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Comment by kowbell | Hacker News Reader

My partner just got a rowing machine that offered "watts" as a unit of how hard you're going (like "calories" or "mph") and got me wondering if they made rowing machines that could slowly charge a battery, and how much I'd need to row to power one of them fancy newfangled M5 Max MacBooks answering prompts.

All that to say, CrankGPT, I am your target demographic and if you don't respond to my request for a demo I'll be cranking my keyboard with bad reviews online. Or cranking a rowing machine that powers an LLM to do it for me. Wait...

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For reference, this is what 700W cycling looks like: https://www.youtube.com/watch?v=S4O5voOCqAQ

1hp/750W or so sustained is insane power for all but a few and that is still for relatively short time periods.

1HP sustained is not insane for a horse. A human OTOH is a very different matter.

1HP is actually ~5 horses. There was a test trying to measure it.

https://youtu.be/7qxTKtlvaVE

Other way around, a horse does more like 5-15hp

Yes, you’re right. My mind is foggy apparently.

Thanks a lot. Unfortunately I can’t edit it anymore.

They don't make them like they used to

One horse power is the rate a horse can sustain while working hard all day long.

I can do 300W for 30mins - does that mean I can barely heat up a Pop-Tart?

Spend 30 minutes charging a battery and you should have enough energy to turn any flavour of pop-tart into carbon flavour.

Even without a battery, I could easily imagine designing an efficient single slice toaster that could handily brown a pop tart on a 300W budget.

You wouldn't need any sort of fancy toaster: anything small, rated >= 300W, would deliver cyclingpower from a rider of any skill.

That actually could toast a few batches of Pop-Tarts.

If you like then "golden," perhaps the entire box.

For more reference how insane 700W is, the average FTP of a world tour pro road cyclist (i.e., Tour de France) is ~350-420W/6-7W/kg. FTP (Functional Threshold Power) being the avg you can sustain for an hour without fatiguing.

My own is ~250W @ 3.12W/kg. I can't even hit 700W yet, let alone for over a minute. My 5 second power is ~640W.

Crazy numbers.

Can you still touch your toes? I doubt Robert could... hopefully your own practice leaves you more balanced.

Haha, yes. Track cyclists are a different breed.

> Haha, yes. Track cyclists are a different breed.

Lost the opportunity to say "bread".

A trained powerlifter probably exerts a few kW on a heavy lift, but only for a second or two.

~3000 watts for 0.75 seconds (not counting pauses)

Talakhadze's 267 kg clean & jerk from 2021 is somewhere well north of 5kw output (I can't find hard numbers, but possibly even like 7kw) for fractions of a second during the second half of the clean. It's wild stuff.

I am a nerdy blue collar electrician and that was incredibly interesting. Only 0.002kWH from that beast of a cyclist.

I would suspect my equivalency to be about 1/3rd a Robert [unit of measure from vidlink].

I'm sure he could have generated way more total energy if he wasn't trying to get get that max power.

Absolutely – he could'a toasted the entire box if he'd'a paced himself.

But that was great youtubes.

I took several biomechanics classes as electives back in my undergrad, and in one assignment I remember comparing the energy outputs between the human and robot equivalents of different tasks, whether or not the robot was humanoid in how it was designed. The most impressive think that stuck with me is that humans are incredibly efficient, from an energy perspective, in anything we do, compared to machines. Every time we delegate a task to a machine, we are using several orders of magnitude of energy to do the same thing. For most tasks, it feels wrong, but it doesn't make me any more willing to give up my car. Maybe if I lived outside the US.

If you live in most places in the US other than the urban heart of a few very large cities you have to take a huge hit to your ability to get places in a reasonable time frame without a car. I have hope some more cities other than NYC are improving the situation, but as it is the closest I got to using public transit for a commute was when I was going to one of our other offices in a different downtown area I would drive my car to the park n ride to take the train the rest of the way. The train saves time and sanity because traffic downtown is a nightmare, but that drive takes 5 minutes, and it would add 20+ minutes if I had to walk to the closest bus stop so I could take the bus up to the train station.

