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http://brilliantbikes.co.uk/966-large/brompton-pentaclip.jpg

Much better.

On that subject, are there any other manufacturers of high-quality clamps for plain top posts? Apart from Brompton I've only found shitty ones of the sort below, and it's one of those ungooglable things. I ask because on the skinny bamboo frame I'm building by far the easiest option is to have an integrated SP with a short length of 22.2mm plain top BMX post out the top and a separate clamp.

main character in some of the cruelest horror films

http://www.theoldbicycleshowroom.co.uk/ekmps/shops/theoldbicycle/images/brooks-twin-rail-traditional-saddle-clamp.-598-p.bmp

I found 205 slow enough for the really very small areas you're working on at a time. Maybe a bit slower would let you put another layer on all the joints from one batch of epoxy though... I'll think about it.

Rake's still the same, trail will be down a tiny bit, probably imperceptible. Put it in BikeCAD and see what it says.

***SURFACE PREPARATION (AND GREAT BOREDOM)

***On my first bike, I left the bamboo finish as it was. Bamboo has a great waterproof and durable finish, but unfortunately it does degrade when it's not longer growing and left outside for a few months. When I had to go without indoor storage for a while, my bike began to go mouldy on the surface. At the time I scoured it all off and oiled it, which more or less did the trick, but it wasn't a very good fix. Surface water would also eventually sink in, which is a Very Bad Thing for a material so prone to cracking.

So this time around I wanted to give it a good artificial coating that would last really well, and look better than my mouldy old one. I thought about painting it with epoxy, but a) it's pretty thin and would be prone to running, and b) it's very stiff. I don't know how much the bamboo poles actually bend - probably an imperceptible amount - but I was pretty sure that it would eventually crack and then blister, and then I'd have to strip it all off... Some people have used spar varnish, the finish used on yacht masts, but it's really expensive and not very nice to work with.

A bit of a brainwave happened when I was reading a rodmaking forum. A guy called Tim Anderson had been using Gorilla Glue to seal his rods, and this seemed like the perfect solution. I love Gorilla Glue and will be using it to tack the frame together, so I had just bought a big pack of it. Applied in very thin coats it makes a really hard, really shiny coating with very little effort, and it is also very slightly flexible. It's essentially a catalysed PU treatment, curing with the humidity in the air. It also gives the grain a really nice deep appearance. I used a cutoff to try it out:

Finished sample of wood by comatus1649, on Flickr

It's not the best picture, but I think it looks pretty damn good considering I quickly filed off the enamel, rubbed the glue in with my finger and let it dry. You can just about see the dust nibs, but they shouldn't be too hard to avoid (for a start, I won't be putting it on just after sanding).

So I was decided on the finish. Unfortunately, the very resistant natural coating on the bamboo has to go first, otherwise nothing will stick to it. And that means a lot of sanding.

A lot more sanding, in fact, than I had ever realised. And once I'd decided to sand it down to the grain (potentially a bad call), I couldn't really back out. The enamel skin on bamboo is quite thick, and really hard to sand. I was about a quarter of the way done on one of the chainstays when I realised that this was going to take a very, very long time. After hours and hours of hand-sanding, I decided it was powertool time:

Sanding gear by comatus1649, on Flickr[[/URL]

This greatly cut down the time, but working through different grades of paper by hand to 400grit still takes almost two hours per pole. The big poles take ages because they're big, the small ones because the grooves and dents where the leaves sprouted off are really tricky to sand. However, when you get down to the grain the poles start to look much nicer than the garden-centre chic look they had to begin with:

[URL="http://www.flickr.com/photos/78998990@N03/8890033461/"]](http://www.flickr.com/people/78998990@N03/)
Sanded seatstay by comatus1649, on Flickr

They'll look brilliant when they're coated with GG, can't wait! That's all for now. I've still got the TT to finish off, and all of the sanding on the DT and ST to do...

***OTHER UPDATES

***My lug decisions have changed a bit. As it's the same price, I'm going to use unidirectional tape rather than tow - it's the same kind of thing, but in 25mm-wide strips rather than 5mm-ish, which should be easier to handle and more economical on the epoxy. I also don't really like the way that tow-wrapped joints look, and don't see the point in using loads of bidirectional fabric like Brano Meres has - about 40% of the strength (and weight) of the fabric is wasted on most of the bike. So I'm going to use tape, then do an overwrap with fabric, like Cognitive Cycles have done on some of their bikes (like here, for example). I think I'll use a carbon-kevlar blend - it's lighter, more abrasion-resistant and less brittle and so good for a top layer. But the main reason is just cos I want a bulletproof bike.

