The Amazing Tesla Semi Truck

"...The truck will automatically keep from jackknifing because it has independent motors on each wheel...it will dynamically adjust the torque on each wheel so that jackknifing is impossible..."

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That doesn't sit right with me. I thought 'jackknifing' described a condition when under hard braking the wheels on the trailer lose lateral grip and the trailer slides to the side out of line with the braking tractor.

If the mass in the trailer is catching up to the tractora forward motion by rotating around the tractor, applying torque to the wheels to attempt to get the tractor and trailer back alligned is likely to have the tractor sliding sideways along with the trailer. Alternately you could just accelerate forward and correct the condition, which is also an option for deisel trucks....but then why where you braking so hard if driving forward is a viable option?

Can someone with actual knowledge of tractor trailer dynamics speak to this?

I go along with that. I don't have actual knowledge, but I think there is an anti-jackknifing device which locks the tractor-trailer pivot during hard braking.

Also in UK an accident of any lorry, artic or rigid, is often referred to as "jackknifing". Sounds more sophisticated than just crashing!

You're correct, there is a device called a "Hope anti jackknifing device" It is fitted to the trailer & basically is a clutch attached to the pin and when the brakes are applied the air pressure is applied to the clutch to lock the pin and fifthwheel plate of the tractor together, it's a bit more complicated than this but it's the general idea. what I gathered from the presentation was that there are electric motors on the trailer as well which would stop the wheels locking & if the wheels can't lock the vehicle can't jackknife even if there aren't motors on the trailer then anti locking sensors would stop the wheels locking.

Bazzer

..."Jackknifing has a few main causes. It can be caused by slippery road condition, especially on a grade. by losing control when backing quickly (often also fatal) or most commonly by poorly maintained brakes.

The leading way to prevent this is to regularly check your brake camber. "...

..."Jackknifing occurs when a vehicle towing a trailer skids and its trailer pushing from behind spins it around until it collides with its own trailer. "...

It's the tractor part, not the trailer, that when losing traction causes a jackknifing situation....usually trailer brake failure is the compounding problem...

https://www.quora.com/How-can-I-avoid-jackknifing-a-tractor-trailer

https://www.wikihow.com/Avoid-Jackknifing

Video mentions a ±15° angle between trailer and tractor as the limits with the NO JACK pin in place.

How does this work in city street turns? I suspect not well.

Since either air or electric could decouple from tractor to trailer in some incident, or other brake failure, is there no other way to use or signal regenerative braking on these trailers, and use that in addition to air brakes, or instead of?

"How does this work in city street turns? I suspect not well."

Then again, one seldom travels at highway speeds on city streets. At low speeds, say, below 40MPH, stopping is fairly easy, and skidding is difficult, unless one is on ice. The sharp turns of city travel are also done at low speeds, making jackknifing almost impossible.

So you are saying that anti-jack-knifing hitch disengages the rigid no turn part of itself if speed is lower?

Yes, that is exactly what I am saying.

It must disengage at low speeds, otherwise the vehicle would be undriveable on city streets, in truck lots, or at loading docks.

It may be tied to the speedometer, it may be tied to the gear selector, but there needs to be a way to have maneuverability at low speeds, as well as stability at high speeds.

So fast will that truck without it engaged undergo a jackknife? How fast would it be expected to disengage? 1 second? 100 milliseconds? Driver reaction time?

No, no, no, you're thinking of it the wrong way.

Let's say it goes by speedometer readings, since truck gear ratios are a bit more complex than car gear ratios. If the truck is traveling below 40MPH, the anti-jacknife pin is retracted, if it is traveling above 40mph, the anti-jacknife pin is extended.

That way, when making turns on city streets, or when maneuvering in a truck lot or backing into a loading dock, the vehicle has full maneuverability, and when it is on the onramp to the highway, it crosses the 40mph threshold and the pin engages for save high-speed travel.

The concept of monitoring speed to engage safeties isn't that hard to understand, if you've been in a car that automatically locks the doors once the vehicle gets above around 20MPH then you've already seen this type of speed-based safety sensor in action.

They have cars like that?

Heck, I can't get my work truck past 40 mph. LOL

Seriously, I do not believe for one minute you can set a lower speed number where it is impossible to jackknife a truck, other than just throw out an arbitrary number, that will not hold up in court (or court of public opinion).

ABS for the drive axles, and all trailer axles is the key. Front steering axle brakes may lock and actually help prevent jackknife, but never the drive axles.

In general, manufacturers are already doing everything within their technology to reduce or eliminate this most dangerous condition. I would say truck with fore and aft ABS, along with king pin swivel lock pin applied under specific conditions is not bad science, but there has to be more inputs on the decision to unlock lock the king pin swivel than just speed. Perhaps a smart app could determine road conditions using a drone wheel (basically in idler wheel applied to road surface to determine an effective slippage rate), or some other passive sensor, even road specular reflectance.

