The Halbach Disc Motor Ebike Project

Safe,

I am stoked to see you are actually building this thing. This will be one of the most innovative efforts in motor biking. Go for it man. Follow your dreams.
To the critics: Whats he got to lose? This is a hobby. He is enjoying himself, researching, learning, designing. It's a great creative outlet regardless of success or failure.
Do it man.
 
Thanks KeepOnKeepnOn it sometimes feels like I need "permission" to simply want to try something new for ebikes.

Having found this image from the NASA Halbach projects it does tend to give me greater optimism that I'm going to be able to pull this off:

attachment.php
 
Last edited:
To Cog, or Not To Cog?

Generally speaking the idea of having cogging in your motor is considered a bad thing. It will set limits on the motor that otherwise might not be there.

However... I have my doubts about the abilities of an RC motor ESC to properly "sense" the backEMF on a Halbach motor when it is made so perfectly as to not cog at all... so one strategy to guarantee that the RC ESC's would work is to reintroduce the cogging if possible. As it turns out it's possible to have cogging with the Halbach and not need iron to do it.

First we look at the Single Block Halbach which is the way you normally want to do it. You can see that the magnetic flux is really smooth and there is no cogging that is visible. Cogging is when the magnetic strength varies (color changes) but it's not related to the flux path direction:

attachment.php


Now we look at a Double Block Halbach where each set of two blocks are pointed in the same direction, but following the Halbach array orientation. The configuration will cut the pole count in half, which may or may not be a good thing. This will give lot's of cogging and a very strong magnetic field:

attachment.php


Lastly we look at the Standard magnet configuration with it's flux lines that loop both above and below:

attachment.php


:unsure: Thoughts...

It's a tough decision to make... if I go with the Double Block Halbach it will make it easier to build the magnet wires (coils) because it doubles the spacing between poles. Also with the Double Block Halbach the cogging will be very significant and that will guarantee that the RC ESC's will recognize the motors behavior, but it will also double the motors base speed. One of the "gotcha's" that I saw with the RC ESC's is that they usually don't go above about 10-12 poles as a maximum in their configuration options. With the Single Block Halbach I'd end up with a 16 pole motor and that might freak out the ESC. By going with the Double Block Halbach the pole count is reduced to 8 pole and that's pretty conservative for the RC ESC's. (it would be a decision of practicality)

I don't see any advantage to the Standard configuration because the magnetic flux strength is not larger and yet it has cogging.

This is one of those times when it would be nice to build two discs, one with Single Blocks and another with Double Blocks and try them both out. However, for the short term I'm going to need to decide one way or the other. :unsure:
 

Attachments

  • Cogging - Double Block Halbach.jpg
    Cogging - Double Block Halbach.jpg
    211.2 KB · Views: 6,610
  • Cogging - Double Block Standard.jpg
    Cogging - Double Block Standard.jpg
    200.7 KB · Views: 6,447
  • Cogging - Single Block Halbach.jpg
    Cogging - Single Block Halbach.jpg
    166.8 KB · Views: 7,299
Last edited:
That Was Easy

Take a regular steel hub, grind off the lip near the threads where you mount the freewheel (inside) then grind the hub down until the side separates from the rest and you are pretty much there. Since the hub is it's own "lathe" you just spin the hub with the grinding wheel friction. So easy.

On top of all that a 36 hole hub has spoke hole spacing that (in this case) perfectly matched the disc holes so that all I had to do was drill. That was sheer luck... and it was just because the steel hub was the right size.

The entire part took an hour. :cool:

It's only taken me about 5-6 hours in total... and if you bought the spider instead of a modified one it would be even quicker. With the right parts is just a little grinding, some drilling and then paint.

attachment.php


...this might also be a useful idea for people that just want to add a motor to the rear wheel through a separate chain.
 

Attachments

  • Halbach Motor Project 004.jpg
    Halbach Motor Project 004.jpg
    159.6 KB · Views: 7,444
Last edited:
.. and if you bought the spider instead of a modified one it would be even quicker.

Recumpence makes an adapter that bolts directly onto the disk brake mounts of a hub to take a sprocket.

file.php

pictured above the astro/reduction drive

This might be another alternative if you want the motor on the left hand side of the wheel would be simple as bolting it on, and you know its accurate its cnc milled.

Theres now 3 separate DIY motor threads on ES safe, one fella has already built the motor out of aluminium cnced on his work mill. Tiz smaller scale to test his ideas at present but he moves fast.

KiM
 
That Was Easy

Take a regular steel hub, grind off the lip near the threads where you mount the freewheel (inside) then grind the hub down until the side separates from the rest and you are pretty much there. Since the hub is it's own "lathe" you just spin the hub with the grinding wheel friction. So easy.

On top of all that a 36 hole hub has spoke hole spacing that (in this case) perfectly matched the disc holes so that all I had to do was drill. That was sheer luck... and it was just because the steel hub was the right size.

The entire part took an hour. :cool:

It's only taken me about 5-6 hours in total... and if you bought the spider instead of a modified one it would be even quicker. With the right parts is just a little grinding, some drilling and then paint.

attachment.php


...this might also be a useful idea for people that just want to add a motor to the rear wheel through a separate chain.

Safe here is the original innovator's post and his idea.
http://www.motoredbikes.com/showthr...otoredbikes.com/showthread.php?t=18548&page=7

And some pictures of his rear sprocket mod.
Check the date LOL.

http://www.motoredbikes.com/showthread.php?t=18548&page=7

http://www.motoredbikes.com/attachment.php?attachmentid=18892&d=1245009870

http://www.motoredbikes.com/attachment.php?attachmentid=18893&d=1245009893


http://www.motoredbikes.com/attachment.php?attachmentid=18894&d=1245009942


I am currently using a copy of treewks rear hub mod.
It was a surprise to me when you invented it LOL
 
Last edited:
Safe here is the original innovator's post and his idea.

A 'first' on this site possibly but not 'first' to do it, using the bottom bracket bearing housing for the freewheels is an old trick matey seen it done many a time on various forums, you can use the left hand threaded one with a SouthPaw freewheel on the left hand side of the rim too (check my worklog i have done exactly that on my cruiser) Interestingly, the left hand threaded bottom bracket housing must come in various thread pitches as i tried 4 before i found one that would screw in successfully!

Safe often is the 'first' to do many things though...according too himself anywayz LoL

Where you been Spad4me anywayz haven't seen you about for ages?

KiM
 
Missing The Point Are We?

You guys are acting like a bunch of girls jealous over being the most beautiful !!!

The point wasn't that it was the "first", but that it was easy and didn't take a lot of time. I've seen them before and AussieJester and I even talked about them before.

When the Halbach Disc Motor is done I suspect that people will immediately jump in and say things like:

"Oh, well that's nothing really new... all the ideas were already there... safe does not deserve any credit for getting it together... blah... blah... blah."

...oh human nature is always such a joke. :giggle:
 
Last edited:
Nothing to add, just posting to get into subscription updates. Also the NASA photo/drawing I do not belive needs an IRON core because it appears to be working off of the immediate boundary field. Iron would only focus the flux on the copper perpendicularly to the coil. I think it works off the outer boundary of the flux, though I could be wrong.
 
Back
Top