URC1

First post would be updated as I work on mod and know something new about. Questions and problems on development I will mark Improvement suggestions are welcome.

Vehicle Class

Thanks to this post now I get difference between touring and saloon.

Mass

According to book "Driving Ambition" kerb weight (incl half tank): 1138kg. Distribution front/rear: 41.2/58.8
Real CoG is currently unknown to me. Model CoG is 0.385 above ground.
Compared to LFS cars (XRT — 0.470; FZ5 — 0.412; LX6 — 0.370; RAC — 0.366) and Blackbird (0.392), say, for first approximation it is acceptable, but need to be clarified later, since a mm make difference.

Mass > Engine

According to audiosignal.co.uk, engine mass 303kg automatically determined by Vehicle Editor a bit heavy: engine+all ancillaries, the exhaust and silencer is 266kg.

Mass > Suspension

Book "Driving Ambition" claims unsprung corner weights are 42kg front and 55kg rear (total 97kg), which I believe consist wheels and suspension. Meanwhile, minimum unsprung weight that LFS Editor allows over 200% target consists of the sum 202 kg:
wheels (within chosen dimensions not customisable) — 81 kg and
suspension (minimal mass constant = 0.1) — 121 kg.

Engine

Quote from Jason Barlow :

it hasn’t got a flywheel.

Plate claims idle 900 rpm and another engine settings, most of all I like ignition timing string. Whole video by James Cottingham (DK Engineering TV) worth watching.

Steering

• Maximum Lock — I figured maximum lock is 33 degrees while testing on Layout Square — according to Autocar magazine turning circle is 13 m.
  
• Steering Wheel Turn (ONE WAY) 504 degrees — according to Autocar magazine lock to lock 2.8 turns.
  
• Parallel steer — quote from C466/007/93 (Concept and design of the McLaren F1 suspension systems), see attachments to post by user flemke on 26-09-2019 (hereinafter the "C466/007/93"): "...around 40% of full ackerman was adopted for F1."
  

Suspension

• Camber — planned: 45' F&R, but user tortoise claimed: 1.75 F; 0.75 R.
  
• Inclination. Front — according to audiosignal.co.uk — 8 degrees. Rear I tentatively figured by freeze frame tracking. Whole video by Tim McNair (Grand Prix Concours) worth watching.
  
• Caster — according to audiosignal.co.uk — 4.6 degrees (46 is written — I think point just lost).
  
• Scrub radius — according to audiosignal.co.uk is 25 mm.
  
• No rear anti-roll bar. Here's what Gordon Murray said about the anti-roll bar at the front only (interview with Henry Catchpole on Carfection YouTube channel):
  Quote from Gordon Murray :

  When you look at the basic physics of roll compensation in a car you are trying to stop the roll in a corner. And you can, if you get frequency balance and percentage, you don't get too crazy on the percentage of roll compensation that's coming from the roll bar, you can do it all at one end. The reason why I never do it at the rear is you'll get all this trouble for traction. Particulary in a racing car. To get best bossible traction, best possible independent suspension ... and then you join left and right axles with the bar. It's nonsense. So on one wheel bump or coming out of a corner on roll you're unloading one side of the car. Artificially. Which is nonsense. If you want the best traction — you don't join the axles.
  
  
  Quote from Driving Ambition page 159 :

  Jonathan Palmer decided the car rolled too much and argued against Gordon's long aversion to using rear anti-roll bars. Ultimately a very thin and flexible one — which should have had minimal effect — was made up and fitted: "To Palmer's credit he came in after a lap, admitting "I see what you mean! It was virtually undriveable."
  
  
• Roll centre — according to C466/007/93: 3.1 Roll centre "...the centres be placed at 30mm and 60mm above the ground, front and rear respectively."
  
• Roll compensation — planned 75% roll compensation (4.4 degrees for 80 mm travel). Later in C466/007/93: "...55-65% roll compensation...". So let's set it to about 3.7 degrees for 80mm travel.
  
• Motion Range — according to audiosignal.co.uk: 170mm (90 bump + 80 rebound).
  
• Ground clearance — 120mm, and there is a little problem. I figure that way:
  
  Lowest: front axle height=192mm-80(rebound)=112mm and rear axle height=228mm-80(rebound)=148mm
  Front corner load: 1138kg*41.2%/2=234kg and rear corner load: 1138kg*58.8%/2=334kg, but spring load does not include unsprung weight — wheels and suspension.
  Wheels unsprung weight: atomatically determined by Vehicle Editor mass of four identical wheels 235/45R17: 69kg. In case URC1 — two 235/45R17 plus two 315/45R17: 81kg. Therefore mass of one front wheel 69kg/4=17.25kg and rear wheel (81kg-17.25kg*2)/2=23.25kg. But!
  Suspension unsprung weight: target ground clearance (120mm) can only be obtained by subtracting front and rear unsprung suspension mass in very strange proportions, namely (per axle): front 10.2kg (8.4% suspension mass) and rear 67.8kg (56% suspension mass). Can't be true.
  Front spring: Load 234-17.25(front wheel)- 5.1(unsprung suspension per corner)=212kg. Stiffness 26N/mm. 212/(26/9.8)=~80mm.
  Rear spring: Load 334-23.25( rear wheel)-33.9(unsprung suspension per corner)=277kg. Stiffness 34N/mm. 277/(34/9.8)=~80mm.
  I must say right away that inclination of the spring is not the case: in the LFS stiffness is set in a vertical projection.
  

