Total braking system failure?

[GWord]

But before that, everyone should ride a motorcycle for a few months

As a side benefit this would help shrink the shortage of transplant organs.

 

[Daniel in SD]

Yes, note the spiral cutting on the mainshaft, and GIANT bearings to the right of the big gray gear. When the gear is turned by the motor, the gear pushes the mainshaft due to the spiral.

To get the pedal to work without the brake motor turning, I could imagine there's actually a concentric shaft, where the outer portion of the mainshaft is threaded, and there's a hidden interior shaft which can feed-through the motorized shaft. The threaded area of the mainshaft to the left of the gray gear seems to be much larger(and has a large black axle beyond the threading), while the stuff actually attached to the pedal to the right of the gear is a relatively narrow silver rod.

I think the shaft from the brake pedal and that bracket connected to the spiral gear both press against the master cylinder. The shaft from the brake pedal moves freely through the center of the spiral gear. The position sensor multiplies the force by measuring the difference between the position of the assist mechanism and the position of the master cylinder.

 

[Raro]

Yes, note the spiral cutting on the mainshaft, and GIANT bearings to the right of the big gray gear. When the gear is turned by the motor, the gear pushes the mainshaft due to the spiral.

To get the pedal to work without the brake motor turning, I could imagine there's actually a concentric shaft, where the outer portion of the mainshaft is threaded, and there's a hidden interior shaft which can feed-through the motorized shaft. The threaded area of the mainshaft to the left of the gray gear seems to be much larger(and has a large black axle beyond the threading), while the stuff actually attached to the pedal to the right of the gear is a relatively narrow silver rod.

i think theres a solid connection thru the whole booster, but with a small designed axial "play" which the differential sensor senses, and then demands motor movement to assist. if the motor doesnt have power the "threads" allow you to turn the "dead" motor along. however if a gear breaks of motor gets jammed its possible you will have a jammed pedal

Check out the video: iBooster

You can see there is a little play in right at the start of pedal movement, which is measured by the sensor, sort if like how power steering works, you have a "pilot" signal that then controls either the hydraulics or electric power steering.

 

[Daniel in SD]

i think theres a solid connection thru the whole booster, but with a small designed axial "play" which the differential sensor senses, and then demands motor movement to assist. if the motor doesnt have power the "threads" allow you to turn the "dead" motor along. however if a gear breaks of motor gets jammed its possible you will have a jammed pedal

Check out the video: iBooster

You can see there is a little play in right at the start of pedal movement, which is measured by the sensor, sort if like how power steering works, you have a "pilot" signal that then controls either the hydraulics or electric power steering.

So if you unplug the iBooster will you lose all braking?

From the description: "Both systems have a direct mechanical push-through on the brakes and can brake the vehicle independently over the entire deceleration range."
https://www.bosch-mobility-solution...ster/ibooster/product_data_sheet_ibooster.pdf

 

[Raro]

So if you unplug the iBooster will you lose all braking?

From the description: "Both systems have a direct mechanical push-through on the brakes and can brake the vehicle independently over the entire deceleration range."
https://www.bosch-mobility-solution...ster/ibooster/product_data_sheet_ibooster.pdf

No, unplugging you would just backdrive the motor and pedal force would increase. only way i can see no brakes scenario in the booster part of the system is if the motor or gears get jammed up by something,

There might even be a failsafe for that, like a breakaway clutch or something. but I cant see it and its not mentioned...

 

[ThomasD]

The booster works by pulling the air out of the booster chamber with a pump creating a low pressure system inside. When the driver steps on the brake pedal, the input rod on the booster is pushed in which lets atmospheric pressure into the booster. This, in turn, pushes the diaphragm toward the master cylinder.

 

[brkaus]

The booster works by pulling the air out of the booster chamber with a pump creating a low pressure system inside. When the driver steps on the brake pedal, the input rod on the booster is pushed in which lets atmospheric pressure into the booster. This, in turn, pushes the diaphragm toward the master cylinder.

Perhaps for a vacuum booster. But Tesla does not use a vacuum booster.

 

[smatthew]

A direct quote from Bosch

"We said we always need direct control from the driver so we developed the iBooster, which has a direct link between the pedal and the master cylinder,” he says. “So if something goes wrong, if there is a failure, we still have the ability to brake by your own foot.”

And another:

In the second safety phase, the mechanical push-through mechanism is available as a backup if the on-board power supply fails: the driver can apply the wheel brakes on all four wheels via a hydraulic mode without the brake booster effect, thereby safely bringing the vehicle to a stop and satisfying statutory requirements in full.

 

[Raro]

A direct quote from Bosch

"We said we always need direct control from the driver so we developed the iBooster, which has a direct link between the pedal and the master cylinder,” he says. “So if something goes wrong, if there is a failure, we still have the ability to brake by your own foot.”

And another:

In the second safety phase, the mechanical push-through mechanism is available as a backup if the on-board power supply fails: the driver can apply the wheel brakes on all four wheels via a hydraulic mode without the brake booster effect, thereby safely bringing the vehicle to a stop and satisfying statutory requirements in full.

This makes sense, however there might very well be failure modes where the booster makes the pedal lock up, but I think the OPs issue is ABS / ABS software related issue brought on by some kind of failure in the 12V system.

 

[smatthew]

This makes sense, however there might very well be failure modes where the booster makes the pedal lock up, but I think the OPs issue is ABS / ABS software related issue brought on by some kind of failure in the 12V system.

I, and most of the people responding to this thread, do not believe the pedal was locked up.

