https://www.youtube.com/watch?v=x79l7UO_qww
Caveat: The bike used is an e-bike with a powered wheel. The pedals have very little load requirements and no long-term or load testing is shown. As one of the most hardcore roadies you’ll ever interact with, personally, I believe this would not last more than a week if it could survive a single ride on a traditional bike and someone like myself based on my first impression of the design. Still, the idea is impressive to me. In practice, a robust enough design will likely outweigh a chain drive by an order of magnitude. The reason the chain and cog transmission is standard is because of the balance of weight to durability. Every single gram matters on a bicycle far more than may be apparent at first.
Sounds like the perfect thing to test and iterate and then use that to have something machined in metal.
Of course with some stronger materials it may be fine. But how resilient will the belts be from the tension/stress and is there any risk of injury when they snap?
These are basically timing belts for cars. Inside the belt are usually metal or aramid fibers that prevent any elongation of the tooth pitch. A lot of the automotive aftermarket principals of a timing chain versus a timing belt drive apply exactly the same here. The belt lasts longer and operates dry with more accuracy over time.
Belts are a standard system for bikes already. Its the printed parts that are scary.
No, some 1200cc motorcycles use them.
Are there any other reasons I’d want this apart from the lack of oil and the decreased noise levels, the coolness factor and the tinkering itself?
Every single one is a valid reason in itself of course, but maybe there is more.
Weight is really the only reason, but even then I think that’s self-defeating on a bicycle.
Believe it or not, a chain and sprocket drive is actually the most efficient method in terms of energy transmission losses. And when it’s you physically pedaling your bicycle, that’s kind of important. Turning any significant fraction of your pedaling input into heat rather than forward locomotion is kind of a raw deal, which is why even fancy high end bicycles are still chain driven even to this day. A chain drive loses 1-4% of energy in the driveline whereas as comparable belt drive is more in the order of 9-15%.
If you compare apples to apples there’s barely even a weight savings. Belt drives are either single speed or hub drive which can work with chains just fine. Once you add tensioner circuitry it’s basically a push. The only kind of advantage is that they don’t need lubrication and are quieter.
Exactly, which is why I was trying to think of any actual reasons I might want a belt, except style.
The positives of a belt drive are maintenance, and that it stays clean so they are most popular with commuters that do not want a dirty pants leg or newbie chain tat. They are only common on heavier bikes like short haul commuters in general and require a “broken frame” that is designed for them in the first place. The lack of transmission gearing means you need to either know exactly what gear ratio you need and deal with only having one speed or you need an internally geared hub. All internally geared hubs have monstrous weight to add. So in practice, you do not find many of these on the market. Even with an e-bike, you still need a geared transmission unless you have throttle control without pedaling.
On the other hand, for a hipster roadie, a fixie with a belt drive is some serious cred. Especially if they can dish it at the local group ride against people on flagship bikes.
Yeah, no lubricants and the look / style factor - that was my conclusion as well.
As for maintenance, while a belt might last 3 times as long, that’s not really a factor, given the price difference between belts and chains.
