Western Railroad Discussion > Engineers, Run 7 is your friend with C4 & P4 locos

This is related to my mention from this thread.

http://www.trainorders.com/discussion/read.php?1,3635269

From Physics we know horsepower = speed. A 4000 hp locomotive will move 1000 tons faster than a 3000 hp unit will. In Physics, F=ma. When mass stays the same a larger Force will provide greater acceleration.

Now let's look at railroading. We have a limitation on how much force may be applied to the mass called adhesion. If the wheels slip on the rail not all of the horsepower is useful to the problem.

So what does this mean? Basically, due to adhesion limits we cannot go any faster. We cannot use all that 4400 hp available, it is wasted, we just might as well apply less horsepower so we are not trying to increase speed.

The easiest way to reduce horsepower with a locomotive is to reduce the throttle to drop output from 4400 hp to 4000 hp. What then happens is the train is not trying to accelerate from 10 mph to 12 mph. The wheels are not trying to go any faster than they really are going. Everything may balance out.

You should find the traction motors are pulling the same number of amps as in run 8 they may do the same load in Run 6 though that may not provide the horsepower necessary to climb the grade.

So you BNSF/MRL engineers need to try this out when you have these 4 powered axle units in a consist to see if it works for you. Let the rest of us know if it helps.

I figured this out running mountain grades with coal and grain trains in Nebraska and Montana. Sometimes there were EMD units getting low on cooling water. Pretty soon the low water button tripped. You could go back and reset the fault button and restart the engine but it would trip low water as soon as you put it back online. I did find if you backed down to Run 7 it would run and load for hours without shutting down. Four motors at Run 7 pulled far better than three motors at Run 8 every time.

Posted from Windows Phone OS 7

BNSF says horsepower per ton solves all the math. A locomotive with 4400 hp and 4 tms pulls just as hard as a 4400 hp unit with 6 tms. Makes you wonder why they just don't go with a C1 loco as in 4400 hp and 1 tm on the unit then.

So where are they wrong? Let's do the math. 4400/6=733 hp/tm. 4400/4=1100 hp/tm.

What if wheel slip occurs at 900/hp per traction motor? The wheel slip system is going to reduce the hp on that traction motor from 1100 hp to 900 hp. If one tm slips at 900 hp then probably another one will, also. So the wheel slip reduces that to 900 hp as well. So now your 4400 hp unit is only applying 4000 hp to the traction motors. That is 1100 hp to one pair and 900 to the other pair. Suddenly your hp/train
tons is short especially in coal and grain service where it starts at .8 hp/t.

How do wheel slip systems work? They reduce horsepower. What happens when a unit slips? You get less hp/t.

Is BNSF living in the real world? Is BNSF even looking at the event recorder downloads from trains stalling out on grade to see what is happening? I think they are just blaming the engineer for train handling and then burying their heads in the sand. That way no one has to blow the whistle on some big wig and tell him his decision to go with 4 traction motors was WRONG. Too many bonuses are involved here. If the idea doesn't work then it is the Operating Department at fault. The Executive bean counters could never screw up.

Posted from Windows Phone OS 7

They're still suffering under the illusion that on paper 4 AC motors will produce the same
torque as 6 DC motors at 10 mph. As you say, if at that point said torque causes monumental
slip it must be the engineer's fault (on an automatic wheelslip system).

Out

I think that may actually be true. If you applied 4400 hp to 6 tms on dynamometers and then 4400 hp to 4 tms on dynamometers you could actually get the same total output out the dynamometers. The problem is the wheel to rail connection is not solid. When the wheel slips the output is reduced.

Posted from Windows Phone OS 7



Edited 1 time(s). Last edit at 01/17/15 12:57 by fbe.

fbe Wrote:
-------------------------------------------------------
> BNSF says horsepower per ton solves all the math.

There is a fundamental relationship, but it must be accompanied with common sense. That's probably the shortfall.


