How many engines are needed to make the grade?

[imnew]

Hi guys. I would like to run a heavy train up say Cajon, Marias or Donner Pass.. Now, I dont wanna "crest the grade" speeding nor do I want to stall out half way there. Is there a way to see how many engines are needed to make the grade? Or do I have to add engines, run the scenario, see if I stall, add more engines, then do the run all over again to see if I stall out?

How do you guys go about this ? Is there a magic button in the scenario editor that will tell me how much power is needed?

[BlueLight]

You did not tell us how long a consist your train will be pulling up the hill. Let's say you want to pull 75 loaded cold cars
up Donner from Rosemont. In freeroam starting at Colfax create your consist plus 5 engines (4 up front, one in the rear) and take off. See how your train is pulling
the hill. If your train requires too little power to climb the hill, remove engines on the lead until you get the desired results.
There are no "magic buttons" only trial and error.

[imnew]

I had a feeling it would be the "trial and error" approach. Thanks for posting Blue Light

[PapaXpress]

I love this site.
Here is a page you might be interested from it:
http://www.alkrug.vcn.com/rrfacts/gradetuf.htm

[imnew]

Thanks papa

[dtrainBNSF1]

For newer stock I've found a couple of formulas that work relatively well.

You need to know horsepower per ton. To figure that out you may need to refer to the consist editor or the bin files in the Freight folder to get the weight of your consist.

Once you know the weight of your consist figure out how much horsepower you have. The locos from more recent routes seem more appropriately powered. So for example if you have 4 SD40-2s as your power. Thats 3000x4=12000hp. Lets say then that you have a 4000t. train. Then you get 12000/4000=3 horsepower per ton.

Now take 3x12=36. With this figure you need to know the ruling gradient of the route you're travelling. Travelling up Donner Pass there's a ruling gradient of 2.4% I believe, so 36/2.4=15. 15=the speed you can expect to be when you crest the grade.

You can also work it backwards if you want to top the grade at a certain speed, like say 25mph. Just do this: 25mph x 2.4% = 60/12= 5Hp/T x 4000t. = 20000hp/3000hp per SD40-2=6.67 SD40-2s. Just round up to 7. BTW: Back in the day when SD40s and SD45s ruled the rails it was common to send trains up to 10000t. out of Roseville up Donner Pass with 10-11 units, 5 in front and 6 in the middle so a figure of 7 isn't too unrealistic.

This is the same thing I did for my H-EVEGAL series on the Workshop for Stevens Pass and I wasn't too far off. I was aiming for climbing the pass at 2.2% to Scenic at 20mph with 6 GEVOs in distributed power but I got 18mph on average. Not bad considering.

Try it out.

UPDATE:

I've got another couple of formulae that I'm testing out on Donner Pass right now:
20 x % of grade x tonnage = lbf needed to top the grade
(lbf x 1.47 x desired speed) / 550 = needed horsepower.

Like the other formula you can also work backwards if you know already the horsepower at your disposal and/or the tonnage you want to haul up the grade. Using these theoretically you can fine tune the speed possible with your consist or determine the total tonnage you can haul with your locomotive consist. In the case of Donner Pass traveling Westbound at least Union Pacific discourages trains travelling below 14 mph for crew safety traveling through the many snow sheds.

UPDATE 2: Finished testing with the new formula last night. I've come to this conclusion: it works, and it doesn't. Here's what I mean.

The HpT formula works better for modern operations due to the sheer amount of high-horsepower (4000hp+) units we have crossing the country today. Evidence suggests that the 2nd formula I posted for lbf is probably more correct for operations in the 70s-80s when it was common to have as many as 10 SD40/45s powering a single consist up places like Donner Pass. I have a theory: True modern diesels like the GEVOs at 4400hp each can fill the horsepower requirement with fewer units compared to an SD40-2 at 3000hp a piece, but because of the sheer amount of SD40s needed to fill the horsepower requirement their combined tractive effort is easily greater than a couple of GEVOs. More testing needs conducting for this theory to be proven.

[imnew]

Hi dtrainBNSF1

This is really useful information. Thanks for taking the time to post. This will come in handy on other routes as well. Will try your method out when I get back from my holiday.

Thanks again for posting

[harryadkins]

I created a quick Excel horsepower calculator based on the calculations above. Hope you enjoy.

