How is downforce exported from Automation to BeamNG.drive? A comprehensive study
related: terminal oversteer at high speeds, wings, downforce, lift, exported car, BeamNG.drive
The following seeks to go into a brief, but robust analysis of three key factors in the aerodinamic characteristics of BeamNG.drive car mods generated with the Automation car exporter.
The three key factors aforementioned are: Car body, fixture type and placement and size of fixture. Other factors have partially been reviewed and not having been deemed relevant.
The findings have been as close to scientifically collected as possible, and informative visual data provided in addition to the parameters for each individual experiment.
The findings can be summarised into the following:
Car body: The Longer the car, the further in back the downforce and vice versa
The relative length of the overhang in front of the front wheels relative to the overall lenght of the car is the biggest factor in how much the mean downforce is shifted to the front. So: Short and long front overhang: mean downforce of body further to the front; Long and short front overhang: mean fownforce of body further to the back.
Fixture type: Only wings inpact downforce
Solely fixtures from the ‘wing’ tab have been found to generate any mesurable impact on aerodynamic properties like downforce. But from these ‘wing’ fixtures does everyone have a mesurable, if from individual fixture to fixture varied, function.
Placement and size of fixture: As to be intuitively expected
The downforce effect is applied at the far corners of the fixture. This means neither orientation nor specific miscellanious shape of the wing have any effect. The amount of downforce scales with size, and the placement bevaves as one would expect: Further left and aft mounted wing will generate downforce accordingly.
Method
One of the debug options in BeamNG.drive is, after activating debug utilities in the general options, available under debug as aerodynamics (citation needed). This shows the COG, center of gravity, and COP, center of pressure (citation needed), as invisible points marked with red and blue text respectively, as well as red and blue lines of variable length indicative of drag (citation needed) and downforce / lift respectively. The blue lines, that have been shown to correlate with aerodynamic downforce and lift, are the main source of information for the following analysis. Note that ground textures obstruct viewing of the lower lines, which is why the cars are driven onto a part of the map without such obstructions.
Example:
Car body
Collapsed for accessability
The inert ability of car bodies to generate lift and downfoce for cars exported from Automation is simplified and represented in BeamNG.drive at four (six) points:
At the very front of the car;
Just in front of the front wheels;
Just behind the front wheels;
(About at the height, where the driver would sit;)
(Just behind the back wheels;)
At the very back of the car.
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The reference car used comes in at least three wheelbases, which allows for a specific analysis of very similar cars, which have different wheelbases. Very much noticable is the difference in the three front points, where at the end points of the lines the shortest wheelbase exhibits a convex curve, whilst the longest wheelbase exhibits a concave one. This seems to closely correlate with high speed stability: The shortest wheelbase is instable, the longest stable at ~266 km/h. The cars are, other than the wheelbase, identical.
Short wheelbase:
Reference car:
Long wheelbase
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The following will illustrate other examples of stock BeamNG.dive cars and exported Automation cars with comments on proportions and high speed stability of the car. Note these cars have different fixtures added to them, but the original six points are often still distinguishable.
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Also: Gerade = Stable, Wankt / Instabil = Unstable.
Stock BeamNG.drive cars:
Civetta Bolide; Low sports car without wing (although according to it’s derby classit’s a mid-sized vehicle)
Hirochi SBR4; Shooting Brake sports car with active spoiler
Automation cars:
‘Hirochi’ ATF6; Big, long, fast SUV with hidden wing fixtures
Omega RV8; Rear v8 engined GT car with hidden wing fixture
WM Adler; Hypercar, big wang
‘Lancia’ Farfalle 91’; Early rendition of 90s sports car, the main inspiration for this analysis
WM Kauz; Small supercar with wing, earliest inspiration to look into aerodynamics on exported Automation cars
Omega 55; Stupid fast car with little aerodynamic fixtures
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Note how when the rearmost line is short, the car becomes unstable at high speeds.
These experiments conclude, that the amount of lift stated in the Automation body selection tooltip seems to be truthful to the exported cars. Further conclusions are stated above in the summary.
Fixture type
Collapsed for accessability
Oftentimes one would hear ‘only wings add downforce (in BeamNG.drive on exported Automation cars)’ and this is, if seldomly supported by evidence, true. The following pictures show the effect of all possibly downforce generating modifications to an Automation car one can do in Automation. All of them are made to the reference car.
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1 Reference car without any modifications: Reference
2 Biggest body morph: Leads to a displacement of the four (six) original points
3 Big rims: No significant change
4 Small rims: No significant change
5 Undertray option ticked: No significant change
6 Downforce slider 100 w/o any fixtures: No significant change
7 Lip added in front: No significant change
8 Lip added in back: No significant change
9 Spoiler added in front: No significant change
10 Spoiler added in back: No significant change
11 Wing added in front: Active generation of downforce at the far corners of the wing
12 Wing added in back: Active generation of downforce at the far corners of the wing
13 Downforce slider to 0 with wing: Fixture generates lift
14 Downforce slider to 100 with wing: Fixture generates more downforce than with a slider of 50
The active aero, that can be added to Automation cars, isn’t carried over to BeamNG.drive.
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The striking similarity in the results of the insignificant changes should be exemplarily for their irrelevance. Actual changes can only be observed with body morphs (comparing 1, 2 at the original six points) and wings (11, 12), where it should be noted, that the downforce slider in Automation strongly affects the generated downforce and lift from the fixtures (compare 6 and 13, 14) when going under a value of 50. The effects of going over and under a value of 50 aren’t linearly proportional; A low value goes so far as to invert the effect of the fixture. Also, even though the models are often similar to wings, Spoilers don’t generate downforce. Further conclusions are stated above in the summary.
Placement and size of fixture
Collapsed for accessability
The effect of placement and size of the wing will be further exemplified by the following pictures, though they behave as expected.
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Wing as far in front as possible
Wing on bonnet
Wing in front of front wheel
Wing behind front wheel
Wing on windshield
Wing on roof
Wing over the rear wheels
Wing on the hear hatch
Wing as far back as possible
Wing as big as possible: Misleading picture, compare to top lines, photo actually angled steeper to get the lines in frame
Wing normal: lower amount of downforce than big, lines closer together
Wing offset to side: Downforce offset, doesn’t seem to affect high speed stability
Wing on the side of the car: Again, downforce offset
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The downforce is generated at the corners of the Wing, so their relative placement is what ultimatiely matters. Big wings also have the benefit of these corners being further apart, aiding stability. Further conclusions are stated above in the summary.
Concluding Tips:
Add a wing fixture to anything that goes over 200 km/h and isn’t either ridiculously heavy or long;
Subscribe to RB interactive Aero (citation needed) and use the most discrete wing fixture to tailor the downforce to where you like it, for example when terminally oversteering at high speeds or to emulate lips;
Never Change the downforce slider in Automation, in fact, disregard everything that Automation tells you about downforce (exept the lift values of the body, but even they are only aproximate).
These experiments have been conducted on the BeamNG.drive, Automation:The car company tycoon game and Automation “To BeamNG.drive” exporter as of the 3rd of September, 2020
