I have finally gotten round to building a new bicycle. Although the last thing I made was a racing bike, I'm not a racer by nature. My first love is road bikes. I have always been motivated by the idea of getting from A to B in the most efficient and agreeable manner possible. Useful transport, in other words. Anyway, a racing bike is a lot of work for very little usage - probably only a few hundred miles a year.

The last road bike I built, the T-5, has been gradually developed over six years, mainly by the addition of a nosecone and an effective lighting system. I don't know how I ever did without either. I am always surprised by how few people use a nosecone. I know a bike so equipped takes up a lot more storage space and the change in mass distribution affects the handling, but you get used to the latter soon enough. The storage issue still annoys even me sometimes...

Despite what some people say, a nosecone definitely makes you go faster. I recon that around here (fairly hilly), at a touring pace, I go 2 - 3 km/h faster with the nosecone fitted, which may not sound like much but that's a bus length every 12 to 18 seconds. (I should point out that the bike also has a tail-box). I'm possibly 4 km/h faster than an upright touring bike - You don't get those sorts of gains from an aero seat-post! Even on the hilliest circular route I can find around here the nosecone doesn't slow me down overall. Add to this the enormous reduction to wind-chill in winter, the big increase in on-road visibility and a degree of crash protection and it's a no-brainer.

What I have noticed is that with the increased speeds possible with a nosecone fitted you start to feel the bumps more acutely and V-Brakes suddenly seem a bit inadequate. I'd also feel happier, especially considering my history, with a bit more crash protection, oh, and even better lights. Hence the need for a new bike with suspension, disc brakes and more bodywork.

Now, I hear you saying, "This all sounds a bit complicated. I thought bicycles were meant to be simple". I have some sympathy with this argument. There is no doubt that for popping down the shops etc., the benefit of a simple machine is obvious, but in order to make a bike that goes faster, stops faster and does it in greater comfort, I will inevitably have to add components. Most other types of vehicle (aircraft, cars, tractors etc.) have become more complex over time in order to advance, so let's try embracing complexity and see where it takes us!

Given my experience with a racing streamliner, the promise of similar speed gains for a road bike was tempting. If I lived in Holland then I'd have a Velomobile without a doubt, but it's horses for courses. In my opinion a two-wheeled streamliner is too unstable in crosswinds to be safe for road use and a 30+ Kg Velomobile would be just too much to lug up the hills we have in North Oxfordshire (UK). Even the ultra-fit Quest pilots objected to riding up the hill to the Brighton Racecourse campsite at the 2001 World Championships!

My design for the new bike started to come together about 2 years ago. I wanted a lower seat height than my existing bike as this is proven to make you go faster. The reason for this is often cited as the mechanical components being more aerodynamically shrouded by the rider, but I believe that the lower wind speed closer to the ground is the largest factor. A low C of G also allows the front brake to work to the limit of the tyre's adhesion, ie: 0.8 to 0.9 g deceleration. I decided on a seat height of around 350 mm because if you go any lower the rider's legs tend to interfere with the steering lock of the front wheel. As I was intending to fit a nosecone I kept the bottom bracket relatively low and the seat back fairly upright. In fact the riding position is much the same as the T-5, with the bottom bracket about 100 mm above the seat, although the seat is slightly more reclined.

I concluded that if I was going to the trouble of having suspension then I might as well make it state of the art. Consequently, I bought some Cane Creek air springs from Inspired Cycle Engineering, who are a useful source of parts and tubing for home-build projects. The I.C.E. boys are lovely people and very helpful, but the machines they build are inexplicably fitted with an extra, superfluous wheel. I don't like to ask why...

The air springs have a natural rising spring rate and weigh just 205 g each. They have a stroke of 25 mm, which combined with a 2:1 leverage ratio, gives me a wheel travel of 50 mm. This should be sufficient for quite a plush ride. I wanted a front suspension system with natural anti-dive and decided early on that I was going to try front wheel drive (FWD). I settled on a 'wishbone' system with geometry similar to a McPherson Strut on a car (turned through 90 degrees), more correctly know in engineering terms as a Slider-Crank Mechanism. The slider is inside the steerer tube and incorporates a spherical joint where it is bolted to the top of the fork. A spherical rod-end bearing connects the fork to the wishbone (crank), just above the tyre. A scissor link transmits steering torque from the steerer tube to the fork. In order to keep the suspension mechanism away from the widest part of the legs (the thighs), I decided to run the wishbone forward from the fork. The advantage of the wishbone in a FWD set-up is that it goes up and down with the suspension but doesn't rotate with the steering, so it can be used to move the chain pulley up and down. If it did not do this then the chain tension would compress the suspension, causing 'pogo-ing' when pedalling.

The steering geometry was largely determined by having to put the pulley (the widest part of the transmission) at the point where the legs are narrowest, that is; just below the knees. I have no desire to wear down bits of my legs on the transmission! I settled on a 10-degree steering head with enough negative fork offset to give 70 mm of trail. This permits direct steering and should have the low-speed stability advantages of steep head angles. The negative offset also gives more clearance between the chain and fork leg when the steering is on right lock. This suspension system has much lower steering inertia than the leading- and trailing-link systems sometimes used to provide anti-dive, as the steered mass is concentrated closer to the steering axis.

