AuthorTopic: BIG RIG Drags Car Up Cajon Pass, Cali.  (Read 1264 times)

Offline azozeo

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BIG RIG Drags Car Up Cajon Pass, Cali.
« on: April 21, 2017, 12:53:46 PM »
<a href="http://www.youtube.com/v/RTdDzSVHCAM&fs=1" target="_blank" class="new_win">http://www.youtube.com/v/RTdDzSVHCAM&fs=1</a>
« Last Edit: April 21, 2017, 12:57:38 PM by azozeo »
I know exactly what you mean. Let me tell you why youíre here. Youíre here because you know something. What you know you canít explain, but you feel it. Youíve felt it your entire life, that thereís something wrong with the world.
You donít know what it is but its there, like a splinter in your mind

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Re: BIG RIG Drags Car Down Cajon Pass, Cali.
« Reply #1 on: April 21, 2017, 12:59:47 PM »
<a href="http://www.youtube.com/v/RTdDzSVHCAM&fs=1" target="_blank" class="new_win">http://www.youtube.com/v/RTdDzSVHCAM&fs=1</a>

Now that is fucking insane.  How could he NOT know this car was hooked?  First off to get in that condition had to be a heck of an impact.  Second, you couldn't miss it out the side mirror.

I wish the video guy had hung around for when the cops showed up.

RE
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Offline azozeo

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Re: BIG RIG Drags Car Down Cajon Pass, Cali.
« Reply #2 on: April 21, 2017, 01:28:12 PM »
<a href="http://www.youtube.com/v/RTdDzSVHCAM&fs=1" target="_blank" class="new_win">http://www.youtube.com/v/RTdDzSVHCAM&fs=1</a>

Now that is fucking insane.  How could he NOT know this car was hooked?  First off to get in that condition had to be a heck of an impact.  Second, you couldn't miss it out the side mirror.

I wish the video guy had hung around for when the cops showed up.

RE


Kathy & I were sitting on the back porch watching nature frolic & havin' a smoke,
so she say's "You have got to check out this insane big rig wreck. She forward it to me & so
I posted it here to get your take on it.

Did the driver of the auto turn into the rear wheel on tandems & get hooke that way.
How does this happen????
I know exactly what you mean. Let me tell you why youíre here. Youíre here because you know something. What you know you canít explain, but you feel it. Youíve felt it your entire life, that thereís something wrong with the world.
You donít know what it is but its there, like a splinter in your mind

Offline agelbert

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Re: BIG RIG Drags Car Up Cajon Pass, Cali.
« Reply #3 on: April 21, 2017, 01:29:13 PM »
<a href="http://www.youtube.com/v/RTdDzSVHCAM&fs=1" target="_blank" class="new_win">http://www.youtube.com/v/RTdDzSVHCAM&fs=1</a>

Now that is fucking insane.  How could he NOT know this car was hooked?  First off to get in that condition had to be a heck of an impact.  Second, you couldn't miss it out the side mirror.

I wish the video guy had hung around for when the cops showed up.


RE

 :o

Agreed.
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Offline azozeo

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Re: BIG RIG Drags Car Up Cajon Pass, Cali.
« Reply #4 on: April 21, 2017, 01:31:08 PM »
Also, for the diners not familiar with Ca-Hone / Cajon pass RE, fill them in on the significance & grade of this bad boy stretch of of concrete.
I know exactly what you mean. Let me tell you why youíre here. Youíre here because you know something. What you know you canít explain, but you feel it. Youíve felt it your entire life, that thereís something wrong with the world.
You donít know what it is but its there, like a splinter in your mind

Offline RE

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Re: BIG RIG Drags Car Down Cajon Pass, Cali.
« Reply #5 on: April 21, 2017, 01:44:50 PM »
Did the driver of the auto turn into the rear wheel on tandems & get hooke that way.
How does this happen????

The only way I can picture it is if the Big Rig driver made a left lane change and wasn't watching what his tandems were doing or what was happening in his side mirror.  The guy in the car was behind him trying to pass when the rig driver pulled to the left lane.  Car hits trailer and gets hooked.

Far as Cajon Pass goes, its one of the longest steep grades out there.  There are some steeper grades in the Appalachians, but none as long as Cajon.  If you got any weight at all in the trailer, it's a very LOOONG and tedious trip up the hill in low gear doing 5-10 mph.  On the way down, its a brake SMOKER, and that is with running the Jake Brake full out, which sounds like you are in a War Zone and NATO is dropping the Death from Above. (Jake Brakes are an engine braking system that put back pressure on the cyclinders, BLAP BLAP BLAP!)

