How to transform the USA bicycle according to the Honda Super Cub model: eBike as revolutionary USA short distance transportation

[Ken M]

What's the difference between Bafang G510 Ultra and M620 Ultra?

They both have the standard 160nm of torque and 1000W.

Also, I don't think the 1000W is peak rating. I believe it's nominal.
Very rarely ebike companie (or motor companies for that matter) post peak power as standard.

On Bafang's website all the mid drive systems now seem to use a "M" prefix. I've seen the G510 used as well and I'm sure it's the same motor but can cause some confusion.

It's my understanding that the OEM cost difference for M620 160nm motor and the M600 120nm motor is approx. $50. The M600 seems to more optimized for high performance mountain ebikes and the M620 for cargo and urban performance ebikes (where a bit more weight is not an issue and the higher torque will allow for better load capacity or a bit higher sustained speeds).

I still believe there is room for a really good 1000-2000W DD hub motor (~32-35mm magnets & stator width) to be a great urban ebike motor because at high cruise speeds they are very efficient and the regenerative braking can be a great plus to recoup some energy and greatly extended brake pad life cycle. I don't even think a rear brake is necessary if the progressive regen is implemented correctly (Grin shows a their GMAC/Phaserunner kit stopping a bike very effectively without using brakes so a front brake only would be for emergency use0.

 

[lkcl]

The Bafang M620 Ultra is a mid-drive with 160nm with a standard peak rating of 1000W

as Timpo mentioned: that's peak rating. as you will no doubt know, the reason why peak rating should not be used is because above nominal rating the motor is unable to cool down. so if you use it at peak rating, sustained, you'll simply burn out the motor.

160nm of torque will be after the gearing. there is not a single 1000W electric motor in the world that will deliver that much torque without gearing. if you do ever find one, they'll be famous for managing to break the laws of physics if you can find out what that gearing ratio is.... ah found it: https://www.electricbike.com/bafang-ultra-max/

triple-reduction, 18:1 (which will result in losses at each reduction, let's ignore those for now)

so the actual motor will be 8 Nm of torque (peak) which is pretty close to the estimate i gave above. bear in mind that the Sur-Ron Motor is Axial Flux, which give a far higher power-to-weight ratio and far greater torque delivery than any other motor design with the exception of the LRK Torque Max design.

 

[Ken M]

as Timpo mentioned: that's peak rating. as you will no doubt know, the reason why peak rating should not be used is because above nominal rating the motor is unable to cool down. so if you use it at peak rating, sustained, you'll simply burn out the motor.

160nm of torque will be after the gearing. there is not a single 1000W electric motor in the world that will deliver that much torque without gearing. if you do ever find one, they'll be famous for managing to break the laws of physics if you can find out what that gearing ratio is.... ah found it: https://www.electricbike.com/bafang-ultra-max/

triple-reduction, 18:1 (which will result in losses at each reduction, let's ignore those for now)

so the actual motor will be 8 Nm of torque (peak) which is pretty close to the estimate i gave above. bear in mind that the Sur-Ron Motor is Axial Flux, which give a far higher power-to-weight ratio and far greater torque delivery than any other motor design with the exception of the LRK Torque Max design.

With the internal 18:1 gear reduction the torque does seem plausible. There are a few companies using it and claiming realistic top assist speeds as high as 55kph but I'm assuming they have bike drive trains that allow reasonable cadence at those speeds even though a lot of torque will be lost via that gearing. I would think a bike drive train gear ration of about 3:1 could allow comfortable cadence around 40kph and then just allow the motor to dominate at that point without worrying about keeping the rider engaged with realistic cadence.

There is like the advantage the Sur-Ron has...it can have a final drive gear ratio that amplifies the torque even at the faster speeds because it's not an ebike. I remember the Izip Express separated the mid drive system and the human system so both could be optimized but that pretty much means there must two independent drive systems (one on each side of the rear wheel).

 

[lkcl]

There is like the advantage the Sur-Ron has...it can have a final drive gear ratio that amplifies the torque even at the faster speeds because it's not an ebike. I remember the Izip Express separated the mid drive system and the human system so both could be optimized but that pretty much means there must two independent drive systems (one on each side of the rear wheel).

interesting to hear about the izip express. separate systems makes a lot more sense, illustrated below.

on the sur-ron, they're basically taking advantage of the e-bike laws to deliver you something via export regulations that are designed for ebikes, which are themselves a part-way-hangover from when scooters didn't have a kickstart or a motor, and you had to pedal the scooter for a few feet in order to get it started

so you get a 3kW motor with a cable attached that strangles the power to 500W, a rear sprocket with 25 teeth on it, a set of pedals with another 25-tooth sprocket on it and a one-way ratchet (yes, 1-to-1 pedalling), and a pair of incredibly dangerous e-brake switches, just so the exporters can slap an "e-bike" label on the customs forms.

when it arrives, you cut that cable (which immediately removes the 500W limit), remove the pedals, put a 61-tooth sprocket on the back and you're up to 75km/h with the stock controller (we can do 110 km/h ). of course, with the e-brake cut-off switches, you hold the brakes (even just touching them lightly is enough), twist the throttle and nothing happens. you sit there, puzzled, and your hand twitches ever so slightly - enough to "let loose" that ultra-dangerous e-brake switch.

result: the bike launches away from you, pulls your arms out their sockets which of course causes your fingers to twist the throttle even further and from that point you're in real trouble unless you have extremely strong wrist muscles. if not: the front wheel goes straight in the air, your feet slip off the stands, and you smash into the nearest object in front of you. the *very* first thing i did was cut those incredibly stupid e-brake cut-off switches on my e-bike. they're absolutely lethal. i cannot believe the stupidity of the EU regulators who thought they were even remotely a good idea.

anyway, back to the point: if you have powerful drivetrains like this, there's just no way you can integrate pedals into the (exact same) drivetrain in any mechanically-meaningful way.

it therefore just makes a huge amount of sense to me to have two separate drivetrains:

* one with a small sprocket on the motor and a large sprocket on the wheel (like a motorcycle)
* one for pedals with a *large* sprocket then a small sprocket on the wheel (like a bicycle).

i "get" why people like the mid-drive systems, because you can integrate the two into one. it looks... "neater". however... the forces (torque) involved, in such a small space, and to put chains under more force to get those kinds of 50+ km/h speeds? as an engineer i'm actually quite alarmed to hear that's what's being done.

although it sounds weird to have double sprockets on the rear wheel *and* double chains, mechanically it is better matched, and there will, ultimately, be far less wear and tear on the whole e-bike.

so let's take a look at what izip express did:

https://electricbikereview.com/wp-content/assets/2012/11/izip-express-electric-bike-review-1-1200x600-c-default.jpg

yep, there you go: you can see a standard derailer on one side, then i *think* it's... a belt drive on the far side, is that right? it almost looks like the drive wheel is touching the back wheel, just like those old french scooters (you've seen "Mr Bean's Holiday"?) but no, it's a separate chain/belt. yeah, that's a really good idea.