Hub motor magnets

Lightweight / Folding / Portable EVs - seats optional
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meashman   10 µW

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Hub motor magnets

Post by meashman » Apr 29 2021 9:24pm

Hi all, I've been searching but I can't find any info about the magnet rating in scooter hubs.

I see motors listed with 45h and 65h. Does this mean anything in terms of motor performance?

Ash


Last edited by meashman on Apr 29 2021 9:24pm, edited 1 time in total.

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markz   100 GW

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Re: Hub motor magnets

Post by markz » Apr 30 2021 6:33pm

meashman wrote:
Apr 29 2021 9:24pm
Hi all, I've been searching but I can't find any info about the magnet rating in scooter hubs.

I see motors listed with 45h and 65h. Does this mean anything in terms of motor performance?

Ash
Yes, higher height magnets is better. Low power is 25H like 9C 1kw, higher power is 45H like mxus 3kw.

Magnet strength is what you are looking for which is N##. Neodymium magnet strength.
I know of one motor which had curved magnets, could be more out there. Not sure if it became a thing or was useful.

https://www.supermagnete.de/eng/faq/Wha ... 0-etc-mean

meashman   10 µW

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Re: Hub motor magnets

Post by meashman » Apr 30 2021 11:54pm

markz wrote:
meashman wrote:
Apr 29 2021 9:24pm
Hi all, I've been searching but I can't find any info about the magnet rating in scooter hubs.

I see motors listed with 45h and 65h. Does this mean anything in terms of motor performance?

Ash
Yes, higher height magnets is better. Low power is 25H like 9C 1kw, higher power is 45H like mxus 3kw.

Magnet strength is what you are looking for which is N##. Neodymium magnet strength.
I know of one motor which had curved magnets, could be more out there. Not sure if it became a thing or was useful.

https://www.supermagnete.de/eng/faq/Wha ... 0-etc-mean
Thank you

Hummina Shadeeba   10 MW

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Re: Hub motor magnets

Post by Hummina Shadeeba » Sep 07 2021 6:37pm

meashman wrote:
Apr 29 2021 9:24pm
45h and 65h.
Ash
no such thing as 65 anything. https://www.kjmagnetics.com/specs.asp

Dacflyer   100 mW

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Re: Hub motor magnets

Post by Dacflyer » May 20 2022 8:53am

N52 is largest i ever seen.. ( JK Magnetics )

Hummina Shadeeba   10 MW

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Re: Hub motor magnets

Post by Hummina Shadeeba » May 20 2022 9:32am

N54 are out there and maybe available in large quantities but low temp ability. I wonder.

larsb   100 MW

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Re: Hub motor magnets

Post by larsb » May 20 2022 10:00am

meashman wrote:
Apr 29 2021 9:24pm

I see motors listed with 45h and 65h. Does this mean anything in terms of motor performance?

Ash
You’re all mixing it up, the 65h or 70h/whatever that the motor manufacturers like QS use stands for magnet height, or actually width of magnets. You can say that a 60h motor with the same stator steel is 2x the motor of a 30h as torque scales proportionally.

The magnet class used in most hubs afaik are not the highest, from memory i’d guess n35-N40 and going to a higher magnet class is expensive so it’s normally not done. It’s also a balance vs losses since stronger magnets give more torque but they also drive increasing eddy losses.

N52:s have no return on investment since their strength dive as soon as temperatures go up a little.

High temp, high strength magnets like N45SH is the top magnet class that i’ve actually seen used in some motors, at least at a reasonable price.

Some info on temperature classes here:
https://www.first4magnets.com/tech-cent ... agnets-i91
Last edited by larsb on May 20 2022 10:24am, edited 2 times in total.

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fechter   100 GW

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Re: Hub motor magnets

Post by fechter » May 20 2022 10:15am

There is probably not much benefit to using magnets over a certain strength. With a higher flux, the hysteresis and eddy current losses will increase to the point of cancelling out the gain in torque. There are trade-offs in most aspects of motor design. Having magnets with a higher temperature rating is what you really want in a bike motor.
"One test is worth a thousand opinions"

Hummina Shadeeba   10 MW

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Re: Hub motor magnets

Post by Hummina Shadeeba » May 20 2022 1:03pm

If the magnetic field is well directed and especially if it’s a slow turning hub with a low erpm then stronger magnets are like..free power. No?

larsb   100 MW

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Re: Hub motor magnets

Post by larsb » May 20 2022 1:07pm

:es:
Aint no such thing as free power

Hummina Shadeeba   10 MW

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Re: Hub motor magnets

Post by Hummina Shadeeba » May 20 2022 1:25pm

Lately I’m of the belief magnets are free power IF they’re oriented correctly. In a motor they’re adding torque for what cost? Other than iron losses it’s free for the life of the magnet, no? “Free power” is a loaded term but still.. taking in to account the energy to make the magnet, and orient it, it seems a net gain when factoring the extra torque they add to what would just be a motor with iron of a reluctance motor.

magnetic fields could be used like gravitational fields to produce ..satellites traveling by piggybacking off fields. It’s not free but calculating the decrease in orbit speed of the objects the satellites interact with isn’t worth it.

hias9   1 kW

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Re: Hub motor magnets

Post by hias9 » May 23 2022 4:11pm

It's not free power. With stronger magnets on a hub motor you have decreased copper losses because you need less amps for the same torque, but you get increased iron (hysteresis+eddy) losses and increased drag when coasting. Depending on your riding style this could increase or decrease efficiency.
Also consider that Kv decreases if you don't also rewind the motor with less turns.
If you never (or rarely) coast like on a race track, or if it is a mid drive / geared hub which has a freewheel clutch, I think the strongest magnets (that are up to the operating temperature) are almost always the best option if you don't consider the cost.
If anybody has a source for curved magnet for a good price and low order quantity, please let me know.