If you live in most cities in Italy you have to take a huge hit to your ability to get places (in a reasonable timeframe or at all) if you must do it with a car.

"Every time we delegate a task to a machine, we are using several orders of magnitude of energy to do the same thing."

Might this just be selection bias? I mean, if humans can't do a task efficiently, we're not going to do the comparison with a machine.

Some actions we do seem (to me) very inefficient when compared with machines. For example: grating carrots and brushing teeth.

There's a difference between consistency and efficiency.

I read efficiency as "Energy inputted to accomplish a task", in which case, biological systems are far more efficient than current-day mechanical ones. It's a tradeoff.

No, it's evolution. Mammals burn a ridiculous amount of energy just existing, so evolutionary pressures tend toward more efficient muscles and body geometry.

Electrochemical reactions in your muscles combined with the mechanical advantage from the geometry of your joints and ligaments is simply more energy efficient than most mechanical or electromechanical systems. On top of that, our learned and evolved kinematic algorithms result in vastly more efficient control. Humans tend to be pretty good at using only exactly as much energy as required for a given action. Overshoot is quite limited compared to robots.

Your suggested actions seem inefficient, but if you look at the actual energy expenditure, mechanical means are much worse simply because mammalian muscle is so efficient.

Unfortunately, humans want houses and cars and vacations and such, which makes them very expensive. ;)

Yessir! I even used AI this week, so I'm adding to the energy death of the universe way faster than if I had done something else. Not to mention my car and other things...

These GenZ kids and their whole "Entropy is sin" thing.

If you're comparing raw calories to output, yes. Even gasoline has a caloric value, but humans can't drink gasoline. Growing and preparing food for human consumption uses a lot more energy than pumping and refining gasoline, so at the end of the day, human efficiency gains are not that impressive.

that's a misleading equivalence because you're also not considering the energy it took to grow the plants that produce that oil millennia ago. perhaps comparing to biodiesel or alike would be better. but even then it underestimates the efficiency of the human body, because food contains not only the energy we use, but also the materials to build the body itself. so you'd need to account for the inputs into that biodiesel and then all the extraction of materials and production of the machine itself. biology is amazing

You also need to consider the energy released during the big bang as a prerequisite for creating that food and gasoline. The big bang released about 10^70 J of energy, roughly equivalent to eating 10^63 big macs

> The most impressive think that stuck with me is that humans are incredibly efficient, from an energy perspective, in anything we do, compared to machines.

Humans are efficient, but not across the board. Trivial counterexample: walking is incredibly energy inefficient vs a bicycle or other wheeled conveyances whose primary dissipater is rolling resistance.

That's a strange comparison. Wheels are incredibly limited in the type of surfaces they can be used on.

> That's a strange comparison

It's not strange at all, I was responding to a specific, incorrect claim. I even quoted the wrong claim in my earlier comment , and I'll repeat it again, with added emphasis

>>> humans are incredibly efficient, from an energy perspective, in anything we do, compared to machines

I simply provided contrary evidence to a well-defined, falsifiable claim. How is that strange?

Yes, but walking and moving on wheels is oranges and apples. It would be a relevant comparison if a robot with a movement mechanism based on two feet was more efficient than a human.

I’ll admit, at first, I thought the human vs machine comparison was about humanoid machines. But that’s too narrowly defined to be a useful comparison. Most machines in use today are not humanoid.

Then to boldly claim that humans are more efficient at anything compared to a machine, just does not follow.

The parent comment is quoted as:

> in one assignment I remember comparing the energy outputs between the human and robot equivalents of different tasks, whether or not the robot was humanoid in how it was designed

So I think the point in this context is relevant, even if it's apples to oranges.

