Cajon pass. Why BNSF run so many more engines per train than UP.

@phill posted:

Watching You tube vids on the pass and seeing BNSF trains with so many more engines per train then the UP I see BNSF trains with up to 8 engines in the lead, going either way, up and down the hill. Why does BNSF have to run sure great numbers of engines to do the same job the UP does with fewer.

I'm pretty sure one reason is, the BNSF tends to operate their "Z Trains", or whatever they call their hot premium service trains these days, at 70 MPH on the "TransCon" mainline from LA to Chicago. That takes LOTS of horsepower!

Is there a fuel efficiency trade off?  Do 6 engines use about the same fuel as 4 engines pulling the same train/track/speed?

Just because there is 5 or 6 engines in the consist, it doesn’t mean all are online and providing traction effort. BNSF is known to keep engines offline and only putting them online when needed for steep grades. Union Pacific often just adds engine along the way when trains are in steep grade territory. Just two different strategies on how to run long and heavy trains across the country. 

@aussteve posted:

Is there a fuel efficiency trade off?  Do 6 engines use about the same fuel as 4 engines pulling the same train/track/speed?

Fuel consumption is pretty closely related to actual work done, so the number of uints doing the same work causes a small increase in fuel consumption, but it's minor compared with the effects of speed, train tonnage (including locomotives) and grade.

In one of my earlier lives (70's, 80's), I did a lot of railroad cost analysis, and fuel consumption was something that I studied closely.  On level track, tractive effort required to move locomotives and train was the sum of rolling resistance and wind resistance (turbulence).   Rolling resistance increases linearly with speed.  Wind resistance increases as the square of speed.

At 60 mph for a passenger train, about half of the power needed was to overcome wind resistance.  Running at 70 mph required 18 % more power than 60 mph.  Relative to 45 mph, about twice as much power/fuel is needed.  Those ratios are for passenger trains.  For freight, they are worse.

Malcolm Laughlin

Something else I should mention v.v UP vs BNSF.  In the 60's when I was with the NYC, we ran intermodal trains at 70 mph.  In the 70's when fuel prices soared, most railroads cut back freight train speeds.  I believe UP cut their fast freight train speed from 60 to 45 because of fuel cost.  Santa Fe was always the high speed railroad.  Maybe some of the SF operating philosophy still lives on BNSF.

When you talk about Cajon you need to be a little more specific.  There are four different tracks with three different grades.   The track all the way to the north is UP only and was built new by the SP in the late 1960s. I believe it has the least grade. At the top of the hill it turns north to Palmdale, but recently there was a crossover added so UP trains headed for their Salt Lake line can go up the hill on their own track, then crossover to BNSF at the top of the grade. The track to the south is the original Santa Fe track from maybe 1870s. It is quite steep and has limited use. The two middle tracks were built, one about 1910 and the other about 2010. These are both BNSF tracks. They have a moderate grade. These two are also used by UP. I do not think UP gets onto the oldest steep track. 

BNSF is not, as of now, into PSR.

And customers pay more for the Z service.  And one of BNSF's best customers is Brown, that is UPS.  One customer you do not want to upset!

My engineer friend on the BNSF tells me that they are limited to the maximum equivalent of 28 powered axles. So, everything else would be tagging along for the ride.

@Big Jim posted:

My engineer friend on the BNSF tells me that they are limited to the maximum equivalent of 28 powered axles. So, everything else would be tagging along for the ride.

Wouldn't that work out to 5 six axle units or 7 four axle units?

How much horsepower are we talking about.  I go back to the 2000 hp per unit was big days.  I don't know what is usual horsepower per unit today.

 I recall that about 8,000 or maybe it was 10,000 hp could move a flexivan train of 100 or more containers at 70 mph.  For speed, it is horsepower that counts.  Number of units or number of cylinders or number of axles or weight on drivers doesn't matter if the gear ratio is good for speed.  When you are talking about dragging tonnage, then weight and number of axles are much more important.

@mlaughlinnyc posted:

How much horsepower are we talking about.  I go back to the 2000 hp per unit was big days.  I don't know what is usual horsepower per unit today.

Most modern units, over the last 10 to 20 years are 4000+ HP EACH.

 I recall that about 8,000 or maybe it was 10,000 hp could move a flexivan train of 100 or more containers at 70 mph. 

On the water level NYC main line, sure. But NOT on the BNSF (former SantaFe) "TransCon" rout from Chicago to LA/Long Beach.

For speed, it is horsepower that counts.  Number of units or number of cylinders or number of axles or weight on drivers doesn't matter if the gear ratio is good for speed. 

For freight service, the standard gear ratios work just fine at speed up to 70 MPH, on the current modern units. Now, the "number of units or number of cylinders or number of axles or weight on drivers" sure as the devil DOES matter, if the train is supposed to have 4 to 6 horse power per ton, requiring 20,000+ HP in order to maintain 70 MPH over the vast majority of the terrain (depending on curvature or speed restrictions).

When you are talking about dragging tonnage, then weight and number of axles are much more important.