This would have been a fuck load worse going down the hill.  :o

RE
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Offline agelbert

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Re: BIG RIG Drags Car Up Cajon Pass, Cali.
« Reply #6 on: April 21, 2017, 01:56:04 PM »
Did the driver of the auto turn into the rear wheel on tandems & get hooke that way.
How does this happen????

The only way I can picture it is if the Big Rig driver made a left lane change and wasn't watching what his tandems were doing or what was happening in his side mirror.  The guy in the car was behind him trying to pass when the rig driver pulled to the left lane.  Car hits trailer and gets hooked.

Far as Cajon Pass goes, its one of the longest steep grades out there.  There are some steeper grades in the Appalachians, but none as long as Cajon.  If you got any weight at all in the trailer, it's a very LOOONG and tedious trip up the hill in low gear doing 5-10 mph.  On the way down, its a brake SMOKER, and that is with running the Jake Brake full out, which sounds like you are in a War Zone and NATO is dropping the Death from Above. (Jake Brakes are an engine braking system that put back pressure on the cyclinders, BLAP BLAP BLAP!)

This would have been a fuck load worse going down the hill.  :o

RE

  for the info.   

When they get electric big rigs, these steep grades won't burn brakes because the motor itself will slow the rig without any "BLAP, BLAP" (no cylinders, of course  ;D) and boost battery life at the same time.  :icon_mrgreen: I expect the trailers on electric rigs will be modified to include some regenerative breaking gizmo to extend battery life AND brake life too.
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Offline RE

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Re: BIG RIG Drags Car Up Cajon Pass, Cali.
« Reply #7 on: April 21, 2017, 02:14:26 PM »
Did the driver of the auto turn into the rear wheel on tandems & get hooke that way.
How does this happen????

The only way I can picture it is if the Big Rig driver made a left lane change and wasn't watching what his tandems were doing or what was happening in his side mirror.  The guy in the car was behind him trying to pass when the rig driver pulled to the left lane.  Car hits trailer and gets hooked.

Far as Cajon Pass goes, its one of the longest steep grades out there.  There are some steeper grades in the Appalachians, but none as long as Cajon.  If you got any weight at all in the trailer, it's a very LOOONG and tedious trip up the hill in low gear doing 5-10 mph.  On the way down, its a brake SMOKER, and that is with running the Jake Brake full out, which sounds like you are in a War Zone and NATO is dropping the Death from Above. (Jake Brakes are an engine braking system that put back pressure on the cyclinders, BLAP BLAP BLAP!)

This would have been a fuck load worse going down the hill.  :o

RE

  for the info.   

When they get electric big rigs, these steep grades won't burn brakes because the motor itself will slow the rig without any "BLAP, BLAP" (no cylinders, of course  ;D) and boost battery life at the same time.  :icon_mrgreen: I expect the trailers on electric rigs will be modified to include some regenerative breaking gizmo to extend battery life AND brake life too.

Yes, regenerative electric braking would be silent, and you would need electromagnets on the hubs of the trailer wheels as well.

Two problems.

First on the way UP the hill, no Batt storage system could hold enough juice to pull 40 tons up that grade without the Batt pack itself being enormous.  So you would need your electrified overhead trolley wires for this.

Second, on the way DOWN the hill, those electromagnets would get fucking HOT!  The energy has to be dissipated as heat.  So you have a similar problem as with mechanical brakes, they get too hot and they smoke out on you.

RE
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Offline agelbert

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Re: BIG RIG Drags Car Up Cajon Pass, Cali.
« Reply #8 on: April 21, 2017, 03:12:37 PM »
Did the driver of the auto turn into the rear wheel on tandems & get hooke that way.
How does this happen????

The only way I can picture it is if the Big Rig driver made a left lane change and wasn't watching what his tandems were doing or what was happening in his side mirror.  The guy in the car was behind him trying to pass when the rig driver pulled to the left lane.  Car hits trailer and gets hooked.

