[Prideisdead]

Hello.
Im new to this forum.
I have a intrest in EV cars and looking to do a budget build.

But firstly doesn anyone know of in in wheel hub electric motors?
I recent read a article about a university that converted a frwd car to awd and had two in hub motors in the rear tires. Supposedley only costing $3000. $3000 sounds very low for this type of build but i was intrested in the in wheel motors.

Anyone know where to start looking for one?

Or maybe even a motor that would connect to the drive shaft of a rwd.

Im intrested in keeping the engine in place and having some type of hybrid build.

Has anyone done this successfully?

Any belp would be appreciated.

 

[nucleus]

They don't exist (in a practical sense), or work for anything much larger than a bicycle.

Bad idea.

Lack of gearing means you need big heavy motor, which means big heavy hub and high unsprung weight.

Big heavy motor needs cooling, how is that dealt with?

Ditto brakes, regenerative braking is not enough, where do you put the brakes?

Recent thread:

http://www.diyelectriccar.com/forums/showthread.php?t=184329

 

[MathisLaurant]

Yes, you will have poor ride quality with hub motors this is one company moving forward with it that i know of

http://www.proteanelectric.com/

 

[Karter2]

Yes, you will have poor ride quality with hub motors this is one company moving forward with it that i know of

http://www.proteanelectric.com/

Dispite being one of the leaders in the field, even Protean dont appear to have "moved forward" with this concept in the last 4-5 years ?
I suspect one of the reasons is because the torque capability of these motors is a fraction of a conventional geared EV drive train (EG Tesla)
Their 1000Nm max is only similar (less infact) than Tesla cam produce at the motor,...before a 9.7:1 multiplication in the final drive gearing !
One other reason is of course the unmentioned cost of the (multiple) hub motors and the control systems required to drive them.

 

[Prideisdead]

Alright thanks for the reply. So i guess nothibg at this point.

I guess a single motors full replacement would be the most economical and easyiest to do.

Im more intrested in the the acceleration EVs.

Hopefully me and the wife will be attending pikes peak this year. A bunch of awesome EVs will be there.
Rimac.
Tesla.
Eo1
Faraday
And possibly a bonda nsx.

 

[Karnaj]

Curious to know if anyone has heard about the YASA or Ecomove hub motors. Haven't been able to find much on the YASA but the numbers reported for the Ecomove don't look bad from my limited understanding. 40kw peak/24.5kw continuous, 361 ft/lb torque in a 46.5 lb package? Sounds good. Going by a formula I was given of ~7hp per 1000lbs of vehicle needed for decent performance (more if hilly terrain expected), these look like a possibility. Assuming this is all true what am I missing? Controllers and price not being factored for this question.

I'm truly curious. In hub motors would clear up SOOO much room for batteries for the project I would like to do, a 33-34 Ford Tudor Sedan. All I have to work with is the engine compartment, the old classics didn't have a trunk in those days.

I would really appreciate input from the more in the know.

 

[brian_]

Going by a formula I was given of ~7hp per 1000lbs of vehicle needed for decent performance (more if hilly terrain expected), these look like a possibility.

7 continuous horsepower per thousand pounds of vehicle is okay to keep the vehicle moving at a constant and moderate speed on level ground. To accelerate well by current automotive standards, 70 horsepower per thousand pounds (for as long as it takes to get up to speed) is closer to a reasonable power budget.

 

[Rustle731]

You're referring to the MTSU project. There are videos and articles and they've had some limited success. Protean purchased a bike/scooter hub motor manufacturer in China, and struck a deal with FAW Volkswagen (China) a few years back, for Hybrid development. Protean also partnered recently, stateside with ConMed in Vancouver Wa, for development of Hybrid vehicle fleets. Here are a few links:
http://www.proteanelectric.com/
https://cleantechnica.com/2012/07/26/mileage-boosting-drop-in-plug-in-hybrid-retrofit-kit/
And a pic:

 

[brian_]

The pictured thing from MTSU is an old dead-end project. An earlier discussion of this particular device can be found starting at post #473 of the open source hub motor/wheel motor thread, but there are lots of wheel motor discussions in the forum.

 

[izzzzzz6]

Hi Guys. I found myself here after asking myself similar questions but for slightly different reasons and hence not exactly hub motors but two motors driving each drive shaft independently.
I'll try to list the reasons, the concept and the questions.
Ps. I have seen many hub motors for sale on Ali Baba but i'm not sure who is actually buying these and weather or not they are just a concept product or not.

Concept: Using two BLDC motors, one to drive each driveshaft.

Reason:
1. Two motors are twice as powerful as one and BLDC can be wired in delta and Star configuration meaning that a virtual (electrical) gearing is available for low and high speed rpm.

