Could chainless drives have a viable future?

[ebikeerwidnes]

getting rid of the chain gets rid of the problem of the chain stretching

Clearly I use an ebike - but I do pedal as well - hence there are times when the motor is going at full power and I am standing on the pedals - normally going uphil

So far I seem to get through one chain a year and at the same time at least one gear cog needs replacing
I presume this is because there is a silly amount of power going through the transmission at times for an old fat bloke

A totally chainless system would get rid of this - and as it is an ebike anyway a lot of the weight in the system would be there anyway

I would think a delay between pedalling and power appearing at the wheels might be a problem
but that lask of maintenance and parts to replace would be nice

 

[Smokin Joe]

Every so often someone comes up with a chainless bike. They sink without trace. Always.

Like solid tyres.

 

[Dogtrousers]

This one comes around regularly, and then dies. Efficiency is nowhere near that of a chain, and unlikely to ever get near, removal of the wheel entails more engineering solutions if you are to avoid having to realign the rear drive each time. The shaft and connecting drives tend to be heavier than a chain system and to get gears you need a hub (Generally fat less efficient and heavier than a derailleur system)

The OP isn't a shaft drive. It's a generator. But there is a shaft drive mentioned later on in the thread.

I always like to give new ideas a fair run for their money. People on here have seen so many daft kickstarter ideas that the understandable reaction is to dismiss everything. An example was the Infinity bike seat, which was universally derided on here when it was released but as it turned out now plenty of people have them and love them (and quite a few didn't like them at all).

ANYWAY, all that said I can't see this as any kind of competitor to/replacement for a chain - just too inefficient (as @Bollo points out) and the chain is just too good a solution. But I don't think that's necessarily what it's intended to be.

As @IanSmithCSE says, there could be a niche where it makes sense. For example, a primarily battery propelled bicycle that has pedals for the user to add some power to prolong battery life or give a bit more oomph, or maybe emergency get-you-home on flat battery. In that case a chain drivetrain would be an added complication that just isn't needed, and the inefficiency isn't a big deal as the battery is the primary source of power. Whether there's a market/use for such bikes I have no idea. As @Jenkins says, such a bike under current regs might officially be a moped.

Maybe it could have regenerative braking too (runs away and hides)

 

[Mike_P]

Would that bike in the video be legal under the current legislation as it is pure electric drive and not pedal assisted and therefore classified as a motorbike/moped?

UK regs say must have pedals that can be used to propel it.

 

[Dogtrousers]

UK regs say must have pedals that can be used to propel it.

What must have pedals that can be used to propel it? A bicycle or a moped?

 

[Mike_P]

What must have pedals that can be used to propel it? A bicycle or a moped?

An electric bicycle https://www.gov.uk/electric-bike-rules

 

[Jenkins]

UK regs say must have pedals that can be used to propel it.

Except on that bike the pedals appear to charge the battery and the battery then provides power to the motor. The pedals are not directly propelling the bike.
Don't get me wrong, I have an ebike and have no problem with them and do wonder if there is a case to be made for allowing pure motor power up to 15mph. It's just that the one shown doesn't meet the current criteria as a pedal bike and, without a change in the regulations, would have to be sold as a motorbike.

 

[TheDoctor]

Maybe it could have regenerative braking too (runs away and hides)

Regenerative braking isn't often (ever?) used on bikes. Because physics.
The kinetic energy is proportional to Mass times Velocity squared.
For a car, that's 2 tonnes times 70ish mph times 70ish mph - about 10000.
Let's not worry about the units. That mish-mash certainly isn't SI units!
For a bike, that's more like 0.1 ton times 15 mph times 15 mph - about 23.
That's a lot less [citation needed] and not worth trying to stuff it back into the battery.
Or, at least, ebike designers don't think it is.

 

[Dogtrousers]

Regenerative braking isn't often (ever?) used on bikes. Because physics.

I was kidding. Hence my "run and hide" comment.

 

[Dogtrousers]

It's just that the one shown doesn't meet the current criteria as a pedal bike and, without a change in the regulations, would have to be sold as a motorbike.

Or, more likely, just sold as-is with a disclaimer not to be used on public roads which people would just ignore, knowing that no one is likely to do anything about it.

 

[andrew_s]

Regenerative braking isn't often (ever?) used on bikes. Because physics.
The kinetic energy is proportional to Mass times Velocity squared.
For a car, that's 2 tonnes times 70ish mph times 70ish mph - about 10000.
Let's not worry about the units. That mish-mash certainly isn't SI units!
For a bike, that's more like 0.1 ton times 15 mph times 15 mph - about 23.
That's a lot less [citation needed] and not worth trying to stuff it back into the battery.
Or, at least, ebike designers don't think it is.

That's not the problem with regenerative braking; after all, the energy required to get back up to speed is also that much less.

The problem is that almost all of the energy from the battery is used to shove air out of the way, and you'll never get that back. Maybe you'd improve the range from 100 km to 101 km, but that's about all.

 

[Dadam]

That's not the problem with regenerative braking; after all, the energy required to get back up to speed is also that much less.

The problem is that almost all of the energy from the battery is used to shove air out of the way, and you'll never get that back. Maybe you'd improve the range from 100 km to 101 km, but that's about all.

But that's exactly the same physics as with cars, and more so because cars go faster. Air resistance increases with the square of velocity and power needed to overcome it increases with the cube of velocity. Additionally, cars have waaay more air to shove out of the way because huge cross sectional area vs a bike + rider. At the end of the day, you're never going to get back all the energy but you can get back quite a bit. Like when you get to the bottom of a steep hill and have to stop. All that kinetic energy disappears in heat in the discs or rims. If you could regen 50% of that it's worth having.

Is it going to replace the chain driven bike? No. But is there a niche for that tech? Absolutely.

 

[Dadam]

to get gears you need a hub (Generally fat less efficient and heavier than a derailleur system)

No. The gears are just the relationship between pedal resistance/rotation speed and bike speed. You may be thinking of a shaft drive. On this kind of bike the pedals drive the generator which puts power into the battery and the battery drives the motor. There can be an infinite number of gears because that can be controlled in software. It's a bit like a CVT transmission.

 

[Bollo]

Like @Dogtrousers I’m very much an “each idea in its merits” kinda guy, but at 50% claimed efficiency (thanks @Baldy) this is all but dead in the water. At 300W I’m riding a respectable club 10. At 150W I’m going to the shops.

 

[DCBassman]

Keep it simple stupid.

This. Always this. Anything even the tiniest bit more complex is simply less efficient, without fundamentally new technology being invented.