I've not had that many different bikes so I can't really say, but the general consensus is that it's much more compliant than alu, so more like steel in that respect, but with carbon's ability to absorb road buzz. I'm aware that this sounds like marketing woo, but this is what people say. Also, I think what people mean when they're talking about stiffness is generally stiffness at the bottom bracket joint, whereas compliance is a matter of absorbing vibration, so I think being stiff and compliant is possible.

Structurally bamboo is very similar to unidirectional carbon fibre (which is being increasingly used for bike parts), for what that's worth. I found my last one to not be stiff enough, verging on noodly before I reinforced it. But as I mentioned above, I'm sure that the noodliness is down to my poor joints.

Though it's gonna be hard work stopping with those heavy wheels and without a brake lever or a clip holding the reaction arm to the fork...

Awesome. If they made slicks in that size it literally could not be better. (I have a shameful love for fat tyres and drum brakes)

Awesome page, cheers gridds!

I'd be surprised if normal single-ring ones didn't work. How did you lose two?! ;)

***BAMBOO SELECTION AND PREPARATION

***
Poles by comatus1649, on Flickr

Preliminary drying
The bamboo arrives in a mostly-dried state, which is a good start, but needs some stuff doing to it before it's useable. It's important that you let it stabilise to the humidity of wherever you're working, or else you risk it changing size or cracking later on. I recommend buying the bamboo a reasonable time in advance so you can leave it to dry - you don't want to put it on radiators, in airing cupboards, or anywhere that's really warm, just leave it inside somewhere with an even, warmish temperature. You should also break as many of the internal nodes as you can to encourage even drying, and to help with later steps ...

From what I've read, I don't think you should heat treat it as many people recommend. Everyone talks about caramelising the sugars in the bamboo to make it stronger, but all the evidence I've found suggests that it reduces the strength by about 20% and makes it more brittle. I found a very useful paper called 'Bamboo in the Laboratory', which was the only properly scientific test of heat-treating bamboo I've seen. It needs to be taken with a pinch of salt because the needs of bamboo rodmakers (who split culms into smaller bits before reforming them into rods) are different to those of framebuilders, but the evidence is useful - heat-treating bamboo up to about 150 degrees C (I estimate - I don't have it to hand) permanently reduces cellular water levels in the bamboo, making it lighter and stronger. Beyond that point, after which the coloration changes, the bamboo is internally scorched and made weaker. (This is why I wouldn't recommend using 'tiger' bamboo unless you can check that it's the species with the natural markings, as some is just burnt moso or similar.)

I don't have a big enough oven to heat my bamboo properly, and all you can do with a propane torch is burn it. So I decided that just letting it dry thoroughly was the best option. Over time the bamboo turns from green to a nice tan colour - if you buy it from the internet, it will already be well into the tan stage, and will need little further treatment. Lots of hobbyist builders have used propane torches and had no long-term problems, but why reduce the strength of your key material?

***Checking the bamboo
***It's quite likely that your bamboo will have some problems. The initial checks are to find and discard poles that are too curved, cracked, or insect-nibbled. Curved poles can be useful if they're curved in one plane (chainstays in particular are better if they're curved) - if they're curved in two directions, like a very stretched out spiral, they'll be very hard to use. Curved culms often grow due to a restricted or light-starved position and may be weaker another reason to beware of extremely-bent poles (and those that are much greener on one side than the other).

Look out very carefully for cracks, both at the ends and on the nodes. Cracks are bamboo cancer. They will only get worse and spread. If, by the way, you find a crack in a pole when you've already built your bike, don't totally despair. Drill out the crack at either end to prevent it spreading, and wrap the pole tightly with CF tow. That should stop it spreading much further. Likewise, if you find any cracks on any of your poles (even ones you don't think you'll use), cut after the crack to keep the rest useable.

Also look for woodwork, rot and other grass maladies. There's often surface discoloration that's not a problem, but sometimes there are bits around the nodes on smaller poles that concern me slightly. Avoid using them if you can.

