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Which Stator width (for direct drive motors) do you think will be the first to use .27mm laminations?

Joined
May 19, 2012
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27mm (or 28mm)?

35mm? (Some consider this to be the best stator width pound for pound)

45mm?

Cast your vote and explain why if you want.
 
If high rpms benefit the most from thinner laminations then marine application of hub motors needs to be considered:


As you can see from the link above Grin is using either a Kv of 21 or 30 for marine motors based on the all axle DD hub motor. With 48v/52v we are looking at an operating range of 1000 rpm to 1500 rpm.
 
I've talked to the owners of 4 major companies on this topic:
- MAC came up with the idea on their own and implemented at some point
- Grin has no interest, asked 2x
- It's been a no from leafbike, asked 3x, thought they would be receptive
- CYC X1 Pro is the only mid drive i know of with very thin lams ( advertised but not confirmed ), makes sense because it spins fast.
- Numerous RC motors spin this fast but consider that they run 10x-50x higher RPM and at these speeds you can get a sizeable benefit.

In DD hub motors you don't see any notable benefits from 0.27mm lams until you are in the 20" wheel size, and that's one of the most uncommon wheel sizes DDs are put in, so no manufacturer got the idea to make a DD specifically for this wheel size, which is ironic because the 20" wheel size is where your typical 9C motor makes peak power/torque/efficiency.

End turn losses are the biggest villain of DD motors so the wider the stator the higher the efficiency tends to get. I think the ol' 50mm cromotor used to hit something like 91-92% efficiency.

An inverse case of that is the CSIRO motor which is a razor thin axial flux unit with the tightest windings i've seen on any motor. It achieved a peak 97.3% efficiency.

1713329271765.png


For whatever reason, nobody can be convinced to make a premium hub motor, meanwhile people are buying $500-$1500 mid drives left and right. It's very disappointing the DD has not seen any evolution for a long time.
 
I've talked to the owners of 4 major companies on this topic:
- Grin has no interest, asked 2x

I'm guessing this was before Grin decided on the marine motor?

That marine motor not only spins fast but also makes much higher power than we normally see.

Because of that power (e.g. 27mm wide stator version of marine motor is rated at 5000 watts nominal) and rpm it seems like the mostly candidate for .27mm laminations.
 
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I think it would be about a year ago.

Yeah the marine motor would benefit a little. It spins at 3x the speed of a regular hub. The added cost of this might be $100. I think most people would not be able to pay for this cost benefit ratio.

But think about this, a few % of efficiency matters on a bike because we are limited by how much battery we can carry. Not such a big problem on a boat, i don't think it would make as much sense as on a bike motor.
 
But think about this, a few % of efficiency matters on a bike because we are limited by how much battery we can carry. Not such a big problem on a boat, i don't think it would make as much sense as on a bike motor.
If we assume the 27mm wide marine motor is 90% efficient at 5000 watts that means it makes 555 watts heat (re: 5555 x .90 = 5000 watts).

If efficiency is increased to 92% heat drops dramatically and a substantially higher power level of 6375 watts is possible (re: 6930 watts x .92 = 6375 watts. Heat load is unchanged because 6930 - 6375 = 555 watts.....which is the same heat output as the 90% efficient motor making only 5000 watts from an input of 5555 watts).

That same 27.5% power increase applied to the 8000 watts nominal 45mm stator motor yields 10,200 nominal watts.
 
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Yes, but the problem is getting motor manufacturers to care about that 2%.
 
true@neptronix. Grin is doing some good things, but their focus seem to be about motor weight reduction, not higher power or more efficient motors
 
Grin is like N.A.S.A let him go and you don't know what kind of ideas will filter down the line. But things and knowledge will come out of it.
One thing I am expecting is the Grin fat all axle hub motor to eventually integrate an igh (e.g. TCDM made a motor a while back that did this using a product specific version of Sturmey Archer 5 speed --> New Product, TDCM Internal Gear Hub Motors.)

1713572106586.png

Integrating igh in a fat hub motor with 135mm/142mm x 12mm rear spacing (or something in the same ballpark like 148mm x 12mm) would allow normal q factor even with 4+" wide tires. Such a motor would be particularly nice on pre-built ebikes (either as DIY or OEM) using integrated mid drive motor and igh.

Another thing I am looking forward is the evolution of the Grin wheel barrow motor which is essentially the bafang G310/G311 spm (i.e. surface permanent magnet) inrunner hub motor married to a second stage of reduction for a total reduction of 29.5:1. The current motor is at this time combined with a large diameter hubshell that is empty along it's circumference but has plenty of room for batteries. (It is very obvious Bafang is intending the use of an integrated battery sometime in the future just looking at the thing).

Furthermore, I expect the bafang spm motor (used in the current version of the Grin Wheel barrow motor) to eventually change to ipm (i.e. interior permanent magnet) for increased torque and higher rpm and power range . This with the FOC controller integrated into the hubshell as well the batteries, of course. Then they will likely finish off the design with integrated torque sensor and Bluetooth so it just as easy to install as the Keyde P130 and P160 all-in-one hub motors. IMO this will be a great motor for both ebikes and wheelbarrows. Being so easy to install the average mainstream user will view it as an appliance rather than something complicated that needs research that use. I am also hoping it charges via 100w USB (or better yet 140w or 240w USB) like the Keyde P130/P160 which uses either a tiny GaN USB charger or a High watt output USB power bank/power station. (Why use AC power when a person could just direct charge via DC power which is more efficient use of the battery in the power bank/power station.)

Speaking of lamination thickness, that wheel barrow motor once it goes ipm (interior permanent magnet) will probably get a good improvement in that department. In fact, with 29.5 :1 reduction it might even justify .20mm laminations.
 
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true@neptronix. Grin is doing some good things, but their focus seem to be about motor weight reduction, not higher power or more efficient motors

Grin does a pretty good job selecting models for efficiency, the problem is they aren't a full motor manufacturer themselves, and their pool of available motor suppliers haven't really improved their products for a decade, with few exceptions.

Sad but true!
 
Ok just run two sets of hall sensors on a multi vented side covers 27mm @ 100v 23amp controller or more with a temp monitor. Maybe 50amp .
Cheap and meant to melt. Go cowboy !
 
Ok just run two sets of hall sensors on a multi vented side covers 27mm @ 100v 23amp controller or more with a temp monitor. Maybe 50amp .
Cheap and meant to melt. Go cowboy !
Most of that has been done before on a very cheap .50mm lamination Nine Continent 2810 motor at 111v nominal with CA limiting amps to 23.


He did use oil cooling rather than vented side covers though. This was back in 2012.
 
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