKS Longboard mudguards.
The pedals were a bit of a faff - I wanted to use Wellgo QRD system pedals so I can swap between straps and clipless easily, but the M138 pedals I got originally were much too small for the Pedalbelt straps from Kickstarter. So after a failed experiment with the Wellgo V12 clones, I got hold of some normal C161 pedals which share the same axle as the M138s, and swapped them for the quick release ones. This is a cheaper way of making up for the fact that only a few QRD models are available in the UK (potential swappers, do note that the QRD axles are both right hand threaded, while the non-QRD axles have one left hand threaded).
Here is a terrible photo of the finished article:
Quick snap of the finished article by comatus1649, on FlickrNaturally you might be wondering why I've not rushed out on it and taken some better photos. This is mostly because I had just finished a long session working on it and began to ride it home, when there was a bad noise, and the tyre began to rub on the chainstay. I took it home and examined it, and the results can be best experienced by flipping backwards and forwards between the two photos labelled 'wibble' and 'wobble' in my photostream. Almost immediately, the joints between the dropouts and the stays had failed - this had been my first time bonding stainless steel with epoxy, and it's not easy.
This presented a bit of a problem, as they were still very strongly attached by the stiff chainstays (the carbon 'lugs' were entirely intact; the dropouts had simply separated from the epoxy plugs inside). After a botched attempt to drill through the lug and pin the joint (stainless steel that has been work-hardened by milling is not only very hard to glue, but also very hard to drill...), I had no choice but to pull them out, a very, very stressful process. When they were out, I did what I should have done in the first place, keying them very aggressively for a strong bond:
Getting rough with the dropouts by comatus1649, on FlickrThey were then glued back into place with Marine JB Weld, more or less the strongest adhesive there is for this kind of application. Learn from my mistakes - smooth, hard stainless steel is extremely difficult to glue, and I shouldn't have made such a pig's ear of it in the first place. It's embarrassing to have such a critical failure documented for all to read but this thread isn't about making me look good ;) This is by far the hardest joint of the entire bike to get right, and it's a pretty important one.
The good news is that I'm pretty sure the bike is ready now, components and all. However, I'm in no great rush to get out on it because the salty roads are playing merry hell with my other bike and by the time I get home from work it's dark... there's also a terrible temptation to never try it in case it breaks again, in which case I've run out of (non-drastic) options and will have to get business cards printed with 'Novelty Bike-Shaped Ornament Maker' on them. This weekend I'm working but the next I'll have a chance to take it for a good test ride and get some decent photos, or that's the plan anyway...
Ben
Belated reply to Djangoberry: garden cane might be your best bet - it is actually generally bamboo, just really skinny stuff (harvested young, I assume). I won't be putting any cable stops on at the moment but will if I decide to run it singlespeed or even geared in future. I'd probably epoxy some normal braze-on cable stops onto the tube rather than using cane/bamboo because of the sizing issues.
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looking fantastic! (apart from the cracked dropouts obs) love the finish you have on the bamboo.
re the dropouts: i wonder if there is quite a large turning moment that pivots around the base of the seat-stays. your rear axle sits cantilevered out a lot further than traditional dropouts (if i think i understand the design of them correctly).
anyway on the repair make sure the carbon weave goes both parallel and perpendicular to the chain stays and you apply lots and lots of it and overlap it as much as possible over the dropouts and the chain-stays and it should be fine. perhaps ride it a bit before applying the beauty layer!
I've been riding my bamboo bike for 6 months or so now and so far its holding up great.
good luck! don't let this set back stop you from riding it into the sunset
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i put a thread on here with some pics from my build a couple of months ago.
found it: http://www.lfgss.com/thread117882.html
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Very nice work!
Well, after (more) delaying, the job's done - the JB Weld is absolutely solid. So far I've taken it on one proper 24 mile ride and commuted on it for 2 weeks (only 6.5 miles each way but a pretty good shakedown test) and I'm extremely satisfied.
http://farm3.staticflickr.com/2842/12751686343_959d658251_h.jpg
Ride quality is excellent, extremely smooth but also responsive due to the springiness of bamboo. But it's hard to isolate the effect of the 35mm Schwalbe Kojaks which are very quick-rolling and supple, with a weight comparable to 23mm Gatorskins (though very little puncture resistance). Flex in the front triangle is noticable under heavy effort but has no negative effects, though combined with the very low trail design it did feel jittery at first. The rear triangle is as stiff as I had hoped.
A very short stem (Cinelli Ant, 60mm opposed to the 90mm Planet-X Superlight one I had before) gave me a better position on the bullhorns - I was previously a little stretched out as I had sized the frame and stem for drop bars - and also actually reduced shimmy by changing the balance of the front end very slightly, an interesting result that I hadn't expected.
Braking performance with the TRP Spyre disc (post-recall revised version) is obscenely good. I know disc brakes on road bikes are a fad etc etc but I wouldn't willingly go back on a new bike now; braking performance is so much better for only a reasonable weight penalty. It pales into insignificance when you take into account my old man Carradice saddlebag and half-kilo steel Bagman support ;)
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Somewhere between woodwork and framebuilding: bamboo bike #2
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Wow, super impressed. I have to admit upon first reading the thread I was expecting something just cobbled together as I didn't really know the properties of bamboo or your skill, but I'm happy to have been proven wrong. Fantastic work, can't wait to see it all built up.