I’ll stop the puns soon. I swear.
Built some standoffs for the headtube and rear end. Check em out:
The degree of accuracy of this jig is probably not within the tolerances of a well made bike, so I’ll have to resort to a lengthy process of alignment checking after the initial tack gluing. I’ve seen laser levels used with jigs to check alignment, so might go get one of them.
Started work today on a flat wooden jig that will hold the frame in place while I tack the joints and generally put it together.
I found an old cupboard door, which to my luck had 33mm holes drilled in it from where the hinges were. 33mm is the size of a bottom bracket ID, making it a perfect fit for the PVC tube which I’ll extend out to hold the BB in place.
I’ve drawn out the centrelines for the frame, to within 1-2% accuracy I’d say. I wonder how accurate I need to be?
Just like the out of work actor Tobias Fünke mistakenly finding a Tractor Pull magazine (thinking it said Actor Pull) and seeing thousands of parts inside, I too became excited when the delivery man arrived today with my bike parts:
But what’s with all that steel tubing Mik? Aren’t these meant to be bamboo bikes? Fear not reader, as the tubes are only there for the bits bamboo can’t handle. The longest tube pictured will be cut down to make maybe three head tubes. The two smaller lengths are seat tube sleeves, which again will be cut down and inserted and glued into the bamboo seat tube so that a regular 27.2mm seat post can fit snugly and tight.
Also pictured are two 73mm bottom brackets, and three sets of dropouts of varying designs. Unfortunately for me they delivered two right-sided dropouts for one pair, so I’ll either have to bend some metal or order two left-sides now.
Finally are some cantilever brake braze ons, stolen from my steel mtb frame which doesn’t use them as it has disk brakes. I’m going to play around with finding out the best way to attach these suckers to the seat stays.
So the end product of my test composite joint making is a bamboo bike stand! Here she is:
I’ve designed it to exactly fit a 700C road wheel, but it could easily be made with wider slots for wider wheels.
The final joint ended up being 3 layers and I experimented with three different types of epoxy.
The first layer used fibreglass resin, the second was the pinkish builders bog you can just see poking through certain areas of the joint and the last was Glass Coat, which is a 1:1 ratio epoxy that’s used for tabletops, pottery etc.
I’ve decided not to sand back this last coat, as it’s nice and glossy and I like the raw look of the sisal twine.
The stand can also be cantilevered back. This is a slightly more stable position for it, but requires that the bamboo sits against the chain stays, so it wouldn’t work for all bikes.
While I’m still waiting on parts and hemp fibre to arrive I decided to have another go at making a composite joint with fibreglass resin, sisal twine and a 3-way bamboo mitred bamboo joint.
Here’s the workspace:
Here’s the initial binding of the sisal, with a coat of Timber Sealer applied (this stuff helps the epoxy resin stick to the wood):
Here’s the 2nd layer of sisal applied and it all drenched in epoxy:
It may not look too crash hot at the moment, but remember this is just the first layer. Once this is dry I’m going to use a more putty like builders epoxy to allow me to mould the shape of the join better.
here’s the first layer sanded back, ready for the filler epoxy layer:
I’ve recently decided to build a cyclocross frame for the first prototype. I figure if anything’s going to test out the durability of a frame it’ll be a cyclocross race. That and it’s the only sort of bike I don’t own that I’ve always wanted (apart from a recumbent, unicycle, downhill, fixie, penny farthing …).
Here’s how it’s looking so far (ignore the colours, I just like designing in red/black/white):
As you can see there’s lots of angles, lengths and diameters to figure out. The BikeCAD above only is only showing the basic frame dimensions and angles, not any of the mitre lengths or tubing diameters.