Marking and cutting by comatus1649, on Flickr

Marking, choosing and cutting
As I go I mark up all the problems with a soft pencil or Sharpie. This way, they're easier to spot when I'm trying to choose poles for particular parts of the bike. In the picture above, I've marked up the bit where the harvester has torn off the leaves, leaving open grain. This isn't a problem for me, but it increases sanding. If I was going for a natural finish on the bamboo, I might chuck this bit.

Choosing the right poles for the different parts of the bike is the real art of this stage. Looking at bike FEA models, the majority of the stress is around the bottom bracket, especially on the downtube. This joint wants to have the sturdiest, densest parts of your tubes.

Take into account your seatpost solution as well, by the way - on my first bike I used a normal seatpost, so I needed a seatpost that had an internal diameter of about 28mm (bamboo in that size has a wall thickness of maybe 4mm or so). It also had to be bolt straight, and I didn't want too many nodes or I'd just have to internally rasp them away (faff!). Some people cut a slot in the seattube for a seatpost clamp on a normal bike - I think this is a terrible idea. I used a double clamp made by eXotic which clamps around the uncut tube, and also onto a seatpost - I shimmed it down from 27.2 to whatever size I had that fitted into the bamboo tube.

However, this time I'm using 35mm tubes that have an internal diameter of about 22mm, so a normal seatpost is out. I intend to extend the seattube almost as far as the saddle, and bond in a 22mm BMX seatpost for the last little bit, with a plain-top saddle clamp. Unless I find an affordable integrated seatpost topper before then ...

As for the chainstays and seatstays, the clearance in this region is pretty tight, but you don't want to use very thin tubes. It's a hard balance to get right, but a very important one. You'll find that smaller tubes have flat sides, which end up being rather like the crimps on steel chainstays.

Once I think that I know which tubes I'll use, I then cut the pieces roughly to length, making sure that I have plenty of leeway. A pull-saw is the ideal tool for this job but anything will do really. The skin may splinter slightly when you cut it because of the longitudinal fibres (the reason it makes such great frames), but resist the urge to peel off the splinters - often if you go overboard they run the whole length of the node and look rubbish. You could wrap the pole in tape before you cut to prevent this but it's no big deal really.

In the next installment, I will cover my top-secret bamboo frame innovation, and my first great error of judgment ...

Dennis looks on approvingly by comatus1649, on Flickr

Definitely intrigued by this. £100 you say? How many hours did it take you recon?

Oh, ages! Something like 100 hours I think altogether, because I was doing it in little chunks here and there, and with no power tools. That time does include building two wheels though, I think. Yeah, I reckon the frame cost about £100 - about £30 for the bamboo, £30 for the glue and twine, and £30 for the metal parts, plus sundries (gloves, brushes, etc.). CF is more expensive than twine though, and the metal parts can go up exponentially from there - for example, the natty sliding dropouts (stainless main bits, alu inserts) I plan to use are really dear, £40 or something mental,* compared to £12 for cast (mild steel) horizontal dropouts.

I reckon you could do it in three to four days if you were efficient and that was all you were doing. The main limiting factor is that you have to wait for glue to go off at various points - it'd probably take a day's work to cut, tack and prep the frame, and another two days to do the joints (with most the time spent waiting), then maybe another day's finishing, depending on what finish you choose to do.

**PLANNING

**I always end up spending way more time planning and researching my projects than actually making them. There's so much great information out there on the internet which has been utterly vital. All of it is easily found so I won't bother citing too many inspirations apart from where they are a bit more esoteric.

Bamboo choice
The first decision I had to make was the variety and size of bamboo to use. My previous bike, like almost all bamboo bikes you'll see on the internet, used quite oversized tubes for maximum strength and stiffness. Because it's a natural, highly variable material, bamboo is usually sold in width bands, and the 40-45mm band is generally used for the main triangle. However, my first bike was a bit over 2kg, and I fancied being lighter this time. Also, I am certain that the vast majority of a bamboo frame's stiffness comes from well laid-up joints made with a suitable material - 45mm tubes seem massive overkill. My last frame was bendier than I liked, but that was because my joints were shit (see below), not because there was any real flex in the tubes.

