MultiSpeed/HubMotor Design Option

[EbikeMaui]

MultiSpeed/Hubmotor Design ?
The best way I can see for a hub motor of 1000 watts or so to be the most efficient and cost effective to put together on a Sram DD hub would to make a radial stator about 3/4 thick X 12" OD. The stator teeth about 1" thick from od to Id. The rotor with high quality magnets on a steel spoked rotor with a housing supported rotor/freewheel bearing that had a Shinamo FreeHub pattern Broached into the OD of the rotor freewheel.
Wala ! a high torque 36 pole rotor in a 12"X 3/4" CD Driver Motor package slides onto the Sram DD Hub and is secured by two frame clamps and two motor bolts. The motor and trans are about 8 pounds of weight.The disk looking motor would also slide onto any rear shimano freehub and still have room for a BMX pedal freewheel on any Shimano style cassette hub.The motor would slide onto Shamino hubs along with a bmx freewheel for plenty of power using a single speed.The 3 speed sram hub already installed on 1000s of bikes would eaisly take "The Disc" for WIDENING your RANGE of performance and EFFICIENCY !
Just a NEW mouse trap but this one works! The hub motor that you cant see spin. The disc brake is on the other side. NO BROKEN SPOKES either. You can also take off the motor and replace the derailer in 5 minutes.

 

[Toorbough ULL-Zeveigh]

The rotor with high quality magnets ... (snip)

Why do you keep going on about the quality of the magnets?
NeFeB is pretty much standard nowadays.
Or are they only now hitting the shores of Maui?

 

[Lowell]

Sounds like an interesting idea... who is going to try it?

 

[EbikeMaui]

The rotor with high quality magnets ... (snip)

Why do you keep going on about the quality of the magnets?
NeFeB is pretty much standard nowadays.
Or are they only now hitting the shores of Maui?

There are many strenths and grades that reflect in much higher costs for commercail use.So they go the cheap route to make them marketable.
Most hub motors have cheaper weaker magnets to help reduce cogging and price.
To get twice the rated torque and power as a 20 lb Xlite in a 7 lb hub motor you will need the strongest magnets available which would cost 10 times price compared to what xlite uses.
Motors are designed so that the magnets are made as strong as possible with acceptable risk of core saturation. This will maximize the torque capability of the motor but also means that during normal operation every motor may at some point, operate close to saturation. How close a motor runs to saturation depends upon the amount and type of core material used. So naturally, this point varies from manufacturer to manufacturer. There really is a difference in motors and you get what you pay for.

 

[EbikeMaui]

Sounds like an interesting idea... who is going to try it?

Whos going to buy it ? or make 1000 ?

 

[Toorbough ULL-Zeveigh]

The rotor with high quality magnets ... (snip)

Why do you keep going on about the quality of the magnets?
NeFeB is pretty much standard nowadays.
Or are they only now hitting the shores of Maui?

There are many strenths and grades that reflect in much higher costs for commercail use.So they go the cheap route to make them marketable.
Most hub motors have cheaper weaker magnets to help reduce cogging and price.
To get twice the rated torque and power as a 20 lb Xlite in a 7 lb hub motor you will need the strongest magnets available which would cost 10 times price compared to what xlite uses.

From what I've read, the largest single expense in building a hub motor is the royalty premium for the Delco-Remy patent on the magnets, that includes the chinese. It doesn't make a lot of sense to make a weak version once the fee has been already paid.

 

[Ypedal]

Can someone explain this saturation thing in normal human terms please ?

 

[eP]

Can someone explain this saturation thing in normal human terms please ?

Saturation is when: more amps = no more torque or very very small increase of torque.

You can realise the core as great collection of very miniature elementary magnets.
At the level of saturation (current level) all those magnets stay theirs faces at the same direction.
So above that current level those magnets cant add additional magnetic force which is source of torque.

Cheers

 

[29a]

What would the effect on a hub motor be if it had weaker than normal magnets
Would it draw more amps to attain the same speed/torque as the same motor with stronger magnets

 

[Ypedal]

I suspect ( and please correct me if i'm wrong ) .. but

Stronger magnets : Will allow the motor to draw more amps resulting in more torque.. but will also create more " Cogging " effect when not-powered..

Weaker magnets : have a result of limiting the amount of amperage the motor can draw and use. But this setup will create less drag when coasting.

is that right ?

 

[EbikeMaui]

I suspect ( and please correct me if i'm wrong ) .. but

Stronger magnets : Will allow the motor to draw more amps resulting in more torque.. but will also create more " Cogging " effect when not-powered..

