3 ms·

Interesting concept, with a few large caveats: Cost: I’d assume the cost is for a single motor; that would be a fairly unstable vehicle to drive with different

Interesting concept, with a few large caveats: Cost: I’d assume the cost is for a single motor; that would be a fairly unstable vehicle to drive with different left/right turning behavior. Wheel offset: Mounting the motor here will require a pretty massive increase in wheel offset or a pretty massive outward push of the wheel centerline, with each having its issues. Brake heat: If the stock brakes are used they will likely cook themselves and the motor. You are essentially requiring the electric motor to do all the braking, or else developing a hybrid braking system. Using hydraulic brakes on just one axle is a non-starter for safety reasons. Very clever idea, and maybe they can make it work. There are more than the reasons I listed as to why this hasn’t been pursued previously.

moralestapia 3y ago
>If the stock brakes are used they will likely cook themselves and the motor. ??? Why? Doesn't it take the same energy to stop a car disregarding what kind of force put it in motion?
- CobaltFire 3y ago
  No; brakes function by turning the kinetic energy of the vehicle into heat via friction; using the motors for braking via regeneration produces some heat, but a fraction of the amount. For reference, it’s not uncommon to see temperatures of 1000F or higher after a single highway speed stop on the front rotors of most passenger vehicles. Having that amount of heat that close to the motor is something that needs to be designed around. The rear brakes will typically be 200-400F cooler depending on the weight bias, but that’s still not a trivial amount of heat.
  - moralestapia 3y ago
    a) An ICE car is going 60 mph and brakes to a standstill. b) An electric car is going 60 mph and brakes to a standstill. How does one generate more heat than the other? Why would the brakes "cook themselves" in b when they don't in a? >For reference, it’s not uncommon to see temperatures of 1000F or higher after a single highway speed stop on the front rotors of most passenger vehicles. I'd like to see that reference. 1000F is F1 tier, lol.
    - iancmceachern 3y ago
      Because in this proposed design the motor is the brake rotor, they're the same part. So when you apply the brakes, they get hot, so does the motor. Motors getting hot is not good.
      - moralestapia 3y ago
        I see, maybe that's why they only add motors to the back wheels, though.
        iancmceachern 3y ago
        Cars Have brakes on all 4, but thr fronts do 70% of the work.
        moralestapia 3y ago
        >but thr fronts do 70% of the work Yes, maybe that's why they only add motors to the back wheels (x2).
        iancmceachern 3y ago
        Yeah but what about the other 30% You can't just start taking parts off of cars without understanding the impacts. Also, ebrake, etc. These things are required by law.
        moralestapia 3y ago
        >Yeah but what about the other 30% Handled by the motor, the motor is the brake IIRC?
        iancmceachern 3y ago
        Electric cars have regenerative braking and also regular brakes. Regenerative braking doesn't replace the need for brakes. There are lots of reasons why, safety reasons, that you need thr brakes to work even if power fails, when the car is parked etc.
- zeckalpha 3y ago
  Additionally, "engine" braking is less stressful on electric motors, which function as generators when used that way.
gs17 3y ago
I don't see why you're assuming one motor: > A retrofitted car can have two or four of these electric wheel motors One motor definitely doesn't seem like a usable product without other changes to the car. Unless we're making an electric Messerschmitt Kabinenroller.
- CobaltFire 3y ago
  I’m assuming one motor at the lowest price point that the site is quoting, and because they state they only have one motor made now. That implies they are comfortable with the trade off and they see two or four as optional. I’d love to see an electric three wheeler, maybe like the old heavy duty Mazda trucks!
lelanthran 3y ago
[EDIT: Mea Culpa - he did modify the rear wheels only in the prototype] Actually, I think it is perfectly practical for a DIYer like me, with the following small caveats (as opposed to your large caveats): 1. Use a front-wheel-drive car as the donor. 2. Mount two motors on the rear wheels (one per wheel). This way: 1. The first instability from torque steer due to driving only a single wheel is gone - car will accelerate in a straight line because equal power is provided to both wheels. The second instability from larger unsprung mass is easier to mitigate on non-steering wheels (i.e. the rear wheels). The third instability from increased wheel offset relative to the kingpin is completely removed. 2. Modifying the offsets on the rear axles (specifically, reducing them) in a FWD car is simpler[1] than doing the same on the drive wheels. If a double-wishbone design is used, it becomes a little complicated, but no more complicated than doing the same on the front. 3. The rear wheels do (IIRC) ~10% of the braking work that the front wheels do, so there is less heat generated. Until recently, quite a lot of the low end cars came with drum brakes on the rear anyway/ I'm curious why he placed the prototype on the front wheels - he must have had a good reason. After al;, someone who came up with the design itself isn't stupid, and someone who actually modded the car knew what they were doing as well, so there's probably a good reason for modifying the front wheels and not the rear. [1] Still complicated, but a lot simpler - because the wheels don't steer there is no need to worry about the steering geometry, track rods/steering rack modifications, etc.
- culopatin 3y ago
  But the rear wheels in a FWD are rarely designed to push the whole car. They are designed to hold the car off the ground, so 10% of braking, and that’s about it. Once you want to apply torque to them, they either fold under the car, or you just bend whatever is holding them there.
smackeyacky 3y ago
Wheel offset might not be an issue id the motor sits within the wheel.

moralestapia 3y ago

>If the stock brakes are used they will likely cook themselves and the motor. ??? Why? Doesn't it take the same energy to stop a car disregarding what kind of force put it in motion?

