The 100mpg target is not impossible. GE claims their Diesel-electric locomotives move 1 ton 500 miles per gallon of diesel. that's 250 mils for a 2-ton car then a 15% loss to use gasoline vs diesel, down to 220 miles. I understand that rails are different than roads and the drafting that each rail-car gets from the engine and previous cars add to aerodynamics but the tires used on these hyper-mile test vehicles and cockpit design are not always realistic either. Just trying to bring a perspective that such efficiency is possible (if few start/stop cycles and few hills are in your path).

And that's 1 ton of freight (payload), so it doesn't count the mass of the train itself!

But one huge difference between a train and a car is the stop-and-go. I installed a driving computer in my old '75 Bronco, that averaged 10 mpg under pretty much any conditions, and it provided real-time fuel-flow rate and mileage. On a level highway at 55 mph I almost got over 40 mpg. I saw similar ratios in my '02 Cherokee using its built in computer. A huge fraction of energy is consumed in accelerating up to speed and then it gets wasted as heat in the brakes when you stop. That is why city mileage is always much worse than highway mileage (since very few cars, even the hybrids and electrics, use waste-energy recovery for breaking). But trains operate on very gentle slopes (seldom over 1%) and the track routing is designed with as few, and as gentle, curves as possible. Then the train is operated at as near constant speed for its entire journey as possible. Furthermore, because they don't do stop and go (and because they are on dedicated lines when they do, as opposed to sharing the road with a bunch of other drivers), they can accelerate very slowly. That means that they can use engines that are way underpowered compared to what a car needs to accelerate away from a stoplight at even a moderate rate. That stacks the deck hugely in favor of the train for fuel efficiency.

To show how significant these effects are, a group of University of Michigan students (senior design project) built a car that had a 16 hp engine, got 80 mpg, and had very fast acceleration from a stop (I don't recall the numbers on that). They did it by having the engine drive a hydraulic pump and used hydraulic motors at the wheels. The car had a good size accumulator that was used to store fluid under pressure for quick starts off the line and also used for braking so that a large fraction of the recoverable energy was recovered when slowing down or stopping. This was sometime back in the '80s, I think.

But even the amazing efficiency of trains pales in comparison to ships. A large container ship can move 1 ton of cargo about 3000 miles on a gallon of fuel.

 

I used to work at our local rail yard fueling locomotives and there is more to that feat than average public knows.

1. Locomotive diesel fuel is not formulated the same as the stuff we get at the local fuel stations. Theirs has a much higher BTU per gallon plus would not pass any over the road clean burn (low/no sulfur) and whatnot regs.

2. Locomotive diesels are built to be as fuel efficient as possible which means they are exempt from EPA and emissions related regs as well.

If the diesel engines used in our vehicles were built the same and ran on locomotive grade fuel most would see close to double if not more than the average MPG numbers than they do now and many of the newest EPA compliant diesel's near triple what they get now.

Basically their not the same engines we get in vehicles and it's not the fuel we get to power them either.

Though now there is a push to force locomotives to adhere to the same emissions standards as over the road truck, despite the fact that if all that freight were moved by trucks the total emissions footprint would be enormously higher. Not to mention that, I think, it would take a couple hundred trucks to move the same payload as a typical full-length train.

 

One of the big claims being pushed is that autonomous vehicles will be inherently so much safer because they won't make the mistakes human drivers will make.

They'll just make different mistakes. Similar calamitous results, though. If corporations the size of M$, with teams of expert software developers and megabuck budgets, can't always (ever?) produce totally bug-free code, what are the chances that these vehicles will be bug-free?

 

And that's 1 ton of freight (payload), so it doesn't count the mass of the train itself!

But one huge difference between a train and a car is the stop-and-go. I installed a driving computer in my old '75 Bronco, that averaged 10 mpg under pretty much any conditions, and it provided real-time fuel-flow rate and mileage. On a level highway at 55 mph I almost got over 40 mpg. I saw similar ratios in my '02 Cherokee using its built in computer. A huge fraction of energy is consumed in accelerating up to speed and then it gets wasted as heat in the brakes when you stop. That is why city mileage is always much worse than highway mileage (since very few cars, even the hybrids and electrics, use waste-energy recovery for breaking). But trains operate on very gentle slopes (seldom over 1%) and the track routing is designed with as few, and as gentle, curves as possible. Then the train is operated at as near constant speed for its entire journey as possible. Furthermore, because they don't do stop and go (and because they are on dedicated lines when they do, as opposed to sharing the road with a bunch of other drivers), they can accelerate very slowly. That means that they can use engines that are way underpowered compared to what a car needs to accelerate away from a stoplight at even a moderate rate. That stacks the deck hugely in favor of the train for fuel efficiency.