Far as Cajon Pass goes, its one of the longest steep grades out there.  There are some steeper grades in the Appalachians, but none as long as Cajon.  If you got any weight at all in the trailer, it's a very LOOONG and tedious trip up the hill in low gear doing 5-10 mph.  On the way down, its a brake SMOKER, and that is with running the Jake Brake full out, which sounds like you are in a War Zone and NATO is dropping the Death from Above. (Jake Brakes are an engine braking system that put back pressure on the cyclinders, BLAP BLAP BLAP!)

This would have been a fuck load worse going down the hill.  :o

RE

  for the info.   

When they get electric big rigs, these steep grades won't burn brakes because the motor itself will slow the rig without any "BLAP, BLAP" (no cylinders, of course  ;D) and boost battery life at the same time.  :icon_mrgreen: I expect the trailers on electric rigs will be modified to include some regenerative breaking gizmo to extend battery life AND brake life too.

Yes, regenerative electric braking would be silent, and you would need electromagnets on the hubs of the trailer wheels as well.

Two problems.

First on the way UP the hill, no Batt storage system could hold enough juice to pull 40 tons up that grade without the Batt pack itself being enormous.  So you would need your electrified overhead trolley wires for this.

Second, on the way DOWN the hill, those electromagnets would get fucking HOT!  The energy has to be dissipated as heat.  So you have a similar problem as with mechanical brakes, they get too hot and they smoke out on you.

RE

Good points. However, I think the heat buildup with regenerative braking systems is much less than with disk or brake pad in-your-face FRICTION. I don't have any stats with me off the top of my head, but hot brakes get a lot hotter than hot magnets. A large portion of the energy that is converted to heat with brakes is used to juice the battery bank on regenerative brake systems.

So, since manual brakes convert ALL the stopping energy to heat and regenerative brakes convert only a portion of the stopping energy to heat, I would think you have a heat load that is lower, all things being equal, with regenerative braking than you do with friction braking.

As you know, when magnets begin to heat, they lose magnetism gradually (as the heat increases) along with the ability to induce current and voltage. So, they have a sort of physics governor on how hot they can get that friction brakes do not have.  :icon_sunny:

At a certain point, the heat in magnets is such that they cannot induce current because their magnetism is zip. At that moment, they stop getting hotter and begin to cool.

As soon as they get to a temperature that they can output a significant magnetic field again, they start to get hot, which weakens the magnetic field and the amount of induced current, and so on and so forth.

Have you read any articles on comparisons that I could read? I'm sure the technology will improve, but I'm interested in the state of the art as it is now.  :coffee:
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Offline azozeo

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Re: BIG RIG Drags Car Up Cajon Pass, Cali.
« Reply #9 on: April 21, 2017, 03:42:43 PM »
What does the BNSF use to come down Cajon Pass with a massive load & steel to steel friction with wheels on tracks.
At least with big rigs there's an emergency sand pit to dive into if your adrift.
I know exactly what you mean. Let me tell you why youíre here. Youíre here because you know something. What you know you canít explain, but you feel it. Youíve felt it your entire life, that thereís something wrong with the world.
You donít know what it is but its there, like a splinter in your mind

Offline RE

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Re: BIG RIG Drags Car Up Cajon Pass, Cali.
« Reply #10 on: April 21, 2017, 03:47:55 PM »
Did the driver of the auto turn into the rear wheel on tandems & get hooke that way.
How does this happen????

The only way I can picture it is if the Big Rig driver made a left lane change and wasn't watching what his tandems were doing or what was happening in his side mirror.  The guy in the car was behind him trying to pass when the rig driver pulled to the left lane.  Car hits trailer and gets hooked.

Far as Cajon Pass goes, its one of the longest steep grades out there.  There are some steeper grades in the Appalachians, but none as long as Cajon.  If you got any weight at all in the trailer, it's a very LOOONG and tedious trip up the hill in low gear doing 5-10 mph.  On the way down, its a brake SMOKER, and that is with running the Jake Brake full out, which sounds like you are in a War Zone and NATO is dropping the Death from Above. (Jake Brakes are an engine braking system that put back pressure on the cyclinders, BLAP BLAP BLAP!)

This would have been a fuck load worse going down the hill.  :o

RE

  for the info.   

When they get electric big rigs, these steep grades won't burn brakes because the motor itself will slow the rig without any "BLAP, BLAP" (no cylinders, of course  ;D) and boost battery life at the same time.  :icon_mrgreen: I expect the trailers on electric rigs will be modified to include some regenerative breaking gizmo to extend battery life AND brake life too.

