Cybertruck has no Parking Pawl in its Tranmission. Lightning does.

[StevenC56]

That's not what he was saying....

So you guys think that the CT wouldn't be a safety risk if either the electrical system that powers the park brake fails or the park brake's mechanics themselves failed?

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[RickKeen]

In the thread on the Cybertruck forum, it was mentioned that the Cybertruck itself can sometimes warn the driver that the brakes may not hold when parking on a hill. That is what started the discussion over there.

In the Munro video, they mention that "other" manufacturers do not include the expensive park brake pawl in their electric drive units. By "other", I took that to include the Tesla, but I have not gone and confirmed that in their Tesla Cybertruck videos.

Nobody on the CT forum chimed in to claim the CT has a parking pawl mechanism in its transmission...

The discussion started in a thread talking about launching boats on a boat ramp, here:
https://www.cybertruckownersclub.co...rtruck-was-great-experience.31335/post-550138

 

[RickKeen]

Additionally, there is this tidbit in the Cybertruck manual:

Warning
Your Cybertruck may display an alert if the road is too steep to safely park, or if the parking brakes are not properly engaged. These alerts are for guidance purposes only and are not a substitute for the driver’s judgment of safe parking conditions, including specific road or weather conditions. Do not depend on these alerts to determine whether or not it is safe to park at any location. You are always responsible for parking safely.

 

[RickKeen]

Parking pawls get tested all the time when parked vehicles are dragged onto flatbed tow trucks and trailers using a winch without bothering (or access to the key) to shift the car out of park. The tires just skid before anything gets damaged.

To destroy the parking pawl in the Lightning, I would imagine you would have to engage it while the vehicle is moving at some speed, causing the rotational inertia of the spinning tire, wheel, hubs, rotors, axles / half shafts, and all the spinning internals of the motor/reduction/differential unit to all hit the pawl. Hopefully the software or mechanism is not ever going to let that happen.

 

[RickKeen]

Here is the Munro video where they tear down the Cybertruck motors. I scanned through it quickly and did not see any mention of a parking lock. I would imagine if it had a parking lock, Munro would mention it.

 

[RickKeen]

Here is a video that explains the electric parking brakes similar to what are used on the Lightning (and I would presume similar on the Cybertruck, except perhaps its a 48v motor instead of a 12v motor).


The small electric motor drives a screw that pushes on the brake caliper. There is a gear set with some ratio between the motor and the screw. So the ultimate amount of caliper force it can generate is going to be the stall torque of the motor x the gear ratio (less the gear and drive screw friction).

 

[RickKeen]

I was unable to find a spec for the exact EPB in the Ford (or the CT), but the typical force an electric parking brake actuator can generate seems to max out around 25kN for heavier duty units. Which is about 5600 lbs. To make the math simple, assume a 12" brake rotor and a 30" tire and an ideal brake pad coefficient of friction of 1.0. That gets you enough braking torque for 2240 lbs of horizontal rolling force on each rear wheel (4480 total). Which is slightly below the rear axle rating of the truck (4900 lbs). If you load the truck to its max axle weight rating front and back, and park on a steep enough hill, it seems you could theoretically get the parking brake to slip (before you can get the tires to skid). That marginal case is likely why Ford includes the parking pawl.

The original thread in the Cybertuck forum involved heavy boat trailers on boat launch ramps. Note that NO parking brake or parking pawl on just the rear axle of the truck can overcome the fact that a heavy trailer can drag the truck down the hill with its rear tires skidding even if the wheels are locked (especially on a wet, algae-slick boat ramp). Because most of the weight of the trailer is not on the rear axle of the truck, the trailer weight cannot contribute to the traction of the truck rear tires, but still contributes to pulling it down the hill.

ALWAYS chock your trailer when parking on a steep hill.
Always use your most aggressive 4WD mode (diff locked) when launching a boat.

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