Tractive Effort - What Could an SW7 *really* do?

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frogpipe

Yesterdayz Trainz Member
I've been doing some tests.

I find that a 517t train with a single SW7, with my own eSpec on point, can do about 8mph up a straight 2% grade.

According to my calculations, it should take about 25850lbs of TE to accelerate up a 2% grade with 570t in tow.

517t * (20lb per percent of grade + 10lb for acceleration) or 570t * 50lb.

An SW7 can is rated for more TE then that, BUT if I try and go above notch 4 the wheels slip.

What I'm looking for here is someone who either has first hand knowledge or really knows what happens in the real world can verify if this sounds more or less like real world performance.

Obviously since I'm using my own eSpec accurate performance is what I am after.

(Default eSpec I can go to notch 8 and at the end of my >1 mile test grade, I was doing 63mph and still accelerating) O_O
 
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Hi Frogpipe,

Locomotives loose tractive effort as they pick up speed, the faster you go the less force that can be produced, where I live 'Australia Victoria' we have what's known as the 'Loads of Goods Trains' which lists the weight of each section of line between stations at 100%, in this case level track is 650tons, the SW7 by our book would be rated around 190% 'which is based on continuous tractive effort' for a 2% grade it's 190% / 270tons which is 513tons for 11mph.

to solve massive slipping add max-tractive-effort tag in the loco and have it converted to Newtons, 'Not kn'.

Cheers.
 
So it sounds like I'm in the right neighborhood then.

So would that be Starting TE converted to Newtons, or Continuous TE converted to Newtons?
 
You only put that tag in the loco config not the e-spec config, it scales it correctly when using Vehicle physics, so when it's 100% the loco won't slip at all, it goes as the maximum force you want it to have before the loco slips. I go a little over so when Vehicle physics is set to 95% it's not too slippery.

EDIT:

Watch this video then, our locomotives are 33,880lbs at 7.5mph , these aren't switchers either, these where built for heavy Branchline and light mainline passenger and freight from 1956.

http://www.youtube.com/watch?v=r5lv41O5-E4 , see how many wagons are on it and it's also 2% grade, I'd say it's about 1,300 tons, each loco is 950hp

Cheers.
 
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I figured out where it went, thanks to the Trainz Wiki, and set it to 275789n which equals 62000lbs which is the starting TE for the SW7. Now I can go to Notch 8 and do ~15mph, but as you said, it never slips...

Where is this "Vehicle Physics" percentage setting? I'm not familiar with it.
 
You have to add it to the session, I've been using it since the TRS2006 day's, steam locos where allot of fun back then as they would slip the wheels at high speeds unlike the physics we have now when you need 100% regulator and cut-off 75 just to get the wheels to slip slightly.

Cheers.
 
frogpipe said:
So it sounds like I'm in the right neighborhood then.

So would that be Starting TE converted to Newtons, or Continuous TE converted to Newtons?
Click to expand...


the continuous TE, if you put the starting TE you started the e-spec config at, it will not reach that point. that only makes sense, because the starting TE is what the engine can do from a standstill, continuous is how much it can do while moving.
 
Hi Frogpipe,

Also makes sure you set the brake pressures to match the type of locomotives or rollingstock your going to be using it with, an example would be a difference between my Physics and JointedRail Physics.

My physics are 70PSI Brake Pipe and 37 PSI Service Brake
JointedRail is 90PSI Brake Pipe and 50PSI Service brake

Now what happens when you couple 2 locos with 2 different physics is the ones with the lower service brake will keep venting brake pipe and the one with the higher service brake will keep charging brake pipe, so it's a conflict between 2 locomotives, one wants 37 PSI brake pipe and another wants 50PSI brake pipe, the one that wants 50PSI will drop in main res pressure as it's trying to keep charging to hold Equalizer pressure of 50PSI.

Default Auran e-specs are the same issue, there 41 PSI Service brake with 70PSI Brake Pipe

Unfortunately there's no table for the brakes, it took me years to get the physics for Standard VR practice to work in trainz, another problem is information, you need to ask around a bit on these things, I asked an ex-loco driver who now runs a hobby shop on brakes and he said 70 PSI Brake Pipe, 70 PSI Brake Cylinder and 110 PSI Main Res, but the best I could get was 65 PSI brake cylinder, I used that set up for about a year in trainz, I asked some drivers for different locomotives over the past few weeks and they told me 50 PSI Brake Cylinder Max, so I've had the physics wrong all this time because I asked one person when I should of asked around to confirm, lol

JointedRail and RRMods are a group that most likely had access to real locos so there physics would be 99.9% accurate with the brakes, I haven't played with RRMods locos for some time as my Original Games Hard Drive suffered a logic failure in December and haven't done a recovery yet and I forgot what the pressures where they used, as the JR locos are built into TS12 I can play with those as it's a fresh install on a different drive :)

Cheers.
 
