The ideal hubmotor

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JackFlorey   100 kW

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The ideal hubmotor

Post by JackFlorey » Jun 08 2021 9:53pm

In another thread people were talking about what the ideal hubmotor would be.

It's going to vary with application of course but for me the 'sweet spot' would be:

-Sensored BLDC
-Geared motor for lower weight
-Magnetic particle clutch (for regen when desired)
-Integrated gear hub with 7-8 speeds (i.e. similar to the TCDM IGH but with something like a Nexus)
-1500ish watts max power (with all the caveats about how it's hard to specify power in a hub motor)
-Rear wheel / single freehub
Last edited by JackFlorey on Jun 08 2021 10:47pm, edited 1 time in total.

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E-HP   100 MW

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Re: The ideal hubmotor

Post by E-HP » Jun 08 2021 10:31pm

JackFlorey wrote:
Jun 08 2021 9:53pm
-Integrated gear hub with 7-8 speeds (i.e. similar to the TCDM IGH but with something like a Nexus)
-Rear wheel, compatible with cassettes
8 integrated, plus a cassette?

JackFlorey   100 kW

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Re: The ideal hubmotor

Post by JackFlorey » Jun 08 2021 10:47pm

E-HP wrote:
Jun 08 2021 10:31pm
8 integrated, plus a cassette?
No, was mixing two different ideals there! Will fix.

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Re: The ideal hubmotor

Post by 999zip999 » Jun 09 2021 5:30am

Get a Mac and 2,000 Watt.

qwerkus   10 kW

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Re: The ideal hubmotor

Post by qwerkus » Jun 09 2021 11:11am

JackFlorey wrote:
Jun 08 2021 9:53pm
In another thread people were talking about what the ideal hubmotor would be.

It's going to vary with application of course but for me the 'sweet spot' would be:

-Sensored BLDC
-Geared motor for lower weight
-Magnetic particle clutch (for regen when desired)
-Integrated gear hub with 7-8 speeds (i.e. similar to the TCDM IGH but with something like a Nexus)
-1500ish watts max power (with all the caveats about how it's hard to specify power in a hub motor)
-Rear wheel / single freehub
integrated hub + 1500w is not possible. That motor would use the axle of the igh as main stator support, and easily dammage it at those power levels, since it's only slotted 10mm steel; not even 12mm like most chinese hub motors.
I think the ideal hub should get rid of gears altogether - single speed type - an move gears into a front gearbox like pinion does. This would allow for wider motors, with better gears and especially better seals around the main bearings, which would allow for efficient oil cooling.

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Chalo   100 GW

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Re: The ideal hubmotor

Post by Chalo » Jun 09 2021 11:14am

E-HP wrote:
Jun 08 2021 10:31pm
JackFlorey wrote:
Jun 08 2021 9:53pm
-Integrated gear hub with 7-8 speeds (i.e. similar to the TCDM IGH but with something like a Nexus)
-Rear wheel, compatible with cassettes
8 integrated, plus a cassette?
It's not completely loony to imagine separating motor gears from pedal gears. That would be one way to do it.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

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Re: The ideal hubmotor

Post by JackFlorey » Jun 09 2021 11:19am

qwerkus wrote:
Jun 09 2021 11:11am
integrated hub + 1500w is not possible. That motor would use the axle of the igh as main stator support, and easily dammage it at those power levels, since it's only slotted 10mm steel; not even 12mm like most chinese hub motors.
Why couldn't an IGH use 12mm axles?
I think the ideal hub should get rid of gears altogether - single speed type - an move gears into a front gearbox like pinion does. This would allow for wider motors, with better gears and especially better seals around the main bearings, which would allow for efficient oil cooling.
That's a good option, although it removes the possibility of doing a conversion on an existing frame. I haven't seen any front gearboxes that can be mounted on a standard BB mount - have you?

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Chalo   100 GW

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Re: The ideal hubmotor

Post by Chalo » Jun 09 2021 11:31am

qwerkus wrote:
Jun 09 2021 11:11am
integrated hub + 1500w is not possible. That motor would use the axle of the igh as main stator support, and easily dammage it at those power levels, since it's only slotted 10mm steel; not even 12mm like most chinese hub motors.
Axle size is arbitrary, even in a gearhub. (See the Kindernay with a thru axle and silly hydraulic shifting.) Anyway, if your "ideal" gearhub uses a flatted axle for torque anchoring, you're suffering a failure of imagination. Integrating a built-in torque arm, like every coaster brake hub ever, is only the first step towards ideal.