Yes, regenerative electric braking would be silent, and you would need electromagnets on the hubs of the trailer wheels as well.

Two problems.

First on the way UP the hill, no Batt storage system could hold enough juice to pull 40 tons up that grade without the Batt pack itself being enormous.  So you would need your electrified overhead trolley wires for this.

Second, on the way DOWN the hill, those electromagnets would get fucking HOT!  The energy has to be dissipated as heat.  So you have a similar problem as with mechanical brakes, they get too hot and they smoke out on you.

RE

Good points. However, I think the heat buildup with regenerative braking systems is much less than with disk or brake pad in-your-face FRICTION. I don't have any stats with me off the top of my head, but hot brakes get a lot hotter than hot magnets. A large portion of the energy that is converted to heat with brakes is used to juice the battery bank on regenerative brake systems.

So, since manual brakes convert ALL the stopping energy to heat and regenerative brakes convert only a portion of the stopping energy to heat, I would think you have a heat load that is lower, all things being equal, with regenerative braking than you do with friction braking.

As you know, when magnets begin to heat, they lose magnetism gradually (as the heat increases) along with the ability to induce current and voltage. So, they have a sort of physics governor on how hot they can get that friction brakes do not have.  :icon_sunny:

At a certain point, the heat in magnets is such that they cannot induce current because their magnetism is zip. At that moment, they stop getting hotter and begin to cool.

As soon as they get to a temperature that they can output a significant magnetic field again, they start to get hot, which weakens the magnetic field and the amount of induced current, and so on and so forth.

Have you read any articles on comparisons that I could read? I'm sure the technology will improve, but I'm interested in the state of the art as it is now.  :coffee:

Below is an article on the topic.

When I visited the Ewz manufacturer we discussed regenerative braking (I was interested in whether his units were designed to do this).  It has a lot of problems, and the efficiency is low, maybe 20% recovery possible.  The motors aren't designed to work the other way as generators.

The bigger problem with Big Rigs pulling a heavy load is that the throughput would be so big on the downhill.  You would need much thicker and heavier wiring to handle the current passing through the wires.  The batts also not designed to take so much juice so fast.  On a Big Rig with 40 tons going down Cajon Pass, I suspect the magnets would overheat in the first few minutes.

RE

---------------------
http://large.stanford.edu/courses/2016/ph240/brown1/

Regenerative Braking Efficiency
Matthew Brown
November 20, 2016
Submitted as coursework for PH240, Stanford University, Fall 2016
Everyday Driving
Fig. 1: An electric truck with regenerative braking capability, made by Smith Electric Vehicles. (Source: Wikimedia Commons)

We spend spend a huge amount of energy on transportation, and on automobiles in particular. Outside of the minor side effect of giving us unprecedented freedom of movement and enabling much of our way of life, all of that energy is "wasted". If a driver burns a tank of gasoline traveling from San Francisco to Los Angeles, 100% of the energy in the gasoline will be converted to heat and not useful for other work. Much of this energy will be converted to heat in the internal combustion engine during the combustion process, a thermodynamically required inefficiency that is the price of admission for use of heat engines. Some will be lost to friction in the drivetrain, but some of the energy in the gasoline will be converted to kinetic energy of the vehicle, the intended purpose. Whenever the driver brakes the vehicle to a stop, all of the kinetic energy of the vehicle will be converted to heat by the brakes. The idea of regenerative braking is capture some of that kinetic energy and store it, instead of discarding it as heat.
Regenerative Braking

This idea of capturing kinetic energy is not new, implementations of electrical regenerative braking have existed since at least 1906. [1] Electrical regenerative braking typically involves a vehicle propelled by an electric motor from a battery, such as the truck in Fig. 1, with the possible addition of an internal combustion engine for hybrids. If the wheels and axles of the car do work on the motor (instead of the other way around), the motor acts as a generator and energy flows back to the battery. There are other methods of recovering kinetic energy; for several years beginning in 2009, Formula One teams used flywheels to store kinetic energy. This idea has not been as popular as electrical regenerative braking, for both safety and implementation difficulty.
Efficiency