Do you think Bosch is selling a product with a known deadly failure mode? It's specifically designed such that the booster can not make the pedal lock up.

 

[mongo]

I, and most of the people responding to this thread, do not believe the pedal was locked up.

Do you think Bosch is selling a product with a known deadly failure mode? It's specifically designed such that the booster can not make the pedal lock up.

Understand the sentiment, but the ABS module is downstream/ separate from the booster.

 

[Puma2020]

I’ve had “total system failure” before (not in the Tesla) ... power steering and power braking suddenly going away. Alternator seized up and snapped the serpentine belt. It definitely takes some manual effort, that’s for sure. But the systems ARE mechanically connected, so without any power whatsoever, it’s still controllable.

When I was teaching my kids how to drive, I had them practice (in a wide open parking lot) how to stop and steer the car when the power went out. Several years later, my daughter was driving the Camry on the highway and the engine just died. Luckily she remembered the no power lesson and got the car safely to the emergency lane without issue. She wasn't a happy camper when she called me but at least she was safe.
I also made them learn on a standard.
We also practice spins during a snow day (I pulled up the emergency brake to lock the rear wheels while they were trying to turn).
Not sure how to teach someone to drive these days with a Tesla or any EV.

 

[Raro]

I, and most of the people responding to this thread, do not believe the pedal was locked up.

Do you think Bosch is selling a product with a known deadly failure mode? It's specifically designed such that the booster can not make the pedal lock up.

no I didn’t say I think they know it has a deadly defect.

I’m saying its possible for it to fail for a multitude of reasons. I’ve worked on a bunch of R&D and qualification projects on geared actuators for aerospace and I have seen actuators that have been rigorously designed, tested, qualified and produced in a strictly controlled system fail in the real world.

But again, I don’t see it likely that it was a mechanical failure on the booster, I think it more plausible that it was the ABS unit that either failed or was told to block pressure from going to the calipers because of some fault having to do with the 12v system.

try pushing the brake when you’re in park, you can easily push it to its stop if you push as you would in a panic situation. The travel is not very long, I can easily see how someone would interpret hitting the pedal stop and not getting any retardation as a “locked” pedal.

 

[Daniel in SD]

try pushing the brake when you’re in park, you can easily push it to its stop if you push as you would in a panic situation. The travel is not very long, I can easily see how someone would interpret hitting the pedal stop and not getting any retardation as a “locked” pedal.

I'm pretty sure that's because the car is "on" and so is the iBooster. When I press the pedal to the floor while parked there is a vibration. To verify one would probably have to disconnect the 12V.

 

[rglore]

If the 12 volt system failed, you would not have the emergency parking brake function since it's a 12 volt motor on each rear brake caliper.

 

[Raro]

I'm pretty sure that's because the car is "on" and so is the iBooster. When I press the pedal to the floor while parked there is a vibration. To verify one would probably have to disconnect the 12V.

Yes, I think it’s on too, I just wanted to point out how short the throw is and how easy it is to floor the brake without doing it out on the road, even if it took 2.5 times the force like in a typical vacuum assisted system, it would be easy to floor it and think it’s “locked”

 

[Tiger]

Not sure how to teach someone to drive these days with a Tesla or any EV.

There's a thing called "Dyno mode" in Tesla's, teach them with that

 

[Fred42]

The physical braking system in my Model 3 completely failed this morning.
I didn't realize it until I got on the freeway ramp and almost hit the car in front of me.
Luckily, the regen braking was enough to slow the car down.

The brake pedal felt like it was in a locked position at the top of its range. Could not depress the pedal at all.

This was an absolute critical safety failure.

The car was acting strange from the first moment this morning.
1. erratic window roll down behavior when I opened the front door
2. dark/blank screen upon entry
3. warning message: vehicle hold feature unavailable
4. warning message: 12 v battery must be replace soon

After I rebooted the car, I drove off to working thinking it was nothing.
After realizing the brake failure, I got off the next freeway and exit and drove it back home safely.
With the road side assistance tech on the phone, I tried rebooting the car with no luck.
Then, tried powering the car off via the lcd screen and waiting a couple of minutes seems to solve the issue this time.

The car is now with the Tesla service center.

How could this happen? This was extremely dangerous and I feel very fortunate.
I could have easily found out the hard way at 70+ mph.

Hope this never happens again to me or anybody else, ever.

Complete brake failure in a modern car is unheard of. But you might have to push hard if the power assist fails.

 

[smatthew]

no I didn’t say I think they know it has a deadly defect.

I’m saying its possible for it to fail for a multitude of reasons. I’ve worked on a bunch of R&D and qualification projects on geared actuators for aerospace and I have seen actuators that have been rigorously designed, tested, qualified and produced in a strictly controlled system fail in the real world.

But again, I don’t see it likely that it was a mechanical failure on the booster, I think it more plausible that it was the ABS unit that either failed or was told to block pressure from going to the calipers because of some fault having to do with the 12v system.

try pushing the brake when you’re in park, you can easily push it to its stop if you push as you would in a panic situation. The travel is not very long, I can easily see how someone would interpret hitting the pedal stop and not getting any retardation as a “locked” pedal.

Ahh, so you think the ABS module (which is still Bosch) has such a simple failure mode? 12V power isn't clean enough so it disables brakes? Or noisy communications cause it to block brakes? Geez man. Do you think every engineer besides yourself is incompetent? This isn't the Wild West. There are standard that automobile components have to live up to.

 

[SlimJim]

I will start my day with a brake check every morning from now on... like being at a track day.