Again, it all depends on how much HP per ton is required in order to maintain minimum continuous speed on the steepest ascending grade. Thus, a 16,000 ton unit coal train may only require three 4000 HP SD70MAC units, providing .75 HP per ton.

 

 

 

@mlaughlinnyc posted:

Fuel consumption is pretty closely related to actual work done, so the number of uints doing the same work causes a small increase in fuel consumption, but it's minor compared with the effects of speed, train tonnage (including locomotives) and grade.

In one of my earlier lives (70's, 80's), I did a lot of railroad cost analysis, and fuel consumption was something that I studied closely.  On level track, tractive effort required to move locomotives and train was the sum of rolling resistance and wind resistance (turbulence).   Rolling resistance increases linearly with speed.  Wind resistance increases as the square of speed.

At 60 mph for a passenger train, about half of the power needed was to overcome wind resistance.  Running at 70 mph required 18 % more power than 60 mph.  Relative to 45 mph, about twice as much power/fuel is needed.  Those ratios are for passenger trains.  For freight, they are worse.

Malcolm Laughlin

The air resistance issue is a big one. I remember UP posting a video a few years ago where they were looking at placing a fairing on the lead container car to reduce wind resistance. They were using #1 gauge models in the wind tunnel testing. I never saw it put into real-world testing -- at least not out here in California.

@Hot Water posted:

Wouldn't that work out to 5 six axle units or 7 four axle units?

3 big GE's and a four axle.

@Big Jim posted:

3 big GE's and a four axle.

But that's only 22 axles, and pretty low on total HP.

@Hot Water posted:

But that's only 22 axles, and pretty low on total HP.

Everything is based on DC motors. The Dynamic braking limit is a lot less axles. And, I think that is pretty much the standard across the nation.

Roadrailer should have less wind resistance.  But seems railroads have a resistance to Roadrailer.  Not the total answer, but maybe something which should be kept in the tool box?

@Dominic Mazoch posted:

Roadrailer should have less wind resistance.  But seems railroads have a resistance to Roadrailer.  Not the total answer, but maybe something which should be kept in the tool box?

If the customers that ship on BNSF don't want/like Roadrailer, then you will not see them on BNSF.

@AGHRMatt posted:

The air resistance issue is a big one. I remember UP posting a video a few years ago where they were looking at placing a fairing on the lead container car to reduce wind resistance. They were using #1 gauge models in the wind tunnel testing. I never saw it put into real-world testing -- at least not out here in California.

Caught this one in Wheaton, Illinois in July 2018.

Rusty

@Hot Water posted:

If the customers that ship on BNSF don't want/like Roadrailer, then you will not see them on BNSF.

Isn't Roadrailer pretty much a dead concept now since NS stopped using them?  I seem to recall the specialized trailers were reaching end of life and they weren't worth ordering replacements.

Plus, I don't recall Roadrailers being used for containers, which appear to be more flexible and the bulk of box-loads nowadays.

Rusty

@Rusty Traque posted:

Caught this one in Wheaton, Illinois in July 2018.

 

Rusty

Thanks Rusty. Definitely looks like a full-size version of the wind tunnel model.

Perhaps BNSF just happened to be swapping power from one part of the railroad to another when you were watching the action on Cajon pass or when the videos were filmed.  Another possibility is that BNSF is using more units to provide dynamic braking for going down the hill.   I know that railroads sometimes add engines just to increase dynamic braking.  NH Joe

Here are some photos that I took of a BNSF train passing through Tehachapi, CA in 2009 heading downhill toward the loop.  

@New Haven Joe posted:

Perhaps BNSF just happened to be swapping power from one part of the railroad to another when you were watching the action on Cajon pass or when the videos were filmed.

A possiblity.

 Another possibility is that BNSF is using more units to provide dynamic braking for going down the hill.   I know that railroads sometimes add engines just to increase dynamic braking.

Nope! There are strict limits on how many traction motors can be used in dynamic braking, no mater how many units are in the consist.

 NH Joe

 

Back in my early CA days a friend and I went regularly to the Pass. In those days we could watch an SP train take forever to struggle upgrade, while the UP and ATSF trains zipped up the hill. I was told that SP assigned power based on factory HP, without regard to the crappy maintenance their locos received. In those days, UP &ATSF shared the ATSF trackage. Once upon a time I was standing in a cut to catch an uphill UP train when I realized that it was *accelerating* uphill. Fastest climb out ever....Anyway, I lost interest when the DDs went away.

There was a hillock between the uphill and downhill tracks, used for some nefarious purposes, given the detritus found there. We'd sit on lawn chairs with our liquid refreshment and take many photos. In those days train consists still gad mostly 40-and 50-cars from everywhere. Glorious fun.

@Rusty Traque posted:

Isn't Roadrailer pretty much a dead concept now since NS stopped using them?  I seem to recall the specialized trailers were reaching end of life and they weren't worth ordering replacements.

Plus, I don't recall Roadrailers being used for containers, which appear to be more flexible and the bulk of box-loads nowadays.

Rusty

There was a prototype RR bed for containers...