Weaker magnets : have a result of limiting the amount of amperage the motor can draw and use. But this setup will create less drag when coasting.

is that right ?

Weaker magnets reduce cogging and are saturated faster which limits torque.Amps and can contionue to build as heat can perminantly destroy the magnets strength.Higher quality magnets can provide more torque and withstand a higher temp.

 

[EbikeMaui]

What would the effect on a hub motor be if it had weaker than normal magnets
Would it draw more amps to attain the same speed/torque as the same motor with stronger magnets

 

[fechter]

What would the effect on a hub motor be if it had weaker than normal magnets
Would it draw more amps to attain the same speed/torque as the same motor with stronger magnets

If you ignore saturation effects, weaker magnets will have the same effect as using fewer turns of wire. Higher no load speed, but less torque per amp. Opposite is true for stronger magnets.

The real difference is the efficiency at high loads, like acceleration. Stronger magnets will maintain a much higher efficiency in that low speed - high torque region of the motor curve where efficiency sucks.

At very light loads (like going downhill), stronger magnets will have increased drag due to core losses. It's sort of a trade-off. I'll put my money on the strongest magnets I can get my hands on.

 

[Toorbough ULL-Zeveigh]

I'll put my money on the strongest magnets I can get my hands on.

Who wouldn't, which is why I find it difficult to accept that any self respecting engineer at a hub motor manufacturer wouldn't want that too. It's a no-brainer.

Then what about variable reluctance motors that have no magnets at all? I would have expected them to have poor efficiency but supposedly that's not the case.

 

[EbikeMaui]

What would the effect on a hub motor be if it had weaker than normal magnets
Would it draw more amps to attain the same speed/torque as the same motor with stronger magnets

If you ignore saturation effects, weaker magnets will have the same effect as using fewer turns of wire. Higher no load speed, but less torque per amp. Opposite is true for stronger magnets.

The real difference is the efficiency at high loads, like acceleration. Stronger magnets will maintain a much higher efficiency in that low speed - high torque region of the motor curve where efficiency sucks.

At very light loads (like going downhill), stronger magnets will have increased drag due to core losses. It's sort of a trade-off. I'll put my money on the strongest magnets I can get my hands on.

With stronger magnets the efficiency at the stall point can be rather high and all through out the low range to 1500 rpm.Less magnets can be used and less iron backing would be required= A larger OD with more poles with a light weight rotor.= More efficient torque in a lighter package.
Since you would have a freewheel there would be 0 cogging at any time!. Runnning at high rpm would not be required to get great efficiency with the right designed Rotor and Sator.Other methods can be implimented to reduce cogging WITHOUT! reducing efficiency at high RPM or coasting..
Field weakening is obtained by electronically
advancing the phase of the stator
currents to produce a demagnetizing
component of stator magnetomotive
force which opposes the rotor magnet
flux, thus reducing the the net effective
flux.

This may help ?
http://www.ee.kth.se/php/modules/publications/reports/2004/IR-EE-EME_2004_006.pdf
Take into consideration that all other hub motors heat radiates OUTwards from the stator traping all the motors heat in the magnets. When the magnets are on the rotor only the small amount of magnet heat goes out quickly through the stator, a direct cooling path to air cooled heat disipating aluminum on the outside.= NO magnet heat. No need to vent.
A thin version of Fig. 7 Rotor would be a ideal design for a hub motor with a freewheel in the rotor.
http://turbolab.tamu.edu/pubs/Turbo35/T35pg103.pdf

 

[eP]

With stronger magnets the efficiency at the stall point can be rather high and all through out the low range to 1500 rpm.

At the stall point EFFICIENCY is always ZERO.

Less magnets can be used and less iron backing would be required= A larger OD with more poles with a light weight rotor.= More efficient torque in a lighter package.

Torque is never efficient - torque is high or low - higher torque mean loss at efficiency always.
A little loss or a more than little but always it is the efficiency loss.

Since you would have a freewheel there would be 0 cogging at any time!. Runnning at high rpm would not be required to get great efficiency with the right designed Rotor and Sator.

Since you would have a iron stator and strong magnets you get relatively strong cogging especially at high torque and low power out.
Only coreless stator would be 0 cogging at any time!.

Other methods can be implimented to reduce cogging WITHOUT! reducing efficiency at high RPM or coasting..

Yes - you are right - coreless axial flux design.
More magnets area, no iron core, much greater efficiency at the same weight and size - much shorter magnetics cirquits.

