[Trains4Ever]

Hi there people,

I have been looking through OPenRails code, and i think i found something incorrect:
As far as I understand from the code, MotiveForce(driving force) is put to 0friction if current speed is above locomotive maximum speed.(correct me if this is wrong)
This seems not correct to me, as some trains without cargo, can go a lot faster then that.
Is this a possible bug?
Could someone explain me why it isn't?(if it isn't)


Thanks

[copperpen]

All trains will eventually reach what is known as a balancing speed, the point at which it will go no faster. The power of a train at any throttle setting is unchanging, the resistance of the train increases with speed, and the motive force decreases with speed. At the balancing speed the motive force can no longer make the train go any faster against the total resistance generated.

Maximum speed is another fixed limit and in OR it is the consist maximum speed above which the train will no longer accelerate. In this case you could consider the consist maximum speed to be the balancing speed.

[Trains4Ever]

copperpen, on 28 February 2018 - 09:37 AM, said:

All trains will eventually reach what is known as a balancing speed, the point at which it will go no faster. The power of a train at any throttle setting is unchanging, the resistance of the train increases with speed, and the motive force decreases with speed. At the balancing speed the motive force can no longer make the train go any faster against the total resistance generated.

Maximum speed is another fixed limit and in OR it is the consist maximum speed above which the train will no longer accelerate. In this case you could consider the consist maximum speed to be the balancing speed.

Thanks for the reply, well, if MaxSpeed parameter is meant for the balancing speed, then it is all okay.
Then i probably got an incorrect .eng file with the train, as it states that the MaxSpeed of the train is 140km/h, while the train can reach more then 250km/h at full throttle.
So i'l probably adjust the file then, thanks for your reply.

[Trains4Ever]

copperpen, on 28 February 2018 - 09:37 AM, said:

All trains will eventually reach what is known as a balancing speed, the point at which it will go no faster. The power of a train at any throttle setting is unchanging, the resistance of the train increases with speed, and the motive force decreases with speed. At the balancing speed the motive force can no longer make the train go any faster against the total resistance generated.

Maximum speed is another fixed limit and in OR it is the consist maximum speed above which the train will no longer accelerate. In this case you could consider the consist maximum speed to be the balancing speed.

I already replied to you that it is probably the mistake of my train, but i have a question:
It is the BR189 train, from SIEMENS model es64f4.
I calculated it's balancing speed to be 300km/h without cargo!.
But it's maximum speed in wikipedia is 140km/h, which is also what is set in the config.
Now am I wrong with my calculation, or is the max speed in wikipedia some max speed that is allowed in europe?(and they just set that to the max, as it is not allowed to go faster anyway?)

Thanks

[copperpen]

Trains4Ever, on 04 March 2018 - 04:56 AM, said:

I already replied to you that it is probably the mistake of my train, but i have a question:
It is the BR189 train, from SIEMENS model es64f4.
I calculated it's balancing speed to be 300km/h without cargo!.
But it's maximum speed in wikipedia is 140km/h, which is also what is set in the config.
Now am I wrong with my calculation, or is the max speed in wikipedia some max speed that is allowed in europe?(and they just set that to the max, as it is not allowed to go faster anyway?)

Thanks

There is another thing that restricts the speed of electric and diesel electric locomotives, the motor windings. If the motor rotates too fast the windings start to come apart, so a locomotive is actually geared to run at a certain maximum speed which is usually displayed in the cab to remind the engineer/driver not to exceed this speed. If it was actually geared to run at 300kmh it would probably not be able to haul much of a load because the gear ratio would have to be quite high. It is a compromise, you must have a ratio low enough to allow the train to start, but high enough to achieve a reasonable maximum speed.

[Trains4Ever]

Ah, i see.
I calculated the balancing speed based on power/speed = TractiveEffort.
And then calculated friction with the davis equation.
So you are saying there is another limiting factor, motor windings.
But is that really a restriction(train is unable to go faster) or a limit(train can easely go faster, but will get damaged)?

[copperpen]

The maximum speed is decided on at the design stage and gearing selected for the duty the locomotive is being designed for. In theory it probably could run at a higher speed, but will suffer damage as a result. If there were no loading gauge restrictions then probably you could get the 300kmh, but you have to fit all systems into a restricted size box which then limits exactly what you can do. Higher speeds mean more heat is generated by the motors which has to be removed by the traction motor blowers. Because your total size you have to work within has to contain all systems the blowers cannot be oversized and are thus restricted in the amount of heat they can remove. Without removing this heat, the motors get hot, the glue/varnish etc that holds the windings in place becomes soft and centrifugal force does the rest of the damage by forcing the windings out of place where major short circuiting will take place.


So, it is not an incorrect way of handling physics, it is the correct way to "simulate" real world physics.

[Trains4Ever]

copperpen, on 04 March 2018 - 09:38 AM, said:

The maximum speed is decided on at the design stage and gearing selected for the duty the locomotive is being designed for. In theory it probably could run at a higher speed, but will suffer damage as a result. If there were no loading gauge restrictions then probably you could get the 300kmh, but you have to fit all systems into a restricted size box which then limits exactly what you can do. Higher speeds mean more heat is generated by the motors which has to be removed by the traction motor blowers. Because your total size you have to work within has to contain all systems the blowers cannot be oversized and are thus restricted in the amount of heat they can remove. Without removing this heat, the motors get hot, the glue/varnish etc that holds the windings in place becomes soft and centrifugal force does the rest of the damage by forcing the windings out of place where major short circuiting will take place.


So, it is not an incorrect way of handling physics, it is the correct way to "simulate" real world physics.

Okay thanks!
I understand now, so i will leave it at 140km/h, just seemed a bit weired to me taht my train reached 140km/h so fast, so i started calculating.
But happy to know that is all normal.

This may be closed if wanted.

[Genma Saotome]

Q: If the consist speed is being used as the maximum speed, why is the software using a literal from the .con file instead of calculating the actual speed at which that consist can no longer accelerate? The calculation would be correct; the literal is often just a guess.

Would it not also be true that whatever speed the consist can no longer accelerate will change on account of the grade? That... and the strong probability that whomever created the .con file has absolutely no idea what speed (at zero grade) will equal no further acceleration.

Or does it all come down to just use the max speed of the route and ignore everything else?

[Trains4Ever]

That is a very good question, would love to hear the answer.