Modelling Torque Discussion

Machinery of War Discussion Ground Vehicle
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I’m making this post in preparation of doing a full suggestion. For modelling torque and torque converters.

As far as I’m aware, the current modelling of the drivetrain in game uses 1 power value, this is presumably supplied at all RPM’s?

Ideally, a full torque graph should be used, in the same way jet engines in game have thrust map with speed.

Nearly every engine in game has a known maximum power and maximum torque, therefore every engine has 2 known datapoints, inbetween, estimated data can be used where it is not publicly available, this is the same for jets, and can be corrected if needed for the required performance. The added benefit of this, is that different engine types produce differing torque curves; this adds an extra level of realism to the game, gas turbines will perform differently and show their benefits over diesel engines in certain conditions and vice versa.
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As for torque converters, a similar technique can be used, a torque converter acts as a fluid coupling between the engine and drive. However the lesser known benefit of a torque converter is torque multiplication. This occurs at the “stall point”, when the drive/vehicle is stationary. At this maximum point, torque can instantaneously increase by upwards of 2 times, for a leopard 2, it is 2.5X, for a Challenger 2, it is 3.5X. This gives tanks extra grunt when the engine speed is high relative to the speed of the connecting transmission.

Leopard 2 - 2.5x
Leclerc - 2.3x
Abrams - 2.2x
Challenger 2 - 3.5x

In game, torque converters are replaced by adding extra gears to vehicles, keeping the engines at a roughly constant rpm when accelerating. However these gears are evenly distributed, the effect of a torque converter is only at low speed/early gears, above these low gears the converter is locked. Meaning these additional high speed gears are meaningless anyway.

As with the torque curves, the maximum multiplication effect can be given a default value for all tanks, and changed when public data is able to prove otherwise, or it is needed to achieve verified performance. The multiplication effect decreases to 1X as the engine rpm comes closer to the transmission input rpm. A generic curve can be used to account for this.
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This will give vehicles a more dynamic drive performance, and improve performance in some areas significantly.

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I’m just a bit confused at how the “speed ratio” for torque converters works.

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So for a torque converter, there is two parts, the input and output side, the input is connected to the engine, the output connected to the transmission, a 1:1 ratio means the input and output are at the same speed, a 0.5:1 ratio means the output is half the of the input and so on. 0 is known as the stall point where the output speed is 0.

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Ah, I see.

So from my understanding and a bit of online reading, the “pump” is always spinning because it is connected to the engine, at low speeds the pump will be spinning faster than the “turbine”, which is directly connected to the transmission, and due to this the stator basically does some fluid magic with the fluid hitting the blades in a very specific way and the output torque gets multiplied.

I knew torque converters multiplied torque in some way, I just didn’t really get why that was the case

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ya the mechanics of it is kind of odd, but quite cool.

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It would certainly be interesting to see how late war and post war US vehicles would be like with actual torque converters instead of just… doubled gears.

I’m more afraid that something would be screwed up once Gaijin attempted it though.

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question is how hard would it be to model and implement

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Not particularly difficult, I’d imagine it would be of similar technical difficulty to aircraft flight models.

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Iv’e been hunting for a reason to why the ITO 90 Is so slow with 10hp per tonn power to weight ratio, and it seems to be laziness? …
I work as a truck driver IRL and i know 10 to 1 hp/ton ratio is good … its what the Volvo FH 540 fully loaded has. and it pulls 50 tons easy . this ITO 90 though has 0 pull … same with the m113 spaa.
and then i see this thread thats pinned , and over a year old!
Is there anyone that has any info on whether or not gajin is going to fix torque? i mean its not rocket science … Torque = Power / RPM. so it shouldn be too difficult??

Annoyed greetings
Basolfse

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10-to-1 HP/tonne is not a good ratio for combat vehicles. The game might not have the automotive functions down as good as they could, but that ratio just isn’t good. My own rule of thumb is that around 15 HP/t is when a vehicle get nice and responsive, gameplay wise.

