Electric Bike Axial Flux Generator and Motor

[chirpbear]

The chinise have over 120 million axial flux motors on bicycles. I am making a motor for the front wheel and an altenator for the back wheel. Where can I get the right coils and magnets?

[Flux]

China?

[TomW]

chirpbear;

Most of what is done here is done from scratch.

Magnets are bought to fit the design. Usually from China.

Coils are hand wound to fit said design.

A motor on the front with an alternator on the back charging a battery or driving the motor will not really add any range from battery power if that is your plan and in fact will have losses for several reasons.

Perhaps you intend to pedal the alternator to charge batteries when stationary? This would work.

Tell us more. Lots of smart folks here that may have a few ideas for you if you elaborate a bit as your plan is rather vague on the actual goal.

Tom

[fabricator]

LOL, perfect Flux.

[REdiculous]

It sounds like he's wanting to build from scratch. Way cool!..

I think the least we need is the wheel size and target speed. The inflated diameter will give more accurate results than the rim dia. From that you can figure out the max rpm you need your motor to spin. I think that would be a good place to start.

Just for a quick reference; at 400rpm a 20" wheel* will want to be traveling 23.7mph, a 26" wheel wants to do 30mph and a 16" wheel likes 19mph. (* most 20" bike wheels don't measure 20")

It seems like 400rpm ought to be enough for most so maybe that's a good target. My guess is he'd want a peak near 1hp, especially since I'm assuming larger tires and a higher top speed.

What would that take? I dunno. Can it be built into a wheel easy enough? Not in my shop, for sure...have a good one!

[thirteen]

as  a side note a sheriff is making the people in jail pedal bikes that run the power for the TV.. Sounds like a good idea. Maybe they should get all of them to do it and get ride of our demand on oil. Just a chuckle.  

[chirpbear]

Hi Tom,

The electric bike motor is for going without peddling. The generator is for going down hills, big ones would be best. A bike with just an electric motor is very cool. I want to build a bike motor from scratch. You can buy one from China on ebay but that is no fun. I got my wife one for Christmas and put it on a new bike for her. She loves it and rides it to work. It is a wilderness 36 Volt and has 3 12 volt seal lead acid batteries on the back rack with a controller. The motor is on the front wheel. It goes 25 mph... PLENTY FAST. It gets 15 miles to a 4 hour charge on flat land. I have a machine shop and do specialized injection molds and molding. We should be able to beat the Chinese at this game. I am a good designer and machinist, just need some guys to help me with this project. I have been following Otherpower for years and love it. I can send a picture of my wife Anne on Christmas Day with her new Bike by email because I do not know how to do it here.

Chirp Shannahan

410 200 5006

[chirpbear]

Hi REdiculous,

Your calculations are right on! I want to keep this at 1 hp. 36 to 48 volt. I have seen some designs for motors but do not know how to fasion the coils/phases/magnets. I am sure it will take a little work but I want to do it. The motor would be in the front hub and looks like a drum brake on a motorcycle. What size magnets would I need?

Chirp

[chirpbear]

Hi Flux

I have been reading your comments for years. It is nice to say Hi to you. Yes China has done jumped up and gone crazy with the axial flux motor on bikes. I want to do them one better. Would you like to join me?

Chirp Shannahan

 

[REdiculous]

I'm a dummy when it comes to motor design or I'd help for sure. I get the basics, just haven't actually made one yet.

400rpm is a good guess though?

Oh, I've heard bad things about front wheel motors...definitely don't use aluminum forks. have a good one!

[Bruce S]

chirpbear;

  One place you might look into would be posts by Windtstuff -Ed, his wave windings are what the early hub motors used and is what the 48Vdc motor uses with very high efficiency. From there you'll be able to begin designing your genset.

Cheers

Bruce S

 

[Flux]

I think it will take a lot of effort to build something to compete with the commercial motors. I am not even sure of the best configuration but somehow I suspect it would be radial with magnets on an outside drum and a smooth laminated core with coils stuck to it. Possibly you may be better off with slots but I am not sure you gain much and you have to be careful with cogging and reactance.

The main motor bit is very similar to a windmill generator but you still have to deal with the commutation problem. There are no doubt fairly crude and simple circuits but for something respectable I can't help feeling you are into Hall sensors and H bridge drivers, not a field that I am familiar with.

There may be some case for looking at the smartdrive washing machine type motor, these seem to use long salient poles which are dreadful for alternators but must have some virtues as a motor.Possibly it makes the drive circuits easier.

Flux

[REdiculous]

The only other thread I've seen on this was several pages long before (it seems) the idea was abandoned. I didn't get anything useful out of that thread or I'd be sharing it here...

How big is a comparable windmill...up to 750w and 400rpm? Anything close? Bonus points for links to build threads.

I'm pretty windmill-dumb but if I had a size range to look for it might be easier to figure out. Not that I want to build one, but it would be cool to see and it would help me 'get' it. later

[Bruce S]

Flux;

   Being a somewhat curious type, I looked into one of those hub add-ons and the rear mounted 48V 550 watt motor on our e-scooter.

The manufacturing in one of those is a work of art.

I concluded that I wanted no part of trying to reverse engineer one of these.

The copper windings in it are so tight they reminded me of -Ed's wave windings.

As the reverse these without very high speeds will not make very good 'mills.

Cheers;

Bruce S

 

[ghurd]

I was thinking the design and implementation of the speed control would be a nightmare in a DIY 'motor' unit.

And I was thinking a more standard regeneration circuit on the drive motor would be more practical than a second generator.  

Mostly because of weight issues, and how 20 pounds of regeneration related weight may use more power to lug around than it would make.

Chirpbear, maybe you already know this,

The alternator will need some fairly serious electronic controls.

An efficient alternator, with a simple switch to go in and out of the charging mode, will pretty much be like locking up the back wheel.

G-

[Bruce S]

G-

Agreed, the controllers for e-bike/scooters are also a miracle of modern technology and SMDs. The newer re-gen units are even more complex.

The 144Vdc units use a algorithm that will take into account the charged level versus the available power to return and adjust accordingly.

I think with enough help and input a picaxe type controller could do it, but not my cup-o-tea.

Cheers;

Bruce S