I've noticed that "View Details" on at least some JR cars and locos give a higher Weight in Tow figure then the generic one seen on other cars. I guess this would explain that.
 
1 AU/UK ton = 1.12 US ton, so the 517tons I wrote is 579.04tons US, kinda makes trains feel lighter if your US or heavier if your UK/AU.
Trainz is in kilograms though. 1 ton can either be 907kg or 1016kg which will make things tricky.

Cheers.
 
no 1t in trainz is always tonnes, unless someone has made a display error.

1 tonne = 1016kg
1 ton = 907kg

all the JR content uses 'ton' or mass / 907.
 
Hi norfolksouthern37,

That's rather interesting as this site here http://www.digitaldutch.com/unitconverter/mass.htm only has US ton and UK ton also known as short tons or long tons, I work in long tons.

Maybe someone from N3V might be able to tell us what weight is actually being used, long or short.
what about if you had a situation like this when the locomotive is in tons and hundred weights *37 tons 10cwt* what would be the correct figure to use? normally I'd just assume 1ton = 1,000 kg and go 37254 and enter that in the mass table.

It's the same with coal loads, I'd go 100 cwt to kg then divide by the unit mass *5080kg / 0.86 = 5906 units*.

Cheers.
 
frogpipe said:
So the "ton" DOESN'T change if you switch from Metric to Imperial or vice versa? Brilliant.
Click to expand...

right. it doesnt appear any such mechanism is available for that yet. i could have placed it in my traincars, but JR does US rolling stock, we dont deal in tonnes.

Azervich said:
Hi norfolksouthern37,

That's rather interesting as this site here http://www.digitaldutch.com/unitconverter/mass.htm only has US ton and UK ton also known as short tons or long tons, I work in long tons.

Maybe someone from N3V might be able to tell us what weight is actually being used, long or short.
what about if you had a situation like this when the locomotive is in tons and hundred weights *37 tons 10cwt* what would be the correct figure to use? normally I'd just assume 1ton = 1,000 kg and go 37254 and enter that in the mass table.

It's the same with coal loads, I'd go 100 cwt to kg then divide by the unit mass *5080kg / 0.86 = 5906 units*.

Cheers.
Click to expand...

it is just as i said above. trainz populates the default train vehicle details box with the total trailing (not counting locomotives) train weight using (totalMass / 1000) so it will say for example "517t" - t meaning tonne.

i have changed this in my own (JR) cars to read the weight of the current selected vehicle, as well as the trailing weight of the train. i use (totalMass / 907) so it will say "570 tons" - tons as in a US ton.
 
For clarification, there are:


[TABLE="class: grid, width: 500, align: center"]
[TR]
[TD]Name[/TD]
[TD]Kilograms[/TD]
[TD]Pounds[/TD]
[/TR]
[TR]
[TD]Short Ton[/TD]
[TD]907.185 kg[/TD]
[TD]2000 lbs[/TD]
[/TR]
[TR]
[TD]Long Ton[/TD]
[TD]1016.05 kg[/TD]
[TD]2240 lbs[/TD]
[/TR]
[TR]
[TD]Metric Ton (or Tonne)[/TD]
[TD]1000 kg[/TD]
[TD]2204.62 lbs[/TD]
[/TR]
[/TABLE]

Hey, it helps me at least, as the term Ton, is what I've heard most of my life, and it turns out that what everyone calls a "ton" is actually a "short ton". I'm left to assume that "Short Ton" is what is meant in various discussions about railroads since the only term used is "Ton" which I find rather vague now.

Oh, and for anyone at N3V that might be lurking, the fact that the train weight is always expressed in "t" meaning Metric Tonnes, even when Imperial measures are in effect, is just plain dumb. To say nothing of not spelling out what "t" was.

Perhaps it's some sort of standard that "t" = Metric Tonne, and "T" means Short Ton, and who knows what means "Long Ton" but as far as I know it's not common knowledge.
 
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standard symbol for tonne is 't'... i do not think there is an abbreviation for the short ton its just a 'ton'.

as for the units not changing depending on what units are selected in the game i agree they should have thought of that, and i wish that the loads for traincars would also follow this. maybe someday...
 
After posting that I dug around and discovered that in the UK, AU "t" means Metric Tonne, where as in the USA "MT" means Metric Tonne and "T" means "Short Ton".

Technically speaking, to a USA audience, my train (at 517t) was 517 teaspoons. LOL
 
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