Harry

[imnew]

Thanks Harry. Will take a look at your hp calc.

[Chacal]

All that time I thought a "HP calculator" meant "Hewlett-Packard calculator".

[Ericmopar]

It all depends on whether you highlight the consist and load it using the upper right flyout as well. A common problem I see in scenarios, is people not loading the trains.

A good example, would be the 3% grade on Cajon. You wouldn't want to drop below about 13MPH on that in notch 8. In real life, they seem to have adopted the idea of a little extra power these days. The trains don't seem to drop below 20MPH under normal use these days. I think someone/s finally realized that underpowered trains are more trouble than they are worth. They stall too easily, they tie up the timetable and they add a lot of wear and tear to engines, causing much higher maintenance costs and more downtime for the engines themselves.
Even the Great Grandads figured out "Speed is Money"

[dtrainBNSF1]

It all depends on whether you highlight the consist and load it using the upper right flyout as well. A common problem I see in scenarios, is people not loading the trains.

A good example, would be the 3% grade on Cajon. You wouldn't want to drop below about 13MPH on that in notch 8. In real life, they seem to have adopted the idea of a little extra power these days. The trains don't seem to drop below 20MPH under normal use these days. I think someone/s finally realized that underpowered trains are more trouble than they are worth. They stall too easily, they tie up the timetable and they add a lot of wear and tear to engines, causing much higher maintenance costs and more downtime for the engines themselves.
Even the Great Grandads figured out "Speed is Money"

Yeah, I see more and more that BNSF is putting as much as 5 ES44DCs/Dash 9s on the head end of some intermodal trains climbing Cajon Pass these days.

[dtrainBNSF1]

Unfortunately Train Simulator suffers from some hiccups and these are unrealistic like the wheel slip problem that occurs on modern day locomotives with advanced wheel slip systems in their computers.

Anyway, 6000 horsepower is able to pull a train of 5000 tonne up a 1/150 grade (0.66% grade) approximately. This is from my experience of heavy haulage rail freight.

So on Cajon Pass with a 3% grade you will want about 22000 hp to lift it (5000 tonne). I didn't calculate it right but it is an educated guess.

I would say researching the timetables and such as (published gradients/horsepower table) issued by the railroads would be helpful.


Daniel

And on that note (at least for Cajon Pass) according to the most recent timetable I could find that's available for public download (March 26, 2008) the minimum horsepower per ton (HPT) requirements for eastbound trains traveling on Main track 1 is 2.5 for trains with no helpers or DP units and 2.3 for trains with helpers or DP units. For eastbound trains traveling on Main track 2 the minimum HPT requirement is 3.0 for trains with no helpers or DP units and 2.8 for trains with helpers or DP units.

Westbound trains on all tracks without helpers or DP units are required to have a HPT rating of at least 2.0 and westbound trains on both tracks with helpers or DP units must have at least 1.8.

I have similar timetables for Marias Pass, Stevens Pass and the San Diego Sub (Surf Line) but none of them mentions anything about a certain HPT requirement. The only details about train makeup are the minimum dynamic brake requirements for certain steep sections of the line based on the train's tonnage and tons per operative brake rating (total trailing tonnage divided by number of cars in the consist).

Recently I got my hands on a Union Pacific timetable for the Roseville Sub (Donner Pass) which introduces measurements like tons per dynamic brake axles (trailing tonnage divided by total number of dynamic brake axles). I've tried attaching the pdf but it simply won't work. If you'd like to see this and the other timetables I've accumulated for BNSF connect with me and I'll be more than happy to try and e-mail them to you.

[dtrainBNSF1]

It's been a while since anybody posted to this thread but I would like to make mention of a couple of things I discovered since last posting that may be of help for answering that question of how many engines does it take to get up a hill. I wanted to figure out what the difference was between the HpT formula and the 20 x % of grade x tonnage formula and its applications. After several trial runs on routes such as Marias Pass, Stevens Pass, Cajon Pass, and Donner Pass I figured out the difference and how to apply both. And I discovered that they do the same thing. Here's what I found:

The first formula I'll talk about is more complicated: 20 x % of grade X tonnage = lbf required. This refers ONLY to how much force is needed to HOLD the train on a the hill and not slide back down. Go through your .bin files of your locos and figure out what lbf each loco produces. For this example we'll go with the SD70Ace with FanRailer's mod. The BNSF ace is capable of a maximum of 189,000lbf. For this example we'll have an eastbound manifest going up the 2.2% grade of Stevens pass. Our train will be approximately 6000t. 20 x 2.2 x 6000 = 264,000 required lbf. That's 2 Aces. Are we done? Nope. We also need to figure in the weight of our 2 Aces (they don't climb for free). So that gives us a total tonnage now of 6422t. (roughly). 20 x 2.2 x 6422 = 282568lbf. 2 aces will still cover it.