A conventional passenger internal combustion engine has an efficiency of about 0.12-0.20. [2] That is, only about 20% of the energy in the gasoline is converted to kinetic energy of the vehicle. This is dominated by the engine efficiency. In contrast, electric motors are quite efficient. While induction motors (IM) have an efficiency ranging from 0.65 to 0.94 (for urban vs highway driving scenarios), permanent magnet AC motors are even more efficient, reaching 0.83 to 0.95 for the same scenarios. [3] So speaking strictly of efficiency, the ratio of work out of the engine/motor to the energy in, there is a big benefit to using electric motors, which lend themselves naturally to electrical regenerative braking. While the efficiency is generally high for electric motors, it does change with both speed and torque. Fig. 2 displays the efficiency of the electric motor/inverter combination used by Sterkenburg et al, showing that efficiency can drop off when the system is operating near maximum torque at low speeds. [4]
Fig. 2: Efficiency for a given induction motor/inverter combination. Efficiency is dependent on operating conditions. (Source: M. Brown, after Van Sterkenburg et al. [5])
Limitations and Capabilities

To consider the efficiency of a vehicle including regenerative braking, we should consider its limitations. First, if the drive motor is being used as a generator, it is restricted by the same power limits as when it is acting as a motor. This is an problem because vehicles typically can brake much harder (with much more power) with conventional, friction- based brakes then they can accelerate forward; a vehicle regenerative braking alone will have less braking capability than a vehicle with friction-based brakes. It seems unlikely that vehicles will forego conventional brakes anytime soon. Braking power is not only limited by the motor's power rating, but by the charging power limit of the battery pack. This limit depends on the battery type (chemical composition) and changes with temperature. [5] This makes analyzing the braking power capability difficult, as a vehicle may be able to regen-brake at full power for a short period of time (a few seconds), but as the temperatures of the battery pack and inverter rise, the braking power will quickly fall. While real-world benefit may vary depending on the scenario, some simulations show that regen braking reduces external energy consumption by a little over 20% in urban driving situations. [4]

While it makes sense to attempt to recover kinetic energy for later driving, the exact amount of energy, and the rate of energy, that can be recovered is dependent on both the myriad of available motor, inverter, and battery types, and the driving scenario.

© Matthew Brown. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
References

[1] A. Raworth, "Regenerative Control of Electric Tramcars and Locomotives," J. Inst. Electr. Eng. 38, 374 (1907).

[2] "Tires and Passenger Vehicle Fuel Economy, Transportation Research Board of the U.S. National Research Council, Special Report 286, 2006.

[3] J. W. Schultz and S. Huard, "Comparing AC Induction with Permanent Magnet Motors in Hybrid Vehicles and the Impact on the Value Proposition, Parker Motion, 2013.

[4] S. Van Sterkenburg et al., "Analysis of Regenerative Braking Efficiency - A Case Study of Two Electric Vehicles Operating in the Rotterdam Area," IEEE 6043109, 6 Sep 11.

[5] K. Smith and C.-Y. Wang, "Power and Thermal Characterization of a Lithium-Ion Battery Pack For Hybrid-Electric Vehicles," J. Power Sources 160, 662 (2006)
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Offline RE

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Re: BIG RIG Drags Car Up Cajon Pass, Cali.
« Reply #11 on: April 21, 2017, 03:50:50 PM »
What does the BNSF use to come down Cajon Pass with a massive load & steel to steel friction with wheels on tracks.
At least with big rigs there's an emergency sand pit to dive into if your adrift.

Lots of brakes.  Trains have a lot of wheels.

RE
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Offline agelbert

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Re: BIG RIG Drags Car Up Cajon Pass, Cali.
« Reply #12 on: April 21, 2017, 04:20:57 PM »
Did the driver of the auto turn into the rear wheel on tandems & get hooke that way.
How does this happen????

The only way I can picture it is if the Big Rig driver made a left lane change and wasn't watching what his tandems were doing or what was happening in his side mirror.  The guy in the car was behind him trying to pass when the rig driver pulled to the left lane.  Car hits trailer and gets hooked.

Far as Cajon Pass goes, its one of the longest steep grades out there.  There are some steeper grades in the Appalachians, but none as long as Cajon.  If you got any weight at all in the trailer, it's a very LOOONG and tedious trip up the hill in low gear doing 5-10 mph.  On the way down, its a brake SMOKER, and that is with running the Jake Brake full out, which sounds like you are in a War Zone and NATO is dropping the Death from Above. (Jake Brakes are an engine braking system that put back pressure on the cyclinders, BLAP BLAP BLAP!)

This would have been a fuck load worse going down the hill.  :o

RE

  for the info.   

