In one webinar, I heard it suggested (I think by Nathan) that it might be possible to remove the hydraulic brakes entirely. Is there any chance this can happen on the Aptera?
If so, this would be amazing. To see those clunky hydraulic pumps, lines, pads, discs and dirty fluids disappear, would just be so satisfying, and could reduce costs too. :)
@Kerbe #12705 So there's no actual pawl, but rather a mechanical brake caliper. My own parking brake is even simpler: Cable actuation of the hydraulic rear calipers.
I suppose other hub-motor vehicles could use 1 of those options on the front for "park" & on the rear for the parking brake.
However that doesn't help Aptera get rid of the unsprung rotational weight of brake discs, the way it would to use a true pawl locking the motor's rotor to the hub.
I don't see why a parking pawl is a lot of additional engineering work. I'd think it could be just a solenoid like my car has, but mounted at the wheel (where the brake caliper used to be?), with its pin going into one of a set of slots or holes in the motor's rotor.
I wonder what other hub-motor vehicles use for "park". Every car I've ever seen has that, even though there's also a parking brake.
If the rear brake fails on an incline, they could program it is engage the front motors if motion is detected and notify the owner. That would work as a backup, at least until the battery runs out.
Eliminating the hydraulic brakes is especially useful on the Aptera, to offset the mass of the hub motor and reduce the unsprung mass.
On the other hand - without front mechanical/hydraulic brakes, the Aptera would be relying on just one rear brake when parked on an incline. No redundancy at all. Unless the motor has a large holding torque, but I don't think that's the case, is it?
I suppose they could design a lightweight locking mechanism on the front wheel (maybe something like the parking pawl on automatic transmissions) but that's a lot of additional engineering work.
I agree. I would love to get rid of the hydraulic system as well and use a rear electromechanical system for low speeds/stoplights with manual cable backup for emergency/parking/fun.
@Biff It would still save a lot of weight & cost of the FWD Aptera to have regen-ABS on the front (delete the front hydraulic-friction brakes) & hydraulic ABS on the rear. In fact, that might qualify as the 2 independent braking systems required for safety/legality. It also leaves one friction brake to attach a cable as a parking brake.
Yes, @zajethesage, the higher the right-pedal regen setting, the more sensitive it is. Like the difference between driving a stick in 2nd gear or 3rd. With my uncalibrated ankle I definitely feel the difference between:
- My own car's unadjustable mild right-pedal regen (like D in a typical ICE automatic☹️).
- My friend's eGolf set a bit higher on its #2 or #3 setting (can't remember exactly which SHE prefered), about like maybe driving a stick in 4th gear out of 5.
- eGolf on #4, which is maybe like driving in 3rd gear out of 5 with a weak engine.
Going from my own pretty mild setting to my preferred eGolf setting definitely takes a few minutes to get used to, but after that I still want a bit more. As a counterpoint, my eGolf friend feels that #4 is too strong. Good thing it's adjustable.
I love a good tangent, but BACK ON TOPIC:
For the skeptics, consider that with traction control off, you can spin the tires when accelerating. Mine once spun at 20mph when a light went yellow & I punched it. In other words, the motors have more power than the tires' grip.
They likely have about equal power to decelerate. Like Nathan said, they can lock any or all wheels. Add ABS to the regen & it's fine even for panic stops where the motors can lock the tires instead of the discs, but just like with those discs, locking is prevented by the ABS.
I have the advantage of having worked with an alternator rotational load testing machine. You could take an alternator which would spin freely by hand, power it up, & it felt LOCKED, impossible to turn by hand no matter how hard I tried. The tester needed a powered drive belt to turn it.
Another point is that I have personally seen 72kW of regen power on my display under hard but not full braking. My motor's entire output is only 83kW but if I was ever braking that hard I'd have to be paying full attention to the road. If I ever have a brave passenger I'll try to remember to ask them to watch it as they're being slammed against the seatbelt.
You most likely would not feel any different , the tactile feedback would be engineered into it
While I have zero personal experience with driving with a regen system, my thinking would be that the higher it is set- the more sensitive the accelerator pedal would be. Is this what you experience? Is it difficult to master on max regen? Do you need a calibrated ankle?
I just noticed an earlier discussion on this topic over in a thread on cost-cutting:
I think@kiteboarder is right about this. The potential cost savings are significant, given all of the parts in hydraulically actuated friction brakes. It's hard to imagine that brakes won't go this way, at least in a decade or two.
I also found a two part article on this topic from 2016. It's mainly about technologies that could make this work, not necessarily the hard realities of a concrete automotive application:
@heistp My point was that even though my 2013 500e uses hydraulic friction brakes for panic stops, Nathan stated quite clearly that it's no longer physically required. As you noted, it may be legally required. The motorcycle laws may be worded such that a super-safe regen system could qualify.
@alexluttrell Not only unsprung weight, but discs are also rotational weight that needs to be accelerated & decelerated. Yes regen makes that LESS important, but it's still a factor due to energy conversion losses.
@Raj Giandeep If I get your meaning, my 2013 500e already pretty much does that: When I release the right pedal there's light regen. Depending on how far/hard I press the brake pedal I get anywhere from light to VERY strong regen. The ONLY exceptions when the hydraulic friction brakes activate are if I suddenly SLAM the brake pedal for a panic stop, or when I brake below 7mph (& 2016 eGolf eliminated even the latter).
How about this idea. The "brake pedal" could be mapped to the heaviest regen available instead of hydraulic brakes. Then the accelerator pedal can be left to light or medium regen
I personally would love to see the hydraulic brakes go away & just use the regen to stop. I had my 2013 Nissan Leaf in for a free battery plate fix. I got the test drive a 2020 Nissan Leaf. I really loved the eBrake option and not having to use any brakes & just 1 pedal drive.
I have a hybrid that I recently had serviced. On pickup, I asked the customer service manager about brake wear and he said they're seeing cars with 100,000 miles on them that are still well outside of the wear limits for both the pads and rotors. They do flush and replace the brake fluid only because it absorbs moisture over time.
I'm pretty sure that the car is brake by wire moderated. When I lightly brake, pulling into my garage, it tends to stop short of where I want it to. Then I decrease pressure on the pedal, it starts to creep forward.
I saw a lot of criticism about that in the early days after the car came out.
This sounds like the “fly by wire” systems that aircraft use today. Maybe instead of a mechanical brake as a backup for hydraulic failure, they will install ejection seats.
Removing the hydraulic brakes would reduce weight too, some of it unsprung!
I found the clip from Nathan where I heard this mentioned (discussion around controller technology, 31:00-32:00):
Despite the fact that a physical e-brake would always be necessary as a backup, I can't shake the idea that there might be some way to use electromagnetism as the primary baking mechanism, instead of hydraulics.
Regenerative braking only helps so much, but if there were also a way to convert any energy that couldn't be transferred to the battery to heat, that seems like it would be an improvement. I don't know if enough braking force can be obtained though, and if it would still work with the vehicle at rest.
the Ford mach e has no mechanical connection. The brake pedal is connected to a reostat just like the accelerator
For safety, hydraulic brake system needs to stay so there is a physical connection from brake pedal.