> A locomotive with 4400 hp and 4 tms pulls just as
> hard as a 4400 hp unit with 6 tms. Makes you
> wonder why they just don't go with a C1 loco as in
> 4400 hp and 1 tm on the unit then.
>
> So where are they wrong? Let's do the math.
> 4400/6=733 hp/tm. 4400/4=1100 hp/tm.

Ah...the very same thing that applied to sticking an F7 in a consist of SD40s. DejaVu all over again.


>
> What if wheel slip occurs at 900/hp per traction
> motor? The wheel slip system is going to reduce
> the hp on that traction motor from 1100 hp to 900
> hp. If one tm slips at 900 hp then probably
> another one will, also. So the wheel slip reduces
> that to 900 hp as well. So now your 4400 hp unit
> is only applying 4000 hp to the traction motors.
> That is 1100 hp to one pair and 900 to the other
> pair. Suddenly your hp/train
> tons is short especially in coal and grain
> service where it starts at .8 hp/t.

I had that argument with the power bureau over and over - on two different railroads.


>
> How do wheel slip systems work? They reduce
> horsepower. What happens when a unit slips? You
> get less hp/t.

I had a guy stall just out of Merritt (WA) one night. The weather wasn't bad..for the Cascades. It was cold and there was an inch of snow on the rail. The No. 103 had only about 4000 tons. The power should have been plenty, but he had to back into Merritt and call me. There was a brand new SD60 on the point. High tech wheel slip system and almost no engineer control of the sand. The way he described it was classic:
I let the wheel slip system keep doing its thing until it turned itself into and SD9, then I put it out of its misery and backed into Merritt. We talked about swapping out the lead unit, but the rest were backwards, so I had him cut off the power, run light to Berne, and run back to Merritt sanding (with the old school leader on the other end).

I called the power bureau to complain. The response was We don't want those engineers grinding up our expensive track with all that sand that they use. You can't make this stuff up.


TAW

TAW Wrote:
-------------------------------------------------------
> I called the power bureau to complain. The
> response was We don't want those engineers
> grinding up our expensive track with all that sand
> that they use. You can't make this stuff up.
>
>
> TAW

Classic Tom, I guess they just want a lot of rail burns every time a train slips it's way to a stall. Then the rail detector comes along and they end up having to replace the rail.

Ted Curphey
Ontario, OR

Al, similar to your low water problem, I have a locomotive that we use that tends to give out a hot engine alarm on a prolonged tonnage pull in run 8. On the long uphill from Wilbur to Creston, WA with something around max tonnage, you are almost sure to get an alarm if you just leave it in run 8. But I've found that by backing off to notch 6 or 7 where the grade eases a little, I can keep the engine from overheating. Sure I don't get the benefit of the extra speed where the grade eases, but it was quickly lost on the steeper sections anyways. And by keeping the engine from going into hot engine mode, I still get to use full throttle where I need it.

Ted Curphey
Ontario, OR



Edited 1 time(s). Last edit at 01/17/15 13:52 by funnelfan.

Well the good news is there not even trying to blame the Engineers in my area when we stall out. The Roadforman and Dispatcher flat out know we are running the low end of the HPT on our trains right now. All it takes is one little problem with a motor and were done. I had to help shove a grain train out of Spokane the other day after both head end units lost a traction motor. Another train stalled out EB at Fishtrap. Pasco ran them out of there at .9 HPT which might be fine in the summer but not on a rainy cold winter day. The engineer complained before he left but the Trainmaster said take it.

They have all the facts from the testing. And still they buy more. I believe the word this is Carl Ice's idea. See why it keeps going.....

Posted from Android

Pacific5th Wrote:
-------------------------------------------------------
> Pasco ran them out of
> there at .9 HPT which might be fine in the summer
> but not on a rainy cold winter day.

One fine Cascade winter, one of my arguments with the power bureau ended with You're being ridiculous. Weather doesn't affect locomotives.

...and me hanging up in disgust.