The next size down is 30-35mm, which is much closer to the tube size of steel frames. They are still extremely stiff and strong. I'm going to push the boundaries of hobbyist framebuilding a bit this time, and use the thinner tubes - if it comes off, I should get a frame that's significantly lighter than my previous effort. If it's too noodly, I'll rework it slightly to add a second top tube a la big Rivendell frames, but I'm hoping it won't be needed. For the chainstays and seatstays, I used 20-25mm poles. If I could handpick the poles, a smaller diameter might be possible, but the smaller you get the more weaknesses there tend to be, so I prefer to overbuild the rear triangle as I don't need cassette clearance.

Bamboo variety is something that's discussed a lot by framebuilders. The general consensus is that the strongest species are iron bamboo, tonkin, henon and guadua. However, in the good old UK it's very difficult to get any of these in the right sizes. Moso and black bamboo are widely available - moso is your classic green/yellow bamboo, while black is a very similar species with darker surface coloration. There's also tiger bamboo, but it's hard to tell whether it's *real *tigerbamboo, which is the same species as black, or something like moso that has been selectively scorches. It's also a lot more expensive. I'm sure that moso and black are easily strong enough, so I'll be using moso as I'd just sand off the black layer anyway.

I bought my bamboo from UK Bamboo Supplies - unfortunately they've just introduced a new shop system with a larger minimum order (10 poles of each size) - if you call them up they might be able to do smaller packs (it used to be 5). Their shipping is expensive and slow, but there's not much choice in the UK. The Bamboo Bicycle Club also sells bamboo kits as well as running courses. They are much more expensive, but they do hand-pick good bits and treat them well. I'm cheap so went for the UK Bamboo option, but you run the risk of getting wonky, cracked or funny-shaped bits so you need to buy with that in mind. Both times I've bought one 5-pack of thick poles, 1m long, and one pack of thin 1m poles, and that's worked out. But you may need to be crafty with the bits you choose.

***Lug choice
***Because I was being even stingier last time, I didn't use carbon fibre for the lugs. Instead I used sisal twine. In hindsight this was a poor idea, because while it's stronger than the hemp tow most non-CF builders use, the tight weave of the twine makes it hard to wet out. You also need to really, really overbuild the joints, which end up being very big. This time, I'm going to use 12k carbon fibre tow from East Coast, which is about 12p/m. I'll need several hundred metres, I think, but I need to research that part more.

If you read up on bamboo framebuilding, sooner or later you'll come across Craig Calfee. As well as his better-known carbon frames, he also makes some great bamboo frames, and his sideline Bamboosero sets up framebuilders in Ghana. Calfee's of the opinion that CF shouldn't be used for lugs because the coefficient of expansion of the two materials are too great and will cause the joints to fail over time. I can see the science behind this, but I have never seen a CF joint on a bamboo frame fail. I have, however, known several cases of hemp / other natural fibre joints failing. I'm sure that Calfee's hemp-lugged frames are as strong as CF and longer-lasting, but it's very easy to make a shitty natural-fibre joint - they're harder to wet out, prone to internal voids, and difficult to get the fibres running in the right directions. It's not just a matter of building up material around the joints. CF is much better suited to epoxy wetting-out, and has a greater margin of error in terms of actual strength. I don't think the thermal expansion issue is a problem considering the temperature changes the bike will experience. Watch this space!

For the glue I'll be using West Systems 105 epoxy. It's strong, odourless, not too unhealthy to have about, and easy to work with. I'll also be using bamboo sawdust to built up joint fillets before wrapping with CF.

***Metal bits
***Unless you're brave or very inventive, you'll need a few metal bits - dropouts, BB shell, and headtube. I'm getting these from Ceeway. Last time I used normal horizontal dropouts and found that they were fiddly to build up strongly, and I made the chainstays slightly too short and had to deflate the tyre to get it in. I'm not a track end fan, so will be going with the Ceeway sliding dropouts. This will allow me to adjust the effective chainstay length, easily run mudguards, remove the wheel and replace it without changing the chain tension, and change the inserts if I ever want to run derailer gears or a Rohloff hub. They're a bit heavier though, and a bit dear.