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I agree that for combat vehicles it is a bad ratio. but compared to ingame mobility it is more than enough.

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Depends, on the road as a truck driver I imagine 10hp/t is way more than fine, but on rougher slipper terrain. Less so.

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Lovely, definitely needed This is the spirit of sims

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From reading the tank files in datamine, the engine’s energy output, minimum and maximum RPM are specified, but there are no individual elements to set the torque value, torque curve, or engine type.

Therefore, it is likely that the torque value corresponding to the RPM value is specified by some constant common to all vehicles, and maximum torque is probably generated at high RPMs even if the engine mechanism is different.

When observing the behavior in manual transmission mode, the amount of acceleration is different at low and high RPMs, so it seems that there is probably a torque curve.

Also, some wheeled vehicles are equipped with a system that causes a delay between the displayed RPM and the actual RPM, in which case the vehicle speed and displayed RPM will not be synchronized.

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Indeed, either power is constant, or it linearly decreases with speed, both aren’t correct to any engine other than an electric motor.

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To add some color to this thread, I will write down the information I know about torque converters.

This text has been machine translated into English, and I’m not very good at writing, so it’s in bullet points. Please feel free to criticize or point out any mistakes.

A typical engine produces the highest output (horsepower) at high revolutions.
However, if the engine is mechanically connected to the axle, the engine speed has to depend on the vehicle speed, and ideal horsepower can only be achieved in a few situations.
This is where the torque converter comes in. By using this, the engine speed and axle speed are freed from the dependency, and horsepower can be freely adjusted over a wide range.

With a simple fluid coupling that is not a torque converter, if there is a difference between the engine speed and the axle speed, the horsepower that can be delivered is reduced. The ideal horsepower can only be delivered when the axle speed begins to synchronize with the engine speed.
In contrast, when the revolution speed is out of sync with the torque converter, the torque converter converts the energy of the revolution speed into “torque” and transports it. This is “torque amplification.”
This allows the engine’s horsepower to be transmitted to the axle without loss at all speeds.

It is important to note that the total amount of energy output by the torque converter does not exceed the engine’s output energy. The torque amplified by the torque converter is the energy of rotation speed in a different form.

Therefore, the torque converter can be seen as a kind of “infinitely variable reduction gear”.

The torque converter realizes a wide ratio transmission. Originally, a transmission with a wide gear ratio interval has a strong drop in engine speed after shifting and has uneven horsepower, making it difficult to use in vehicles that are always underpowered, such as tanks.

If a torque converter is inserted here, it prevents the horsepower drop immediately after shifting. This is because the engine can always maintain a high rotation range.

If a wide ratio can be achieved, the theoretical maximum speed can be increased even with a small number of gears. Transmissions with a small number of gears are generally small, which is advantageous. Many modern NATO MBTs have this design.

However, torque converters also have their weaknesses. When a torque converter amplifies torque, losses always occur due to fluid resistance. In other words, a few percent of the engine’s horsepower is lost before it is transmitted to the axle.

The horsepower that could be increased by always having the engine in the high RPM range is also partially lost in this loss. If the design is incorrect, it will become a completely inefficient system.

For this reason, modern torque converters are equipped with a “lock-up mechanism” that directly connects the output shaft and the input shaft and fixes them in situations where amplifying the torque is not very meaningful.

Torque converters have another useful function. They can be installed as a substitute for the clutch between the transmission and the engine. This is very useful for automating the transmission.

Among the vehicles implemented in WT, there are surprisingly many vehicles that are equipped with torque converters in the real world.

The M18 self-propelled gun also uses a torque converter to achieve a wide ratio transmission. The transmission is supposed to be a three-speed, but because the game is unable to replicate a torque converter, it is treated as a six-speed, which is exactly what Fireball_2020 has pointed out as a problem with the game.

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