Basic Engine and Transmission Design Tips 1.1

Basic tips to help players design engines and transmissions and avoid breakdowns

This is not a guide to build fast or powerful tanks, rather to establish stable operating limits

1.1 Updated to include, rule of thumb twin transmission design for improved responsiveness when turning.

Introduction

It would appear as if there is a certain amount of confusion when interpreting the WW1 technology limits for Tank Design in game; namely power available to the engine, power available for elevating and slewing the gun when compared to the freedom given to players in sandbox. This guide is designed to be a basic introduction to engine design parameters and how they can build basic engines at the upper and lower size limits.



Most players will encounter engine trouble during the "No Tanks Land" scenario. Unlike the sandbox mode, "No Tanks Land" imposes restriction of engine size and number of cylinders. Additionally there are limits on the max rpms of a given engine for a given size.

This is meant to help players overcome some engine design issues, but is by no means exhaustive. Unfortunately I am still coming to grips with the game myself and this is guide is not intended for optimising or maximising performance.

Engine Sizing

Engines will typically burnt out and fail as a result of enemy fire or by exceeding max RPMs (red lining). Two elements must be managed, the engine itself and the transmission. Below is an example of a small set of small engine parameters for "No Tanks Land" WW1 design limitations.

A 6 Cylinder engine with a displacement of 1.0L per cylinder will have a Max RPM of 1700. As a result you should be adjusting the maximum and minimum target RPM range to be below the max RPM. Additionally, you should be selecting power to be rated within your target RPM range.

As for engine idle settings, I have not observed any noticeable changes in performance resulting from higher or lower idle rpm settings. It might be more important for mid to late war tanks where the engine may be responsible for supplying power to the turret traverse motor or elevation, wherein a minimum idle rpm is required to power the additional systems.



If you compare the larger displacement engine below, with 4.0L per cylinder, the Max RPM has reduced to 1100, as such the remaining variables should be adjusted accordingly.



Ignoring transmission design:

• Larger engines operate at lower RPMs, and smaller engines at Higher RPMs;
  
• Larger engines develop greater torque and acceleration, but are bulky and suffer from lower top speeds;
  
• Smaller engines are more compact and can develop higher top speeds but may struggle under the weight of heavier tanks.

In summary, I strongly recommend experimenting with different engine displacement to get a feel for how the engines in game perform.

Transmission Design

The purpose of the transmission is to attempt to match the driving conditions (speed and load) to the characteristics of the engine (torque and power available at a given engine RPM) by selecting an appropriate gear ratio. Selecting one gear (gear ratio) over another exchanges rotational speed for torque (or vice versa).

Transmission design is less intuitive than the Engine Design Process, and an effective gearing ratio will need to consider:

• Gross Vehicle Weight;
  
• Engine Power;
  
• Torque;
  
• Target/Max RPM

Scenarios set during early tank development limit the capacity of Transmissions. For "No Tanks Land" you will be limited to 3 Gears forward and 2 Gears Reverse. When adjusting gear ratios to prevent red-lining the engine, the first culprit is typically the highest gear. The solution is then to reduce the gear ratio until the engine runs at a suitable RPM. Until the player base develops a sound understanding of the game mechanics, I imagine that the transmission design will remain a process of trial and error.

Below is an example of a transmission setup for a 24.0L WW1 engine



Below is an example of a transmission setup for a 6.0L WW1 engine

Twin Transmission Design

Introduction (Design Details Below)

I was frustrated with the handling of some of my tanks, unfortunately I have narrowed down all of the variables that govern tank handling yet but I did notice the driver struggling to select a gear when turning the tank. When turning on the move, I had been suffering from my tank seeming to lose control, or turn in the opposite direction whilst using a twin transmission. I also noticed that if I held the turn long enough, the driver would eventually select a gear typically (1st gear on the inside track, and 3rd on the outside track) and the tank would start to turn as intended. I also worked out that the turning circle appears to be a function of power and speed of the outside track. So to turn the tank, the driver needs to be able to select from two gears (left and right) that have the correct balance of power and speed to turn the tank. So if your tank is sliding in the opposite direction, there might not be a strong enough gear, that is fast enough to turn your tank, when the opposite track is in 1st for example. Note a tank cannot turn with twin transmission with the same gear select on both sides so in order to turn effectively, you need at least 2 gears set up for turning.