To show how significant these effects are, a group of University of Michigan students (senior design project) built a car that had a 16 hp engine, got 80 mpg, and had very fast acceleration from a stop (I don't recall the numbers on that). They did it by having the engine drive a hydraulic pump and used hydraulic motors at the wheels. The car had a good size accumulator that was used to store fluid under pressure for quick starts off the line and also used for braking so that a large fraction of the recoverable energy was recovered when slowing down or stopping. This was sometime back in the '80s, I think.

All obvious, that is why I hedged my statement with "few start/stop cycles and few hills in your path). F = ma. When maintaining a constant speed, only friction is your enemy (air, ground and mechanicals), it is only physics.

 

They'll just make different mistakes. Similar calamitous results, though. If corporations the size of M$, with teams of expert software developers and megabuck budgets, can't always (ever?) produce totally bug-free code, what are the chances that these vehicles will be bug-free?

Zero. I don't buy the claims that are being made and I see numerous potential problems, mostly deliberate, that don't even seem to be being looked at (publicly, anyway).

But I'm still curious why you think that more structural integrity will be needed (i.e., why the current level of structural integrity will not be sufficient).

 

Though now there is a push to force locomotives to adhere to the same emissions standards as over the road truck, despite the fact that if all that freight were moved by trucks the total emissions footprint would be enormously higher. Not to mention that, I think, it would take a couple hundred trucks to move the same payload as a typical full-length train.

There was always a push to make locomotives meet any emission standards but every time the EPA has pushed the rail industry gave them the finger and told them to go 'stuff themselves'.

The EPA may be the 800 pound Gorilla of environmental rule enforcement but the rail industry is the 900 pound Gorilla of commerce and it knows how to fight.

The rail industry may be made up of a few larger and many smaller companies but one thing they do very well is cooperate on standing their ground when pushed. There is no other industry that can move the types of loads at the volumes that they do for as low of cost as they do so their best tactic is to simply threaten to shut everything down and wait things out.

The thing is if the rail industry as a whole dis a full 100% shut down within 24 hours countless power plants would be shutting down due to no coal shipments. Oil refineries would be shutting down due to no way to ship the bulk of their crude oil stocks in and refined products out, our food production and distribution would shut down for the same reasons and so on.

I find the rail industry to be an interesting beast. If you play nice with it it plays nice with you but if you start poking it with a stick and telling it to do something it does not see as gainful to its operations it has no problem shutting down all your critical systems it has its very big fingers in and letting you starve to death in the dark while you rethink your actions.

 

All obvious, that is why I hedged my statement with "few start/stop cycles and few hills in your path). F = ma. When maintaining a constant speed, only friction is your enemy (air, ground and mechanicals), it is only physics.

There's that and then there is the lesser seen and very overlooked aspect of the politics behind how things are done.

Ever think about how if you took a new 8000-pound 350 HP diesel pickup out and ran it flat out accelerating every time you started moving why it would only get 4 - 6 MPG yet a fully loaded 80,000 pound 350 HP semi truck does that every time it gets moving until it gets up to speed and they average 5 - 7 MPG?

How's the physics add up that a 350 HP pickup engine taking 4 - 5 seconds on four wheels to get 8000 pounds up to 60 MPH uses more fuel energy than 350 HP industrial engine taking 40 - 50 seconds on 18+ wheels to get 80,000 pounds up to 60 MPH does?

Some physics numbers don't quite add up there between the two engines.

 

Zero. I don't buy the claims that are being made and I see numerous potential problems, mostly deliberate, that don't even seem to be being looked at (publicly, anyway).

But I'm still curious why you think that more structural integrity will be needed (i.e., why the current level of structural integrity will not be sufficient).