2. Disposing of a gearbox will save space, weight and resistance.

Questions:
1. Will the torque be adequate to get a very small car rolling at a modest acceleration (not for racing along, just enough to be drivable).
2. If the motors are connected (wired) in parallel. Will this work as a differential.
Meaning that; When turning corners will the wheel that is moving faster transfer the extra electrical energy into the motor that is trying to turn slower or will the motors soak up the difference in energy and naturally let more energy go to the motor that is trying to spin faster through the corner.

Other possible problems:
1. Might be difficult to fit two motors between the driveshafts in a front wheel drive, might be easier on a rear wheel drive.
2. Switching from delta to Y or Star could be tricky at high current loads.
3. Finding a controller which can produce enough current and be able to over-volt the motors without surpassing their Max KW rating (for higher rolling speeds)

 

[dcb]

fyi the need for delta/wye switching (like series parallel switching) is largely overcome with a better controller and battery.

You *can* change the peak torque/peak rpm with pole changing motors (non linearly) in an induction motor at least, but with bldc/pmac I doubt it since the poles are fixed by the rotor.

 

[brian_]

Concept: Using two BLDC motors, one to drive each driveshaft.

Reason:
1. Two motors are twice as powerful as one and BLDC can be wired in delta and Star configuration meaning that a virtual (electrical) gearing is available for low and high speed rpm.

2. Disposing of a gearbox will save space, weight and resistance.

There seem to be two separate ideas being mixed up here.

1. Separate motors for each wheel
   
   This eliminates the differential, not the transmission.​
2. Changing wiring configuration of whatever you consider to be a "BLDC" motor
   
   This might help reduce the need for a multi-speed transmission, but has nothing to do with separate motors for each wheel.​

As already noted, this really isn't about in-wheel motors; the only connection is that in-wheel motors are inherently one-per-wheel.

What isn't clear is whether the intention is to use the motors to drive the wheels without any reduction gearing. Again, this is unrelated to in-wheel motors, which can be used with or without gearing. I don't any sense in using motors without gearing... and that's why essentially no one does it.

Two motors are obviously twice as powerful of one of the same motors, but more obvious solution to getting twice as much power is to simply use a bigger motor.

 

[brian_]

2. If the motors are connected (wired) in parallel. Will this work as a differential.
Meaning that; When turning corners will the wheel that is moving faster transfer the extra electrical energy into the motor that is trying to turn slower or will the motors soak up the difference in energy and naturally let more energy go to the motor that is trying to spin faster through the corner.

This depends on the motor type, but seems unlikely to me to work acceptably for any type of motor. At a first approximation motor torque output is dependent on current, so maintaining equal current between the motors would provide the equal torque split provided by a mechanical differential; however, parallel connection will provide equal voltage (not equal current) and if one wheel slips due to inadequate traction the result would not likely be good.

Managing the speed difference is a well-known issue. I noticed that Curtis Instruments has a standard solution: Dual-Drive. It is mentioned as a feature in many of their controllers, and a typical application is described in an article on their site.

The idea of Dual-Drive is:

• each motor has its own controller
• the controllers are connected to communicate with each other
• one controller is designated as the master (and the other the slave), just so that the control logic runs in one place
• an angle sensor provides steering position input to the master controller
• control parameters are set appropriately for the wheelbase, track, and steering sensor calibration
• the motors are driven to maintain the speed difference corresponding to the current steering angle

... or from the article:

The standard Curtis dual-drive
software allows the 1236 controllers (one master, one slave) to correctly control the dual-drive operation of the truck. This includes varying motor speed on inner and outer wheels during turns to provide true differential control.

Current production EVs generally use a single motor per axle and a conventional mechanical differential, so they resort to using the same methods for individual control of wheel torque for traction and stability control. A trend toward separate wheel motors is starting, to allow this control to be executed by the motors, without dissipating power in brakes. This makes sense, but implies an advanced level of control.

 

[brian_]

1. Might be difficult to fit two motors between the driveshafts in a front wheel drive, might be easier on a rear wheel drive.

This is an issue at front or rear, since

1. the width of the motor assembly (across the outputs) must fit between the shortest acceptable axle shafts, and
2. the width of the motor assembly (across the housing) must fit between the suspension mounting points.

The most common drivetrain configuration in modern cars is a transverse engine with the transmission on the end of the engine, and despite the combined length this all fits in the front of the car. The popularity of McPherson strut front suspensions is largely due the amount of space this design leaves for the engine. To address the shaft length issue, the differential is always arranged to be near the engine/transmission connection. Rear suspensions typically leave less space for a wide motor assembly, because they are designed to fit under a floor (rather than around an engine) and only need to accommodate a small final drive unit (differential).