No anti-dive confirmed.

Quote from Jason Barlow :

more body roll than was fashionable in supercars

Quote from Tiff Needell :

rolled too much on the track

I like road car behavior with noticeable suspension travel, that real feel no other sim but LFS simulates so well.

Final drive

Lock is 40% — according to netcarshow.com.
Maximum speed with claimed gearbox ratios from Autocar magazine allegedly doesn't match well-known record 386.7 kph as redline was raised for record run, detailed information on Racing Line magazine.

Tyres

Tyre pressure information.

Aerodynamics

Maybe the coolest thing about this car, described by Gordon Murray (on Speedvision channel):

Quote from Gordon Murray :

did a little bit of styling and a lot of aerodynamic ... Styling was part of the process rather than dictating what the car should be

Mesh

Mainly using this main reference sketch, which has accurate object positions.
Some progress (GIF)




Sizes correspond to manual.

Rims modelled by converting NURBS spoke profile to mesh with shrinkwrap modifier.

Rear lights: red COBO 02.279, amber COBO 02.282.
Article in Racecar Engineering (June 1996) has very detailed monocoque description, including center beams dimensions: height 250mm (match main reference sketch) and width 150mm on floor, as well as distance between them — 22 inches.

Vehicle Editor does not allow place two kinda-rear passengers due well-known unique three-seat layout.
Steering wheel was modelled using pic from book "Driving Ambition" which I redrawn to better mesh align.

Clocks
Interesting statement about about the first implemented feature:

Quote from Gordon Murray :

Ron Dennis suggested the needles swept the dials on start-up. This is now mimicked by many others.

Thanks to Jay Leno we can see McLaren F1 fuel cell and know it must be replaced proximly every five years (same tells whichcar.com.au).

People working on IRL

Barry Lett had arrived from Lotus to oversee body engineering.
Paul Martin was in charge of composites.
Steve Randle did stress analysis and ended up working on the car’s suspension.
(source)
Peter Stevens — stylist

Very good to see that! I cant wait to drive and race that car

This mod deserve the level of attention you’re giving it! The best car in the world! Can’t wait to see more progress

Level of making mods: "Engineer"
Very exciting to follow this project.

Thank you guys! Some progress in the following sequence:
1 external shape
2 external shape mesh + SubD
3 semifinal mesh + Subd
4 check
5 after shrinkwrap (3) to mesh (1)
6 final mesh
7 final

A couple of workflow tricks.

While working on external shape to see clearly how adjust shape put marks, such as windows, doors, headlights, etc. by projecting NURBS curves:

Later, these contours were used to build the final mesh:
1 draw nurbs curve
2 add Shrinkwrap modifier (wrap method: Project, select Axis, allow Negative direction as curve is outside)
3 choose curve resolution (object data properties > Resolution Preview)
4 convert curve to mesh (check keep original)
5 join (Ctlr+J) converted curve to the final mesh

Since back of air duct meant to fit smoothly into external shape, I applied Lattice modifier to its part.

Image source: https://cars.mclaren.com/us-en/legacy/mclaren-f1

Mirrors special placement problem Car has two internal mirrors and two external mirrors: four mirrors total, but LFS support only three: two external and one internal, which have to be centered.

Using two separate "internal mirror" subobjects, mapped with different cutouts (doesn't matter cutout flipped or not) — mappings rotated along Z together with last subobject towards "eyes".


After removing left "internal mirror" subobject, mapping rotated, same as before, but in the opposite direction.


Using united "internal mirror" subobject (doesn't matter build mirrored or not, or using flipped opposite side cutout or not).


Changing internal mirrors subobject to "attachment" (two external mirrors already mapped) leads to all mirrors turn black (doesn't matter build mirrored or not, or using flipped opposite side cutout or not).

After removing mappings from external mirrors, internal works like this:


Сonsidering central seating position, default POV=90deg, vehicle width, looking straight you can't see external mirrors, it makes sense to stick with last scheme for a while.

Can't wait to drive this car (on VR)!
Maybe make two internal mirrors as one subobject? I know it will cause problem with left to right adjustability but...

Quote from versiu :

Maybe make two internal mirrors as one subobject?

