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Rivian's TM-B electric bike

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190 points hasheddan | 3 comments | 22 Oct 25 18:00 UTC | HN request time: 0.601s | source
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soco ◴[22 Oct 25 18:48 UTC] No.45673474[source]▶
Bear with me I don't know much about bikes but I have this honest question: why does it need a chain, and won't place the engine (or whatever gear box it has) directly on the wheel?
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roadside_picnic ◴[22 Oct 25 19:11 UTC] No.45673738[source]▶
Dirt bikes and many motorcycles also have chains, this allows you to change gears to adjust torque (alternatives include shaft and belt drives).

E-bikes can have the motors on the wheel (hub-drive) or on the pedal (mid-drive). This choice is largely related to how much you want your e-bike to really be a scooter or really be providing pedal assist. As a consequence hub-drive e-bikes typically have a throttle while mid-drive do not.

A good mid-drive e-bike really makes it feel like you are a super human cyclist rather than riding a scooter. It leads to a much smoother riding experience if your aim is to still be essentially bicycling but you'd like to get moving faster and not break a sweet even on the most extreme hills.

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1. pqtyw ◴[22 Oct 25 19:24 UTC] No.45673931[source]▶
> A good mid-drive e-bike really makes it feel like you are a super human cyclist

Of course. But the pedals on this thing aren't even connected to the drivetrain. So what is the benefit in this specific case?

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2. dreamcompiler ◴[22 Oct 25 19:28 UTC] No.45673985[source]▶
Completely agree. They should probably just remove the pedals and generator entirely and save that weight. But then legally it becomes a scooter and probably would require a license and be more limited as to where it could go.
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3. soco ◴[22 Oct 25 23:16 UTC] No.45676360[source]▶
But what if the pedals are connected to the wheel only in a "symbolic" way, say, some electrical contact or something? So technically you still have to pedal to qualify as e-bike, just without real mechanical transmission? And if you lose power bad luck, don't commute with an empty battery...