3 ms·

Springs are terrible when driven by biological "pistons". Applying a certain amount of force is much harder in some phases of the pedal stroke cycle than in oth

by usrusr 8y ago

Springs are terrible when driven by biological "pistons". Applying a certain amount of force is much harder in some phases of the pedal stroke cycle than in others and springs would make it impossible to go easy when you want/need to.

jacquesm 8y ago
It is a very hard spring, not something squishy like front fork suspension. The biggest downside would be eventual wear of the driveshaft, the losses will be very low. Note that almost every part of your bike acts as a spring in that sense, the frame flexes a bit when you pedal, as do the cranks and the shaft. Even the spokes in the rear wheel act as springs transmitting the force from the hub to the rim (which is one reason why they are oriented the way they are, that way they pull the rim along rather than that the spoke gets bent, the spoke is stronger in that direction).
- usrusr 8y ago
  Everything acts as a spring, and performance bicycle engineering goes to great lengths to make them as as hard as possible. Frame flex under pedaling load is measured, optimized against and a driver of buying decisions. Replacing the chain with something more springy? Good luck in that market.
  - jacquesm 8y ago
    > Everything acts as a spring, and performance bicycle engineering goes to great lengths to make them as as hard as possible. Indeed. So if you use a shaft to drive the rear wheel that would definitely be part of the equation, I note they are using a hollow carbon fibre tube, which in that particular dimension is likely not ideal for the application unless it is given some more cross section. Even so, it is an interesting development. > Replacing the chain with something more springy? Chains stretch quite a bit, you'd be surprised.
    - mrob 8y ago
      "Chain stretch" is usually slang for chain wear. The chain gets longer as the rolling elements wear down so people call it "stretch" even though the metal isn't stretching. The actual stretch under load is very small.
      - jacquesm 8y ago
        I'm aware of the difference, but thank you anyway. You can see the effect for yourself if you lock your rear hub and proceed to push down on the pedal (you can see it because the pedal is a nice long indicator effectively multiplying the distance the chain stretches). A bit nicer setup is a micrometer at the end of a fixed section of chain with a weight attached. Chain does stretch. About 1.5 mm under full load. That's why you want chains with solid pins and solid plates. What you are talking about is chain elongation as a result of wear, essentially the accumulation of slop in the bushings the pins go through.
    - deleted 8y ago
      [deleted]

by usrusr 8y ago

jacquesm 8y ago

It is a very hard spring, not something squishy like front fork suspension. The biggest downside would be eventual wear of the driveshaft, the losses will be very low. Note that almost every part of your bike acts as a spring in that sense, the frame flexes a bit when you pedal, as do the cranks and the shaft. Even the spokes in the rear wheel act as springs transmitting the force from the hub to the rim (which is one reason why they are oriented the way they are, that way they pull the rim along rather than that the spoke gets bent, the spoke is stronger in that direction).

usrusr 8y ago
Everything acts as a spring, and performance bicycle engineering goes to great lengths to make them as as hard as possible. Frame flex under pedaling load is measured, optimized against and a driver of buying decisions. Replacing the chain with something more springy? Good luck in that market.
- jacquesm 8y ago
  > Everything acts as a spring, and performance bicycle engineering goes to great lengths to make them as as hard as possible. Indeed. So if you use a shaft to drive the rear wheel that would definitely be part of the equation, I note they are using a hollow carbon fibre tube, which in that particular dimension is likely not ideal for the application unless it is given some more cross section. Even so, it is an interesting development. > Replacing the chain with something more springy? Chains stretch quite a bit, you'd be surprised.
  - mrob 8y ago
    "Chain stretch" is usually slang for chain wear. The chain gets longer as the rolling elements wear down so people call it "stretch" even though the metal isn't stretching. The actual stretch under load is very small.
    - jacquesm 8y ago
      I'm aware of the difference, but thank you anyway. You can see the effect for yourself if you lock your rear hub and proceed to push down on the pedal (you can see it because the pedal is a nice long indicator effectively multiplying the distance the chain stretches). A bit nicer setup is a micrometer at the end of a fixed section of chain with a weight attached. Chain does stretch. About 1.5 mm under full load. That's why you want chains with solid pins and solid plates. What you are talking about is chain elongation as a result of wear, essentially the accumulation of slop in the bushings the pins go through.
  - deleted 8y ago
    [deleted]