The point isn't that a humanoid robot walking is less efficient than a human walking, is that moving on a wheel is not the same thing as walking. For example, using wheels is not only less efficient it is barely usable for climbing rocks, going up the stairs and many other surfaces that makes the comparison irrelevant.

You could say that a robotic gun is much more efficient than a human in killing, that's another easy easy comparison of different tasks where robots win, but it totally miss the point.

You're not wrong.

But annoyingly pedantic.

Doesn't seem pedantic to me. It's responding to the central thesis of the parent comment.

We're still pretty efficient while not having wheel shaped limbs. Running like humans works pretty well. So well even that we can chase a lot of animals longer than they can outrun us.

There might be more efficient ways to move but we are pretty well equipped by evolution.

> We're still pretty efficient while not having wheel shaped limbs.

Agreed, but it was gp that brought up the human vs. machine efficiency argument. Machines can have wheels.

Now compare human on bicycle to human driving a car for energy efficiency.

> humans are incredibly efficient

Humans cannot fly.

The efficient mode of transportation is a human on a bicycle.

I have the opposite idea after reading physiology books. The number I remember was 22%, for efficiency of a human being as a motor, driving pedals to create mechanical power. That's quite poor compared to an electric motor. And unless you want your fuel to be high-fructose corn syrup, your fuel is inefficient to make as well.

... at 1:03 he hits steady 700W. At 1:29 shows they kept increasing the incline at least to 40 degrees. Why not keep it at the same incline? . . .

It was hard to see from the video, but I suspect the machine he was on increases resistance as pedal speed decreases to try and keep him at a constant output.

That's a pretty common device for elite fitness testing.

When I was 11 or 12 I powered an incandescent bulb with an exercise bicycle. I think it was 40 or 60 watts. I can totally understand why that guy was exhausted: 60 watts wasn't hard for me, because I used to ride uphill every day after school, but the other kids could only get a dim glow.

It’s basically well known to cyclists that training with a power meter that tells you “watts” more accurately gauges effort and caloric expenditure. (Heart rate gauges subjective effort however, taking into account stress, caffeine intake, etc.)

It’s also interesting that the industry has settled on using watts to mean rate of useful work whereas calories to mean the total work including inefficiencies, despite that calories is just a unit of energy. A rule of thumb for cyclists is that in addition to usual unit conversions, the “calories” figure should be multiplied by four to account for energy expended by the body but not used for rotating the pedals. I don’t use rowing machines but I’m sure they would have a similar conversion factor in order to calculate calories.

You can get a dynamo hub front wheel for push bikes: https://bikepacking.com/plan/dynamo-hubs-lighting-charging-g...

However you can expect around only 3 watts of output at normal speeds and you will need to put in around 5-7 watts of power for the same speed. This is barely enough to trickle charge modern phones.

Annoying. Blame the Germans and their lighting laws for bicycles. I want human powered USB-C with enough oomph to power a modest sound system or lights, whilst charging my phone. The allure of USB-C is what interests me, but 3W is not much to work with. Also annoying, no rear dynamo for my bike, so I can't even double up to 6W.

I will probably end up with no sound system and just expensive dynamo lights, using a USB speaker that doubles up as a power brick.

There is a nice USB battery kit for dynamo that fits in the steerer, so it is soldering iron time for that, so might as well learn how to do USB-C power things.

One day there will be structural solar panel batteries that can be 3D printed into lightweight bicycle frames, so maybe I will stick to throwaway lights until then!

> power a modest sound system

please don't inflict your music on everyone around you.

A literally modest system would center around headphones. :)

So, 72 decibels in a car is fine, with that just being noise pollution, not even music?

And there is you on your high horse telling me this?

How patronising!

Some of the bottle style ones claim to go up to 6W, they would also be easier to double or triple up. They are not nearly as nice and efficient as the hub dynamos though

> offered "watts" as a unit of how hard you're going (like "calories" or "mph")

It's the only unit that makes sense tbh

> got me wondering if they made rowing machines that could slowly charge a battery

The Concept2 rowing machines can power itself using the power you generate by rowing, so we're partly there.

