SimHQ.com - Motorsports Zone - Preview: Behind the Scenes: The GPL 1969 Mod

Simulating different seasons would not be quite the same fun if the physics stayed the same. The different mods need to attempt to simulate the properties of the real cars.

Another reason to mod the physics was that some concern had been raised in the GPL community, regarding the otherwise fantastic tire model in the default 1967 physics.

The concern was directed at the fact that the cars seemed to suffer from having too low grip at low speeds. This meant that drivers had to slide their cars around slow corners at low speeds in order to achieve good laptimes.

It was also considered that the cars were sliding a bit too much, at all speeds.

I cannot give you the definitive explanation in this matter, as I'm not that deep into the technical argumentation.

Let me just say that IMO this small bug in the original GPL physics is one that it took the GPL community several years to discover, and that many drivers, including myself felt that the default tire model as supplied out-of-the-box was just as close to perfect as could be had.

Still, the GPL community is renowned for its quest for absolute historical accuracy, so the tire-model deficiency has been dealt with in the 65 and 69 mods.

Note please that I refer to the "tire-model deficiency". I admit to not knowing how exactly it was corrected. So I'll be deliberately vague about this issue, and I'll probably be speaking of a corrected tire-model, not really knowing if it was the tire-model itself that was corrected, or something else.

The physics for the carsets will be the same for the high-wing and low-wing cars.

Piers Courage leads Chris Amon

Enter the Downforce

When wings are fitted to cars, they generate downforce that press the car and the tires onto the road. It works the opposite of an aeroplane's wings, because the shape of the wing on a car is more or less an aeroplane wing turned upside down.

However, any body moving sufficiently fast over ground or water, will also be subject to forces attempting to lift that body off the ground, especially when that said body is aerodynamically sleek, but not producing a lot of downforce.

And that is aerolift, the short version.

The wings on Formula 1 cars in the early seventies were fairly crude devices designed perhaps with pen and a piece of paper and by a lot of trial and error. Wind tunnels were not yet available to the teams in a sport which was only beginning to explore the possibilities of commercialism and ever increasing budgets. Wing adjustments in the early years was very crude, typically the front wings cold be adjusted to 3 or 4 different positions.

With the introduction of the powerful Ford Cosworth DFV engine, car-designers faced a very big problem in terms of lacking grip. The 3 liter cars were too fast for their tires, and adding wings to the cars was found to help considerably in persuading the tires with their relatively unsophisticated rubber compounds to stick to the road.

Four-wheel drive cars were built and tested as the principle of 4WD was explored for its potential, as in theory it should offer more grip. But the advent of wings and general trouble in terms of adding weight and complexity to the car by using 4WD, led to this idea being abandoned rather quickly.

A short video demonstrating downforce in GPL was presented at RaceSimCentral in October 2004, illustrating a working example of a car in-game being pressed to the road as a function of the car's speed., The jaws of every GPL fan around the globe dropped and hit the floor., You can still hear the echo, because we all thought, and had even told each other time and again, that aero would never become a feature in any GPL mod, simply because GPL doesn't model it.

Thank goodness for people who do not know of the word impossible!

The dreadful December 2004 when RaceSimCentral was down for most of the month was used to refine the aero-experiments and to attempt to build them into a working solution, because with such an opportunity being presented to you, who could resist attempting to incorporate this breakthrough into the 1969 mod? And here we are, several months later, testing the ingenious implementation of downforce in GPL, getting ever closer to the scheduled release date some time this December, barring last minute and unexpected bugs.

I've just about lost count of the numbers of experiments we've been through, and the laps that have been driven by the beta-testers, but I can assure you that they have been many. Doubtless they are to be counted in thousands, rather than hundreds. A lot of testing has gone into determining whether speeds, laptimes, slip angles and g-forces were as correct as possible, so the testers had to get back into the cars on many occasions and drive them for yet more laps.

Loving attention to detail from modders and testers alike plus an intensive online test program should guarantee a very fine mod with hopefully no or only a few bugs, although it is tempting fate, to state so in advance.

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