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Schaeffler’s Free Drive is a chainless electric drive system for e-bikes

8 comments

2 months 2 weeks ago

Ditching the entire heavy oily drive-train, and a no-dish rear wheel, look more genius than bonkers to me.

Even without a battery it could match, for efficiency, a typical real-life urban bike with its dry, worn and rusty chain and flabby tyres. Not saying much, I know, but people ride these wrecks quite happily.

As an e-bike with pre-charged battery, human-powered recharging is a minor but real benefit.

Regenerative braking, a separate technology on its way in (the system retarding the wheel through the motor/dynamo), is another. 

With a conventional front rim- or hub-brake added, this should be street-legal in the UK.

Put me on the waiting list for a Free Drive recumbent, a tandem and a burly cargo rig. I'm selling the furniture and going for 'E+1'!

 

  

 

2 months 4 weeks ago

This looks similar to the system used in diesel trains, where the engine drives a generator which is connected to an electric motor. So maybe this isn't too bonkers, will be interesting to see if this makes it past the prototype stage.

https://en.wikipedia.org/wiki/Diesel_locomotive#Diesel%E2%80%93electric

2 months 4 weeks ago

The question is whether the regenerative braking provides enough benefit to allow for the losses between generator and motor, as this must surely be less efficient than direct chain drive.

2 months 4 weeks ago

It's probably totally inefficient, but that's not the point. I can see this as a way of making a large cargo vehicle conform to the pedalec standards, so not requiring insurance, licensing tax etc. The pedals are almost sacrificial, like the old pedal-and-pop mopeds, but allow for a vehicle to be designed without the need to factor in a chainline (and the maintenance nightmare that might be).

2 months 4 weeks ago

Typo in my message above. I mean 80-120w. not 180!

2 months 4 weeks ago

Im going for bonkers. Even without accounting for losses the motor is going to be significantly under run by the power a recreational cyclist  (ie not a road.cc reader) can generate.  Less than 150W output from the crank I would suggest, possibly as low as 180-120w.  Which means there is little leftover to charge the battery, which means the minute they hit a hill they'll be on an empty battery almost immediately, unless its pre-charged before the journey.

The million dollar question is whats the relative effeciency difference between a normal chain and this system.  It seems like there are 2 effeciency levels - one when electricity goes straight from the cranks to the motor and a second lesser one that takes into account the conversion loss when the the riders power goes into the battery.

 

Its not a bad idea - its a pure electric bike unlike most of the current hybrids - but I cant see the power output from an average rider making much difference to the range which means it will always be pulling from battery and thus have a very very short range.  Pure electric cars get around this by having a massive battery and junking a mechanical engine.  A bike doesnt have the room/weight limit for a massive battery and a chainset is much less of a bikes mass than that of a cars engine.

2 months 4 weeks ago

I wonder how efficient the generator is? I imagine not very, and I imagine that (for the average rider) most of the power will come from the battery. That's not a bad thing per se, but it does mean the generator is more for show than practicalty. 

I also wonder if this would comply with UK (or EU) legislation on electrically assisted pedal cycles. 

2 months 4 weeks ago

I can't decide whether this is bonkers or genius.