DIY Electric Car Forums banner

In wheel hub electric motors??

11693 Views 39 Replies 13 Participants Last post by  Duncan
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.
1 - 8 of 40 Posts
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.

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.

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)
See less See more
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.
See less See more
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..
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.
Nice to hear about some real life results. So it could really be worth trying a double BLDC drive without transmission?
Does your truck also have a tranny or is it direct drive from the motor?
Is that with a three phase AC or DC motor?
I'll have to check it out. Do you have some posts on the forum with some more info?
Controllers will always have a nominal efficiency at some point of their power curve.
I'm thinking for example, if we were talking about Brushed DC, then beyond a certain speed (when trying to reach top speed). It might be better to just eliminate the controller and have a direct connection to the batteries (assuming the setup is well balanced and the motor won't burn out).
By doing this you can eliminate any losses in the controller.
if the speed becomes too great you just power off from the pedal and roll until you need to boost again. (could be annoying if your not just holding top speed). Then perhaps there is reason to switch in a different type of controller solely for top speeds. By designing one that is more efficient at those high rpm high current demands there may be a little leeway as far as tweaking for speed or economy gained.
If we are talking in wheel motors then that is potentially 4 controllers worth of lost economy when operating outside of the nominal range for efficiency.
I'm getting carried away. I really don't know enough about efficiency of brushless motors and their controllers. I'm guessing a computer can control a variable frequency type drive and tune for efficiency continually. Although everything does have a nominal range at the end of the day depending on what it was designed for.
I doubt that there exists much of a solution for brushless apart from changing the timing perhaps.
It would be interesting to see the difference in top speeds with and without the controller in a brushed setup.
I remember my 1st RC car's speed controller. It was manual and controlled by a servo. at full speed it was just a straight connection to the battery, otherwise it had to pass through a high power resistor or two.
As far as the controller limiting rpm or speed, that may be the case but there is often a way around that by re-programming, over-volting or modification.
Once you have unlocked the full potential of the system, you would just need to be aware of your motors limitations in the respective wiring configurations.
You would need a watt meter or perhaps even an ammeter for each mode and just treat it like a rev counter. Don't red line for too long! Or just ask the controller to do this for you.
Perhaps have one controller for Delta and one for Wye. Each one setup differently to work best at those speeds. The switching relay could switch controllers at the same time as switching the wiring configuration.
See less See more
Well Weather or not 4 controllers have more or less loss than one 4x their size is hard to say. But i guess my point was that there is always some loss in a speed controller and that they are probably made to be more efficient at nominal speeds (depending on the application).
I really think there could be a significant amount of power saved by eliminating the controller at top speeds which could work with a brushed motor especially if you were maxed out on a freeway for example.
I was just wondering if there might be a way to do something similar with three phase in order to get the best efficiency possible at top speeds. Since you need some sort of controller for three phase the only other option i could think of is to have multiple controllers that are designed to give better efficiency at different speeds. So for town driving the car would switch to the controller that was made to be most efficient at lower rpm. And when of the freeway the controller best suited to high speeds would kick in and the other/s would switch out and turn off.
The difference might not be much but who knows it might be as much as a 5% increase in range or it could potentially decrease the battery size by 5% which could result in a saving of weight (depending on the weight of the extra/modified controller).
See less See more
Great point but perhaps 1% is not being generous enough :D
If i told you that there were two battery types available for your project and that one of them had 1% or 2% more stored energy available then you might decide to buy the better battery no?

If enough other tweaks could be made in other areas then might it be possible to see an even higher overall gain in efficiency?
If in the future electric cars start to cover longer distances as standard then this concept might prove worth while.

Cars could be covering many more motorway miles and thus the advantage may be realised more than 20% of the overall driving time, which is the ratio that you had suggested that we might be benefiting from if high speed economies were achieved if we changed the controller at different rpm (or by redesigning the controller to have a wider efficiency characteristics whilst still providing adequate output power across the rev range).

Also since motorway driving is done at higher speeds this also means that it is most likely going to be the time we see the highest current draw from the batteries. Which means that just a few percentage gained in efficiency will go a longer way at 300A per say when compared to the saving of a few percent at 80A for example whilst poodling around town or when driving at medium speeds around the suburbs.
If battery exchange / charging stations or perhaps even super fast charging stations are to be implemented in the future then perhaps these small gains will not be worth it, perhaps such technology would only be implemented in the higher end cars.
But at least for anyone out there who might be running brushed DC motors, it might be worth considering.
I doubt even the best controllers are actually more than 90% efficient in real life conditions. So imagine gaining 10% efficiency when running at full speed.
A pain in the ass when the only speed control becomes pedal on pedal off but perhaps there is still something to be gained here for someone reading this.
See less See more
1 - 8 of 40 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.