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Notation inconsistency

Started by Ranran, January 05, 2020, 04:26:39 PM

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Ranran

I noticed that the values in the depot dialog and the convoy detail dialog are inconsistent. (´・ω・`)

See Power and Tractive Force in these two images. These convoy are the same convoy.




The issue is that the values in the convoy detail dialog are multiplied by "gear".
Also, the vehicle specs in convoy detail are not multiplied by gear, so those who sum the vehicle spec values will notice inconsistencies.

Although it is a trivial issue, the number of displayed digits after the decimal point of Max. Brake force is different. (´・ω・`)

jamespetts

Interesting. I suspect that this is historical. Certainly, the power and tractive effort shown in the convoy detail window should not be multiplied by the "gear".

I wonder whether this is the same in Standard and whether there is a reason for it?
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Sirius

Convoy detail does not show a gear as summing gear up makes no sense.
However, as gear affects the effective power it does not make sense imho to show the base power or tractife effort without the gear.
So the current behavior is not bad but still inconsistent.

Imho we should show effective power and force in both windows as that actually matters for ingame physics.
Gear is one of the most misunderstood values, so I would suggest adding base power and force to both windows for real-world comparisation reasons and removing the gear to reduce confusion.

Vladki

I think it is better to show the power/force values multiplied by gear in all places, to allow easier comparison of real performance of vehicles/convoys.
The only place where it makes sense to show the "original" value is depot, and even there it should be in less prominent place (in parenthesis), that the gear multiplied value.

jamespetts

It is important to show the unmodified power so that the displayed power can match the statistics of real vehicles; I suspect that the better ultimate solution would be to show "nominal power" and "effective power" in all places where power is shown rather than showing "power" and "gear".

Incidentally, I believe that "gear" no longer affects tractive effort.
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Ranran

In Japan, the English translation of the published tractive force of railway vehicles generally uses "tractive effort".

wikipedia(English) says:
https://en.wikipedia.org/wiki/Tractive_force
Quotetractive effort is generally higher than tractive force by the amount of rolling resistance present, and both terms are higher than the amount of drawbar pull by the total resistance present (including air resistance and grade).

How about using the spec value to tractive effort and using the effective traction force to tractive force?

Quote from: jamespetts on January 05, 2020, 05:21:40 PMIncidentally, I believe that "gear" no longer affects tractive effort.
I recently read the code on acceleration, but the power used for acceleration is multiplied by gear. That is, the force used for acceleration is the value displayed at the top of the convoy detail dialog.

jamespetts

I suspect that most players would not understand the subtle distinction between "tractive effort" and "tractive force": "tractive effort" is the term usually used for railway vehicles, so I suggest retaining this and using "nominal" and "effective" as with power.

Quote from: RanRAnI recently read the code on acceleration, but the power used for acceleration is multiplied by gear. That is, the force used for acceleration is the value displayed at the top of the convoy detail dialog.

I am not entirely clear on this - you refer to "the power used for acceleration", which is not the same as tractive effort; from what I understand, the gear does not affect tractive effort, only power, although I have not checked the code recently.
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Sirius

From the convoy info it seems like gear affects the force but I did not check this in the physics code.
This assumed, I guess we should display effective power (base power) and effective forve (base force) in both windows.

Ranran

#8
When rewriting gear in dat file and trying it out, it's clear that the gear change is affecting acceleration. For example, try rewriting to gear = 1. That vehicle will not be able to move by itself anymore.
Does this mean that tractive effort is not affected?

jamespetts

Changing the power will also affect acceleration to an extent, especially at extreme settings.
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Sirius

#10
I know where the physic was in the code and will have a look at it this afternoon.
As I will get killed by my gf if I launch my dev machine and search in the code for it now ;)

Ranran

Quote from: jamespetts on January 06, 2020, 11:28:01 AMChanging the power will also affect acceleration to an extent, especially at extreme settings.
If power is changed by gear but tractive effort is not changed, then these balances will break and the rated speed should change.
That is, the characteristics of the vehicle may change. This can be inconsistent with the nominal specs of real-world vehicles.
However, no such behavior is currently seen.

jamespetts

Quote from: Ranran on January 06, 2020, 12:39:43 PM
If power is changed by gear but tractive effort is not changed, then these balances will break and the rated speed should change.
That is, the characteristics of the vehicle may change. This can be inconsistent with the nominal specs of real-world vehicles.
However, no such behavior is currently seen.

I am not sure that that is right - but I do not know enough about physics to be sure either way. We had better await Freahk's code dive to discover the position.

However, affecting tractive effort by gear is potentially problematic, as tractive effort I think is not usually given as a nominal figure, but rather as an effective figure (although that is not entirely beyond doubt either; if anyone has data on this, that would be helpful).
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Sirius

#13
I just started at the physics code and jumped around...
In the physics code get_force is used, which calls get_force_summary, which sums up forces of each indivudual vehicle in the convoy obtained by get_effective_force_index, which returns the geared_force for the given speed.

In short:
Vehicle physics will use the force affected by the gear.

This indeed makes my recent force calculations too low, as these were calculated directly from acceleration data in most cases.

jamespetts

Thank you - that is very helpful.
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