Building a more efficient bike [video] | Hacker News Reader

Building a more efficient bike [video]

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14 pointsDeathArrow16 comments

I forget my mech-e skills but those large oscillating masses (the up down linear motion) would seem to be hinderance to efficiency. In a bike almost everything is moving in a circle on a bearing, it's the legs that are inefficient.

Another thing is he's not really accounting for lifting the pedals like you do with clip-ins nor back forth motion you do when you get better at biking. I wonder what the torque curve of a trained biker looks like. I'm assuming a bunch of folks here have that in their training data set.

I'm just here reading HN in the shade outside relaxing after walking the course yesterday. :)

I doubt this will be a gain, too, but those masses are large in this crude prototype, but not necessarily in the final product.

At 30 seconds in, shouldn’t we reach 1/√2 or about 70% of the torque at 45°?

Also, the gain for such a new system will depend on how good are cyclists at applying force mostly at the points where torque is maximal. I wouldn’t know, but would think the net gain is smaller than what a model of “cyclists applies the same force all the time” predicts.

I also wonder about friction losses in this setup. Ignoring the additional chain (it can be engineered away in the final product), I would think those perpendicular gears and the rollers on the track will add significant losses.

With clipless pedals [1] it is possible to produce torque through the cycle.

[1] https://en.wikipedia.org/wiki/Bicycle_pedal#Clipless_pedals

Torque is never zero with these pedals.

A more efficient bike is already there. Just use right gear.

Also if you just wanted to broaden the time graph of when torque is applied around the crank circle, they already make oval chainrings for that. Although many people say there is no objective advantage.

Surprisingly that article suggests otherwise

> Despite wide usage, there is no proven advantage of clipless pedals over flat pedals in pedaling effectiveness, net mechanical efficiency, and muscular activity for both non-cyclists and elite cyclists.

[1] https://en.wikipedia.org/wiki/Bicycle_pedal#cite_note-Mornie...

Quill I prefer still. Because once I did jump high. Over the top, of the car from a cop. Blocking my way. Kicking the traffic wand out of the policemans hand, waving STOP in red over his head. Hard, From ABOVE! It shattered. Not that it mattered. Smooth landing, while standing upright, at about 80 kph, yeehaaaaw! Racing away uncaught, who would have thought?

They need no special shoes either, fitting into everyday life, why the strife with something that does neither?

Can anything be more efficient than a recumbent with an oval?

A faired recumbent with an oval and a regen direct drive motor as torque assist

Hard thing with bikes is they're so light, that regen and battery system will add significant weight and rolling resistance to the bike. It's a saturday so I'm not doing the math to see what the function for tradeoff is :)

Well the main problem with recumbents are hills due to higher weight and reduced aero advantage. The motor allows you to trade some rolling resistance for torque assistance

Rolling resistance is a function of tyre and road surface, not weight.

On a flat course, weight only affects acceleration (which the motor helps with). Once you’re at a constant speed, weight is a non factor and it’s all wind resistance.

I'm an ideal system yes. But I'm fat so if I don't have my tires well or over inflated they're almost flat at most speeds on a road bike where you might be just on the ideal edge. So rolling resistance will be worse for me than I due to energy lost folding and unfolding the tire

The extra system weight is inconsequential compared to your additional weight in this instance.

I live in seattle, my entire commute is either up or down hill

> Rolling resistance is a function of tyre and road surface, not weight.

Except the contact surface between tires and the road depends on tire pressure and weight (because it affects the shape of the tires on the road).

Increasing pressure can compensate for weight, but only up to some point, and increasing pressure also make the tires more rigid, which makes the cyclist spend much more energy to actively (albeit subconsciously) dampen the vibrations coming from the road (while most of this is done passively by the tires when the pressure is at the optimum level).

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