Towing capacity of LOCOMOTIVES

rcaptain17

New member
I notice if you click on a locomotive of a train it tells you in tonnes the weight of what it is towing. How can you find out how much maximum weight one Locomotive can Tow without struggling?

Courious
Rcaptain17
 
I notice if you click on a locomotive of a train it tells you in tonnes the weight of what it is towing. How can you find out how much maximum weight one Locomotive can Tow without struggling?

Courious
Rcaptain17

cant really tell in this game. just hook up some loaded cars and have a go at it. i had 13000 tons hooked up to the UP GTEL on a 2% grade and it moved just fine. it also has a lot to do with how accurate the engine file is for the train.
 
actually, your wrong KC,
NS can use one GP-38 and tow 100 roadrailers, with ease.
cheers,
Sean
 
Just as important in both the real world and in Trainz is the braking capability of a loco when you're heading downhill with a heavy train and approaching a red signal.

BTW does the choice of track also affect traction?

John
 
Yes.

Over here, we have a system of Route Availability that dictates what motive power can be used and where...

Then there are specific instructions relating to motive power and places it definitely cannot run.

TRS, however, will run anything anywhere.

regards

Harry
 
usually how much an engine pulls depends on the grade, terrain, weather, and how long the load may be pulled


example:

1 engine would not be pulling 60 cars up a 2% grade in a snow storm

3 or so engines may be pulling 60 cars up a 2% grade when it is sunny
 
It doesn't matter how many cars you're pulling, but, it does matter how much the train weighs. Down here, one AC4400 can pull 100+ Potash empties. Try the same train with the same power, just load the cars. The train won't get too far. Somebody said something about more units means more braking power. This is only true for dynamic braking. It doesn't matter if you have 3 AC4400s on a coal load or a single SD40-2, (not very probable) the air will dump just as fast. It may take a little longer to pump though, since you only have one compressor onboard. In Trainz, you just have to know the route and know the locomotives. Speed and acceleration also matters. On BNSF's Transcon, those intermodals you see with 5 or more units could probably be easily moved by a single C44. However, the acceleration and top speed will be terrible. On the Transcon, the speed limits are usually 70mph. These trains are top-priority. You can't cheap out on power. Just because it'll move the loads doesn't mean it will move it well. For realism in Trainz, don't overpower it- so, we don't want 7 SD70MACs on a coal empty- that's WASTING power.
Also, too much power on a grade or hill is also bad. Too much amperage will be put through the traction motors, and it will cause the units to lose their footing and slip.

To sum it up, there is no definate number or stat that can tell you how much a unit can pull. It depends on many different things. You just need to be familliar with what you're using.
 
...enginespec...

:cool: In the config.txt folder of the content is the enginespec file. It references by kuid, the file for calculating the operating parameters of the locomotive. This file is changeable, and is the core factor in how the locomotive behaves.
Working with default content for example, the 3000 hp SD40 enginespec works twice the pull of the 1500 hp F7 enginespec.
Factors such as locomotive mass weight, grade, wind resistance, front surface area, etc, are all factored into the enginespec file, along with tractive effort and horsepower for each throttle position, the same for brake pipe pressure, etc, for braking effort, including dynamic electric braking.
These factors have algorithms, that are calculated by Auran Jet™Engine(our render engine).
These factors only are used, in Cab Mode. The DCC control, is a default setting, and one locomotive, any locomotive, may pull 5000 cars.
There is a Railroad Forces Calculator, as well as other related topics, on Al Krugs Homepage.
 
...enginespec...

:cool: In the config.txt folder of the content is the enginespec file. It references by kuid, the file for calculating the operating parameters of the locomotive. This file is changeable, and is the core factor in how the locomotive behaves.
Working with default content for example, the 3000 hp SD40 enginespec works twice the pull of the 1500 hp F7 enginespec.
Factors such as locomotive mass weight, grade, wind resistance, front surface area, etc, are all factored into the enginespec file, along with tractive effort and horsepower for each throttle position, the same for brake pipe pressure, etc, for braking effort, including dynamic electric braking.
These factors have algorithms, that are calculated by Auran Jet™Engine(our render engine).
These factors only are used, in Cab Mode. The DCC control, is a default setting, and one locomotive, any locomotive, may pull 5000 cars.
There is a Railroad Forces Calculator, as well as other related topics, on Al Krugs Homepage.
 
also depends on your traction package too...

