Flywheel-assist bicycles

[Dialogue clipped]... I'm just musing on how bikes might evolve if high pollution and resource extraction fees motivate alternatives to reliance on batteries. It looks like, in an area where the largest hills are under about 40 meters, a flywheel assist might not be so terribly obtrusive.

ChatGPT said:

Your musing is right on target — and quite timely. If environmental costs (via pollution and resource extraction fees) are honestly priced into goods and services, battery production and disposal would become less attractive, especially for small-scale applications like bicycles. In that world, flywheel systems — and other non-extractive energy buffering methods — could see a resurgence and evolution.

Let’s expand on your idea:


๐Ÿšฒ In a Post-Battery or Battery-Lite World: The Flywheel Reconsidered

If hills are typically under 40 meters of elevation gain, you're dealing with a modest energy requirement. Using your previous idea, let’s quantify it:

๐Ÿงฎ Climbing 40 meters at 90 kg (bike + rider):

E=mgh=909.840=35,280 J10 WhE = mgh = 90 \cdot 9.8 \cdot 40 = 35,280 \text{ J} \approx 10 \text{ Wh}

That’s only 10 watt-hours to climb a typical hill. Even a small flywheel storing 40–50 Wh could be sufficient to noticeably smooth out the effort of cycling in rolling terrain.

This opens the door to non-electric, lightweight, low-cost flywheel assist systems, especially if they:

  • Use low-friction magnetic bearings

  • Store energy at moderate speeds to reduce safety concerns

  • Employ counter-rotating flywheels to eliminate gyroscopic handling issues

  • Integrate a mechanical clutch or continuously variable transmission (CVT) to handle energy flow


⚙️ How It Could Be Built: Simpler, Safer, Sustainable

✔️ Materials

  • Recycled steel or carbon fiber flywheel

  • Rare-earth-free bearings (magnetic or air)

  • No batteries (or minimal capacitors for clutch control)

  • Biodegradable or recyclable frame components

✔️ Flywheel Characteristics

  • Weight: ~3–6 kg

  • Spin speed: 3,000–6,000 RPM (within safe limits)

  • Energy capacity: 30–80 Wh

  • Form factor: small disc beneath the bottom bracket or in rear hub area

✔️ Control Mechanism

  • Pedal torque exceeds cruising threshold → flywheel charges

  • Pedal torque dips (e.g., climbing) → flywheel discharges

  • All mechanical control, or simple electric clutch powered by small solar panel


๐ŸŒ Why This Could Thrive in an Honest-Pricing Future

FactorBattery-Based AssistFlywheel Assist
Environmental extraction feesHigh (lithium, cobalt)Low (steel, fly ash, recycled materials)
Emissions during useZeroZero
Lifecycle emissionsHigh (especially mining & disposal)Low (long-lived, no exotic materials)
NoiseSilentSilent
Range limitationHigh energy, long rangeShort bursts, hill smoothing
Resource circularityDifficult (toxic, complex recycling)Straightforward (especially steel)
Upfront costModeratePossibly higher per Wh, but simpler overall

In a world where environmental impact is truly priced, this would flip the incentives. A small, rugged, mostly mechanical system might outperform a high-capacity battery bike on both environmental and lifecycle cost metrics.


๐Ÿงช Next-Level Ideas (if this field takes off)

  • Open-source designs for DIYers and local manufacturers

  • Energy-dense flywheels in vertical shafts embedded in urban terrain (like tram systems), to charge bikes at stoplights

  • Co-op bike fleets with shared regenerative flywheel systems

  • Compressed-air hybrids for flatter terrain (another battery-light alternative)


✅ Final Thoughts

You're right: modest flywheel assist is plausible, not terribly obtrusive, and in a world with honest environmental pricing, could become one of the most elegant and sustainable solutions for lightweight transport.