 

[EbikeMaui]

While coreless eliminates cogging it also eliminates high torque at low end. EMBEDED magnet rorors inhance the core use to make a stronger magnetic field using less iron core and less magnetic material at the same time creating more torque and efficiency at low and mid range rpm.Using a freewheeling one way clutch bearing eliminates all negitive effectecs of cogging.FYI cogging is from the magnet tetent on the stator teeth that is only felt when no stator power is used while coasting without a freewheel.Cogging with strong magnets always hepls increase efficiency at low end when under power.Coasting is a different story.
Most axial flux disc motors have cores unless made for high RPM only.For HIGH torque low RPM (1-3000 RPM) Cogging motors using a freewheel will fix all negitive effects.Coreless motors the same size will NOT have nearly as much torque or efficiency at low end rpms.
A procedure to design low speed radial PM motors was presented. Different types of rotors were investigated. The advantages and drawbacks of the different rotors used for the low speed application were given. The methods to calculate the airgap flux density and the inductances and currents, which depend on the rotor configuration investigated, were introduced.
http://www.ee.kth.se/php/modules/publications/reports/2004/IR-EE-EME_2004_006.pdf
While at Stall there is O efficiency a motor that has has a much stronger magnetic core or field is a lot more efficient from 1 to 3000 RPM.
You would think some one would just make a THIN 30 pole 3/4" wide inside rotor design hub motor that will just slide onto any Shimano freehub for a HIGH TORQUE single speed motor with GREAT EFFICIENCY using very strong, small EMBEDED magnets.. At less costs overall! You can also benifit in a single chain reduction by reducing the motor size by the same ratio factor that your redudcion ratio is.
A 8 to 1 redidtion on a chain drive motor will save you 80% of motor size and weight. to get the same results minus only a couple percent in inefficiency due to chain spin.

 

[eP]

While coreless eliminates cogging it also eliminates high torque at low end.

It is not true.

1800 W @ 1080 rpm @ 97.5% eff. - you have pretty nice torque at high end.

So at low end you still have even higher torque at good efficiency.

Most axial flux disc motors have cores unless made for high RPM only.For HIGH torque low RPM (1-3000 RPM)

It is not true again.

You can get high torque at nominal 1000 rpm, and much more at lower rpm.

Lets lok at this

As seen in Table 2 and Figure 12, theUltracommuter direct drive wheel motordemonstrates that brushless ironless motors canproduce extremely high torque densities (torque per unit mass) with appropriate design, and are notlimited to high speed applications. Because of their very low spinning losses, efficiency at low torquesand varying speeds is very high, ensuring highefficiency in their actual application as vehicletraction drives as measured using driving cycles. The wheel motors are currently in the final stages of manufacture and experimental results will bepresented in future publications

Cogging motors using a freewheel will fix all negitive effects.Coreless motors the same size will NOT have nearly as much torque or efficiency at low end rpms.
A procedure to design low speed radial PM motors was presented. Different types of rotors were investigated. The advantages and drawbacks of the different rotors used for the low speed application were given. The methods to calculate the airgap flux density and the inductances and currents, which depend on the rotor configuration investigated, were introduced.
http://www.ee.kth.se/php/modules/publications/reports/2004/IR-EE-EME_2004_006.pdf
While at Stall there is O efficiency a motor that has has a much stronger magnetic core or field is a lot more efficient from 1 to 3000 RPM.

You completly dont know what you writing about.

If you have 0 efficiency at stall and less than 20% at less than 50 rpm you cannot get a lot more efficiency.

What you talking about is completely FALSE

Show me iron core motor under 2000 W which is more efficient (more than 97.5%).

You would think some one would just make a THIN 30 pole 3/4" wide inside rotor design hub motor that will just slide onto any Shimano freehub for a HIGH TORQUE single speed motor with GREAT EFFICIENCY using very strong, small EMBEDED magnets.. At less costs overall!

So tell us the costs and efficiency Randy.

You can also benifit in a single chain reduction by reducing the motor size by the same ratio factor that your redudcion ratio is.
A 8 to 1 redidtion on a chain drive motor will save you 80% of motor size and weight. to get the same results minus only a couple percent in inefficiency due to chain spin.

This is the true, so it is a good way if you cannot afford for powerful flexible (efficient at wide range of rpm) motor hub.

Regards

 

[Miles]

eP, why are you wasting your valuable time here? You seem to have all the answers, why don't you just get on with it....?

At least Randy has actually built something.

 

[Lowell]

eP, why are you wasting your valuable time here? You seem to have all the answers, why don't you just get on with it....?