The 3,300 horse GM built class 59s (SD40-2 engine mated with an SD-50 Alternator with SSWC built into the loco) regularly hauled 5,500 ton aggregates on their own. Maximum Tractive Effort is 530 to 550kN.

The 3,250 horse Class 56s on the same traffic needed to be double headed on the same weight trains.

Why? It's the traction package.

Generally, the rule I use is 'take the total engine horsepower and load the train with no more than 1 horsepower per ton of train.

That'll climb practically anything up to a 2.5% grade...

regards

harry
 
i herd somewhere there is a program for making the trainz engine config if you can get the data from the real world train to convert in to train figures. i could really use this program if anyone can find a copy. if not does anyone know how to convert a TE/speed graph to trainz values? wish that the folks at auran used real world numbers for there engine data.
thanks
 
i herd somewhere there is a program for making the trainz engine config if you can get the data from the real world train to convert in to train figures. i could really use this program if anyone can find a copy. if not does anyone know how to convert a TE/speed graph to trainz values? wish that the folks at auran used real world numbers for there engine data.
thanks

Yes... as it does, I do....

...and it's not easy mainly because tractive effort is logarithmic.

regards

Harry
 
There is, or was such a program at www.stw.se - TEE=Trainz Engine Editor. You can atleast look at it and drool a bit, downloading doesn't work. According to Rc1166 who used to be a moderator here, they where going to upgrade the server but that was ages ago...... Kenny?

Meanwhile I suggest you read up at Al Krug's homepage there you'll get some good figures on the well used SD40 and then make your own enginefiles manually. Which isn't easy unless you have a TE vs speed-graph for every loco you want to use.

Remember Trainz uses meters/second for speed and kilo-Newtons for tractive effort in the config as for use in cab-mode, where 1kN equals 224,8098237 lbf.

Rolling resistance of the trailing cars is also a factor. According to my own tests with Trainz default wagon engine, gave these interesting results;

Railcar weight (mass) - 5kg - 1,1kN each (difficult to release brakes)
20000kg - 1,15kN each
40000kg - 1,3kN each
100000kg - 2,85kN each
200000kg - 5kN each

So for example a hundered 40ton cars uses up 130kN on flat ground just for the rolling-resistance, adding to that the extra draw if you're going uphill which Trainz is calculating right. But as stated by some already, calculating is one thing whilst knowing the route and your material is another...
 
There have been a number of ways to calculate train resistance (force opposing motion) over the years. Resistance calculations in Trainz appear to follow a formula proposed by J.W. Davis early in the last century.

Rail car resistance can be broken down into 5 parts - journal (or axle bearing), rolling (or flange), air, grade and curve. Each can be calculated seperately and then summed to get the total resistance. Trainz considers all but the curve resistance as far as I'm aware and have been able to verify by testing. The Davis formula considers 3 of these - journal, rolling and air.

The formula as given below is based on US units which interestingly Trainz seems to also follow in this instance. Most everything else for Trainz is specified in metric units but the input for train car resistance is specified in US units. (See section on motor container of the engine specification in the Technical Manual provided with UTC and TRS2004 for description of the various coefficients which are clearly not non-dimensional by inspecting the formula). Edit - Just to reiterate only the input for the train resistance coefficients in the engine spec is in US units - internally Trainz does everything in metric units.

In the following, W is the weight of the train car in tons (2000 lbs) and V is its velocity in mph. R represents resistance in lbs force.
Code:
R journal = 1.3W + 29n  where n is total number of wheel axles on the car
R rolling = CrWV where Cr is rolling resistance coefficent (lbs/ton/mph)
R air = CaAV^2 where Ca is the air resistance coeficient (lbs/ft^2/mph^2)
                      and A is the cross sectional area of a transverse 
                      section thru the car (ft^2)
 
So journal + rolling + air resistance for a car or loco is:
 
R = 1.3W + 29n + CrWV + CaAV^2 (lbs)
 
1) n - axle-count param in e-spec for the car
2) Cr - moving-friction-coefficient param in e-spec for the car (lbs/ton/mph)
3) A - surface-area param in the e-spec for the car (ft^2)
4) Ca - air-drag-coefficient param in the e-spec for the car (lbs/ft^2/mph^2)
Grade resistance is easily calculated as the weight of the train car times the sin of the grade angle which is equal to the weight of the car times the % of grade/100.