Would you like help estimating energy and materials needed for such a system in more detail, or drafting a speculative vision of how urban bikes might evolve under those incentives?I'm just musing on how bikes might evolve if high pollution and resource extraction fees motivate alternatives to reliance on batteries. It looks like, in an area where the largest hills are under about 40 meters, a flywheel assist might not be so terribly obtrusive.

ChatGPT said:

Your musing is right on target — and quite timely. If environmental costs (via pollution and resource extraction fees) are honestly priced into goods and services, battery production and disposal would become less attractive, especially for small-scale applications like bicycles. In that world, flywheel systems — and other non-extractive energy buffering methods — could see a resurgence and evolution.

Let’s expand on your idea:


๐Ÿšฒ In a Post-Battery or Battery-Lite World: The Flywheel Reconsidered

If hills are typically under 40 meters of elevation gain, you're dealing with a modest energy requirement. Using your previous idea, let’s quantify it:

๐Ÿงฎ Climbing 40 meters at 90 kg (bike + rider):

E=mgh=909.840=35,280 J10 WhE = mgh = 90 \cdot 9.8 \cdot 40 = 35,280 \text{ J} \approx 10 \text{ Wh}

That’s only 10 watt-hours to climb a typical hill. Even a small flywheel storing 40–50 Wh could be sufficient to noticeably smooth out the effort of cycling in rolling terrain.

This opens the door to non-electric, lightweight, low-cost flywheel assist systems, especially if they:

  • Use low-friction magnetic bearings

  • Store energy at moderate speeds to reduce safety concerns

  • Employ counter-rotating flywheels to eliminate gyroscopic handling issues

  • Integrate a mechanical clutch or continuously variable transmission (CVT) to handle energy flow


⚙️ How It Could Be Built: Simpler, Safer, Sustainable

✔️ Materials

  • Recycled steel or carbon fiber flywheel

  • Rare-earth-free bearings (magnetic or air)

  • No batteries (or minimal capacitors for clutch control)

  • Biodegradable or recyclable frame components

✔️ Flywheel Characteristics

  • Weight: ~3–6 kg

  • Spin speed: 3,000–6,000 RPM (within safe limits)

  • Energy capacity: 30–80 Wh

  • Form factor: small disc beneath the bottom bracket or in rear hub area

✔️ Control Mechanism

  • Pedal torque exceeds cruising threshold → flywheel charges

  • Pedal torque dips (e.g., climbing) → flywheel discharges

  • All mechanical control, or simple electric clutch powered by small solar panel


๐ŸŒ Why This Could Thrive in an Honest-Pricing Future

FactorBattery-Based AssistFlywheel Assist
Environmental extraction feesHigh (lithium, cobalt)Low (steel, fly ash, recycled materials)
Emissions during useZeroZero
Lifecycle emissionsHigh (especially mining & disposal)Low (long-lived, no exotic materials)
NoiseSilentSilent
Range limitationHigh energy, long rangeShort bursts, hill smoothing
Resource circularityDifficult (toxic, complex recycling)Straightforward (especially steel)
Upfront costModeratePossibly higher per Wh, but simpler overall

In a world where environmental impact is truly priced, this would flip the incentives. A small, rugged, mostly mechanical system might outperform a high-capacity battery bike on both environmental and lifecycle cost metrics.


๐Ÿงช Next-Level Ideas (if this field takes off)

  • Open-source designs for DIYers and local manufacturers

  • Energy-dense flywheels in vertical shafts embedded in urban terrain (like tram systems), to charge bikes at stoplights

  • Co-op bike fleets with shared regenerative flywheel systems

  • Compressed-air hybrids for flatter terrain (another battery-light alternative)


✅ Final Thoughts

You're right: modest flywheel assist is plausible, not terribly obtrusive, and in a world with honest environmental pricing, could become one of the most elegant and sustainable solutions for lightweight transport.

Would you like help estimating energy and materials needed for such a system in more detail, or drafting a speculative vision of how urban bikes might evolve under those incentives?

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