I was at a steering wheel manufacturer (whole steering column). The discussion turned to autonomous cars. They shuttered. The automotive companies are counting on removing the steering column as soon as possible - there are so many parts in a steering wheel and molding the soft foam onto the wheel, assembling the switches, running wires, allowing all wires to connect to entertainment system, cruise control, and what ever while turning the wheel stop-to-stop is not trivial and all is expensive. All that while making sure the airbag will not be damaged and will not interfere with operation of airbag when needed. $1500 for a steering column is not uncommon (plus air bag and installation) and over $2500 on certain high-end models - making it the most expensive part of the interior in most new cars. The dashboard with hvac duct work and controls used to be the most expensive before all the buttons and airbags played a role on the steering wheel.

Autonomous vehicles are desireable to the OEMs because the cost of a human driver are steep. Even drive-by-wire systems save money - less worries about fire-wall failure, more portability for left-right driver models, less weight. Most of the do-dads needed for autonomous cars is in the Infinity 50 and Tesla S. The only thing missing is confidence.

https://www.wired.com/2014/06/infiniti-q50-steer-by-wire/

 

As an aside, Union Pacific is restoring a Big Boy to running order and last year there was a flurry of activity when they moved it from the museum they got it from to their yard in Wyoming. One person asked on their website how they could donate to the effort. The response from UP was (paraphrasing fairly closely), "Thanks, but we are a Fortune 125 company. I think we can handle the cost."

 

There's that and then there is the lesser seen and very overlooked aspect of the politics behind how things are done.

Ever think about how if you took a new 8000-pound 350 HP diesel pickup out and ran it flat out accelerating every time you started moving why it would only get 4 - 6 MPG yet a fully loaded 80,000 pound 350 HP semi truck does that every time it gets moving until it gets up to speed and they average 5 - 7 MPG?

How's the physics add up that a 350 HP pickup engine taking 4 - 5 seconds on four wheels to get 8000 pounds up to 60 MPH uses more fuel energy than 350 HP industrial engine taking 40 - 50 seconds on 18+ wheels to get 80,000 pounds up to 60 MPH does?

Some physics numbers don't quite add up there between the two engines.

physically accelerating a vehicle is much different in terms of fuel comparisons than constant speed. At a constant speed, the only "a" terms we have to worry about is the acceleration to over come frictional forces and actually maintain a constant speed. Once you start talking about how fast we get going fast, the number of variables multiply. I understood those are big variables and that is why I specifically excluded them (and so did GE). The number of stops and starts on a long-haul freight train are minimal. Those engines are immediately changed out once the train enters an urban area with lots of switching because, as you said, each vehicle is tuned to do something well. A short haul locomotive or switch yard locomotive is designed for those tasks. and a long haul locomotive has its tuned specialties so I have left acceleration out of the discussion. If you need more information on this topic, I suggest google.com. Finally, physics always adds up.

 

Curious, why would we need more? One of the big claims being pushed is that autonomous vehicles will be inherently so much safer because they won't make the mistakes human drivers will make.

Exactly. The cars we have now are designed for our mistakes. For the first one or two decades, autonomous cars will make mistakes we literally are not capable of imagining.

ak

 

autonomous cars will make mistakes we literally are not capable of imagining.

I have no doubt about that. But I guess there are always risks involved when dealing with progress.

 

Ever think about how if you took a new 8000-pound 350 HP diesel pickup out and ran it flat out accelerating every time you started moving why it would only get 4 - 6 MPG yet a fully loaded 80,000 pound 350 HP semi truck does that every time it gets moving until it gets up to speed and they average 5 - 7 MPG? How's the physics add up that a 350 HP pickup engine taking 4 - 5 seconds on four wheels to get 8000 pounds up to 60 MPH uses more fuel energy than 350 HP industrial engine taking 40 - 50 seconds on 18+ wheels to get 80,000 pounds up to 60 MPH does? Some physics numbers don't quite add up there between the two engines.

I think they do, right in your numbers. F = ma, and a is a time-dependent function. In *very* round numbers, you have 10 times the weight taking 10 times as long to come up to the same speed at approx. the same mpg. The pickup is a bit less efficient because the semi has many more gears, so the engine spends more time in the sweet spot of its torque curve. From a distance, seems fair to me.

ak

 

I think the do, right in your numbers. F = ma, and a is a time-dependent function. In *very* round numbers, you have 10 times the weight taking 10 times as long to come up to the same speed at approx. the same mpg. The pickup is a bit less efficient because the semi has many more gears, so the engine spends more time in the sweet spot of its torque curve. From a distance, seems fair to me.

ak

But with ten times the mass, the truck has to dump ten times the energy every time it stops. So even if rolling friction and air resistance were zero, the truck would be consuming ten times the fuel at the same efficiency for the same profile.

