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this post was submitted on 04 Sep 2023
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micromobility - Ebikes, scooters, longboards: Whatever floats your goat, this is micromobility
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Ebikes, bicycles, scooters, skateboards, longboards, eboards, motorcycles, skates, unicycles: Whatever floats your goat, this is all things micromobility!
"Transportation using lightweight vehicles such as bicycles or scooters, especially electric ones that may be borrowed as part of a self-service rental program in which people rent vehicles for short-term use within a town or city.
micromobility is seen as a potential solution to moving people more efficiently around cities"
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Chains are efficient for transmitting power but this doesn't speak to the gear ratio. Not a mechanical engineer but I have a decent understanding of this so forgive bad terminology... but if you have a huge input gear and small output gear, you get a lot of leverage to apply torque to to wheel, while you're able to more effortlessly apply work (?) at higher speeds when it's the other way around, that's the basic spectrum. The individual gears emulate a continuously variable transmission, but as a step function instead of a continuous function, so there's the space in between two consecutive gears that's more optimal than either surrounding gear for most speeds/inclines/acceleration/etc., but inaccessible. A continuously variable transmission (on a car, bike, w/e) fills in those gaps by using actuators to change the position of a chain on conical pieces in the transmission so you have perfect efficiency in that department. It's still a chain transmitting the actual power. Mostly it comes down to being able to control the gear ratio in a way that's ideal for the user - cars get that part wrong a lot, resulting in some infuriating side effects. The whole reason they've been adding them to cars is because they help squeeze out another ~3 mpg versus a traditional manual/automatic transmission which relies on imperfect gear ratios. With some serious fallout because CVTs are pretty complex and some of them are not well designed (Hyundai/Kia comes to mind).
Both rear cassettes and internal gear hubs these days can come with a ridiculous fuck-ton of gears (they literally go up to eleven!*). And that's before you add a front derailleur and multiply by three! How many more ratios in between those do you need?!
(*Or more, now. The ridiculousness has surpassed Spinal Tap!)
I bike a lot and the traditional gear systems, while they're pretty rock solid, easy enough to service, etc., definitely leave a little room for improvement. When you're exerting a ton of force uphill and have to shift, for example, it can be a total disaster (especially if your derailleur stops are bad and your chain slips, which I'm dealing with this moment after a rebuild).
The CVTs in hybrid applications in Prius and (Toyota designed) Subaru gas electric hybrids are very different from traditional CVTs.
There aren’t any belts or chains for changing ratios, they have a clever used of a planetary gear with the outer ring gear connected to the electric motor. This allows the output ratio to be continuously changed (which for the gas end of hybrids, allows the engine to be held at its most efficient RPM, while the vehicle speed changes as the driver wants).
I’m not sure when it comes to pedaling cadence, that maintaining a constant speed is as helpful. Though being able to adjust that continuously would be nice-on demand.