TAW

Ted,

I know it is cold now, maybe the unit is not so problematic. When it gets warm out someone could climb to the top of the rear ladders and look down to see if all three fans are working. Sometimes one stays in low speed or just doesn't come on. There are also panels inside the doors below the radiators which fall out. Thse separate the compressor area from the radiator intakes and if missing can screw up the air flow. I am sure things are different on the tunnel motor, though.

Posted from Windows Phone OS 7

I wonder how much money the BNSF paid they guy to make all the smoke and mirrors to make them believe that the C4's are good. I have had one on the point over Donner pass and it never would grip the rail.

TAW,

That guy got promoted account he was too out of touch to do work in the field. Since he was made the boss everyone in the field who disagreed with him had to be wrong.

Sometimes on the railroad I just had to switch the radio to a dead channel so I could reply without getting fired.

Posted from Windows Phone OS 7

>You should find the traction motors are pulling the same number of amps as in run 8 they may do the same load in Run 6 though that may not provide the horsepower necessary to climb the grade.

Not quite sure what you mean here, but a series wound motor (DC) will draw the current it needs to do the job required of it and no more. This means that if a traction motor is drawing x number of amps in run 6 and you advance the throttle to run 8, the engine-generator system will try to force more than x amps through the traction motor. If x in run 6 is at the limit of adhesion, then the x-plus amps in run 8 will cause wheel slip.

An AC tm is similar, except that ti has a more drooping characteristic curve.

>How do wheel slip systems work? They reduce horsepower.

They reduce the amperage in the traction motor(s) but do not reduce diesel engine rpms. Losses arise when you rely on the wheel slip system to compensate for trying to make tm current exceed adhesion.

The trick is to adjust your throttle setting so the current to the motors doesn't exceed adhesion. If this happens to be run 6, then don't go to run 7. BTDT successfully many times.

> I called the power bureau to complain. The
> response was We don't want those engineers
> grinding up our expensive track with all that sand
> that they use. You can't make this stuff up.

The Canadians have even convinced themselves that sand is not necessary. Canadian engines without sanders are not permitted in the US.

Okay. . . . what is 'BTDT' ?

Been
There
Done
That
...

Jim Montague
IRVINE, CA
Train and Nature photo Art

">You should find the traction motors are pulling the same number of amps as in run 8 they may do the same load in Run 6 though that may not provide the horsepower necessary to climb the grade."

What I have found is if the load meter shows 1100 amps in run 8 on a steep grade it will also show 1100 amps in Run 7. It might not show quite 1100 amps in Run 6. That depends on a lot of things. I have seen it go either way. AC locos rely on frequency for speed control over voltage like DC. Railroads quit teaching those things to crews some time ago.

Posted from Windows Phone OS 7

Been there done that

Posted from Android

It's the same with six axle Gevo's also, in the Blue's from October till April run 8 is a waste. Except on the DPU's, myself and most the other engineer's rarely use number 8 in the bad weather. Number 7 is usually the throttle position is what we go up the hill in, I'll be bored going up the hill and go over and look at the tractive effort be put out, 90% of the time the unit is pulling x amount of tractive effort, and 4000-4200hp. It's not always a good thing to be using all the HP or tractive effort, younger engineer's find that out the hard way quickly.. As for the C4's, occasionally the Boardman coal trains will show up with one in the consist, going up t0 the coal plant from Castle siding is a pretty good pull. I've never gone up there with a C4 in the consist above number 7, it's a slower climb, but, I'm not doubling the train, or pulling it in two.. To me it's a waste of money to buy a unit, six axle at that and only putting power to four of them...

The $ saved costs redundancy.
Loosing 1 tm out of 6 is way different than 1 out of 4!!
Planning for the occasional failure is frowned upon by everybody NOT involved in handling that situation.
happens in lots of things now as accountants find ways to reduce expenses, by reducing the margins of error, redundancy, backup staff/equipment, etc.

Posted from Android