This is shown in the third scheme — neither mesh nor mapping rotates towards "eyes" because mirrors median point and "eyes" are in center (X=0).

Quote from Egor K :

Using united "internal mirror" subobject (doesn't matter build mirrored or not, or using flipped opposite side cutout or not).

I've tried manually rotating both mesh and mapping towards "eyes" to look backwards, but this doesn't change anything — in mirrors you see side windows.

Approaching version 2. Today's post about exterior progress.

Wiper subobject

Engine+exhaust subobject

Tubes created by converting NURBS curves.
Object Data Properties > Geometry > Bevel > Round. "Depth" sets tube radius and "Resolution" sets transverse polycount.
Object Data Properties > Active Spline: "Order U" sets curve shape transition and "Resolution U" sets longitudinal polycount.

Head- and taillights

Modeled diffuser, bulb and parabolic parabolic focus-balanced reflector for baking lamp textures.
Diffuser textures baked using procedural normal map according to tutorial by pyrotechnick.
Parabolic focus-balanced reflector modeled using Extra Objects add-on: Add > Mesh > Math Function > Z Math Surface. I chose low-beam headlamp reflector focus=23mm Z Equantion: ( x**2 + y**2 )/(4*.023) and high-beam headlamp reflector focus=19mm. Formula from here. Sounds like overkill, but I only achieved nice reflection with parabolic reflector with focus on centre of bulb.

Headlights rendered

Headlight baked textures, improved front air intake shape, added wings and molding below. Textures baked in Blender according to tutorial by Gamedev Fred.

Taillight rendered

Taillight baked textures, engine bay vent grille baked textures, exhaust.

More streamlined external mirrors.

Brake calipers (different front and rear according to disc size).

Steering wheel flange rendered using procedural carbon texture (here and below) according to tutorial by Chris Plush.

Steering wheel flange rendered

Dashboard rendered

Closer view from opposite angle. Just to show details.

Icons drawn from scratch, for these I used photos from GTspirit article and photos by Alex Bellus as reference:


and for these I used photo (12/24) from roadandtrack.com:

Improved driver's seat using fSpy to match camera with the photo by Richard Owen (item 65/150):

Just... Beautiful

I like the way you present the changes.
Oh and the mirrors. I like that you noticed and changed the shape.

Excellent detailed work! Keep it up!

Wow, I’m so glad to see someone actually care about the real world figures for once. Amazing work!

Perfection, this could be a benchmark for mod quality

Appreciate both the level of craftsmanship and the background research. I like the way how the technical specifications are cited. It adds a very special credibility to the realism of the mod which is very rare among mods. Also, thanks for the technical details about realistic parabolic headlights

Thank you guys for the kind words, although there are still textures and aerodynamics to be completed.

By the way, yesterday model was tested on Sim Racing Bible stream. Phil decided to repeat speed record, but did not reach 240 mph. Thing is for the speed record XP5 (experimental prototype number five) engine redline was raised to 8300 rpm, but URC1 has standard redline 7500 rpm.

For those who want to know more about record run there is "Racing Line" magazine article scans, though text hard to read, so you may use archived page with the same text.

Anti roll bar!, dont worry about upsetting Gordon Murray

U still can make ur setup ;p

IMO it should be kept as it is

Thank you for this one! Planning to make GTR version of it? Or even "no-limit" version?

EDIT: Max Speed I got this vehicle was exactly 400km/h ( very briefly )

Quote from Jardim :

Anti roll bar!

I want the mod to be as accurate as possible. By the way, thanks to terga for link to the explanation:

Quote from interview with Gordon Murray on Carfection (30:04) :

When you look at the basic physics of roll compensation in a car you are trying to stop the roll in a corner. And you can, if you get frequency balance and percentage, you don't get too crazy on the percentage of roll compensation that's coming from the roll bar, you can do it all at one end. The reason why I never do it at the rear is you'll get all this trouble for traction. Particulary in a racing car. To get best bossible traction, best possible independent suspension ... and then you join left and right axles with the bar. It's nonsense. So on one wheel bump or coming out of a corner on roll you're unloading one side of the car. Artificially. Which is nonsense. If you want the best traction — you don't join the axles.

Quote from UnknownMaster21 :

Planning to make GTR version of it?

Yes, but a lot of GTR's specs (such as CoG height, suspension motion range, roll centre and roll compensation, etc.) still to be found.

Quote from UnknownMaster21 :

Or even "no-limit" version?

Also want make 'XP5' version as separate mod (raised redline, speed measuring equipment and fixed black color).

Quote from UnknownMaster21 :

Max Speed I got this vehicle was exactly 400km/h

Official record is 386.7km/h, although XP5 (experimental prototype number five) for 22 seconds kept at least 390km/h: 2:42 — 390 km/h, 3:00 — "not going faster", 3:04 — descending.