Hummina Shadeeba   10 MW

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Re: Hub motor magnets

Post by Hummina Shadeeba » May 25 2022 2:29pm

The benefit of adding stronger magnets or just magnets period is still there despite iron losses. The spinning motor is able to orient the magnets to be a benefit and get what is practically a never ending magnetic field. How is this form of energy different from a gravitational field and a satellite piggybacking across space without needing to add energy?

Dacflyer   100 mW

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Re: Hub motor magnets

Post by Dacflyer » Jul 27 2022 9:19am

I'm looking for magnets as well.. I haven't had any luck to find what i need..
I'm Needing 2" x 3/4" x 1/8" N42 type, I only can find N52 in the size i need..Can't use them, because they can't handle the heat..
Anyone able to help me find any ? searching desperately here..

Hummina Shadeeba   10 MW

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Re: Hub motor magnets

Post by Hummina Shadeeba » Jul 27 2022 12:49pm

Dacflyer wrote:
Jul 27 2022 9:19am
I'm looking for magnets as well.. I haven't had any luck to find what i need..
I'm Needing 2" x 3/4" x 1/8" N42 type, I only can find N52 in the size i need..Can't use them, because they can't handle the heat..
Anyone able to help me find any ? searching desperately here..
alibaba has lots of custom magnet makers but you’ll have to buy a minimum

Dacflyer   100 mW

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Re: Hub motor magnets

Post by Dacflyer » Jul 27 2022 4:35pm

Ya, I've seen that, but the smallest amount I could order is 300pcs or $ 3,000 worth.... not possible in my budget..I'd be willing to spend 2 or 3 hundred but not more...

Hummina Shadeeba   10 MW

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Re: Hub motor magnets

Post by Hummina Shadeeba » Jul 27 2022 4:46pm

Dacflyer wrote:
Jul 27 2022 4:35pm
Ya, I've seen that, but the smallest amount I could order is 300pcs or $ 3,000 worth.... not possible in my budget..I'd be willing to spend 2 or 3 hundred but not more...

Look around on there and u can definitely find places that will do a lot less. I forget the name and can’t find them in my email.

could try to make a hallbach array n glue magnets together.

Dacflyer   100 mW

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Re: Hub motor magnets

Post by Dacflyer » Jul 28 2022 8:33am

I kinda thought about that..but didn't know if it would work or not...perhaps some 1/4 x 3/4 x 1/8? Glue them on the side where the hall sensors are ? Would that work or not. I didn't know if putting them end to end would cause any issues.
I do know that 2 magnets end to end are not the same as a whole one..or am i wrong..( eddy currents not linear etc.)

Hummina Shadeeba   10 MW

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Re: Hub motor magnets

Post by Hummina Shadeeba » Jul 28 2022 8:59am

less eddy currents with 2 magnets where would’ve been one. Glueing two magnets together can be very hard. If ur gluing them together in a hallbach I think you’d be better doing three magnets or more for better effect.

Dacflyer   100 mW

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Re: Hub motor magnets

Post by Dacflyer » Jul 30 2022 10:34pm

I was thinking, the add ons should all line up pole wise. I can't explain on here, but theoretically there shouldn't be any poles fighting..
they should all attract just fine ? I'm hoping it would be just enough to trigger the hall sensors, so the motor would run..
I have been searching and searching, I just can't find the size i need, Even less luck if i try with mm sizes.

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fechter   100 GW

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Re: Hub motor magnets

Post by fechter » Aug 02 2022 3:55pm

You can tile together smaller magnets and it will work. It's very difficult to tile them though, since the pieces will strongly repel each other or try to flip over. You need to use some kind of clamps to hold them together while the glue hardens.
"One test is worth a thousand opinions"

Dacflyer   100 mW

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Re: Hub motor magnets

Post by Dacflyer » Aug 04 2022 9:56am

They shouldn't flip from what I played with...I have some other magnets, and I laid them out, The edges just pulled together. and the flat sides stuck to the ring just fine. So i ordered me some 3/4 x 1/4 x 1/8 size from K&J Magnetics..
Unfortunately, they will not be here before i go on vacation,, But i'll get to it when I get back,,
Hopefully, they will be enough to trigger the hall sensors.. Really wish I could find the proper ones I need..But Oh well, I'll try this.
Otherwise, I think I Might Just Scrap the Bike and sell The components...It Is full of goodies..

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Ianhill   100 MW

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Re: Hub motor magnets

Post by Ianhill » Aug 04 2022 11:49am

I had a motor that got real hot and had chewed a magnet up, the event left a 1/3rd of the magnet in place and the rest had turned to dust made a mess but the motor still spun just could hear it clicking as the remainder rubbed away somemore.

I noticed it when riding didnt hear the clicking through all my gear and coming down the mountain but i could feel the power was pulsing a lumpy spot in the motor that delivered naff all torque but been an 8 pole if i remember correctly it was only for 1/8th of each rpm so could proberly of done simular to another magnet and still run some shape.
Infinite hrspwrs.

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