The axle stud or bolt must be no bigger than 10mm. But the axle face where it contacts the frame can be say 25mm in diameter and still fit any frame I can think of.
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Re: The ideal hubmotor

Post by DAND214 » Jun 09 2021 11:42am

999zip999 wrote:
Jun 09 2021 5:30am
Get a Mac and 2,000 Watt.
I'm with you ZIP,
I love my MACs!
I have too many to use.

Dan

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Re: The ideal hubmotor

Post by qwerkus » Jun 09 2021 2:54pm

Chalo wrote:
Jun 09 2021 11:31am
qwerkus wrote:
Jun 09 2021 11:11am
integrated hub + 1500w is not possible. That motor would use the axle of the igh as main stator support, and easily dammage it at those power levels, since it's only slotted 10mm steel; not even 12mm like most chinese hub motors.
Axle size is arbitrary, even in a gearhub. (See the Kindernay with a thru axle and silly hydraulic shifting.) Anyway, if your "ideal" gearhub uses a flatted axle for torque anchoring, you're suffering a failure of imagination. Integrating a built-in torque arm, like every coaster brake hub ever, is only the first step towards ideal.

The axle stud or bolt must be no bigger than 10mm. But the axle face where it contacts the frame can be say 25mm in diameter and still fit any frame I can think of.
Never said or wrote that - thanks for inquiring about the health of my imagination. I don't think axle size is arbitrary and yes, the axle of common shimano IGH is too weak for high power. Didn't now about the kindernay - thanks for the tip - It s about time rohloff gets some serious competition.

Now amongs the various ways to lock a hub motor stator, I do think that slotted / square axles are not that bad. It is the only clean way to clamp a motor using only the bike's dropouts; everything else would require either a torque arm bolted to the chainstay somewhere, or a special plate around the dropouts with bolting holes matching a surface on the hub. The problem is that it's only possible on the left (brake) side, and hence limited by the 44mm bcd of the disc brake mount.

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Chalo   100 GW

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Re: The ideal hubmotor

Post by Chalo » Jun 09 2021 6:31pm

qwerkus wrote:
Jun 09 2021 2:54pm
Now amongs the various ways to lock a hub motor stator, I do think that slotted / square axles are not that bad. It is the only clean way to clamp a motor using only the bike's dropouts; everything else would require either a torque arm bolted to the chainstay somewhere, or a special plate around the dropouts with bolting holes matching a surface on the hub. The problem is that it's only possible on the left (brake) side, and hence limited by the 44mm bcd of the disc brake mount.
Why would it only be possible on the left? If we're assuming internal gears, then one chain sprocket can easily share quarters with a coaster brake type torque arm.

If you check out the torque arm splines of coaster brakes, the IS disc rotor mounting pattern offers enough room on the left side too.
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Re: The ideal hubmotor

Post by qwerkus » Jun 10 2021 7:24am

Chalo wrote:
Jun 09 2021 6:31pm
Why would it only be possible on the left? If we're assuming internal gears, then one chain sprocket can easily share quarters with a coaster brake type torque arm.

If you check out the torque arm splines of coaster brakes, the IS disc rotor mounting pattern offers enough room on the left side too.

s-l300.jpgimages.jpegs-l500.jpg
That would only work with an axle shifting mechanism of the IGH, like SA/Sachs did until the 90s, and those would easily break when the bike falls on the drive side. Nowadays all hubs besides 3sp have shifting units attached to the sprocket; no space left for a torque arm. While I agree that a powerful geared hub + IGH would be paramount, I doubt its realistic unless the same company re-redesigns motor + igh hub from scratch. You'd have to figure out a way to shrink the igh enough to fit inside the stator of the hub motor, and shorten it enough to make room for the motor reduction. Sounds like a serious challenge!

But thanks for the short trip back in time with those coaster torque arms. Back in the 90s nearly all city bikes had coaster brakes around here. I remember one of the first wheel I tried to take off to fix a flat - took me a while to figure out the extra torque arm bolt!

EDIT: just wondering; what would be the ideal igh size for this type of combination in your opinion ? I think 5sp 263% like the new nexus 5 is quite good.