When they get electric big rigs, these steep grades won't burn brakes because the motor itself will slow the rig without any "BLAP, BLAP" (no cylinders, of course  ;D) and boost battery life at the same time.  :icon_mrgreen: I expect the trailers on electric rigs will be modified to include some regenerative breaking gizmo to extend battery life AND brake life too.

Yes, regenerative electric braking would be silent, and you would need electromagnets on the hubs of the trailer wheels as well.

Two problems.

First on the way UP the hill, no Batt storage system could hold enough juice to pull 40 tons up that grade without the Batt pack itself being enormous.  So you would need your electrified overhead trolley wires for this.

Second, on the way DOWN the hill, those electromagnets would get fucking HOT!  The energy has to be dissipated as heat.  So you have a similar problem as with mechanical brakes, they get too hot and they smoke out on you.

RE

Good points. However, I think the heat buildup with regenerative braking systems is much less than with disk or brake pad in-your-face FRICTION. I don't have any stats with me off the top of my head, but hot brakes get a lot hotter than hot magnets. A large portion of the energy that is converted to heat with brakes is used to juice the battery bank on regenerative brake systems.

So, since manual brakes convert ALL the stopping energy to heat and regenerative brakes convert only a portion of the stopping energy to heat, I would think you have a heat load that is lower, all things being equal, with regenerative braking than you do with friction braking.

As you know, when magnets begin to heat, they lose magnetism gradually (as the heat increases) along with the ability to induce current and voltage. So, they have a sort of physics governor on how hot they can get that friction brakes do not have.  :icon_sunny:

At a certain point, the heat in magnets is such that they cannot induce current because their magnetism is zip. At that moment, they stop getting hotter and begin to cool.

As soon as they get to a temperature that they can output a significant magnetic field again, they start to get hot, which weakens the magnetic field and the amount of induced current, and so on and so forth.

Have you read any articles on comparisons that I could read? I'm sure the technology will improve, but I'm interested in the state of the art as it is now.  :coffee:

Below is an article on the topic.

When I visited the Ewz manufacturer we discussed regenerative braking (I was interested in whether his units were designed to do this).  It has a lot of problems, and the efficiency is low, maybe 20% recovery possible.  The motors aren't designed to work the other way as generators.

The bigger problem with Big Rigs pulling a heavy load is that the throughput would be so big on the downhill.  You would need much thicker and heavier wiring to handle the current passing through the wires.  The batts also not designed to take so much juice so fast.  On a Big Rig with 40 tons going down Cajon Pass, I suspect the magnets would overheat in the first few minutes.

RE


---------------------
http://large.stanford.edu/courses/2016/ph240/brown1/

Regenerative Braking Efficiency
Matthew Brown
November 20, 2016
Submitted as coursework for PH240, Stanford University, Fall 2016
Everyday Driving
Fig. 1: An electric truck with regenerative braking capability, made by Smith Electric Vehicles. (Source: Wikimedia Commons)

We spend spend a huge amount of energy on transportation, and on automobiles in particular. Outside of the minor side effect of giving us unprecedented freedom of movement and enabling much of our way of life, all of that energy is "wasted". If a driver burns a tank of gasoline traveling from San Francisco to Los Angeles, 100% of the energy in the gasoline will be converted to heat and not useful for other work. Much of this energy will be converted to heat in the internal combustion engine during the combustion process, a thermodynamically required inefficiency that is the price of admission for use of heat engines. Some will be lost to friction in the drivetrain, but some of the energy in the gasoline will be converted to kinetic energy of the vehicle, the intended purpose. Whenever the driver brakes the vehicle to a stop, all of the kinetic energy of the vehicle will be converted to heat by the brakes. The idea of regenerative braking is capture some of that kinetic energy and store it, instead of discarding it as heat.
Regenerative Braking

This idea of capturing kinetic energy is not new, implementations of electrical regenerative braking have existed since at least 1906. [1] Electrical regenerative braking typically involves a vehicle propelled by an electric motor from a battery, such as the truck in Fig. 1, with the possible addition of an internal combustion engine for hybrids. If the wheels and axles of the car do work on the motor (instead of the other way around), the motor acts as a generator and energy flows back to the battery. There are other methods of recovering kinetic energy; for several years beginning in 2009, Formula One teams used flywheels to store kinetic energy. This idea has not been as popular as electrical regenerative braking, for both safety and implementation difficulty.
Efficiency

