# The Carbon Fibre Unicycle

**URL:** https://unicyclist.com/t/the-carbon-fibre-unicycle/43437
**Category:** Unicycles and Equipment
**Created:** [January 29, 1995, 11:01am UTC](https://unicyclist.com/t/the-carbon-fibre-unicycle/43437 "1995-01-29T11:01:35Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![system](https://unicyclist.com/uploads/default/original/3X/d/4/d44cf5a6365651cf6b50671d1ff0c84adf0c7726.png) [@system](https://unicyclist.com/u/system)
#### Post date: [January 29, 1995, 11:01am UTC](https://unicyclist.com/t/the-carbon-fibre-unicycle/43437/1 "1995-01-29T11:01:35Z")

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This failed to post itself last time so here goes again:

\> Yes, after much hassle and sorting out of all the little niggly bits, my  
\> carbon fibre unicycle is finished and I’m rather chuffed. Originally (3 months  
\> ago) it was a Pashley. Talk about heavy. The biggest improvement was chucking  
\> the steel rim and putting on a Mavic 231 mtb rim with a skinny Specialised  
\> slick tyre. But it was still an excessively chunky steel frame and those  
\> horrid, horrid Pashley bearing mounts. So it was time to make a decent frame.  
\>  
\> The frame is three carbon epoxy tubes held together by a Pace mtb fork crown.  
\> The tubes are T300 carbon fibre wrapped 0,90 made by mandrel wrapping. They  
\> get a big metal rod, 25.4mm dia, soak the carbon cloth is epoxy, wrap it  
\> around the mandrel, cover in heatshrink tape and heat. As I only wanted a  
\> metre length of each of 1.6mm and 3.2mm wall thicknesses it was tricky to get  
\> a wrapping company to deal in such a small order but Custom Composites in  
\> Rochdale managed it nicely. The fork legs are  
\> 28.6 mm o.d., the seat tube 31.4 mm o.d. Carbon is a devil to cut cleanly - a  
\> hacksaw will go through it easily enough but make a mess of the tube.  
\> Luckily the departement I’m in had a diamond saw in the basement. Did it  
\> make my day to find that out? Just a tad. Anyway, perfectly clean square  
\> cuts to the ends of the tube and a 50 mm slit down the back of the seat  
\> tube to allow a bit of flex when clamping the seat post.  
\>  
\> The fork crown (sold by Stif in Leeds) is a beautifull piece of machined and  
\> polished aluminium. The tubes just slide in and clamp up. Now carbon tubes  
\> tend to crush if you clamp them so BERTs were needed (BERT - Bar End  
\> Reinforcement Thingy). These were 25.4 mm o.d. bits of aluminium that go  
\> inside the tubes where you are clamping them. Clamping bolt torque was  
\> determined by acoustic emission - I did the bolts up untill I heard the carbon  
\> begin to crack, then I stopped.  
\>  
\> The seat post is clamped by two seat collars, bought from the local bike shop.  
\> My Pashley saddle lasted ~2 months so I’m now running a DM. Weighs a veritable  
\> ton so the seat tube of the uni was extended to allow the seat post of the  
\> saddle to be cut down to 150 mm.  
\>  
\> The bearing holders were the tricky part. I replaced the Pashley bearings with  
\> four sealed SKF ball bearing units. Talk about a tight fit! The axle is  
\> slightly oversize. Consequently getting the bearings off nearly destroyed the  
\> bearing puller; putting the new ones on nearly bent the beefy pillar drill I  
\> was using as a press. The bearing holders themselves I machined down from a  
\> big chunk of aluminium magnesium I found lying around the lab - oh I do love  
\> working in materials science. Each piece started at ~600 grams, finished at  
\> 100 grams. Lots of machining.(I’ve a DWG if anyones desperate to see what they  
\> look like.) These holders just push fit onto the bearings and have 50 mm long  
\> cylindrical spigots that just push up into the ends of the fork legs. Epoxy  
\> adhesive holds them in and provides load transfer. I know this bit sounds a  
\> bit shaky, I mean its held together with glue! ferchrissake, but so far  
\> they’re solid. As for long term durability, ask me in a years time.  
\>  
\> Well, I haven’t weighed the whole thing but the frame and bearing holders feel  
\> at least half the weight of what they replace. The difference in ridability is  
\> immense and that’s what counts, not the polishability of it all. I came back  
\> after xmas and sussed idling in a couple of hours. Its so much easier to move  
\> it about under your self. All that’s left of the Pashley is the hub and cranks  
\> and, hey, I’m not sure I like the cranks either. The pedals, by the way, are  
\> now Odessey SharkBite BMX ones (well, I couldn’t get any DX’s in the right  
\> threading). Like having a pair of pitbulls grabbing at your feet. Mind you,  
\> get it wrong and its like having a pitbull chewing on your shins so I’m off to  
\> the BMX shop for some pads shortly. The first time my foot came off and the  
\> pedal grabbed it back I was so surprised I slammed. Oops. But i love the  
\> machine now. Masses of grip, seriously responsive, now all it needs is a  
\> decent rider.

I’ve now been riding it for 4 weeks, it’s still stupidly light and hasn’t broken  
yet. I cut down some old Campy aluminium cranks, less than half the weight of  
those steel ones, put them on, picked it and broke into a huge grin that lasted  
most of the week. Rode Paul Makepeace’s steel 24" machine today and was like:  
hey, major exercise, whats this lead weight on a wheel? Should hopefully be at  
the Brussels con. in Feb so any of you europeans reading this may well see me  
there falling off it.

Jez [jpw24@cam.ac.uk](mailto:jpw24@cam.ac.uk) and for my next trick, a recumbent…