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TSW: Diesel-Electric Simulation Improvements

We recently announced that the team have been working hard on the Diesel-Electric Simulation and I know it's something our community have given us some great feedback on, so I took the opportunity to catch up with Matt Peddlesden, Senior Producer for Train Sim World, and get you some more information about exactly what this is all about.

Hi Matt, thanks for joining me! Can you tell us some more about what Diesel Electric Simulation is?

Thanks Steve! Absolutely. This article gets into some real technical detail about how a specific type of locomotive works, so if anyone reading this doesn't understand it, then the short version is: Diesel Electric locomotives are going to be seeing a fairly significant change in how they react to throttle and how they feel when they're driving. Other than that, the game will remain familiar and you have nothing to worry about!

Still here? Good, I hope you brought your overalls!

Diesel Electric locomotives have an on-board diesel engine which is connected to a generator or an alternator to create electric power, that power is then fed in to several traction motors (often one per axle) which takes the electricity and uses it to turn the wheels, which moves the locomotive and hauls the train behind it. It's one of the most prevalent forms of power used throughout the World alongside overhead electric powered trains which, put simply, lose the on-board diesel “powerplant” and instead get their electricity directly from the overhead wires to power the traction motors.

Throughout the last year we've talked about our SimuGraph® system several times, which is the core of the power and braking systems of all trains in Train Sim World. Within SimuGraph are many components that represent the different subsystems such as valves, gears, engines and electric motors. What we're talking about here are specifically all the components that deliver a Diesel-Electric power system on locomotives, this includes the Diesel Engine, Traction Motors, Generators, Load Regulators and so on and so forth.

simugraph1

Figure 1: Under the hood, this is a Class 66 in SimuGraph!

On the left half of Figure 1 you can see all the SimuGraph components handling the braking systems and, on the right, the power systems and finally the very right has the axles and bogies.

The green lines and the components linked are the important bit in this discussion.

simugraph2

So, what have we done to improve it?

We've been reviewing all the components of our Diesel-Electric Simulation in SimuGraph and how they work together, studying some complex mathematics and gaining a much better understanding of how we can improve the overall quality of our simulation. Most of our work has focused on creating an all new simulation for the traction motors but also vastly expanding the simulation for components such as the load regulators and other crucial components in the system.

SimuGraph works by allowing us to define a system by placing components on a graph and then wiring them together in a drag-and-drop style visual editor. We can then click on each component and configure it using a vast array of possible settings and then finally we can put the finished simulation in to Train Sim World and have it produce real-time graphing data which shows us visually what is happening with the generated power, tractive effort and so on. Using this system, the team have spent a lot of time reviewing data, tuning settings and behaviours, re-running tests and refining the system to be able to map the graphs as closely as possible to the prototype.

In the graph below, you can see the solid black line is the Tractive Effort curve for the de-rated Class 47, as presented in our upcoming Train Sim World: West Somerset Railway add-on. The feint orange line is the actual data recorded from our BR Class 47 and, as you can see, it demonstrates key important factors such as field diverts and matches the curve almost perfectly.

47Finished

We also spent some time improving the stability of the traction motors which can be clearly seen in the following two graphs. In the left image, you can see the unstable blurred graph which would result in needles perhaps wobbling or would require other aspects of the simulation to be adjusted to account for the variations. In the right image, the new clean line which provides more accurate data and is simpler to account for across the entire simulation.

stability

Sounds like quite a big change, but what does it mean for our players?

Players are going to find the locos quite different to control. The primary change players will notice is that they will need to watch their speed and keep adjusting the throttle handle to carefully balance speed. The sounds play slightly differently because the engine is reacting in a different way, and the ammeter will also behave differently.

Driving the locomotives will be done in the same way as players are used to; the throttle handle still controls the power the locomotive is putting down to the rail, it's just doing it in a more natural and intuitive way. All the keyboard controls, mouse and controller inputs are the same.

Which products will benefit from this change?

Initially we are rolling this out as part of Train Sim World: West Somerset Railway for the included BR Class 47 and BR Class 09 Diesel-Electric locomotives. In the background, the team are already working on upgrading the BR Class 66 and BR Class 43 from Train Sim World: Great Western Express (the BR Class 166 is a Diesel Hydraulic unit and already works as it should). Finally, we plan to take a good look at the US locomotives included with Train Sim World: CSX Heavy Haul and Train Sim World: Northeast Corridor New York - specifically the CSX GP38-2, GP40-2, SD40-2 and the CSX AC4400CW (the Amtrak ACS-64 is pure electric and already works exactly as it should). These require some additional work (such as for the Dynamic Brake system) and that's why they're taking a bit longer.

So, in summary:

Train Sim World: CSX Heavy Haul

  • CSX SD40-2 - To be done
  • CSX GP38-2 - To be done
  • CSX AC4400CW - To be done

Loco Add-On

  • CSX GP40-2 - To be done

Train Sim World: Great Western Express

  • DBS BR Class 66 - In progress
  • GWR BR Class 43 - In progress
  • GWR BR Class 166 - Unaffected

Train Sim World: Rapid Transit

  • DB BR 1442 - Unaffected

Train Sim World: Northeast Corridor New York

  • CSX GP38-2 - To be done
  • Amtrak ACS-64 - Unaffected

Are there any wider impacts that will be experienced?

As part of this update we are going to be re-testing all scenarios and re-running the service mode simulations to see whether the timings are all still achievable and then make any necessary adjustments. However, fundamentally I would expect this to be minimal and if we need to make changes to the GWE timetable as a result then we'll update and re-issue the timetable as part of the release.

We’ll be back with a further update on how we’re getting along on all of this next month!

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Screenshots and images displayed in this article may depict content that is still in development. The licensed brands may not have been approved by their respective owner and some artwork may still be pending approval.
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