Human (& banana)-powered makerspace tools

General CNC
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Hola amigos!

In Medellín Colombia, every Sunday the city closes off major streets to cars and has “Ciclovia” - people and dogs are welcome to run, walk, bicycle, rollerblade, & dance their way around the city - a great way to encourage exercise, and meet healthy people. Along the route, there are vendors selling fruit, juice, empanadas, ice cream, dog treats, and more.

From time to time I’ve noticed Maker Space technology in the streets! For example, I saw a man with a galvo fiber laser, on-demand etching metal dog tags with dogs’ names! Such a great idea! On the technical side, I saw that he’s running a small gasoline-powered generator to power the laser. That part, I don’t love, because it contributes noise & smoke to the environment.

It got me thinking, what is the “state of the art” of bicycle-style electricity generators, and how much human effort (and bananas!) would be required to run my CNC router stack in the Ciclovia. I know there’s a fun math problem in here, so I’ll try to lay out the gear, and I’m hoping some of you can help me figure out how feasible this would be.

(1) Computer (“small form-factor” Dell Optiplex, Intel Core i5; could also use a laptop, MacBook Pro from 2022’ish)

(2) LCD screen - 21" (could be replaced by laptop)

(3) CNC router - 500 watt spindle + CNC motors

(4) Vacuum - small “shop-vac” style.

(This part I am unfamiliar with, but taking a guess)

(5) 2+ stationary bicycles, with a motion–>electricity generator

(6) Solar panels

(7) Batteries

(8) Energetic / athletic clients :slight_smile:

(9) Bananas & fruit juice as fuel

Who can help provide some napkin-style energy calculations, and perhaps suggest equipment ideas for the power generation / storage equipment?

I hope you all find this an interesting exercise (pun somewhat intended) - it contributes to the macro idea of an “off the grid” maker-space (think: space stations, underwater makerspaces, use your imagination!)

Have a great day!

// JRO

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I think I see a problem here…

Looks up watts of power that cyclists can expend over a significant amount of time. Even elite cyclists would have trouble here. You could use bicycles as a novelty here, but you’d need more of the batteries and solar for the real grunt.

LiFePO4 batteries are safe but heavy. Li-ion batteries are more powerful for weight. Sadly, those tend to be in 20V or 40V instead of 24V or 48V multiples when you go above 12V… But if you have a 48V spindle, you could run it at 40V and it just won’t turn as fast; you’ll have to adjust your feeds and speeds to account for that.

To use bicycles with generators as part of your system, you need to work out how to get some electricity out of them. Did you have something in mind?

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I live in South Africa and our mains supply is epically bad.

I’ve converted my CNC to 24V using SLA batteries and BLDC model airplane motors. Converting to different voltages is easy.

I aim to cut both wood and aluminium and do some laser ingraving with a diode laser.
I’m still getting the whole thing operational.

It’s been a steep learning curve - especially getting the ridgidity I need for aluminium to make the parts I need.
You need to save power wherever you can… according to Google, elite cyclists can sustain 400W for an hour. I would struggle to generate 100W for a few minutes.

Float charging batteries using cyclists and solar panel is possibly a good way to go. I float off mains and can keep running for two hours or so.

Can you pre-fabricate some of the parts and leave customisation and engraving for the field?

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I wonder about a 50/50 solution…

Have the CNC part running from a battery (the 24V controller on my small CNC 'only; draws about 1 amp when all three Nema17 steppers are energised. That should be runnable for several hrs from a pair of batteries, and is pretty ‘conventional’.

Then, you need some sort of mechanical drive from a fixed bicycle to the spindle… which is the fun part. Basically you need to peddle to do the cut; and of course peddle fast when the spindle is ‘on’.

I can see numerous problems… and many broken bits etc. But it could be quite a ‘fun’ thing to build and would certainly attract a audience. Basically ‘your name tag will be as good as your peddling’.

There are various ways to transfer a mechanical drive with belts etc. But using a 'flexible shaft of the sort you often see in DIY shops plus a pulley and belt in place of the rear wheel on the bike is probably a good place tostart.

For added fun; get a tandem. Turn it into a family sport.

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I used to have a rowing machine (Concept 2) which had a Fish video game on its digital screen - you navigated the pixel fish up and down to avoid sharks, by varying your rowing speed.

The bicycle-powered spindle could have a speed target, that matched the last G-Code “M3” setting :joy:. Yes to the tandem bike.

I like idea of an “power’s out, still gotta make something” maker-space capability, and could come in handy for emergency situations.

Thanks for sharing the information about human wattage - impressed by how efficient we are!

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One of my offspring rows crew, so I’m familiar with that game — though only that he ignores it on his erg because it’s not compatible with his workout needs as a serious rower… :grin:

I have a 12V 20Ah LiFePO4 battery for ham radio operation away from my home station. It can source 240W for an hour (it’s a 1C battery). If you have a 24V system, you could put two of those batteries in series and get 480W for an hour — and normally the spindle isn’t actually pulling full load. If you do that, separate them and charge them separately so they don’t get out of balance.

You could top the batteries off using a buck-boost converter from a rectifier driven from the bike, but I would suggest that a bike-powered vacuum is probably a more visceral experience. :grin: And it is lower impact if people can’t pedal perfectly…

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I will note that for a while, folks were trying out the battery-powered compact trim routers as spindles (it was an easy way to get a brushless motor) — it seemed to work well (for folks who had the option of swapping out the battery at tool change for one fresh from a charger).

Running the stepper motors/controller is far more workable as noted — perhaps a drag knife/pen plotter?

That said, I am looking forward to buying a human-powered lathe:

and do use by preference a small human-powered tablesaw (as has been noted in other threads):

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@WillAdams that treadle lathe looks wonderful, i must confess to being somewhat jealous :wink:

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No need to be jealous yet — I still need to get it past the finance committee — my argument is it costs less than the various gym memberships and exercise gear my wife has bought, but never used to their fullest extent.

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