I don't have much experience with big trucks, but I have asked quite a few truck drivers out of curiosity over the years and most of them have said that when they are fully loaded they get 3 to 5 mpg around down and 6 to 11 on the highway. They've also noted the significant improvements over time in fuel economy. But the same is true for pickups as well. My '88 F-250 gets about 8 mpg while my stepmom's '00 Ram gets 16 mpg and a '12 F-350 that I briefly flirted with buying last year got 21 mpg, which floored me (only the last one of those was diesel).

 

But with ten times the mass, the truck has to dump ten times the energy every time it stops. So even if rolling friction and air resistance were zero, the truck would be consuming ten times the fuel at the same efficiency for the same profile.

But, IMHO, the profiles are not the same. First, all of the energy is dissipated as heat and lost for both vehicles. so that is a wash. Taking 10 times longer to accelerate to a benchmark velocity just plain takes less energy, piling on nine times more weight takes more energy, back to even (-ish).

ak

 

But, IMHO, the profiles are not the same. First, all of the energy is dissipated as heat and lost for both vehicles. so that is a wash. Taking 10 times longer to accelerate to a benchmark velocity just plain takes less energy, piling on nine times more weight takes more energy, back to even (-ish).

ak

No. The energy of an object of mass, m, moving at a speed, v, is

E = mv²/2

So if you have two vehicles that go from rest to a speed v and one of them is ten times as massive as the other, the more massive vehicle has ten times the kinetic energy as the other. That energy had to come from the fuel.

You are confusing energy with power.

If I have a fixed amount of power, then I can accelerate an object that is ten times as massive as another at just one tenth of the acceleration as the lighter object, but given ten times the amount of time I can get it up to the same final speed. But that fixed power is expending the same amount of energy per unit time in both cases and it is expending that fixed amount of energy per unit time for ten times as long. Hence ten times the energy is expending in bringing the more massive object to the same speed as the lighter object. So every time they stop, the brakes of the more massive object have to dissipate ten times as much energy and then ten times as much energy must be drawn from the fuel of the more massive object once they start moving again.

 

Finally! someone sees the problem behind the fuel consumption Vs physics at play problem! Smal vehicle and big truck have equally rated engine power but the big truck takes ten times and much energy to get up to speed as the small vehicle yet only burns twice as much fuel doing it?

So where's the problem? Is the big truck engine super efficient or are our common vehicle engines extremely inefficient? (As if I don't already know. )

BTW one of my more favorite comparisons of modern emissions compliant fuel economy Vs old school non-emissions is the trip I made when I got my 1962 International Fire truck.

It was a 300-mile trip and my wife followed me with my 99 Ford F250 super duty with the 6.8L V10 that weighs ~8000 pounds. The fire truck is 16,000+ pound a cab over brick with the LV 549 V8 (well known engine for being a fuel pig in its day) anyway, I drove the old truck flat out against the governor at ~62 MPH for most of the 300 miles and it averaged 1 MPG worse for the whole trip than the 99 F250 did.

 

damn i feel sorry for some of you's

i get peeved when i use more that 8.5litres/100km (for the imperials - 2-1/4 gallons/62miles)

 

damn i feel sorry for some of you's

i get peeved when i use more that 8.5litres/100km (for the imperials - 2-1/4 gallons/62miles)

That's 27.6 mpg, which is probably middle-of-the-pack these days. I have a '99 Toyota Camry that usually gets right at 30 mpg. But I wouldn't make a very good snow plow or handle hauling a ton of materials around or pulling a two-axle trailer. That's why I also have an '88 F-250 that gets about 8 mpg (closer to 3 mpg when pushing snow). Different tools have different purposes.

 

I have 1994 Mercury Grand Marquis with the 4.6L Ford V8 thatI stripped all most all of the emission crap off of or rerouted to defeat it purpose. Normal driving was mid 20's MPG in town and long haul highway at 75 - 80+ MPH interstate speeds was pretty consistent at upper 20's to low 30's which was a good 5 MPG gain over it's initial emission compliance setup it had when I got it.

Not bad for a 20+ year old full sized four door sedan that rolled across the local scales at just a hair over 4000 pounds!