Has muscle-based power generation been nerfed/removed?


#1

After two days of not playing I went back into my current world where I have foot cranks hooked up for power generation, and have discovered that I can no longer start pedaling to generate power. As such I’m wondering if it’s been altered for more requirements to function or removed altogether?


#2

You can no longer hook up most alternators to hand or foot cranks.
There’s IIRC one specific smaller generator that does work, but the remainder were basically an exploit, because a standard car alternator takes in excess of 1HP to operate at nominal production rate, which is not the kind of output a person can produce.


#3

Even a mutated superhuman?


#4

Is it the one found on electric bikes?


#5

I’m already being super generous and giving you 1600 Watts of power on a footcrank to start, plus 140 W per point of ST over 8 You can actually power a car alternator with 1500 W, it’s just maximum effort for a normal human.

Manual engines produce 45% of their maximum output at safe levels, so ( 140 * ( ST - 8 ) + 1600 ) = 1500 / 0.45, solve for ST, and you need ST 21 to crank a car alternator without strain as a mutated superhuman.


#6

Some very rough numbers says no.
http://sustainability.blogs.brynmawr.edu/2012/07/31/understanding-energy-part-1/
http://mapawatt.com/2009/07/19/bicycle-power-watts/

Peak sustained output for a world class athelete seems to be something like 430W
“The world record holder furthest biked in one hour, Ondrej Sonsenka, generated an average of 430 watts during his ride of about 30 miles.”

“There are about 746 watts in one unit of horsepower.”

So sustained human output maxes out at roughly 0.5HP, you’d have to double that to be able to achieve it at all, and even then you’re working at “world record attempt” level, not, “casually recharge my batteries” level.


#7

I don’t like “cannot” in this game, lol

IMHO one should be able to attach car alternator to pedals, but it should work with reduced output (to match human power x efficiency, or equall to that “one specific smaller generator that does work”). if you run alternator with less rpm you get less power, but you also need less power to run it.


#8

It reminds me of a scene from Breaking Bad,where they’re stuck out in the desertand their RV/lab was out of power. They hand cranked for several hours to try to get enough power to turn the engine over.

That wouldn’t really be practical from an apocalyptic survival situation if you’re trying to keep an eye out for predators and such. Way too time consuming for little to no real payoff.


#9

Feel free to recode vehicle::power_parts() to have a sliding scale of alternator efficiency. I’m happy to give advice on how to do it and I’ll support the resulting code. I’m not going to write it myself.

It looks like almost all modern alternators generate an alternating current and rectify it to DC. Given that your car alternator expects a 5,000 RPM drive shaft, and you’re not going to be handcranking it that fast, the rectification is going to be pretty choppy and inefficient. But that’s an implementation detail.


#10

Car alternators are not the best thing to rely on, especially in settings like in the game, as they actually need electricity to start generating electricity. Bicycle alternators however, together with those, used in portable wind or water generators use static magnets and thus do not need so high RPM. I have one such, that works at 500-1000RPM and gives about 10-24A at 12V. With a 1:11 reductor and a flywheel i managed to keep it half-loaded (~14A load, or ~80W) for a hour and win a bet without actually forcing myself to much.


#11

There is a bike alternator that I added to the game, that draws 75W to produce 36W, so I’m familiar with the concept.

My EE days are far enough in the past that I don’t really know what happens if you attach a bike alternator directly to an engine crankshaft and run it at 10x the design input power. It might up the output power to 360W, or it might break the rotor from too much centripetal acceleration - I suspect closer to the latter.


#12

Unlike car alternators bike ones are synchronous motors with static magnets on the rotor used as generators (can work both ways). This means that while theoretically output will increase practically you will most likely burn the wire in stator coils long before reaching their mechanical limits.
The one i was speaking about was not bike one, it was much larger one, vandalized from… let’s say “military appliance”.


#13

We are expecting that this is something the survivor is capable of patching in, along with something to prevent them from overdriving and burning out a low-spec alternator.


#14

Believe me, math is enough here. In the example it could have been impossible for me to go over around 1/2 speed/load (~500 rpm for a dynamo that works optimally at 1000RPM). As for rotating by other means it had simple, but efficient purely mechanical system to prevent overspeeding in it’s original form that can easily be re-implemented if using as portable hydroelectric plant for example.


#15

A bunch of you guys are saying a bunch of numbers and stuff I do not understand.
I’m confuzzled.
Don’t try to explain it better to me though. It’s just be a waste of time.

I didn’t actually know this was a thing in the first place so that’s interesting.


#16

I actually think I can help you here redlaser.

Basically it’s the difference between a helicopter and you’re ceiling fan. The hardware isn’t built to really handle the power of the other. So your ceiling fan would break if attached to a helicopter motor, and a helicopter rotor wouldn’t turn if it was attached to your ceiling fan motor.


#17

I may be missing the point, but i feel like i need to throw out something we use in the auto field: underdrive pulleys. They allow turning of pulley driven accessories (such as an alternator) to allow the same nominal performance of the accessory at lower hp draw to the engine. (Or legs if applied to the human driven object)

Which actually is essentially what a transmission could do as well. But all of this is above the scope of the discussion i assume, correct?


#18

I would be 100% fine with a recipe that adds parts to an alternator that allows it to be driven with lower mechanical power and lower output.


#19

I am a little confused on the underdrive pulleys: I’ve got an alternator that takes 1.5 kW of kinetic power to drive and outputs 0.8 kW of electrical power. I might be able to drive it with less kinetic power, but it’s going to output less electrical power, too, right? 2nd law of thermo and all that.

That’s what we’re talking about here, driving a 1.5 kW alternator with a pair of foot pedals that are realistically putting out 0.1 kW. So we need the sliding scale stuff I mentioned upthread. Which I looked at doing today while I was fixing another bug in that part of the code, and it’s modestly complex bit of code to cover a rare corner case. Or we can do what we do now, which is a 1.5 kW alternator stops the engine if you try to drive with a 1.2 kW input - which isn’t totally realistic but isn’t absurd, either.


#20

Yes. Using underdrive pulleys can be tricky, its a balancing act, but there is that sweet spot.

The basic idea was to use less power to drive the alternator but still create enough useable electricty from said alternator for it to be a viable option.

I had a thought of using pulleys/gears set up to basically overdrive the alternator (like a transmission) but that may be too complex for a survivor.

Kevin seemed to like the first option. So that alone can add some options and flavor for power production via human legs. It is the simplest option and easiest for a survivor to pull of succeasfully.

Edit so i guess I added little to the convo then, LOL i apologize.