CobaltFire 3y ago
No; brakes function by turning the kinetic energy of the vehicle into heat via friction; using the motors for braking via regeneration produces some heat, but a fraction of the amount. For reference, it’s not uncommon to see temperatures of 1000F or higher after a single highway speed stop on the front rotors of most passenger vehicles. Having that amount of heat that close to the motor is something that needs to be designed around. The rear brakes will typically be 200-400F cooler depending on the weight bias, but that’s still not a trivial amount of heat.
- moralestapia 3y ago
  a) An ICE car is going 60 mph and brakes to a standstill. b) An electric car is going 60 mph and brakes to a standstill. How does one generate more heat than the other? Why would the brakes "cook themselves" in b when they don't in a? >For reference, it’s not uncommon to see temperatures of 1000F or higher after a single highway speed stop on the front rotors of most passenger vehicles. I'd like to see that reference. 1000F is F1 tier, lol.
  - iancmceachern 3y ago
    Because in this proposed design the motor is the brake rotor, they're the same part. So when you apply the brakes, they get hot, so does the motor. Motors getting hot is not good.
    - moralestapia 3y ago
      I see, maybe that's why they only add motors to the back wheels, though.
      - iancmceachern 3y ago
        Cars Have brakes on all 4, but thr fronts do 70% of the work.
        moralestapia 3y ago
        >but thr fronts do 70% of the work Yes, maybe that's why they only add motors to the back wheels (x2).
        iancmceachern 3y ago
        Yeah but what about the other 30% You can't just start taking parts off of cars without understanding the impacts. Also, ebrake, etc. These things are required by law.
        moralestapia 3y ago
        >Yeah but what about the other 30% Handled by the motor, the motor is the brake IIRC?
        iancmceachern 3y ago
        Electric cars have regenerative braking and also regular brakes. Regenerative braking doesn't replace the need for brakes. There are lots of reasons why, safety reasons, that you need thr brakes to work even if power fails, when the car is parked etc.
zeckalpha 3y ago
Additionally, "engine" braking is less stressful on electric motors, which function as generators when used that way.

gs17 3y ago

I don't see why you're assuming one motor: > A retrofitted car can have two or four of these electric wheel motors One motor definitely doesn't seem like a usable product without other changes to the car. Unless we're making an electric Messerschmitt Kabinenroller.

CobaltFire 3y ago
I’m assuming one motor at the lowest price point that the site is quoting, and because they state they only have one motor made now. That implies they are comfortable with the trade off and they see two or four as optional. I’d love to see an electric three wheeler, maybe like the old heavy duty Mazda trucks!

lelanthran 3y ago

[EDIT: Mea Culpa - he did modify the rear wheels only in the prototype] Actually, I think it is perfectly practical for a DIYer like me, with the following small caveats (as opposed to your large caveats): 1. Use a front-wheel-drive car as the donor. 2. Mount two motors on the rear wheels (one per wheel). This way: 1. The first instability from torque steer due to driving only a single wheel is gone - car will accelerate in a straight line because equal power is provided to both wheels. The second instability from larger unsprung mass is easier to mitigate on non-steering wheels (i.e. the rear wheels). The third instability from increased wheel offset relative to the kingpin is completely removed. 2. Modifying the offsets on the rear axles (specifically, reducing them) in a FWD car is simpler[1] than doing the same on the drive wheels. If a double-wishbone design is used, it becomes a little complicated, but no more complicated than doing the same on the front. 3. The rear wheels do (IIRC) ~10% of the braking work that the front wheels do, so there is less heat generated. Until recently, quite a lot of the low end cars came with drum brakes on the rear anyway/ I'm curious why he placed the prototype on the front wheels - he must have had a good reason. After al;, someone who came up with the design itself isn't stupid, and someone who actually modded the car knew what they were doing as well, so there's probably a good reason for modifying the front wheels and not the rear. [1] Still complicated, but a lot simpler - because the wheels don't steer there is no need to worry about the steering geometry, track rods/steering rack modifications, etc.

culopatin 3y ago
But the rear wheels in a FWD are rarely designed to push the whole car. They are designed to hold the car off the ground, so 10% of braking, and that’s about it. Once you want to apply torque to them, they either fold under the car, or you just bend whatever is holding them there.

smackeyacky 3y ago

Wheel offset might not be an issue id the motor sits within the wheel.