[WheelMotor]

Please read again the first post of this thread . "I want to produce"

So the purpose of this thread is to meet people to set up the business. I am not pretending that I know it all and that it's a peace of a cake.

However, before we commit substantial money and time to this, we would like to be already in contact with the market. The idea is to let the project grow as a partnership between the producer and the sales promoter.

[major]

Hey WM,

All the desire, money, business planning, partnerships, open source forums, and so on will be for naught if you don't have a competitive product. And my many years in the motor and EV business tell me that is a big problem for you.

Still say Good Luck,

major

[WheelMotor]

Originally Posted by major

Hey WM,

All the desire, money, business planning, partnerships, open source forums, and so on will be for naught if you don't have a competitive product. And my many years in the motor and EV business tell me that is a big problem for you.

Still say Good Luck,

major

Major,

you are a pessimist . Within a few months I will be back here with a video of a prototype installed in a car. Than we speak again !

In the meanwhile everybody who has a tip for the sales promotion please post here.

[major]

Originally Posted by WheelMotor

Major,

you are a pessimist . Within a few months I will be back here with a video of a prototype installed in a car.

Hi WM,

I can hardly wait. Good luck.

major

[samborambo]

WheelMotor,

The concept of a hub motor with the rotor fixed to or part of the wheel rim and the stator attached to the caliper assembly is something I've been toying with for the past month or so.

It's an outrunner design but with similar torque / speed characteristics to the Etel torque motor range: http://www.etel.ch/torque_motors (the Etel motors are actually inrunners but you get the idea)

I've started working with FEMM 4.0 to model the motor but I haven't had a lot of time lately to do it. Once I have something presentable, I'll share it here.

My goal is retrofit kits for the existing small passenger fleet - focusing on the most popular and / or efficient car models to begin with. The rotor / stator may remain the same design for many different vehicles, just the mounting arrangement may differ. It makes the most logical sense - there's no point reinventing the wheel (excuse the pun) but if you start replacing axle stubs, disk brakes, etc you end up getting involved in a lot of unnecessary design work.

It's an excellent concept with a couple of obvious challenges. First is the air gap clearance between the stator and rotor. In most BLDC motors the air gap is kept within the order of 0.5mm to maintain a high flux and therefore keep the torque constant high. With this design, you're relying on the wheel's bearings to enforce the air gap - and we all know how shaky wheel bearings can get over time/miles. The rotor may start rubbing on the stator leading to a quick demise. You could have a large bearing ring between the rotor and stator also but this may introduce unnecesary losses and may make tyre changing tricky.

Secondly is the issue of space. On most larger cars with alloy rims of at least 14" and standard brake disk/calipers this shouldn't be too much of an issue. However, if you want to convert a "smart car" with tiny rims, you'll need a more custom arrangement like pushing the magnets deeper into the tyre rim.

I'm an electronics / computer / HV electrical engineer so I've been working on the drive electronics too. We really need someone who's had experience programming automotive computers for stability control, etc since the hub motors need to work in unison and therefore need to be integrated into one drive control unit.

Cheers WheelMotor, hopefully we can get the ball rolling on this one.

Sam.

[WheelMotor]

Hi Samborambo,

Happy to hear you are less pessimistic than Major !

I am devoting all my time now to getting a prototype on a car asap. The coming week I will try to have a low cost FET motor controller with Hall sensors finished.

A cooperation between us could be fruitful. My approach is to make a complete set of 2 Wheel Motors + controller manufactured in Low Cost Egypt available at a price level in the range of the classic in board DC motor + controller.

I could produce and you commercialise. Exciting days ! Lets see how far we get .

[samborambo]

I'm curious now - you'll have your drive design completed in a week? Can I see what you've got so far?

MOSFETs wouldn't really be suitable for a high voltage (~300V) design because of the ohmic losses. Drive systems in this power range almost exclusively use IGBTs due to the lower losses. IGBTs' losses (volt drop) are proportional to current whereas MOSFETs' losses (ohmic) are proportional to the current squared. You can get suitable MOSFETs in that power range but they won't perform as well. The drawback with IGBTs is more complex transistor driver circuit (require negative bias for efficient turn-off).

These IGBT six packs are specifically designed for hybrids and would suit individual wheel motors:

http://www.infineon.com/cms/en/produ...1370f45ed90441

I think we need to turn conventional motor construction on its head in a few respects. Most industrial electric machines are designed for constant power / speed applications. That's where most development has happened over the past few decades. I believe there's a lot of room for pioneering work in automotive traction motors.

