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Generating Power¤

It's not a totally off Idea, there are devices on the market:

Amazon offering

First attempts with my neodym magnets and some coils were a bit ... demotivating.

Embarrassing Attempt

But in YT University I found these - more below:

YT Builds¤

The idea is simple: Buy a motor - but use it as a generator. All of the YT builds I found are doing this.

Gene's Greenmachine¤

https://genesgreenmachine.com/

Components: See video above, trivial:

Everything here: https://genesgreenmachine.com/best-design-diy-bike-trainer-pedal-generator/

Hyprid E-Cycle¤

Here a real freak, which also does it, using a bike motor: https://www.youtube.com/watch?v=7hfClQh3rxM

The actual motor for the ebike he built himeself...

Scooter Motor Build¤

Parts...

500 Watts Build¤

Bicycle Generators¤

[2022-04-13 11:20] Opening YT - then this is offered:

A whole collection about the subject:

Incl. website: https://pedalpowergenerator.com/shop-pedal-power/dynamo/

Our Own Build¤

Possibly needed: Shaft Coupler: https://www.amazon.de/dp/B06X9RS6D6?linkCode=gs2&tag=gensgremac05-21&th=1

Motor: The only one available in the household was from an old electric drill:

Close match:

https://www.amazon.com/RS-550s-18v-Electronic-Controlled-Replacement/dp/B00TE42PME

Spec: https://m.media-amazon.com/images/I/81-5JDOeJ8L.pdf

233.725 Watts. No Idea how long, until it burns through though.

Such drills can generate a lot of torque, might be comparable to what I can do with my legs. So, maybe it would survive, ampere wise, when I load it with my legs => Lets try it.

Positioning / Coupling¤

That's not obvious. I tried a few alternatives:

Position One: Wheel 1, Direct¤

Motor axis (7mm dia), directly coupled to first wheel of the drive:

At this point I get 4Volts at normal pedal speed:

Means: I'm not (yet) Robert, so I guess 100Watts is realistic => 25 Ampere... => That will kill the motor.

Ups, actually, maybe not, see spec again, >40 amps at "stall"

Position Two: Belt¤

The fly wheel is translated to around the double the speed of wheel 1, i.e. I'll get higher rpm here - but I need a drive belt, can not directly couple

Trying this point, using black tape as a belt:

Result: 8Volt (until the improvised "belt" ripped apart)

But that is still 12 Amps. at 100W input.

Again Spec:

Motor stall – In electric motor understanding for both AC or DC, we will meet torque, where torque is the ability of the motor to maintain its inertia force. Stalling is when the motor stops rotating because the load torque is greater than motor torque or breakdown torque characteristics. In a simple explanation, motor stall means the electric motor is overloaded and the motor can’t produce more torque to keep rotating.

Bigger problem yet: The drive belt, required at position 2.

Checked the market and I did not find thin enough belts for being able to keep the manually shifted permanent magnet where it is mounted out of the box - at its axis some 3mm away from the flywheel:

Position 3: Direct Coupling With Fly Wheel¤

For this one I built a prototype, in order to finally generate some real power with my feet...

You can, at this position, not directly couple the 8mm motor axis with the flywheel because of the radius of the motor housing colliding with the first gear wheel. I.e. you loose a lot of RPMs by increasing the motor axis diameter.

Was relatively simple to build - only challenging thing was to drill an exact 8mm hole through the plastic furniture roller wheel, so that it is well balanced (thanks Alex ;-)

Material is from here.

The white soft rubber coating coupling with the flywheel is from kitchen equipment, some sealing. I had to connect it with the black wheel, using double-sided duct tape, so that it remains on the wheel.

Findings¤

Good:

  • Runs supermooth. I do not feel it with my feet, while pedalling, no shaking or stuttering whatsoever.

  • Is mechanically stable. I write this after pedalling for an hour, with high cadence. It's not degrading. BUT(!) there is not yet any resistor attached, I'm just turning the motor, w/o load and check the volts.

So so:

  • Not sure if the coupler can transmitt the torque at 100 Watts..

Bad:

  • RPM:

The wheel is increasing the diameter of the axis from 8mm to 4.5 cm. Means: I loose over 5 times the RPMs (i.e. Voltage). When I pedal es fast as I can I get barely over 4.5 Volts. Normal cadence: 2-3V. I won't be able to power anything w/o ruining the motor, with too high current, at say, 100Watts.

"Will have to check if there are motors which have their best perf at around those RPM."

Edit: Stupid me - Think about it: How can more Volts at same RPM be done? Yes - geometry. Bigger motor...

Wich means: Yet more distance from the flywheel....

And the other solution, more current tolerability through fatter wires inside: Again bigger motor, at same amount of loops.

Seems a principal problem at this position 3.

  • It's loud. Awfully loud. No comparison to the zero volume pedalling against the magnet brake.

Here is a recording:

The needle is at 3.8v - hard to see (why ditch a fully working multimeter, just because of digital ones better in, well, ... anything?)

Motor is only having contact with rubber:

-> Not much to optimize here.

Have to think about that.... Can I reduce that noise??

Here links to the other builds right while pedalling - they all are pretty loud:

I keep cycling a few days and see.

Electronics: Which Motor is the Best Generator¤

YT finally realized what I'm interested in, getting good suggestions - instead of free energy crap...

Great Scott has it all:

https://www.youtube.com/watch?v=cJ_vDA7xsGs

So there are geared motors, for my position3 problem above:

- but lousy efficiency!

  • DC Motors are the worst option (brushes => wearoff)

  • Simple no worries: Stepper motor

  • Complicated but professional: BLDC Motor with a gear box

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