I did quite a few stress calculations for this bike. The more one strays from using conventional cycle components and tubing, the more it is likely something is going to break if you are not very careful. The part of the fork that goes inside the steerer could not be more than 16 mm in diameter, in order to give angular clearance. I was going to make it out of a mild steel tube, but having done the bending-load calculations for the maximum braking condition, I realised that it not only needed to be solid, but had to made of something with a UTS (Ultimate Tensile Strength) of around 1000 MPa (N/mm2). Mike Burrows suggested I used a cut down M16 Cap-Head Bolt (12.9 grade), which is what I did.

In September 2004 I had the opportunity to start building the bike, as I was between contracts. I had already designed the main components on CAD and after much hack-sawing and filing, had most of the tubing profiled. This is much easier with a CAD system as you know the exact profile you are aiming for. The main frame was jigged up on a sheet of 18 mm MDF with various spacers and angle brackets to hold the mounting points and headset in the correct positions. This should be supported on a flat surface during welding, to avoid any bowing of the MDF. My friend Charlie brazed it together in various stages, leaving the most critical parts until last, so that any distortion could be compensated for. The result was a remarkably straight frame, weighing 1.8 kg. The main tubes are 1 3/4 " dia. x 20 swg T45, from I.C.E. The fork was set up on an L-shaped, steel jig I normally use for frames and was TIG welded by a local company that does race car work. It weighs a rather hefty 990 g (1100 g including the separate steerer), but it is made of low-tech 16 swg mild steel. The blades are 15 x 30 mm 'flat oval' ERW. It needed a bit of tweaking after welding to get it straight (filing out a dropout) and the OLN dimension correct. I had to make a separate jig to hold the brake calliper mount in the correct place using an old axle and an aluminium plate. This mount was a real pain to get as straight as the brake set-up requires. Hope Technology now make a facing tool for this purpose - LA Cycles in Coventry have one. The rear swing arm was made in two halves on a plywood jig and then the two halves joined on the steel jig I usually use for front forks to get the critical dimensions right. It weighs 750 g, but is not as stiff in torsion as I would like. With the bike fully assembled, the wheels were out of line by less than 2mm. There were numerous other little bits that needed making, including the front 'wishbone', which is of bolted-up aluminium construction (450g inc. the rose joint). The aluminium plates were largely hand-shaped, using a bandsaw, a drill-mill, a disc sander and lots of careful filing. The 100 mm diameter chain pulley is from RS Catalogues (Part No. 231-5663, £15.70 + VAT). It has an unshielded ball race and I stretched a large diameter plumbing seal around it to reduce transmission noise. The finished bike, including the temporary seat (the finished bike will have a combined seat / tail-box), weighs 13.5 kg (30 lb), which is slightly more than I had hoped, but then - aren't they always? It is fitted with a Schlumpf 'Speed-Drive' turning a 9-Speed 11-32 cassette. The brakes are a Hope M4 4-piston disc on the front and Magura hydraulic rim brakes at the rear.
 

To date I have ridden just 17 miles, but first impressions are encouraging. It steers well and feels quite quick. The suspension is brilliant! The air springs absorb fine ripples and potholes with equal distain and even a cattle grid caused no distress to either bike or rider. I'm using 170 psi front and 160 psi rear in the springs at present, which is pretty much what Cane Creek recommend for my weight (no, I'm not telling you what that is). The anti-dive isn't as effective as I had hoped, but then the brakes are fairly awesome. Hard pedalling causes no bobbing of the front suspension at all. However, the front of the frame does flex when you really give it some. The steering link has a tiny bit of play in it - you don't notice it when you're riding but I will try replacing some plastic bushes in the top of the link with brass ones.

Setting off on slippery surfaces requires a bit of technique. Like a front-wheel drive car, if you stomp on it from standstill, in bottom gear, on a slippery road, you get wheel-spin and go nowhere fast. So, was FWD a good idea? The jury is still out at present, although it does make the derailleur cable very short, which seems like a small point, but it is very difficult to keep the long derailleur cables on my RWD bikes running freely throughout the winter.

I've already managed to crash once. I tried out the bike before I had installed all the chain management hardware (I still have to make a guard for the pulley), allowing the chain to come off and jam in the front wheel. The resulting deceleration was sufficient to throw me over the handlebars, which is quite impressive on a bike with a 350 mm seat height! As a couple of Rat Racer riders have also found to their cost, you do not want to risk the chain coming off if it might end up tangling with the front wheel. Development continues.

The next step is to design the front and rear fairings. It may be a while before I have a chance to start making them, as I have a rather demanding day job at present. Still, I now have one of the World's very few, front wheel drive, dual-suspension bicycles and initial signs are that it might work quite well.