After some testing, my observations of the twin transmission for steering are as follows.

Generally, the driver wants to select a low gear to slow the track and a high gear to turn the tank (similar to clutch braking but using the transmission to slow one track and speed the other instead). In order for the driver to accomplish this, there's needs to be a considerable difference in track speeds in order to turn effectively. However, the faster track needs to be geared in such a way that it has enough power (mechanical advantage) to turn the weight of the tank

Twin Transmission Design for More Responsive Turns

Using my best attempt at a Char B1 replica:


Length: 6.5m;
Width (Hull): 1.2m;
Tracks: 0.55m wide; 0.15m thick; 0.4m length.
Engine: 162 hp; 1,100Nm of torque.

According to rule of thumb tank design, I selected a gear ration (see above) For "No Tanks Land" as in WW1 the player is limited to 3 gears.

Gear 1: 6
Gear 2: 3
Gear 3: 1



For the "Interwar" and later eras of tank design, I find that the first 3 gears are the most important for twin transmission turning, the remainder (4, 5, and 6) can be geared to suit the max power/rpm of your engine.



Gear 1: 8 (1/1)
Gear 2: 4 (1/2)
Gear 3: 2 (1/4)
Gear 4: 1.5 (Adjustable for top speed)
Gear 5: 1 (Adjustable for top speed)

Please note, this twin transmission guide is by no means exhaustive. I noticed a bit of a trend as I was playing through some long narrow tank designs and was experiencing difficulty when turning on the move. After adjusting the gears up and down and narrowing the range. I found that the above gear ratios worked for a number of my tanks and improved turning with the twin transmission. Finally, in order to fine tune the performance of the tank, specifically mobility. You the player will need to optimise the length to width ratio, the traction of the tracks, the suspension, the power and the weight of the vehicle. The undesirable length to width ratio of a tank like the B1 assisted with Isolating the transmission as a key variable for turning, it is not however, the only variable.

Conclusions

I hope this has been useful. Sincere apologies if any information contained is inaccurate of contrary to established facts.

Any feedback that would serve to develop this guide would be greatly appreciated.

Kind Regards

[Enderminion]

@EscargoingOutTheDoor both HP and kW are units of power, which is work over time, 1 Horse Power equals about 745 Watts

[EscargoingOutTheDoor]

I immediately changed the engine display to horse power so I can only assume that kW in its place means kilowatts, which I thought was a unit of electricity. I am very confused because of this.

[Ghovarus86]

most of the time i just use a 6 cylinder 1.5L to not take up too much space, the HP makes up for it so it isn't bad, the gears tho, kinda complicated.
I made a Pz.35(t) (not too detailed sadly) and i put a 1.5L 4 cylinder and somehow it only got to 6th gear and it had 8 gears, so yeah, it seems like the gears can only go up to 6 at max, in sandbox that is.
So if you want more speed just put literally longer gears, lower leters mean better, because both, RPM increase and space is increased. While more Top Speed decreases weight and increases space, take this as a Tip if you're planning on making a good heavy tank, those engines are REALLY good. Never get the big engines, they are a bad idea.

[Papa Duck]

this seems like math homework

[LukavMineav]

@Ms. Puffball, NTL imposes the harshest restrictions on tank design, as a result it is far easier to to design a tank that is unusable, and it's not obvious why. This is the reason that I chose NTL as the Interwar and Beyond Periods are much more forgiving and players can typically troubleshoot their own designs.

[Sir Puffball]

there's tech limits on every map determined by the era that map takes place in, not just on no tanks land

[Grey Warrior]

@Appletank that only applies when you build French tanks

[AppleTank]

FYI, you are not limited to 2 reverse gears, you can increase it to 3, too.