Approaching version 3.

Improved lod3

0.7E patch changes: dashboard, lights, passengers

Realistic dashboard.

with shift light (just like IRL)

Analog speedo with dashboard backing texture can only be used with one speed measurement unit, decided to use mph: after all, it's a British car plus kph dial too small to read on a low resolution screen. But below analog dial is now preferred unit digital speedo.
Still need to do metal pivots covers textures instead of black default ones, but I'll do that on texturing stage
Also added rear fog light icon and now high beam icon works correctly

High beam

Passengers (leg intersection with floor beams is known)

Minor animation improvements

Improved interior shading

However, the most important about new version is improved aerodynamics! Research almost done and I'll post it soon.

Amazing!

Aerodynamics > Lift (Downforce)

Quote from Driving Ambition page 76 :

Initial targets were a realistic 0.35Cd, CoP almost coincident about the centre of gravity and 160lbs (712N) downforce at 150mph (241km/h).

Quote from Racecar Vol6 No1 page 35 :

According to Murray, the McLaren F1 road car produces 500-600lb lift at its road maximum speed, at which it is able to cancel this lift and leave a nett 200lbs downforce.

Here's the tricky part, if stated downforce (200lbs or 890N) is correct for top speed of a serial car 221 mph or 98.8m/s, then by quadratic function at 150mph or 67.1m/s it will be 93lbs or 411N, which is 58% of the Initial target. Perhaps downforce generated by fans reaches maximum already at 150 mph and does not increase further because their speed can be controlled by some program.

Also print-out of tunnel 3/10 scale model run results is used as an illustration on Driving Ambition page 74, this one and above data summarized in table below.



Anyway, I see no reason to assign less downforce than planned, so 0.158 N @ m/s is chosen.

Spoiler - click to reveal

Have to mention "BB 'Foil" (spoiler), however, LFS currently doesn't simulate active downforce.

Quote from Driving Ambition page 79 :

Activated automatically by electronic control sensing heavy breaking, this "BB 'Foil" would deploy at 30-degrees, slightly raising Cd but crucially enhancing base-suction at the tail to generate greater downforce from the diffuser with its CoP in the right place.

How much "greater downforce" exactly? Gordon says twice:

Quote from Gordon Murray :

We have an active aerodynamic control system on the car which pops up a flap, which not only doubles downforce on each wheel, but doubles downforce in right proportion front to rear axle, so it helps stabilize the car...

Aerodynamics > Drag

Knowing frontal area=1.79 m^2 and drag coefficient Cd=0.32 (ρ is air density) drag force can be calculated, so for V=67.1m/s (150mph) Fd=1580N.

To find body drag for LFS Editor divide drag force (1580N) by square of speed (V=67.1m/s)^2 = 0.351 N @ m/s.
But using this value LFS Estimated Maximum Speed Calculator (hereinafter — LFS.EMSC) indicates 373 km/h (232 mph), moreover acceleration from 255 to 350 takes 20 sec (16 sec IRL) and from 350 to 370 takes 20 sec again (8 sec IRL).

To match LFS.EMSC and Ehra-Lessien 391 km/h (243 mph) XP5 (experimental prototype number five) record run (not to be confused with official two-way average measured 386.7km/h or 240.3mph) body drag must be 0.304 N @ m/s.
Apart from fact that accelerating from 360 to 370km/h and from 370 to 380km/h takes one sec longer than IRL, even across Layout Square is not enough to reach 390km/h.

So 0.293 N @ m/s (LFS.EMSC 396 km/h) chosen because this body drag ensures acceleration coincides across all control ranges with deviation of less than a second.

Version 3 Aerodynamic changes

reduced Body lift from –0.450 to –0.158 N @ 1 m/s
increased Body drag from 0.270 to 0.293 N @ 1 m/s
reduced Side drag from 0.600 to 0.586 N @ 1 m/s

Other changes in addition to those listed here

gear ratios according to Autocar magazine: second from 2.21 to 2.19 and third from 1.68 to 1.71

final ratio from 2.99 to 3.03 to ensure maximum speed with

original starter sound from youtu.be/LSUvgTFp5Ts 0.740s (0.742s max)

original gear shift sound from youtu.be/KXihJTDSWb4 0.180s (0.184s max)

second (right) internal mirror disabled (not supported)

Thanks to Rony for helping me stop procrastination with improving the aerodynamics

Thanks to Martin because I had previously speculatively decided original tacho's four-digit readings must be too large to be readable on low resolution screen, but after he asked I tried and realized I was wrong.

One of the best mods i've seen

What an amazing progress thread!

Quote from Egor K :

Also want make 'XP5' version as separate mod (raised redline, speed measuring equipment and fixed black color).

Thank you for this! Perhaps "PIONEER" code is finally worth having used in NFSIISE game.