Homemade carbon xc frame - Part 3

To start the build I first made foam cores for all the complex sections such as chain-stay and seatstay bridges, which I used to mold the carbon around. For the main tubes I molded them around PVC drainage pipe using the method described here. For each section I just used 1-2 layers of carbon as the aim was just to make pieces the correct shape, as I would be adding the strength later once the pieces were assembled.

The foam cores for chainstay and seatstay bridges

After making all the individual component sections, I jigged the headtube, BB shell, seattube and dropouts into the positions they needed to be. I then used a small amount of fast set epoxy (araldite) to tack the pieces together so I could join them permanently and then build up the layers of carbon.

The frame with about 2-4 layers of carbon

Once the frame was fully assembled it was simply a case of adding layers of carbon, I'm not 100% sure of these numbers, but I used about 7 layers around the BB and headtube, 5 on chainstay and seatstays (and the bridges), and 4 for the center sections of the 3 main tubes.

The completed frame V1.0

Once the frame was completed I painted the rear triangle and sanded the surface to a reasonably smooth finish. I wasn't too bothered about a mirror or perfectly flat finish as I wanted to keep the garage made look!

The brake mount is simply an adapter bonded in place and then a few layers of carbon for strength

The finished bike in Austria during summer 2013

The frame has had a few teething issues, one was at Cannock Chase, where I had a hard pedal strike which dislodged the bottom bracket shell from the frame, it kept in place but had about 20 degrees of movement

The broken BB shell

When I got home I cut the shell out to see what the cause was, and it turned out that the top half of the shell wasn't attached to anything, as it looked like the lay of carbon I had used to hold it in place had crumbled leaving it free to move should the pedals be knocked in an upward direction.

Investigative surgery 

To fix is I wrapped the shell in a few layers of carbon and the built the area up with about 4 layers. This seems to have worked as I haven't had any issues since - and I know I have had quite a few pedal strikes!

The fixed BB area - V1.1

Homemade carbon xc frame - Part 2 - buying, scrounging and lot of carbon fibre

Building a carbon fibre frame on a student budget (eg - next to nothing), was always going to be tricky, especially as carbon fibre is upwards of £21 ($35) per square meter and for a bike frame 2-3 m^2 of material is required. I was able to scrounge about 16 m^2 for a D&T project  while in school, so I had enough to spare for this, and probably a few more projects too.

             A complete list of the materials I used - all will be explained later;

                                   - Carbon sheet (approx 3m)

                                   - Epoxy resin (about 1Kg) as some goes to waste

                                   - PVC pipe for molding tubes around - clicky

                                   - Mold release wax

                                   - Blue modeling foam - various sources on eBay

                                   - Rubber tubing to make routing for internal cables 

                                   - Glass bubble filler for smoothing curves 

Unless linked the easiest and best place to get these is probably easycomposites.co.uk if you're in the UK, and elsewhere google is your friend. Research what is available as there are other methods that may be more appropriate for your project.

As for tools used I have a pretty well equipped garage, but a good supply of gloves, brushes, pots and old rags is useful for lay-up, for shaping and cutting carbon, decent waterproof sandpaper and a sharp hacksaw is advisable. 

I opted to use 32 and 40mm plastic pipe to mold the main tubes around, the 32mm would be for the top tube and the 40mm would be for the downtube, I had considered using the 50mm tubing but felt it ma have been a bit too oversized - it hindsight a larger downtube may have been a better idea to help stiffen the frame a bit

For the aluminium inserts for the headtube and bottom bracket I used the parts from the Cadex frame and for the dropouts and some of the rear triangle I decided to use part of the Cadex frame - as my aim for the initial build was to keep it simple and that it was already carbon and roughly the same cross section that I had designed.

An unmodified Giant Cadex rear dropout with an added disc mount  - retrobike.co.uk

This left me with two options for adding a rear disc mount, one would be to do something similar to the above picture, and the other would be to bond a mount onto the seatstay, which is what I decided to do.