The main issue to solve with using bamboo is tyre clearance for the chain and seat stays. I’m picturing that the diameter of this bamboo will be slightly larger than a steel/alu/carbon bike in order to get the greatest stiffness. To help overcome the larger than normal tube diameters I’m using a 73mm bottom bracket as well as a wider than normal seat stay attachment angle. If that doesn’t alleviate the problem I’ll try using skinnier bamboo, but fill it with expanding foam filler, which I’ve been told increases stiffness markedly.
The drop outs, bottom bracket, seat tube sleeve and head tube have all been ordered and are on their way. Soon it’ll be mitre time!
I’ve flown up to Queensland this week to see Bamboo Australia and their amazing supply of bamboo.
Arrived there today and spent a good 3 hours breaking the ears off the lovely staff and asking possibly too many questions. Here’s my good buddy Nat at the entrance to the farm:
Here’s the cutting shed, where I gathered various sizes of Tonkin and Aurea species bamboo poles and had them cut to 70cm long each (mainly so they’ll fit in my bag, but also because the bottom tube is never really any longer than this).
I came away with about 20kg of poles, both green and dried, as well as 5 pairs of bamboo socks and the bible of bamboo: Bamboo, The Gift of the Gods
Here’s hoping it’ll make it back to Melbourne without splitting from the various temperatures and humidities of flight.
Today we started the process of learning about how to make joints with bamboo. Using a Dremel we cut mitres into the 3 bits of wood and then stuck them together with an epoxy paste. Once that’s dry we’ll start the lay up process with sisal twine, followed by epoxy resin. This mini project will result in a simple 3 joint bike stand. You can see in the first picture where the rear wheel of the bike will slide into.
Testing the mitred joints:
Applying epoxy paste:
Letting the epoxy dry. We’ve temporarily lashed it together with some sisal:
Titanium seems to top the list in CO2 footprint… ouch!
I’ve been researching bio resins for use in the bamboo frames and discovering a whole beautiful world of people making resins out of things like soy. There’s an interesting PDF here that details the environment costs and benefits of creating such resins.
I’ve contacted Bioresin to see if their products have made it to market yet, and whether or not they’re available locally. Let’s hope so!
I’ve selected the 7 culms (fancy word for a bamboo pole) for the first frame. Here’s a pic of them laid out into the respective parts of the frame:
And here’s a view of the thickness of the downtube:
I also ventured to my local hardware store and picked up some epoxy resin, glass coat, borax, beeswax and some other glues and finishes to test the curing and joint making processes with:
I haven’t managed to find Boric Acid anywhere yet thou. I suspect I’ll be able order it online somewhere, or it might be available at a chemist.
Bamboo is susceptible to mould and bugs if left untreated so I’m planning on following this procedure for curing the bamboo, which basically involves soaking it in borax and boric acid solution for 2 weeks. After this I’ll dry the bamboo for a few months and periodically check to see if it’s cracking or not. Apparently cracking is the main problem with bamboo frames!
I’m starting a journey of discovery into 2 things. The way of bamboo and the way of the bike frame. I plan on making 2 prototype bikes with mostly bamboo frames. One with lugged steel joints, the other with woven fibre and epoxy resin. Based on the successes or failures of each prototype I then plan on producing custom frames for demanding customers who’re after something a bit different in their daily ride.
The prototype bikes are going to be simple single-speed flat-bar commuters, similar in geometry and style to a Giant CRX or Apollo Blade.
Using BikeCAD and a tape measure I’ll measure and design the requirements for each frame, and decide upon what’s going to be bamboo, and what’s best left to steel or other material.
I’ve sourced enough bamboo (from my kind parent’s garden) for two bikes. But before I can use it I need to cure and treat it against bugs, mould and cracking. Hopefully I’ve got enough to play with after all the experimenting!
After treating the bamboo I’ll be examining diameters to see which will best suit the various parts of the frames. From there I’ll explore the joining process with metals and other materials.
Protecting the bamboo against the elements will also require some research. What oils, paints or varnishes can I use?
This site will seek to be a resource of information about bamboo bikes as well as a documentation of the building process from start to finish for others to follow.