At least Randy has actually built something.

Actually it's kind of funny to watch.

 

[Miles]

Actually it's kind of funny to watch.

True

 

[EbikeMaui]

eP, why are you wasting your valuable time here? You seem to have all the answers, why don't you just get on with it....?

At least Randy has actually built something.

Actually it's kind of funny to watch.

The funny part about it is for spending a $1000. on any other system YOU are getting Jippped..BIG TIME ! :lol:

 

[EbikeMaui]

I suspect ( and please correct me if i'm wrong ) .. but

Stronger magnets : Will allow the motor to draw more amps resulting in more torque.. but will also create more " Cogging " effect when not-powered..

Weaker magnets : have a result of limiting the amount of amperage the motor can draw and use. But this setup will create less drag when coasting.

is that right ?

besides cost thats why hub motors are ineifficient and need freewheels with stronger magnetic fields along with quality controllers to only be somewhat efficient...

 

[EbikeMaui]

With stronger magnets the efficiency at the stall point can be rather high and all through out the low range to 1500 rpm.

At the stall point EFFICIENCY is always ZERO.

Less magnets can be used and less iron backing would be required= A larger OD with more poles with a light weight rotor.= More efficient torque in a lighter package.

Torque is never efficient - torque is high or low - higher torque mean loss at efficiency always.
A little loss or a more than little but always it is the efficiency loss.

Since you would have a freewheel there would be 0 cogging at any time!. Runnning at high rpm would not be required to get great efficiency with the right designed Rotor and Sator.

Since you would have a iron stator and strong magnets you get relatively strong cogging especially at high torque and low power out.
Only coreless stator would be 0 cogging at any time!.

Other methods can be implimented to reduce cogging WITHOUT! reducing efficiency at high RPM or coasting..

Yes - you are right - coreless axial flux design.
More magnets area, no iron core, much greater efficiency at the same weight and size - much shorter magnetics cirquits.

Coreless motors suck unless at high RPM.

 

[EbikeMaui]

While coreless eliminates cogging it also eliminates high torque at low end.

It is not true.

1800 W @ 1080 rpm @ 97.5% eff. - you have pretty nice torque at high end.

So at low end you still have even higher torque at good efficiency.

Most axial flux disc motors have cores unless made for high RPM only.For HIGH torque low RPM (1-3000 RPM)

It is not true again.

You can get high torque at nominal 1000 rpm, and much more at lower rpm.

Lets lok at this

As seen in Table 2 and Figure 12, theUltracommuter direct drive wheel motordemonstrates that brushless ironless motors canproduce extremely high torque densities (torque per unit mass) with appropriate design, and are notlimited to high speed applications. Because of their very low spinning losses, efficiency at low torquesand varying speeds is very high, ensuring highefficiency in their actual application as vehicletraction drives as measured using driving cycles. The wheel motors are currently in the final stages of manufacture and experimental results will bepresented in future publications

Cogging motors using a freewheel will fix all negitive effects.Coreless motors the same size will NOT have nearly as much torque or efficiency at low end rpms.
A procedure to design low speed radial PM motors was presented. Different types of rotors were investigated. The advantages and drawbacks of the different rotors used for the low speed application were given. The methods to calculate the airgap flux density and the inductances and currents, which depend on the rotor configuration investigated, were introduced.
http://www.ee.kth.se/php/modules/publications/reports/2004/IR-EE-EME_2004_006.pdf
While at Stall there is O efficiency a motor that has has a much stronger magnetic core or field is a lot more efficient from 1 to 3000 RPM.

You completly dont know what you writing about.

If you have 0 efficiency at stall and less than 20% at less than 50 rpm you cannot get a lot more efficiency.

What you talking about is completely FALSE

Show me iron core motor under 2000 W which is more efficient (more than 97.5%).

You would think some one would just make a THIN 30 pole 3/4" wide inside rotor design hub motor that will just slide onto any Shimano freehub for a HIGH TORQUE single speed motor with GREAT EFFICIENCY using very strong, small EMBEDED magnets.. At less costs overall!

So tell us the costs and efficiency Randy.

You can also benifit in a single chain reduction by reducing the motor size by the same ratio factor that your redudcion ratio is.
A 8 to 1 redidtion on a chain drive motor will save you 80% of motor size and weight. to get the same results minus only a couple percent in inefficiency due to chain spin.

This is the true, so it is a good way if you cannot afford for powerful flexible (efficient at wide range of rpm) motor hub.

Regards

Show us any coreless motor that can produce more torque than the specs of this disk motor at low RPM for its size..