I'm keen to use aluminium tape or foil for the magnet wire instead of copper for two reasons. First, aluminium has a higher specific heat capacity (temperature rise for a given mass and heating energy) so the motor will have 16% greater peak power including the Weight Reduction. For an equivalent conductive CSA, aluminium is HALF the weight of copper. The drawbacks of aluminium are 60% greater volume for equivalent copper CSA and thermal deformation - both of which can be designed for. Using tape or foil, the winding window would be almost the same area as copper since copper wire typically has a winding factor of 70% and even less for litz wire. A drawback of wide tape or foil could be increased eddy current losses in the windings. I haven't calculated the losses that eddy currents introduce but even in the worst case scenario, chokes can be added to reduce the effect.

The reduction in weight would greatly reduce the impact on unsprung weight. I'd like to aim to keep the rotor and stator together under 10kgs.

The second idea I had is to incorporate the ability to switch the configuration of the torque motor. For instance, with a 36 finger stator, 12 parallel x 1 serial per phase for high speed / half torque and 6p2s per phase for lower speed / full torque. This would keep the BEMF within a manageable range and increase efficiency of the IGBTs. Think of it somewhat like an electrical gear box - you're altering the turns ratio of the motor windings. The transition would be seamless since its the controller causing the switching based on speed thresholds and then halves or doubles the current.

Wheelmotor, please post up your design so far for both the motor and electronics. You said you want to participate in open source development of the motor. Please let others contribute too.

Sam.

[WheelMotor]

High Samborambo,

Happy with your contribution in this discussion !

The reason I did not shared openly my progression is that I felt no input (only scepticism ) from the other members at first. Second point is that I have no ambition to teach, I want to do business. Therefore I want an approach inspired by practicality.

So far:
Thanks for the tip about Insulated Gate Bipolar Transistor. I am 52 and my knowledge of electronics is getting a bit rusty.
I ringed to the Distributor of Infineon in Brussels where I asked them for this "six pack". They said they did not followed this item because of infrequent demand, but they should investigate. They could/would not give a price.
However, I was not anticipating 300V. Normal should be 8 x 12 volt = 96 v. If we start with 8 V Trojans of 2 banks in parallel ... it gets bulky to get to even 150V.
For what the controller is considered: I will see what I can find here in Belgium and than start from there. If I can't get it working within 10 days or so, I can always postpone this item and by simply a Kelly controller.
http://www.kellycontroller.com/mot/B...ontroller.html

For the wiring I was indeed intend to use aluminium, because as I see it now, unsprung weight is the (only?) possible hurdle to success.

For what is considered the total construction of the wheel motor, I gave up on the idea to put the magnets in the rim and use the brake caliper to hold the rest of the engine. Because of the huge forces that the magnets will apply to the stator of the engine, it will be very difficult to change a tire + rim by the side of the road in case of a flat. The magnets can be destroyed if they smash in to the stator. Also the aluminium rim can flex a few mm and the airgap must be to big. Better to have the assembly under control in the factory.
An other possibility is a custom made 2 piece rim.

A 36 finger stator ??? Have you measured the dimension of 1 coil with a 3 mm thick wire? and the brake caliper?

I don't want to go open source anymore. Because the feedback in this forum is to theoretical and to far from practical reality.

However Samborambo I will PM you about how we could cooperate.

Please let this thread be only dedicated to commercial contacting and brainstorming.

[Technologic]

Originally Posted by samborambo

I'm keen to use aluminium tape or foil for the magnet wire instead of copper for two reasons.

Use copper clad aluminum wound between nomex (thin flat sheets)... that'll work just fine for the wire (flat wire being the OBVIOUS necessity here... but good luck finding it in egypt... seriously... good luck)

I'd use an electromagnetic braking DC motor... ie. a controller MUST be custom designed to permanently drive a variable (based upon braking power) voltage that would exert resistive forces on the stator and coils (DC not AC voltage... unless you wanted to get fancy with electro-anti-lock braking)

Neodymium is a must (did I say must must)

Sorry for my non-engineering help, this is more a hands on help here. I can help you with your FEMM btw samb, very familiar with the program.

[WheelMotor]

Hi Tech,
Is the skin effect in the CCAW sufficient at the low frequency of only a few 100 Hz to justify its use ?