A bike with strings attached


Hungarians pride themselves as great inventors. The products of Hungarian ingenuity range from Rubik's cube to the world's biggest blow dryer. So it is perhaps not a surprise that they came out with a complete reinvention of the bicycle, doing away with the chain and anything remotely similar.


I heard of the Stringbike last year, when it made a bit of a splash at Interbike 2010. So when I got the offer of actually getting my hands on one, loaned by the developers, I jumped at the opportunity. And this is what I found.




Before the first ride, I was forced to just eyeball the bike in the living room for two days. Which is great, because you really need a close look to figure out how it might work. The invention itself concerns the drive mechanism, and is called the Stringdrive. The chain is replaced with plastic strings that are apparently strong enough to lift an elephant. A small one. More interestingly, the string does not go round continuously like a chain or a belt. Instead, it is pulled with every turn of the pedal, and then it rewinds onto a drum mounted on the rear axle. It is completely beyond me to fully describe it, so you should rather check out this video.


The string is pulled by a lever (ominously called a swinging member by the makers) that is made to pivot by the pedal crank. This only pulls the wheel for half the turn. To make the drive continuous, the same mechanism is fitted on both sides, so each pedal independently drives the wheel.



The bike they put it on is an MTB/tourer/commuter hybrid, with a sturdy frame and a short suspension fork. The first pedal strokes already revealed one main feature of the Stringdrive: the rotation speed of the pedals is not quite uniform. They go through the top/bottom position a bit faster, and slow down nearing the horizontal. This is plugged as a feature by the designers, and has much the same effect as the oval chainring of the sort Millar rode in this year's Giro TT. The effect with the Stringdrive is gear-dependent and more pronounced with the slower gears. This worries me a bit, as it could overload one's knees when struggling up a steep hill. 


Otherwise it did not take long to get used to the funny feel of the pedals, and I was darting around on the bike soon enough quite happily. It's pretty hilly round here, and the awesome Magura hydraulic rim brakes could not fail to put a smile on my face, even if they had nothing to do with the new drive. I also discovered the odd feature that you cannot turn the pedals backwards, or rather if you do, you still propel the bike forwards! And when you get off, the pedals move to a horizontal position.


The bike itself looks good enough to turn some heads, and you can see the amazement on the faces when people notice the drive mechanism. You can't hear it, though there was some clicking noise at high speeds in high gear.


And now to the gears. I do believe that gears are the main weakness of most bikes. I'm a guy who happily rearranges the plumbing in the house or plasters the ceiling (OK, maybe not the ceiling), but derailleurs are not my friend. I don't have a single bike where all the gears work properly, I keep cursing the damn things when they fail to switch just before the steepest section, and I hate having to fiddle with the set-up all the bloody time. So there is certainly room for improvement.




The Stringdrive has a very clever gear mechanism, but it may also provide its main weakness. Gearing is provided by changing the position of the string pulley on the swinging arm at the cranks (see the photo above). You can move the pulley into any one of 19 recesses. You need to do this on both sides, so one gear cable splits into two and moves both pulleys. With separate controls, it would be possible to change gears separately on each pedal! It took me a while to get my head around this one. Anyway, in the standard setting the two pulleys need to change position in perfect synchrony. They did not do this on the test bike, which made the gear changing a bit awkward, and suggested that this system also needs fiddly fine tuning.


You can change gears while stationary, or any other time unless pedalling hard. The nineteen gears are all in linear order, which makes their number rather an overkill. Especially that altogether they only cover a twofold range. Which meant that I was definitely undergeared when going down a long gentle slope, but I only just managed to get home on slopes of around 15% with what I thought deservedly qualified as superhuman effort.


What is the advantage of the Stringdrive then? First of all, it is not oily, supposedly needs no maintenance, and lasts longer than a chain. It may also be very efficient, as you are only bending a very light string on pulleys. The gear system is conceptually very simple and probably reliable. I think the jury is out whether the altered pedalling mechanics are an advantage. Finally, it certainly has a great effect at turning heads. 


But is this enough to overcome the downside of short-range non-alterable gearing, the high initial price, and the slightly increased weight? The price and the weight could easily come down, but with this gear system the bike will probably only ever appeal to commuters and flatland bike tourers. Which is not a bad market, and you don't need to try and convince the UCI.


And when I got back on my trusted old bike, it somehow felt all wrong!


(photos are my own)

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