***Geometry
***Before I could do anything, I needed to decide on my geometry. Last time I think I just copied the Steamroller frame design; this time, I've done it from the ground up. Sheldon Brown links to numerous websites which have sensible modern bike sizing and geometry advice, which I used to get an idea of what I wanted. I then used BikeCAD to draw up my design:

Bike geometry is boring as fuck if you don't care about such things, but basically it was built to have short chainstays (for fat tyres and full 'guards, anyway - I wanted to stiffen up the rear - a wishbone seat stay will be used for the same reason), stack and reach which suit my size, and trail of about 55mm, maybe a bit less. This is a relatively low amount of trail which will give fast handling. For that you sacrifice high speed stability but I'm not going to be doing many 60mph alpine descents on a fixed gear...

http://farm3.staticflickr.com/2858/12751550945_1b28a12861_h.jpg

INTRODUCTION

A couple of summers ago I built myself a bamboo bike frame in my kitchen, using about £100 of materials. I rode it hard, leaving it outside most of the time, and had great fun with it until around Easter, when I broke it supporting some friends doing the Devizes-Westminster Canoe Race (which is to say they were doing the race, I was cycling alongside. If I'd literally been supporting them, I wouldn't have been surprised that I broke it). I'm sure it was fine when I put it on the rack, but when I got home I found that TT/ST joint had gone rather wobbly. I could mend it, but I can't be bothered. It's time for iteration #2,* with all the lessons I've learned put into use...

This thread is intended to force me to properly document my build and decision process. Last time I hardly documented it at all, and I regretted not having photos of the process. Hopefully this will be interesting in its own right, plus helpful for the growing number of people considering making a bike out of bamboo. Bamboo is by far the easiest material for a novice or more experienced hobbyist framebuilder, requiring only the most basic tools. But it can also yield frames that are great to ride - fairly light, shock-absorbing, and great-looking.

Hope people enjoy reading!

• It's coincidentally also bamboo bike #2 currently on the forum - see also http://www.lfgss.com/thread105686.html
  

Nobody tell skrtluv.

^ bikedogging.

Assuming skidding the rear wheel is the fastest way to stop with only a rear braking mechanism (which it may or may not be - paging Tester), they'd only be able to stop as quickly as the rider with a brake, and it'd probably be harder. With a decent rear brake you should be able to lock up the rear wheel with as much weight as possible over the rear axle pretty easily, whereas skidding in that position would be rather difficult.

It isn't; sliding friction is less than the friction of a wheel just the other side of the skid threshold.

As for front / rear braking, braking with either brake or a combination thereof will shift momentum forward to the point at which no weight is on the rear wheel and it's contributing nothing to the stopping process. So why, in normal circumstances, use the brake which gets less effective the more you use it? The bike doesn't know whether you're spreading out the braking over two rims or one, it's all just forces. Rim overheating etc. might play a role in some situations, and there are other pragmatic concerns. Like if it's very icy, or if you're going slowly down a steep decline and can't get off the back of the saddle, or if your front brake grabs, you might wish to use the back brake more by preference.

**BUT **I only wanted to know a) so I look cool and can actually DAS if someone challenges me, and b) so that I have another option for long descents of the sort IR mentions where resisting is not terribly helpful. I have a front brake and have never found a combination of resisting and front brake to be inadequate. But it'd be nice to know, right?

Anyway, this is boring and I feel a terrible responsibility for having a) brought it up and b) downloading the dull speech above which I normally reserve for nodders who are terrified about endoing off the front of their bikes if they use the front brake more than the rear. New confession >

Something pretty normal, about 70GI?

Do it in heavy rain and traffic, whilst crossing Waterloo Bridge. It also helps if you are being filmed by a mate.

Sounds just like a cherished masturbation technique of mine.

Anyway, I think I just need to practice. What you describe, IR, is basically what I do, just with limited success. Maybe I should get the knack on a spinny little gear first. sigh

Not seen a Surly with SS joints before, that's nice. Big chainring and QR pointing up and that'd be pornworthy.

Go on then, what's the trick? :) I know the theory but unless it's damp out it just doesn't seem to work very often. I'm sure it's just a matter of getting the knack.

Couple of obvious changes to be made but I think it's fucking awesome.

In other news, debate solved:

Hit axle with hammer twice, gently

ftfy.

God, I'd love a compact Roberts. Not this ww, but still, looks cracking

Astonishing feat of engineering but I think it's just too compact - looks funny. We need a separate category for things that give you a techboner.

I can't skid. I like to blame it on the fat grippy tyres I have and my bendy frame, but I think it's just my weak constitution.

Planet X / On-One have got a pretty big sale on for the next week, fyi.

(this seemed like the best place to put things like this)