R grade = %gr x W x 2000/100 (lbs)

Curve resistance isn't considered (afaik) but is a function of the sharpness of the rail curve as measured by degree of curvature (function of the inverse of the radius of curve)

R curve = CcDW (lbs) with Cc a coeficient typically between 0.07 and 0.1 lb/ton/degree of curve.

Of course weight of the train car can be determined from the mass in kgs specified in its config. W = m x 2.2046/2000 (tons).

Apply the above formulas to each train car/loco in the train and sum up the individual resistance to obtain the total for the train.

If you're careful about the units used you can calculate fairly accurately the resistance Tranz calculates based on train weight, speed and track grade.

I ran a number of tests several years ago to help Stuart Thurstan (weevil) convince Auran there was a problem with the grade resistance calculated in TRS2004. For the most part all the resistances agreed well with the above formulas except for grade resistance which was out by about 20%. There were some minor differences but I currently use the above to predict resistance calculated by Trainz.

Bob Pearson

PS Where am I going with this - I'm not sure yet but stay tuned.

I hope TEE will find a new home if the current server problems can't be solved. I was looking to host it on my web page at one point since I have a link to it to use with a program I wrote, tzSTEC, that calcs steam loco power curves.

Here's the section from the Technical Manual distributed with TRS2004:
Code:
axle-count                               (self explanatory) 
surface-area                              expressed in sq.ft 
moving-friction-coefficient               locomotives 0.03 
                                          freight cars 0.045 
air-drag-coefficient                      streamlined locos 0.0017 
                                          locos 0.0025 
                                          freight cars 0.0005 
                                          pass. cars 0.00034
The values provided are pretty much the coefficients that Davis proposed.
 
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this is very informative and just what i was looking for. thank you bob. i noticed a few things that sound like they are a bit out of whack. in the stander air-drag-coefficients it says that a freights car has more drag then a passenger. i understand that this is a game and all but this is my view on it. you would expect that this a/d would be correct if the car was by itself and not in a consist but in a consist most "not all" passenger cars should create more drag then a freight car as the passenger car has windows and a smooth side that would foul the air. i think a box car would have just about as much a/d as a passenger car and a covered hopper less. then you have the flat car with no load. that wold have a very low a/d. then you get in to mixed and all one type consists. where you have to worry about hight and width difference in the types of cars. if you really want to melt you brain look at the pdf at this link. http://www.diva-portal.org/diva/getDocument?urn_nbn_se_kth_diva-3185-2__fulltext.pdf

but all this is not what i am really looking for. i am just trying to figure how to take a te/mph chart and make it in to data that trianz can use to get the right acceleration and pulling power for a locomotive. i realy wish i could get my hands on TEE but like you said the link was dead. anyone have a excel spread sheet that i can use?

thanks again for the wealth of information. it clears up enough of it that i think i can make a half decent file for now.
 
lazersgm, the freight cars do have higher air drag coefficients so they will have more air resistance for same cross sectional area. The value is based on mixed train type consists with freight cars of different sizes in the consist. The value quoted for passenger is really for the old heavy weight vestibuled cars. If streamlined it would be abt 30% lower. For locos if streamlined they'd be 30-50% lower. The value for the loco actually includes the head end pressure increase and train end suction effects which is why they're so high. Mulitple locos within the train wouldn't have the same air resistance per unit as a single one but that's a price we pay for some simplifications. Maybe Trainz is smart enough to simulate that but I doubt it.

As for TEE you could program most everything it does in a spreadsheet including setting up the throttle-power curves and save them to text file to cut and paste into the config. Mats covered it all in the old forum quite thoroughly. If you want to discuss TEE drop me a line thru my profile.

Bob Pearson
 
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