That's going to be very interesting to see failure rates and modes on the road over time.
We at least know it could potentially have really low failure rates since airplanes have the same type of systems today, and that's highly regulated
I'm more concerned about the failure mode than the failure rates. Mechanical and hydraulic brakes can experience gradual failure, giving the driver a chance to pull over get the car repaired.
EVs usually have a single motor and a single inverter , both of which can fail suddenly. Electronics usually work perfectly fine until they suddenly don't work at all (blown fuse, bad connection, blown capacitor etc)
How are they gonna build redundancy so that no single component failure means youre freewheeling downhill on the highway
single component failure means youre freewheeling downhill on the highway
Do people really think Professional Engineers are stupid?
No, but their bosses might be.
Brakes on airplanes are used infrequently (though when they're used, they're safety-critical) so the usage pattern is very different than for cars.
And inspected after every use.
That's the real difference to me, maintenance. Planes have a strict schedule of inspection and replacement. Moms minivan last saw an oil change before the kids made it to middle school. There's going to be some failures.
Does at least once per flight really count as "infrequent?"
I mean, airplane brakes probably have about a 3% duty cycle (the percentage of time they're in use), so they're generally idle. For city driving, car brakes probably have about a 25% duty cycle.
If those numbers are close to accurate, that means planes are using their brakes about 10x less than cars.
BTW, I didn't pull those plane numbers directly out of my ass, but they're definitely a rough estimate. I'm figuring about 5 minutes of breaking time per flight, counting landing and during the taxi to and from the runway. And I'm assuming a 2.5 hour flight, figuring that could be close to an average flight time.
I don’t think taxi and landing wear the brakes evenly. Landing must be something like 99% of the brake wear in <30 seconds of braking it takes for the plane to stop.
Well that sounds terrifying. There's a reason why the brake hydraulicsystem is actually two separate hydraulic systems, for diagonally opposite wheels. The only single-point-of-failure is the brake pedal.
Their leaving out the critical details on how this will electric system will be fail safe, or even legal.
The announcement was light on details about both the system itself and how its fail-safes are implemented.
Maybe they'll return to spring actuated mechanical brakes that are released when everything is working. (More common in heavy industry, and I believe also truck brakes)
The only single-point-of-failure is the brake pedal.
And even then, only on cars with those stupid electronic parking brakes instead of a proper mechanical emergency brake.
Come with me on an ADHD journey!
Spring actuated, or well, any type of ‘fail closed’ brake design would definitely work.
But what happens if it fails closed (due to no power - the only failure mode I’ve considered below) and the vehicle needs to be moved?
Are they gonna do that thing they do with elevator emergency brakes with the spinning balls that engage the brakes only if a certain inertial threshold is reached? That way as long as they aren’t going too fast, the car can be pushed off the road?
Or are they gonna let you plug in a phone to charge the brake system enough to disengage the failsafe?
Maybe there will be a sweet-ass lever under the center console like the one in the first Jurassic Park movie where people have to pump it to prime the system?
My favorite iteration of this nonsensical idea is that new cars are going to come with a crank in the front, like old-school model T’s, so that in an emergency, people can wind up their cars to release the brakes.
(Please consider all of the above as me having too much time on my hands, and not a real critique of your statements. I think failsafes are a good idea. I’m just a silly.)
Diagonally opposite? No, it's front and rear. However, brake fluid reservoirs haven't been split for decades now, so if your fluid leaks out, every wheel is affected. It's still highly unlikely that you're going to have a leak that suddenly dumps all the fluid, unless you're driving a very old and rotten car, in which case you probably know what you've gotten into.
Brakes that "fail on" while the vehicle is moving can be catastrophic for some dingus in a car. Truck drivers have much more intensive training and specialized licensing.
Hydraulic brakes in a car will still stop the car in a relatively controlled fashion even if the system is incredibly degraded, and they are purely mechanical. With wires, there's a chance that the brakes go from "working normally" to "not working at all" without any warning. Hydraulic brakes fail gradually.
Yeah no. Hydraulic brakes can fail at any of the slave cylinders or the master cylinder.
If a single slave cylinder fails there is still the other pair in a tandem system but braking effectiveness is substantially reduced.
The tiniest tear in the seals of a master cylinder will lead to total and absolute brake failure. Your only brake left is the hand brake.
It would be trivial to keep the car from starting if the brakes don't pass a system check, and make the main electric motor of the car apply maximum regen braking if the system fails en route.
And you'd have one motor per wheel, so if one fails you still have more than enough braking power.
In principle, a system based on electric motors should be a lot more reliable than one based on hydraulics.
This is a terrible idea.
Braking systems need MORE redundancy. Not less.
Electronics are mostly solid state and are therefore virtually wear-free.
If it’s designed well, they could actually be more reliable than pushing fluids through tubes. But pushing fluids through tubes is already pretty fucking reliable.
I think the main point is to eliminate rusting brake discs from EVs, which rely largely on regenerative braking anyway. I know mine are constantly crusty; like I can always hear them scraping for the first few hundred meters of driving. Which is prolly not great.
Love how people in this post believe THE brake manufacturing company, single supplier for virtually all competition-level vehicles, not to mention billions of road vehicles, are a bunch of dumbasses who can't design a different version of their MAIN PRODUCT.
Love how people are going on about regenerative brakes when this is simply deleting the hydraulic lines for wires and actuators in a normal friction brake system.
Brembo’s new “Sensify” braking system takes that one step further, eliminating the hydraulic system entirely and relying instead purely on electronic brake-by-wire and electric motors.
I can see it catch on for EV, pretty sure it won't be used on ICEV considering brake is the only thing that can stop the car
Downshifting used to be a thing people would do to slow down a car significantly.
Takes quite a bit of practice to use it in emergency though, but for normal slowing down it's pretty handy, and manual transmission tend to slow down car a lot when releasing the gas pedal.
In fact, according to BMW, drivers of current EVs pretty much never activate their mechanical braking systems, relying instead on their electric motors to handle the job.
I didn't think the regen could bring a car to a complete stop, like at a stop sign or a red light. They're certainly not using the motors to hold your place on a hill, are they?
Or are they just saying BMW drivers never stop when they're supposed to?
I didn’t think the regen could bring a car to a complete stop
Yes, it can. Newer axial motors can actually put -700hp of stopping power per wheel, and the whole motor hub assembly weighs less than a brake assembly. All that energy was previously wasted as heat by braking.
Yes I use regen braking for nearly all my stops at lights and stop signs. I’d say 80-90% of the time.
I never apply brakes when on a hill, as regen braking covers that to.
I'm sure no more messy bleeding the brakes will be cheered by those who need to do brake fluids (I dislike doing it on my motorcycles). Multiple motors and pistons should still mean adequate redundancy, but more details from the manufacturer would be nice.
This makes sense on EVs. Couple the regen braking with fail closed brakes, and you should never have a failure.
And hope that doesn’t happen at highway speeds in front of an Amazon semi.
I drive solely using one pedal on my Bolt, and brake only when I need to stop faster. As long as it's reliable and safe this should be fine. Regenerative braking is really fun.
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