Re: bicycle generator
 

I've been reading through this old thread and wondered what you might think of having lots of magnets around the wheel rim and coils placed close to them so the whole thing becomes the generator. Does that seem practical at all?

Super Magnets can be dangerous
 

LOL, I was just reading some of this thread.. I saw one my posts said,
"I think my next bike might need electrical assist.. I'll be 65 next month.."
That was the old days.. I'll be 78 next month!

Yesterday, I found my old Shake-to-charge flashlight.
It still works, but the tiny battery is on it's last legs.
I'm thinking about looking for a small Lipo-4 pack for it.
It might have a capacitor inside! I see one that looks a little like mine on Amazon. https://www.amazon.com/HaveLight-Nig...dp/B00NNYH814/


I think you could get some power out of some strong magnets on the rim. But, if the rim has a lot of iron in the steel, it might dilute the fields from the mags, into one big doughnut field.
Might work better with a non-magnetic rim. Aluminum or carbon fiber etc.
Anyways, if you alternate the N&S poles of the mags, you can get AC out of your coils. That means you will need a "Full-Wave-Bridge" diode array to get a good DC output.

~~~
Yikes, I just rubbed some real-strong-magnets on that old flashlight. It's staying ON! It's been on for 20 minutes! The battery is about the size of an aspirin.

Before, it was running out of power within a few seconds, after a few minutes of shaking.
Here a link to the mags I use..
https://www.amazon.com/gp/product/B08NJWM6YD/
If you are one of those guys who never read the instructions, DO NOT BUY these mags.
They are not safe to handle, without reading the instructions. I'm not kidding..

Hi Xringer, yes I'm feeling old myself. I was 80 last week. I have a bunch of the neodymium magnets. They can nip you if you're not careful. It seems everyone who makes their own wind turbine uses them. I think another problem is making the wheel run true as the coils need to be very near the magnets. If you've ever trimmed a wheel so it didn't bind somewhere you will know how hard it is to get it even near to true.

Making all that hardware and making it work right, Is something I would never try.
I wonder if it would be possible to create a thin-walled bike tire that you could load up with magnets (and spacers) inside of it?
Seems like you could get the pickup coils within 5mm or so.
Maybe design a coil loop that was curved inwards in the shape of the bottom of the tire.
(With the curved section as long as one magnet).
With the other side the loop extended directly away from the tire.

When I had my Novice Ham Ticket
 

Back in the late 1960s, the guys at the CD Ham Radio club couldn't get any 120AC out of the old gas generator. The IC engine ran fine, but no AC power out..
I asked if there were any magnets in the generator. They said no.
So, I sparked 12VDC onto the gen terminals.
They started the IC and the 120AC came on.
It worked fine after that.

It just needed a tiny bit of magnetism to start driving some current into the electromagnets (the 'fake' magnets).
My Zapping of the windings magnetized some iron..

I must have learned that when I was a kid.
We had portable gas gens on some of the fire trucks.
I did two years in the USN fire station on Bermuda.
Best two years of my life. Every other day off..
When I came back to the states, I had an English & Texas accent.

I can imagine why it was your best years:)
I got interested in electronics when I was 12. Built a crystal set and listened to the local factory delivery drivers. Soon got roped in to mending radios and TVs for family and friends and once I was working ( in a lab ) fixing them for workmates. I enjoyed doing it as they were much easier to work on then and you could easily get the parts. No chance now with tiny surface mount devices and multi layer boards.
Thinking about the bike-gen now I have a 3D printer I guess I could print something to wind the coils on if I had a go at it.

I'm not that good with electrical motors, but I think there might be at least 4 reasons:

1. Required precision of making/keeping the wheel's rim true, as mentioned above,
2. Keeping the magnets and coils in a compact housing (in the hub or external alt/motor connected via pullies/gears) reduces the rare/expensive materials needed,
3. Having the forces in the center vs on the outside... something about torque, leverage whatever,
4. Magnets on the rim will increase rotational mass, might not be that bad for smooth operation.

As xringer says an aluminium rim would eliminate the problem but also the speed at which the magnets pass the coils would be much higher than at the hub so that would improve the output I think. I wonder if it would be possible to have the magnets on a band which could be strapped around the the tyre, Let the air out of the tyre first, tighten the band then pump air into the tyre. That way the magnets would be on the top rather than the side so the coil(s) could likely stay pretty close to the magnets without the worry of trimming the wheel to run true.

Ahh forgetting this is an American site so aluminum and tire :<)

Haha, I read the 2 above post and never noticed the Englishness! Only when I saw this one, did I realize.

Yeah, between April 1963 & April 1965, I learned how to say, Vitamins, schedule & many other words.

But not aluminium. For some reason I learned to say it English style, when I was Del Rio boy, learning to speak proper Texan & Spanish.

I still have some of those old accents, but they have been contaminated by Boston Speak..

Pak da Karr in Havad yad and go haft a Beeya.
Translates to:
Park the Car in Harvard Yard and go have a beer.

Today, when I heard Mexicans talking, I can only understand 10% of the conversation.
But I can still understand 100% of the curse words.. :o