The packaging is particularly difficult - due to the first dimensional limitation - if the motors are placed end-to-end with outputs (including reduction gearboxes) on the outboard ends. Despite the width, this configuration is used in a few cases, such as the Rimac Concept One (which is a wide car) and the front of the new Acura NSX (which has very small front motors). The normal solution is to face the motor outputs inboard, with the gearboxes between them, placing the gearbox outputs very close together near the centre; this requires that the gearbox shift the shaft centreline far enough to clear the motor cases... such as in this Xtrac:

 

[izzzzzz6]

Sorry. I know it is not exactly relevant to in wheel motors but it is a similar system that is up against similar obstacles. It was more of a question that i was throwing out there.
The thing with 3 phase motors and i believe it included brushless is that you can change the wiring from Delta to Star mid rev. This acts like an electronic gear to some extent thus potentially helping to eliminate the transmission, perhaps it is enough to have these two modes rather than gears, assuming that the direct drive was geared up correctly and that the motor had lots of overhead and also assuming that you don't need tonnes of torque at low speeds. If your motor(s) is/are well overrated then as long as you don't exceed it's rated power level you can push it a bit at low speeds or over volt it a bit at high speeds (potentially risking premature damage to the bearings or speed wobble from parts not being balanced at those speeds + timing issues etc).
With the gains from less weight and less friction plus more space for bigger motors and batteries it might suit some people to go single speed as far as gears go.
The question about differential was just to see what people think or if anybody knows if there would be enough forgiveness between the two motors if they were connected in parallel or would such a simple setup potentially cause damage to AC and BLDC 3 phase motors ?
Perhaps it would work well with other types of brushed DC motors or perhaps the motor turning fastest would start to act like a generator and try to power the slower turning wheel causing tyre ware etc.?
It just might be an easier or cheaper option than buying what appears to be not easily available in wheel motors. If you can fit them in.
But I'm sure there is an easy way to correct the wheel speeds electronically if going diff-less. I just don't know the answers sorry.

 

[izzzzzz6]

Good answer. Might also help to go this route if you can get 2 fairly large controllers with this feature. To double the power by doubling your controller count and motor count etc..

 

[izzzzzz6]

That photo looks like a sweet setup, which OEM makes that one? Have you seen the guy with the dual motor 4x4? He has a chain link between the two.
I'm guessing that a motor won't always have the same performance in reverse? actually i don't think it's a problem with 3phase BLDC as you can usually reverse any 2 of the 3 windings to change direction. that way you could stack motors and just reverse the direction of the one that is powering the other wheel. Or perhaps there is enough play in the driveshafts to off set the two motors?
In wheel sounds like a great idea though. I like the idea of the electric skateboard which has it's motors built into the wheels. I would lie to get my hands on some of those motor wheels.

 

[dcb]

can change the wiring from Delta to Star mid rev. This acts like an electronic gear to some extent thus potentially helping to eliminate the transmission,

I don't think it does actually, that was more of a hack for controllers that couldn't deliver a lot of current or voltage.

however pole changing does have potential, as you are changing the circumferential distance between the poles on the fixed vs rotating bits, and the attraction isn't linear with distance.

 

[WolfTronix]

The old Brusa AMC motor controllers (circa 1993), have a Delta / Wye input...

Delta is about twice the RPM, and about half the torque of Wye.
Wye is about twice the torque, and about half the RPM of Delta.

An external contactor is used to switch the ACgtx20 motor between the two wiring configurations (all coils are in the junction box):

Delta:

Wye:

Note: you would bring all the coils out to your Delta/Wye contactor.

The Delta / Wye input tells the AMC motor controller which parameter set to use (resistance, inductance, back EMF, etc... changes between the two modes).

My test box even supports this feature:

My truck in Delta has a max speed of 70MPH.
My truck in Wye has a max speed of 35MPH (but acceleration is twice that of Delta).

 

[dcb]

Delta is about twice the RPM, and about half the torque of Wye.
Wye is about twice the torque, and about half the RPM of Delta.

The thing is (and I assume you are aware of this) that it is probably current limited by the controller (and/or rpm limited by bus voltage).

So that a better controller/battery will negate any benefit from delta/wye switching, and is much simpler conceptually. In delta each phase is seeing 1.73 times less current unless you dial up the current from the controller. In wye it takes 1.73 times more voltage to cancel out the back emf at a given rpm.

This isn't the case with pole changing (i.e. dahlander) motors I don't believe. You can change the toque/rpm capabilities of the machine. So while delta and wye (as a machine with its own limits, independent of controller limitations) operate in the same torque/rpm modes, pole changing can indeed act like a gearbox, kinda, within limits.

I did an armchair analysis of ABB motors here:
http://www.diyelectriccar.com/forums/showthread.php/number-poles-revisited-again-164921.html