Tech bros think this is what we want in an ebike

[harrisonpatm]

Tl;dr

Rivian is making an ebike. There's no direct connection between the cranks and the rear wheel. When you pedal, you activate some sort of PAS which triggers the middrive motor to turn the rear wheel via belt drive. Pedaling also..., um... charges the battery. So you pedal the bike, to turn a generator, to power the battery, which sends power to the motor, which drives the belt, which turns the rear wheel. My head hurts...

My favorite part is what happens if the battery is empty. Your pedaling doesn't turn the rear wheel. You're forced to pedal enough energy, accepting 1/3-1/2 energy loss via mechanical and electrical inefficiencies, to propel a 90-pound bike. Thanks for revolutionizing cycling, Silicon Valley!

 

[slaphappygamer]

Ugh. Sounds a bit like this POS.

Wait till you get to the part when the bike runs away.

Really, as long as it looks good on paper, it should be made. Lol

 

[neptronix]

That's what the bicycle needs. More complexity, weight, and less efficiency.

 

[docw009]

Ten years ago, the Mando Footlose came out with the same concept, and failed.

https://www.cnet.com/roadshow/reviews/mando-footloose-im-review/

 

[lnanek]

I'd be fine with pedal by wire. My ebike is either going 30mph or accelerating up to it 99% of the time. I use a huge 75t chain ring so I can get some exercise pedaling along at that speed and I never shift out of highest gear, but it is kind of silly having all that pointless manual drive chain hardware bolted on there just to get exercise.

I don't even have any use for the pedal generated power. I commute 20 miles to work, my primary battery can get that far, I always carry a spare that can as well, and I charge at work. As long as it has a little set screw to set the exercise resistance level I'd be happy with the pedals.

 

[Epithemeus]

Pedal by wire does have some advantages (also significant disadvantages) but one of the biggest advantages is not having to have a chain or belt....

 

[gromike]

One would think, but the Rivian is a belted mid drive.

 

[Comrade]

I'd be fine with pedal by wire.

I'd love that too. Especially if, and it probably does, lets you set your cadence and resistance without constantly shifting. I would not be surprised that the electrical losses, which will only get smaller as time goes on, are smaller than one would expect because they are offset by being able to pedal in a more optimum power band, and not frequently go to 0W output while shifting.

 

[maiz]

Tl;dr

Rivian is making an ebike. There's no direct connection between the cranks and the rear wheel. When you pedal, you activate some sort of PAS which triggers the middrive motor to turn the rear wheel via belt drive. Pedaling also..., um... charges the battery. So you pedal the bike, to turn a generator, to power the battery, which sends power to the motor, which drives the belt, which turns the rear wheel. My head hurts...

My favorite part is what happens if the battery is empty. Your pedaling doesn't turn the rear wheel. You're forced to pedal enough energy, accepting 1/3-1/2 energy loss via mechanical and electrical inefficiencies, to propel a 90-pound bike. Thanks for revolutionizing cycling, Silicon Valley!

I find some aspects interesting; the chainstays (beltstays?) are long and center the weight of the rider between the two wheels in a way that modern geometries don't. The f/r suspension looks well designed. Multi-utility via test seatpost is clever, though the stresses on that mechanism suggest it may be a point of failure. The non-adjustability of the front cockpit area is confounding. Looks like a proprietary stem and hbar. And the front basket is mounted on the forks?! With all that chonky aluminum on the downtube, a frame mounted front rack would have been a better option.

 

[Nix Liou]

I'd love that too. Especially if, and it probably does, lets you set your cadence and resistance without constantly shifting. I would not be surprised that the electrical losses, which will only get smaller as time goes on, are smaller than one would expect because they are offset by being able to pedal in a more optimum power band, and not frequently go to 0W output while shifting.

I mean, no, it can only get so efficient for pedal by wire. It can't really be more than 75% efficient or so, on top of the bike weighing 90 pounds...
Generally you would go to 0 W for a second, as you shift a couple times maybe? Not that big of an impact on efficiency.
The only benefit is it lets you set the cadence. So basically, you can use an exercise bike while on your e motorcycle, and it happens to help a bit with range.

 

[Zambam]

Will it become a failure? Time will tell. I'd want a test ride first before discounting it.

Video from Rivian Also

https://cdn.shopify.com/videos/c/o/v/644c02bc1e9545a9b84edb68c2dd84b5.mp4

 

[Comrade]

It can't really be more than 75% efficient or so

Why not?

you would go to 0 W for a second, as you shift a couple times maybe?

That depends on the terrain. Riding a flat bicycle trail is one thing. Commuting in a dense urban environment is another. Going in a hilly off road environment is yet another. Shifting losses both mechanical and mental are not insignificant.

 

[harrisonpatm]

Why not?

I think its possible for efficiency to be above 75%, maybe... when the battery is full. But I can't get over what's required to move the bike if the battery runs out. Pedaling to turn the generator, mechanical losses. Generator sending power to the controller, electrical losses. Controller converting voltage and delivering current to the motor, electrical losses. Motor driving the belt, mechanical losses. There's no way all that is any better than 75% efficient, and in the video at some point it's said to be perhaps only 60%. On a 90-pound bike, too.

 

[Comrade]

Generator sending power to the controller, electrical losses. Controller converting voltage and delivering current to the motor, electrical losses.