A conventional passenger internal combustion engine has an efficiency of about 0.12-0.20. [2] That is, only about 20% of the energy in the gasoline is converted to kinetic energy of the vehicle. This is dominated by the engine efficiency. In contrast, electric motors are quite efficient. While induction motors (IM) have an efficiency ranging from 0.65 to 0.94 (for urban vs highway driving scenarios), permanent magnet AC motors are even more efficient, reaching 0.83 to 0.95 for the same scenarios. [3] So speaking strictly of efficiency, the ratio of work out of the engine/motor to the energy in, there is a big benefit to using electric motors, which lend themselves naturally to electrical regenerative braking. While the efficiency is generally high for electric motors, it does change with both speed and torque. Fig. 2 displays the efficiency of the electric motor/inverter combination used by Sterkenburg et al, showing that efficiency can drop off when the system is operating near maximum torque at low speeds. [4]
Fig. 2: Efficiency for a given induction motor/inverter combination. Efficiency is dependent on operating conditions. (Source: M. Brown, after Van Sterkenburg et al. [5])
Limitations and Capabilities

To consider the efficiency of a vehicle including regenerative braking, we should consider its limitations. First, if the drive motor is being used as a generator, it is restricted by the same power limits as when it is acting as a motor. This is an problem because vehicles typically can brake much harder (with much more power) with conventional, friction- based brakes then they can accelerate forward; a vehicle regenerative braking alone will have less braking capability than a vehicle with friction-based brakes. It seems unlikely that vehicles will forego conventional brakes anytime soon. Braking power is not only limited by the motor's power rating, but by the charging power limit of the battery pack. This limit depends on the battery type (chemical composition) and changes with temperature. [5] This makes analyzing the braking power capability difficult, as a vehicle may be able to regen-brake at full power for a short period of time (a few seconds), but as the temperatures of the battery pack and inverter rise, the braking power will quickly fall. While real-world benefit may vary depending on the scenario, some simulations show that regen braking reduces external energy consumption by a little over 20% in urban driving situations. [4]

While it makes sense to attempt to recover kinetic energy for later driving, the exact amount of energy, and the rate of energy, that can be recovered is dependent on both the myriad of available motor, inverter, and battery types, and the driving scenario.

© Matthew Brown. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
References

[1] A. Raworth, "Regenerative Control of Electric Tramcars and Locomotives," J. Inst. Electr. Eng. 38, 374 (1907).

[2] "Tires and Passenger Vehicle Fuel Economy, Transportation Research Board of the U.S. National Research Council, Special Report 286, 2006.

[3] J. W. Schultz and S. Huard, "Comparing AC Induction with Permanent Magnet Motors in Hybrid Vehicles and the Impact on the Value Proposition, Parker Motion, 2013.

[4] S. Van Sterkenburg et al., "Analysis of Regenerative Braking Efficiency - A Case Study of Two Electric Vehicles Operating in the Rotterdam Area," IEEE 6043109, 6 Sep 11.

[5] K. Smith and C.-Y. Wang, "Power and Thermal Characterization of a Lithium-Ion Battery Pack For Hybrid-Electric Vehicles," J. Power Sources 160, 662 (2006)

Thank you  :emthup:  I see that Regenerative braking needs some significant improvements for really heavy loads.  :(
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Offline RE

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Re: BIG RIG Drags Car Up Cajon Pass, Cali.
« Reply #13 on: April 21, 2017, 05:03:11 PM »
Thank you  :emthup:  I see that Regenerative braking needs some significant improvements for really heavy loads.  :(

The solution to the problem is not to use trucks to bring heavy loads down a long grade like that.

Transfer the trailer to a funicular railway and counter weight it with a tank of water to go up the hill while the trailer goes down.  On arrival at the top of the hill, you send the water back down via a pipeline, and then the tanker car is light and easy to brake on its way down to handle the next load.  :icon_sunny:

This is the kind of shit you think about when your brakes are SMOKIN' heading down Cajon Pass.  :icon_sunny:

<a href="http://www.youtube.com/v/kVWdRsq-v2g" target="_blank" class="new_win">http://www.youtube.com/v/kVWdRsq-v2g</a>

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Offline Surly1

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Re: BIG RIG Drags Car Up Cajon Pass, Cali.
« Reply #14 on: April 21, 2017, 05:17:07 PM »
  How could he NOT know this car was hooked? 
Agreed.

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