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Re: The ideal hubmotor

Post by qwerkus » Jun 10 2021 9:30am

Made a quick draft of a dual reduction hub motor to see where we could squeeze in an IGH. Doesn't look good for now, even by stretching the whole hub to 138mm and moving the igh shifter to the left side. Chainline is 58mm. Feel free to annotate / change things. I probably made a few mistakes. For an instance, I don't see how the power transfer between the spocket and the igh could work in this setup.
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EDIT: made a second version. This one should have enough space for everything. IGH moved inside the rotor - not sure how well this would fare but at least we have now 55mm to work with. Chainline still at 56mm (similar to rohloff) and OLD pushed to 138mm for max width.
Since the cable exit is left, this setup requires some bbs-style phases and hall plugs to be able to assemble / disassemble the motor. Also no clutch - since we're going to oil cool everything, I guess we'd also want regen :)
highpower_igh_hubmotor1.jpg
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All we need now is a mechanical engineer to turn those crude sketch into something that would actually work!
Last edited by qwerkus on Jun 10 2021 5:29pm, edited 4 times in total.

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Re: The ideal hubmotor

Post by neptronix » Jun 10 2021 10:00am

To me the ideal hub hub is either:

9C design with 0.27mm laminations and the flattest and tightest windings possible - this could produce a peak of 93% efficiency at best, while also dropping the weight of the motor. Add a cooling solution and this gets even better.

Large-ish dual stage geared motor with a cooling fluid such as Opticool H or some proposed alternatives which are compatible with the wide range of materials inside. Mind blowing power density is possible here because dual stage geared motors are severely handicapped by thermal restrictions.
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dogman dan   100 GW

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Re: The ideal hubmotor

Post by dogman dan » Jun 11 2021 5:19am

For sure, a better integrated torque arm would be a great starting point. Then after that attaches, the axle can be 10 mm round, or through hub round, whatever.

The old brushed heinzmanns had this, and it was a fantastic, but simple bit of engineering. I simply can't believe that china won't copy this design. What,, they afraid of patent lawsuits?

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Re: The ideal hubmotor

Post by 1boris » Jun 12 2021 5:31am

The perfect hub would be a Mac motor .The new version with round axle and intergrated torque arm with an 2 speed gear box like Xiongda but better made.

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Re: The ideal hubmotor

Post by MadRhino » Jun 12 2021 6:32am

It will be a long time before ebike hub motors improve significantly, because all the western Industry adopted the integrated BB drives, and the laws are restricting performance.

The ideal hub motor will be DD, made of composite materials, CF casing and ceramic stator, with integrated liquid cooling and variable KV reluctance motor. Only then, the ´weight vs performance’ ratio will improve considerably, and reliably. A 10 lbs 10 kw hub motor is possible, only nobody is willing to invest in making it.
Make it fool-proof, and I will make a better fool.

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Re: The ideal hubmotor

Post by MadRhino » Jun 20 2021 3:40pm

They are affordable for sure, but they are primitive engineering and cheap Chinese manufacturing. We build fast ebikes with them, and they are reliable because hub motors are simple, but powerful hubs are heavy and that is the main concern for improvements.
Make it fool-proof, and I will make a better fool.

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Re: The ideal hubmotor

Post by LewTwo » Jun 20 2021 8:25pm

Chalo wrote:
Jun 09 2021 11:14am
It's not completely loony to imagine separating motor gears from pedal gears. That would be one way to do it.
Another way to do it is to put the hub motor in the front and the IGH in the rear.
That is several feet of separation and does not require a special frame.
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Re: The ideal hubmotor

Post by sleepy_tired » Jun 21 2021 12:15am

The ideal hub motor is a in runner motor on the outside of the hub driving the hub with a chain or gear. Just something very compact and close to the central hub; off of one side. Something like those old brushed gear reduction motors from 20 years ago. Just something modern.

That way weight issue is solved, torque issue are solved, cooling issues are solved. No need for any liquid cooling or anything bizarre like that.

The trouble with this is that it would need to be customized to the bike frame.

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Re: The ideal hubmotor

Post by MadRhino » Jun 21 2021 1:15am

Small motors with gears and chain or clutches will never replace a plain DD hub motor that has true power output. Reduction does not make power, nor speed. It does make torque with lighter weight, at the cost of speed and reliability.

The improvements that hub motors need is power density. We need a better power to weight ratio, to gain some of the weight advantage of mid drives without the gears and chain that are making them slow and unreliable. Cooling is not bizarre. It is the practical, proven solution to obtain more power from lighter motors. If one pound of radiator and coolant can save 10 pounds of motor mass to produce the same HP... it is a solution.

Small mid motors are for low power bikes, slow and high maintenance. Big mid motors are for motorcycles, with heavy drive trains and ideally, transmission and clutch. The hub is the solution for fast ebikes, even with the cheap engineering that they are today. But, fast ebikes are not in the plans of the industry, so the hubs will not improve anytime soon. The industry will continue to develop little steps of improvement to BB drives until they cost a fortune to make and repair.
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