I'm not saying this specific bike will be great, but the idea itself with the right implementation is more than likely viable and could find widespread adoption. I don't see a reason why a generator could not drive a motor "directly" without voltage conversion to battery level. Very efficient PWM control, sure. A geared hub motor would probably be more efficient and reliable too.

 

[Zambam]

Rivian spinoff ALSO invents the future of e-bikes, but will it sell?

We’ve long known that inside of Rivian, the popular electric pickup and SUV maker, lived a tiny skunkworks of e-bike...

electrek.co

 

[amberwolf]

AFAICR Tigcross's big customizable bike model he sells uses series hybrid drive to control it (or did at one time).

A few other builds here on ES have, over the years; there was a big stainless steel enclosed trike in Germany that did but he wiped out all his pics and videos and some of the posted info a long time ago. Can't remember the username ATM.

I thought there was another commercial bike that did, by PiCycle, but I couldn't find it in a few second's websearch. :/


But, it's still way less efficient than a direct pedal-to-wheel connection, even via the least efficient mechanical means, and much more prone to failure that will leave the bike unridable.

The efficiency loss means that it will be much harder to pedal under the same conditions a regular mechanically-connected bike would be, and would be unrideable under pedal power for a significant number of people (like me) who can barely make a plain pedal bike work.

 

[Zambam]

Battery voltage not stated. Any guess what it is?

 

[Hillhater]

but one of the biggest advantages is not having to have a chain or belt.

That is also one of the biggest disadvantages !

Shifting losses both mechanical and mental are not insignificant.

..?? Mental losses ?
The biggest loss by far will be financial,..and Rivians reputation .

 

[neptronix]

Will it become a failure? Time will tell. I'd want a test ride first before discounting it.

It's not in test riding it but noticing that it has worse efficiency, higher cost, and higher weight than a pedaled ebike that is going to sour the long term experience.

It's amazing how many companies get away with selling products like that short term. maybe they will sell a couple units. but series hybrid is nearly always a bad idea by every metric compared to a parallel hybrid ( example: hub motor with regen ) or two drivetrain system ( a typical mid drive )

 

[Zambam]

It's not in test riding it but noticing that it has worse efficiency, higher cost, and higher weight than a pedaled ebike that is going to sour the long term experience.

It's amazing how many companies get away with selling products like that short term. maybe they will sell a couple units. but series hybrid is nearly always a bad idea by every metric compared to a parallel hybrid ( example: hub motor with regen ) or two drivetrain system ( a typical mid drive )

Efficiency will never be close to a real bicycle. ALSO knows that I'm sure! I'm also sure ALSO do not recommend riding it with a dead battery! Actual efficiency will be revealed soon enough.

https://www.rivianforums.com/forum/threads/review-i-rode-the-also-tm-b-e-bike-rivian-micromobility-startup%E2%80%99s-first-ev.51873/

 

[JackFlorey]

My head hurts...

It shouldn't. It's the same system a modern diesel locomotive uses.

It's also dumb. No reason for all that extra complexity and loss. A bike drivetrain is 95% efficient, which is critical when your source of power is you. They are not going to come near that with a series generator/motor drive.

Only reason I could see to justify this is to comply with a law that says you need pedals or it's not an ebike. But again, there are easier and more efficient ways to accommodate that.

 

[Comrade]

A bike drivetrain is 95% efficient

That's just one part of a bigger picture. This bike could do regen very well. It can generate power when a chain bike shifts. It can generate power going down a hill. It can generate more power from the human by keeping the cadence in a more optimum range. And other things that nobody here is even thinking about.

So comparing a chain and saying it's 95% but this electrical thing is 60%, so it's 35% harder to pedal from point A to point B is quite likely erroneous.

 

[neptronix]

It's still a 10-20% loss on the way in and a 10-20% loss on the way out for the pedal power, due to the mechanical to electric, then electric to mechanical conversion.

If you did an enormous amount of regen ( lots of start/stop in NYC? rollercoaster ride in the mountains? ), in the perfect gear, you still wouldn't break even on the efficiency loss because of the enormous loss.

I guess it's ok for people who don't like pedaling.

This large amount of losses is the same reason CVTs are super unpopular on bikes. Yes, you can hone in on an ideal gear ratio and gain ~5% more efficiency that way but that doesn't outstrip the 20% efficiency you are losing all the time.

 

[amberwolf]

We wont' really know all the downsides until someone has one in their hands for testing and abuse.


But....none of hte efficiency stuff, even if it was 100%, totally lossless, addresses the significant problem that a system failure means the bike cannot be ridden at all, making it useless in this kind of event.

Depending on the complexity of the system, and whatever authorization method it uses to authenticate the rider (since so many systems foist "smartness" on the user these days, this one might too), this could become a significant issue.

 

[Comrade]

I guess it's ok for people who don't like pedaling.

There are lot of people who live in apartments in urban environments. Something as simple as maintenance of the drive train is a very dirty choir incompatible with apartment living. Then there is storage. If the battery can last a week of commuting without charging, because human power augments the battery enough, then the bike can stay in some basement or ground level bike storage area, without the need of taking it up to the living unit. The bike can be dirty in the winter. I'd guess that there are very few people on this forum that fit this type demographic, so it's not as easy for them to see the benefits of this design.