The Halbach Disc Motor Ebike Project

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More Simulation Fun...

No real hard info to add today because I'm still figuring out how to do things with the Simulation software. What I want to do is get as exact of a Simulation of the motor as possible and be able to at least visually look at what will happen. The tool has some more advanced stuff too that will give good feedback about things like torque produced... so by the time I actually have the thing built I'm hoping to have some predictions about performance in advance. By the end of my brushed motor rewinding experiences I had gotten all the formula's figured out and was recording results that were the same as predicted.

Today I finally got the electrical coils figured out and this is a first look at how the magnetic flux lines bend:

...just by looking at the colors the efficiency looks to be good with an air gap on each side of about 1/4". So in total the overall air gap separating the magnets would be 1/4" + 1/2" + 1/4" = 1" which is very relaxed as far as tolerances. (makes getting a grinder in there easier)

The fact that the CSIRO solar racer is reporting efficiencies as high as 97% gives me something to shoot for. My existing bike has a "best" efficiency of about 78%, but then the geardown takes away about 5%, then another 5% for the drive chain and more because of the averaging of the powerband so that in the end I'm probably getting about 65% efficiency at the rear wheel.

97% - 65% = 32% difference... which is a lot...

For a 1000 watt input that means 970 watts at the rear wheel verses 650 watts at the rear wheel or a difference of 320 watts.

For a 2000 watt input that means 1940 watts at the rear wheel verses 1300 watts at the rear wheel or a difference of 640 watts. (1 hp = 750 watts)

My old bike is wasting nearly a full horsepower because of efficiency losses...

 

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NdFeB vs Copper Shootout

This is another kind of fun thing to look at...

How much current must you pass through copper of equal cross section to a NdFeB (N40) magnet before you get the same magnetic field?

The answer isn't exact, but if you figure out for 20AWG (series) the answer is roughly 50 amps of current.

On the right is the copper, the left is the NdFeB:

 

[AussieJester]

The theory was developed on the other thread and now I'm going to begin the actual "build" process of the Halbach Disc Motor idea.

Yet you continue on with more talk and graphs...The whole point of this SECOND thread about THE SAME motor was what exactly??

KiM

 

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Yet you continue on with more talk and graphs...The whole point of this SECOND thread about THE SAME motor was what exactly??

You have a point...

I started this one as the build thread and at the time I was going to go with a radial design so the axial flux title of the other was wrong. Now after thinking about it I've switched back to the axial design because I've figured out it's possible to do so and it's the preferred way. The first thread was filled with a lot of random concepts and this one is a little more focused on the actual design for my actual bike.

So this one has either theory or build activity on my actual Halbach motor. The other one is still open to discussion about Halbach in general or anything else. The other thread would be a good place just to chat.

There's another thread that was for non-Halbach axial designs too, but there's no one that seems to want to push it forward.

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When it's a "project thread" and there is the level of complexity that exists in designing a motor from the ground up you are going to need a lot of theory and a lot of Simulations. You can't just go and do it without hours and hours of homework. This is the homework as well as the build. You can't avoid long discussions or monologues because the topic is complex enough to need it.

I guess the idea was to sort of make the thread sort of "my own" to say to others that this is not really so much a place for random talk. As I see it I'm more or less reporting the thought process as I learn so that others that might want to try something similiar can say:

"Okay... I see why he thought that and why he went in that direction."

My garage is already down below 50 degrees and it's dropping each day.

Ideally I would have preferred "Thread Level Blocking" so that I would simply have this thread a "read only" thread. But that's not going to happen so I just live with the occasional banter.

Just ignore my thread if you aren't interested in the topic !!!

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Building a motor from the ground up is more complex than most things... :scholar:

 

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The Intellectual Road Ahead

Where do I need to go with the project?

First of all I need to get comfortable with the Simulation software I've been using so that I can trust that I'm doing the right things in the designs. (just basic things like knowing the layout of everything)

Second... there's the whole "math thing" about getting the right number of coils so that I get the correct torque I desire with these magnets. All the volts / amps / turns stuff needs figuring out.

...the first part is pretty easy because I can fiddle around with the software until I stumble upon how to use it. Software tends to sort of grow on you so that after a while you can put it to better use. The second part is the harder part because I'm going to need to be able to make actual estimates about how things are going to perform. Unlike with the motor rewinding process this is a significantly harder math problem to solve.

If the weather were nice I'd just slop something together and try it using no math and getting a "seat of the pants" feel for what is going on. It's fun to just "wing it". But with the weather being bad now it's the time to get into the intellectual stuff.

I've got several months to ponder the math...

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A month ago I thought I'd be building an AC Induction motor, so where I am at the moment is not what I expected just weeks ago. You have to learn as you go.

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Funny Observation

This applies to AussieJester for the most part...

During the summer all I do is "act" and I don't think very much. AussieJester, you tend to accuse me of not thinking or listening to advice. (remember the brush pressure issue?)

During the winter all I do is think and can't "act" on anything and you (AussieJester) accuse me of inaction.

Dont want input go make a blog..

I want "constructive input" that advances the discussion technically. There are a limited number of places where people are as specialized as this (ebikes) so if there were a blog with an audience that was this specialized I might be interested.

 

[AussieJester]

Ideally I would have preferred "Thread Level Blocking" so that I would simply have this thread a "read only" thread. But that's not going to happen so I just live with the occasional banter.

Dont want input go make a blog..


KiM

 

[AussieJester]

This applies to AussieJester for the most part...

During the summer all I do is "act" and I don't think very much. AussieJester, you tend to accuse me of not thinking or listening to advice. (remember the brush pressure issue?)

During the winter all I do is think and can't "act" on anything and you (AussieJester) accuse me of inaction.

Yup i also remember i told you about motor timing YOU IGNORED IT took you 15 pages to accept that... OH and yes the brush pressure issue...same deal. You IGNORE any advice that doesn't fit in with your ideas seen it dozens of times here and on ES.

KiM

 

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The particular week you are talking about was when it was 90-95 degrees and very high humidity (90%) in the middle of the summer.

I repeat... in the summer months the heat completely wipes away any ability for me to think clearly.

That was my point... (which you missed)

Winter is my time for thinking... then when summer comes and the heat and humidity makes me mentally "challenged" I stop thinking and just ride or do manual labor. Manual labor can be done with very little mental activity going on so it's perfect for summertime. You just "act" in the heat, but "think" in the cold... at least that's how I am...

Got it?

Summer months have me just reporting but not "processing" anything.

I plan to do all my homework now and then get back into autopilot mode when the heat comes back...

 

[AussieJester]

So let me get this right, the point of starting this thread specifically to document the BUILDING of the motor was what exactly? Seeing you have just admitted you wont be actually making anything for months...

KiM

EDIT: P.S We have these items for heating outdoor entertainment areas in winter called patio heaters maybe invest in one or two for your workshop you might actually get something done in months when yo can 'think' :: rolls eyes::

 

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Theory and building of the Halbach Disc motor... yes.