Part 3 -  coming soon but some pictures of how it all happened to keep you happy 

Homemade carbon xc frame - Part 1 - planning, designing and a little bit of luck

I had been planning to make a frame of some description since doing my final year school D&T project, where I made a bamboo and carbon bike trailer, after my teacher told me a bike frame was too difficult a task to do.

I had thought of copying the idea used by Yeti, Raleigh and a few other bike manufacturers back in the early 90's, where they bonded carbon tubes into a steel or titanium set of lugs, this idea has some major advantages, such that I could butcher an old frame and only have to make a few tubes which I could then bond into the old frame, disadvantages were that I would have to buy and destroy a perfectly good frame.

A Yeti C-26 with bonded carbon main tubes and steel rear triangle 

Another alternative would be to buy the dropouts, head-tube and BB inserts from a frame building supplier, but after looking into this it turned out that it would cost about £50 to get steel parts and upwards of £80 to get aluminium or titanium. This is where the bit of luck came in, I decided on a whim to see if anyone had any old or broken aluminium frames lying around which I could use for parts, turned out nobody did, but someone had a 1992 Giant Cadex with a cracked downtube that he was willing to sell me for £20!

A Giant Cadex - not the one I used as can't find the photos of it at the moment

This frame had the advantages that it was already partially carbon and had replaceable dropouts (gotta give SSUK champs a go), but it had a standard 1 1/8 headtube which would make future fork upgrades more difficult , as a tapered headtube had been my original plan - but for a first prototype on a budget I decided I could live with it.

To design the frames geometry I used bikecad.ca where you can alter the geometry and tube sizes to get the desired look, shape and size. I based the geometry on my 1994 Raleigh m-trax Ti as I liked the way it handled and was the only bike that I had available to copy   

A basic mock-up of what I had aimed the bike to look like

Designing more intricate parts such as the top of the seat-stays and chain-stays I used pen and paper, with help from Sheldon Browns website on clearances for chainrings and a few other sources (googled) for tyre dimensions and recommended mud clearances, this was especially important as Oxfordshire mud is particularly clingy 

The first draft designs for the chainstay (left) and seatstay (right) bridges

An early design - I had planned on a lugged carbon frame at some points

Top and side views of the seatpost/toptube/seatstay junction 

The revised design for the same area - this is a bit sleeker and easier to make

Dropout and disc mount designs 

Introduction - plans, projects and a few pictures

Following a few forum posts on singletrackworld.com detailing a few of my bike related projects and ideas for future projects and making many a promises on putting up a guide and a how to, I think I have finally managed to get a large enough collection of pictures and enough time to write the promised guides. 

The first of guide I'll try to get up will be for the above bike (or more specifically the carbon frame), where I built the frame from pretty much scratch. I'll also do a quick write up for a simple carbon bash guard, and my A-level final year project which is a bamboo and carbon bike trailer (below). 

I'll try to get the initial part of the guide for the carbon frame up by the end of next week, but for those who can't wait the initial write up I did is on singletrackworld forums - clicky 

Full Suspension Frame - Afan report and planning repairs

Got back from my weekend riding at afan and after 95km of Afan trails I can happily say I love the way it rides! 

The weekend wasn't without problems as I discovered a crack in the linkage at the end of the first day, but it didn't seem to affect the way it rode so I decided to keep an eye on it but keep riding.

by the end of the second day the crack/gap was about 3mm wide and the bearing was completely loose! Ooops!

I have also broken the main pivot area, I'm not exactly sure how I did it, but I suspect it was when I pushed hard on the pedals to get over a rock as there was a cracking sound, but it wasn't until about 20 minutes later did I notice any play in the pivot, I was able to finish W2, but I had to push the bike up the steeper sections as pedaling hard caused the swingarm to flex into the chainring.

I was expecting it to have been the steel insert debonding from the carbon, but it turns out it was carbon debonding from carbon! - this will be much easier to fix and shouldn't be an issue long term (if it had been the steel debonding it would be an indication of bad design - but this just looks like a bad batch resin or not enough compression)

For the broken pivot I plan to just rebond the area but pay close attention to make sure a good bond is achieved, and for the linkage I intend to make a new one from scratch out of carbon!