The chain and the future of cycling
Pretty much ever since the dawn of the bicycle, once the pedals had been removed from the front wheel of the Penny Farthing and moved to the bottom bracket, the rider’s energy has been transferred via the rotating cranks and chain wheel, via a steel chain, to the rear wheel. This is still the accepted wisdom in bicycle design today. Chain drive, which was employed extensively during the Industrial Revolution as a means of powering machines indirectly, has resulted in some finely engineered bicycle drive chains being available today. But they all have one or two fundamental flaws built in – not because they are badly made, but because the paradigm of the ‘chain’ as such is flawed.
What happens every time your pedals rotate is that hundreds of metal links, which are joined to rollers with metal pins, run through a 360 degree revolution that involves hundreds of moving parts wearing against one another. Chuck in some road grit and grime, some water, and some oil to mix it all up and form a nice abrasive paste, and you have a pretty nasty outlook for your chain. But hang on, I’m talking about my own single sprocket, single chain wheel set up here. Let’s move to derailleurs and throw constant lateral flexing of the chain into the mix for good measure.
No wonder chain sales are so strong!
Now when you look at other ‘indirect drive’ components, such as the alternator in a car engine, you will see that the drive belt has largely replaced the chain. Yes, some manufacturers such as BMW still employ chains, but their weight and cost make them a rarity these days. Instead, a fibre and rubber belt is often used instead. And so, it seems, the world of cycle design may slowly be catching up.
When James Bowthorpe returned from his record-breaking round the world trip in the Autumn of 2009, he showed off his Santos Travelmaster bike, with Rohloff hub gears, and a belt instead of a chain. The cycling world was fascinated. The fitting of the belt had been a trial, with Santos and Rohloff observing and versioning the set up until they had reached a point where they were prepared to officially sanction belt drive as a method of transmission. Bowthorpe reported at the time that this was a trouble-free set up and that, because the belt has no moving parts and is not coated in oil and grime, it was clean, quiet and long lasting. He fitted a second belt in Australia, and the mileage was far in excess of what a typical chain would manage in those conditions.
Some of the big manufacturers are now releasing bikes with belt drive – for example the already mentioned Santos, Trek’s Urban range, Tout Terrain, and others have all ironed out early issues and claim to have viable belt drive systems. The part normally used is the Gates belt, Gates being the largest manufacturer of drive belts in the world. The pluses are obvious –
- No mess on the rider’s trousers
- Quieter than a chain
- Lack of moving parts
- No lubrication needed
- Longer service life
- No stretching or snapping on the road
However, there is one problem with the ‘no snapping’ point listed above. If you need to, you can push a link pin out of a chain and take it off the bike. With a belt, you can’t do that – so bike manufacturers have had to find a solution to the problem; this has manifested itself in the split rear dropout. In other words, if you can’t break the belt, break the bike! The seat stay and chain stay are not welded together at the rear dropout like on chain driven bikes. They are instead both bolted to a removable rear dropout, meaning that you un bolt the dropout and a gap appears to enable the belt to be taken off. Clever.
But can you retro-fit a belt drive system to your existing bike, you ask?
Well, having enjoyed the undoubted benefits of a Rohloff internally geared hub for some while, the idea has occurred to me. But I’m not going to take a hacksaw to my lovely Reynolds steel frame. I guess that a belt drive chainwheel could be obtained, Rohloff supplies a belt drive sprocket, but the actual frame modifications would have to be sanctioned and carried out by the frame builder themselves – in my case, Thorn cycles. As far as I know, they have no plans at the moment to manufacture belt driven bikes, although if the demand was there, who knows?
This fellow in Scotland builds custom frames with belt drive dropouts, and seems to have created some rather lovely machines. Watch this space for more developments!