The "Low Tech Magazine" has a guide to building a DIY bike generator https://solar.lowtechmagazine.com/2022/03/how-to-build-a-pra...

Unfortunately even with the bike it seems like you really need to find one machine that can be repurposed, a rowing machine seems a bit of a stretch.

Soon enough we will see rowing machines rated in max TFLOPS.

We already get TFLOP per watt so you can compute how much flops you are doing while cycling

A fairly untrained cyclist is usually able to maintain 200W, so yes this is definitely possible

And a good sprinter can make some toast!

I'm still sour they had only one toast in, in a two slot toaster

I've had the same thought and it's been a topic I've been this close to talking about at parties. If I did I'm sure I'd bore everyone to death.

Considering the difficulty of sustaining 700 watts vs 350 watts, we could've had some very well-burnt toast if they uninstalled the heating coils for the 2nd piece of bread!

I thought toasters took ~1.6 kW, just like any other resistive heating device (space heater, oil-filled radiator, microwave oven, oven oven, hairdryer, kettle, under-sink water heater: it's allways 1500-1850W!) except for the ones on special circuits (shower, stove). Turns out, our toaster draws 850W!

While watching the video, I was wondering how they modified the >1kW device to produce a toasted toast in that short amount of time (I guess you could substitute instantaneous power for time up to a point, but the video wasn't that long), thinking maybe they removed one of the sides' circuits. Now I'm disappointed as well. Thanks xD

Woah there, gotta watch that waistline! :)

My best is 980W - for 1 second

That's solid. If my memory is correct, and my teachers were correct (both of these are suspect) back in high school, a human should be able to momentarily exert about 1 horsepower at maximum effort. We did an experiment on how much power we could output at maximum effort. We tested it by sprinting up some number of flights of stairs, and timing it. As I recall we did conclude that in round numbers the hypothesis was correct.

But that was 35 years ago and it was a high school physics experiment meant to be entertaining more than precise.

An untrained cyclist is not able to maintain 200 watts.

For an average untrained male cyclist who is 175lb, they should be able to maintain 1.5-2 w/kg over an hour, or 120-160watts. A beginner cyclist who's been cycling recreationally over over a year should be able to attain 2-2.5w/kg which is 160-200 watts. A recreational cyclist who's be training for several years should be able to maintain 200 watts.

Trust me, I'm a cyclist, and I cycle with a power meter.

As an average male who is ~175lbs and untrained at cycling, this is hugely validating for my terrible idea; 140 watts is the max charging speed for 16" M5 MacBooks. I can finally stop thinking for myself and have my computer do it all for me, powered by my big beefy legs.

140 watts is the FTP. That means you can do it for an hour, and it will be an extremely exhausting hour and you will want at least two days of rest to recover from this workout before doing it again.

If you are not chasing watts, it’s much more sustainable to do 70 watts for two hours. You can probably do this every day.

This exactly. FTP is functional threshold power, it's the maximum you can physically maintain in zone 4 heart rate for 40-60 minutes and it's physically exhausting. This is hard work, hardest work honestly. If you have gas left in the tank after you could had a higher FTP. I'll get out on the bike and do a zone 4 workout and keep a steady state of 180-200 watts through the first 20-30 minutes, by the end of the hour or hour and a half of my workout, even with breaks to break, reset heart rate, have some water, salt and glucose, I'm down to 120-150 watts at the end of the ride.

Basically, you can probably charge your macbook at peek power for an hour every other day, or every day for a short while if you're okay with burning out eventually.

Expect to need to eat 400-600 calories and a lot of water each time you do this.

Just one more follow up and I'll be done, promise. The average power output (FTP) of someone on zwift, a indoor cycling game, is a whooping 185 watts.

I just rode with an untrained cyclist (new to cycling) yesterday. The person averaged 80W over five hours. It’s about right for an actual untrained cyclist.

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