Now we need to compute our speed. For that we need horsepower, or haulage capacity at speed. We want our train to travel about 10-15mph (decent speed for heavy freight trains). We now multiply our lbf. by 1.47, then by our max speed (15).

282568 x 1.47 x 15 = 6230624.4. Take this number and divide it by 550 to compute the needed horsepower to move our train up the hill at 15mph.

623064.4 / 550 = 11329 hp (roughly).

Each Ace is capable of 4300 hp, right? Yes and no. It depends on the efficiency of the transmission. Generally a locomotive's transmission only delivers 80% of the locomotive's rated horsepower. In the case of FanRailer's mod, the Ace will deliver only 3850 hp out of it's total 4300 hp.

Here we have a problem. We've only got 2 aces. We are going to need at least 1 more if we are going to meet the hp requirement to get this train up Stevens Pass at a top speed of 15mph.

Now on the way up we may slow down a bit due to curvature as curvature adds more resistance and therefore increases the required force to pull it up the grade. Just to say we did go ahead and add another Ace for good measure. I'd recommend 2 on front and 2 in back due to operating rules for dynamic braking and power regulation if you decide to use another Ace.

As you can see, as we progress further and further into this first formula we went from 2 Aces to 4 Aces. We ended up doubling our power by the time we were though.

And that's the first method. It's a little longer and requires more knowledge about the train besides total horsepower and total tonnage. Remember that for this to work you need to satisfy both the tractive effort requirement and the horsepower requirement. This can work even for high horsepower units such as the SD90 that's been released - you just have to know the engine's weight and tractive effort rating (although I wouldn't recommend using SD90s on drag freights - put 'em on intermodal trains that are typically lighter and can climb mountains at 25mph or so). Remember that the weight of locomotives in their bin files is measured in metric tons NOT long tons and not short tons. You need to convert the weight FROM metric tons to short tons. This only applies to locomotives and tenders. Cars are still listed in long tons in the bin files.

Earlier in this thread I talked about horsepower-per-ton. Do me a favor. Take the horsepower of 4 aces at their full 4300 hp (17200) and divide it by 6000 (our train's base weight). You get a HpT rating of 2.86-repeating. Multiply this by 12. You get 34.4. Now divide this figure by 2.2 (the ruling gradient). You end up with 15.6363-repeating. This right here is your projected top speed while climbing Stevens Pass.

Comparing the 2 results we come out with pretty much the same answer: Use 4 aces on your 6000t. freight and you'll get up the grade at a top speed of 15mph. The nice thing about the HpT formula is that it already takes into account the weight of the locomotives and the efficiency of the locomotive's transmission and thus it becomes very easy to use. That's why BNSF uses the HpT formula on all of their trains.

Conclusion: just use the HpT formula. It's easier.

[Ericmopar]

The whole thing is also complicated by the fact that some cars like the coal cars in N American DLC don't have proper physics even when loaded.
Unless someone goes into the bins and makes the mass something like 80-120 they don't work right, even when a person highlights the consist and checks the loaded option.
That's one reason I prefer manifests and unit oil trains. They work more like they are supposed too when loaded.
The auto rack cars are pretty good for heavy trains as well.
The low side gondolas have the same loaded physics issue as the coal cars, so they must use the same basic blueprint and physics in game.

I've wondered if it would be as simple as telling the coal cars and gondolas to use the same physics as say a tank car or box car when in the loaded state, but I have no idea how that would be done.
It's clear though that different classes of car draw on different physics setups in game. Possibly a core program issue?
I bet it would be relatively easy to fix that, if someone knows where in the core game engine, to tell a coal car to act like a loaded box or tank car.
It could potentially fix all of them at one time, without going into a dozen bins.