"but there has to be more inputs on the decision to unlock lock the king pin swivel than just speed. Perhaps a smart app could determine road conditions using a drone wheel (basically in idler wheel applied to road surface to determine an effective slippage rate), or some other passive sensor, even road specular reflectance."

Those are all good ideas, I was just speculating on a basic system to explain how the pin could be engaged on the highway and disengaged when the truck needs to make sharp turns. Heck, It could even be a toggle switch on the dashboard with a sign "Remember to engage anti-jack pin when entering highway." and "Remember to turn off anti-jack when leaving highway."

Also, the only times I've seen a semi jacknife on city streets is when the driver made an error while backing up and, in essence, backed the cab up into the side of the trailer. I've seen many more semi trailers opened like tuna cans against an underpass than I have trucks jacknifed on city streets.

Sounds about right. Thanks for the dialogue.

Always a pleasure talking tech with you.

We just need to remember to NOT bring up politics with each other, I think there's only one thing we can agree on there: Third Party Candidates just screw things up in the Presidential race. All they do is steal votes from the Major party they are more aligned with, and toss the election to the Other Side.

That much is true, but I suspect there is even more to agree upon:

• polity and politics mix like oil and water
• a politician's statement should never be construed as actual intent
• a statesman's statement may be relied upon with caution
• a government employee was never hired to be a political operative, and when this is found to exist, there needs to be a removal of said employee from influence of any task related to investigation of "the other side". (hard call to make? I don't think so).
• time spent on arguing politics is time lost for us, and lost posterity for future generations, especially when it is merely a doubtful disputation of no resolute end.
• less time should be spent on elections, more time spent on actual service.

"less time should be spent on elections, more time spent on actual service."

Also, less MONEY should be spent on elections. If we took the money from the campaign fundraising (Looking at you, 2016 election "war chests"), and instead spent it on infrastructure and health care, we could slash the federal income tax by at least 25-50%, as a rough estimate.

"So, Senator Placeholder, you were able to raise three million dollar for your re-election campaign, why can't you use those skills to raise the mere three hundred thousand you need for your state's highway maintenance?"

They can get the money for re-election without having to wear their sponsors names like a NASCAR driver, they should be able to get the money for their pet projects without having to "sell out" to their donors the same way.

Or maybe they should be required to wear their sponsor's colors, brand, logo, etc. on their person somewhere.

Nondisclosure of any non-profit fund raising organization should be viewed as simple tax evasion by whomever is receiving these ill-gotten funds.

Taxpayer money should never be used to pay for out of court settlements where the accused is a member of the House or Senate. That just is not right.

No more witch hunts - if you have solid evidence of a crime (financial, security, or otherwise) that has been committed, the accused should face the charges in court as originally intended when the Constitution was written. No more "shotgun approach" unending investigations where nothing really is accomplished, but rather all investigations should be taken to a grand jury, but only when sufficient evidence is there to make it stick.

We cannot any longer ruin people's careers merely on the word of one or two accusers with no evidence to back it up. Synthesizing accusatory evidence should be worse than mere perjury.

My guess is it's like anti-lock brakes on your car. The trailer jackknifes because the wheels are locked, and when no longer rolling, the wheels can slide sideways as easily as in the forward direction.

The thing is, Musk was talking about using the motors at the wheels to apply torque to counter the jacknifing... which means the wheels on the trailer are not what is being used for the prevention.

AFAIK, antilock brakes have been available for semis as well as airplane landing gear long before they were standard on cars.

Presumably the torque would be applied in the braking direction, but I don't see how that would be any more effective ln preventing jackknifing than applying the brakes.

Actually, I agree the comments in the blurb about anti-jack-knifing were off.

Only way I see around it would be to have drives on the trailer wheels also (in reverse).

500 miles and then what?

.. jackknife.. seems like jackin' around or pocketknife.. ing...

Yes, I read the blurb in "The Engineer" this morning.

I think what is even more important is the new Roadster that seems to have gotten lost here in all the excitement.... 0-100 in 4.2 sec .. 630 mile range .. 8.9 sec 1/4 mile...

....and pretty sweet looking ride to boot....

https://techcrunch.com/2017/11/16/tesla-unveils-the-new-roadster/

To me, the most impressive thing about the Roadster is that he managed to get it all the way to road ready prototype without any auto mag catching wind of it let alone a picture.

How fast....real fast

This is well for those that feel that need. I need a cheap, reliable means of hauling my personal stuff around, i.e. 1/2 ton pickup truck. I have about zero desire for a fast car that will assist me in arriving at the scene of the traffic stop.