Basic Manual  

Car Page

'Based on existing rFactor mod':  Choose this setting to browse for an existing .hdv file.  carFactory will import the tracks and wheelbase, wheel and upright locations and use them unchanged in the generated .pm and .hdv snippets.

'A new rFactor mod': Choose this setting to start from scratch, entering new values for track and wheelbase.

Suspension

Roll centre:
All suspension has a geometric roll centre about which the car pivots. Enter a value in mm above the ground. Unfortunately the geometry alters as the suspension deflects and one of the aims of good suspension design is to prevent the roll centre from migrating wildly.

Roll camber rate:
This is the amount of camber you would like added to the static camber for each degree of body roll. Tyres like a bit of negative (top in) camber to compensate for contact patch distortion in cornering. As the car rolls, if the wheels to not have any camber gain they will present a reduced contact patch to the track.
e.g. A rate of 1 deg/deg will add 1 degree of additional negative camber for every degree of roll causing compression and add 1 degree of positive camber for every degree of roll causing rebound.

Ride height:
This is used as a constraint to prevent the generation of solutions with suspension control arms dangling below the car!

King Pin Inclination:
The angle that the virtual king pin formed by the outer ends of the two wishbones makes with the vertical. Positive angle is top towards the centreline of the car. Also known as SAI or steering axis inclination.

Scrub Radius:
The lateral distance between the centre of the tyre's contact patch and the point where the extended line of the kingpin intersects the tyre's contact patch. Positive scrub radius adds feel under braking for rwd cars as the tyre with most grip exerts a trque efect around the steering axis. Fwd cars should have this set nearer to zero to avoid torque steer.

Castor:
Angle that the virtual king pin formed by the outer ends of the two wishbones makes with the vertical. Positive angle is top towards the back of the car. Adds stability but causes mechanical trail.

Trail:
The longitudinal distance between the centre of the tyre contact patch and the point where the extended line of the kingpin intersects the tyre's contact patch. Adds stability but causes mechanical trail.

Ackerman %:
For a normal road car that never slides this should be 100%. There is a good explanation on Wikipedia. For a race car it is not so straightforward as the tyres are always sliding (hopefully at their maximum slip angle) while cornering. The ackerman angle is therefore dependent on the relative slip angles of the tyres on the front and rear axles. In extreme cases 100% negative Ackerman might be appropriate.

Rear Suspension

Settings as for front.

Build

1. Choose an axle.

2. Choose how many cups of tea you want to drink :-; The low setting should not really be used except as a test to make sure that carFactory is happy with the settings you have entered. The solution envelope produced at this level is so 'lumpy' as to be next to useless. The setting was more to help me debug without waiting 90 seconds for a sensible build.

3. At the moment I have greyed out the server option for the downloads, I am not sure I want half the rFactor community hammering away just yet . . . .

Choosing a Solution

At the moment carFactory will only offer Double Wishbone or DeDion solutions.  In the future multilink arrangements may be available. (and then you will have time to seed a tea plantation, wait until harvest, crush the leaves yourself and make a well deserved cup of ta before the solution envelope completes, or ask nicely to use a server or two . . .:-)

Don't bother playing too much with a Low quality build, the results of moving the sliders may become counter intuitive due to the low quality of the solution set.

carFactory has selected the best configuration it could find for every permutation and combination of the trade-offs between scrub, roll centre migration and camber rate accuracy. You use the sliders to explore this envelope to choose the configuration you would like to drive.

The Envelope

(Skip this bit if Mathematics send you into a coma)
The solution set is a three pointed circle. Either visualise an equilateral triangle with curved sides or a circle with three equidistant points marked around the circumference.
In a perfect solution the circle would be dished downwards somewhere between a disc and a hemisphere. Double Wishbones are constrained by the track / wheel rim size (got to fit the upright inside the rim) / ride height etc. (I will add more constraints later) So the solution set is an undulating dish. The higher the build quality the more smoothly it undulates. Quality is not proportional to the number of solutions but is proportional to the smoothness.
Imagine the sliders as three magnets that attract or repel a ball bearing inside this dish. With a slider set to zero you repel the ball to the far side, with the slider set to 100 you are on full tractor beam. As the ball slides around the charts are loaded with the behaviour of each solution the ball is resting upon.
The statistical accuracy of any single solution is proportional to its distance from the geometric centre of the three pointed circle. If ever you achieved a perfect hemisphere then the lowest point, in the middle would imply zero scrub, zero roll centre migration and perfect camber rate.
When you click the search button , it finds the point on the surface that is furthest from the centre of the circle. This may not be the best point for you. For example if the total range of scrub is less than 5mm over full scale deflection of the suspension you may be willing to ignore scrub completely and manipulate the sliders to find the best trade off between roll centre migration and camber rate.

Ride and Roll

This tab lets you define your handling requirements for the chassis.

Specify spring rates either as front and rear frequencies, in Hz.  (You can enter values manually for either Wheelrate or Springrate).  In general rear frequency should be 20-25% higher than front frequency to prevent harmonics.  Typical settings are about 1Hz for a comfortable road car, 2Hz for a track-day car and possibly as high as 10Hz for extreme downforce sports cars.

Damping ratios are typically 0.25 for comfortable road cars, with lots of suspension travel, about 0.5 for a track day car and maybe 0.75 for a very racy ride.

The transition speed may be changed.  This speed is the damper piston velocity at which the suspension is no longer coping with handling behaviour but is starting to cope with bumping over kerbs.  Ideally the transmissibility should be reduced for these impacts by having reduced high speed forces.

The roll bars can be specified by a roll gradient and TLLTD or by entering the values manually.

The roll gradient is the degrees of body roll required in a 1-G corner.  Not many zero-downforce cars, 2CV for example, will achieve 1G so you must extrapolate a value.  Typical values might be 40 deg for a 2CV! , 2 deg for a hot Gti, 1 deg for a track car down to a fraction of a degree for formulae cars - in the mid-90s Williams F1 cars appeared to be rolling into the corner, a negative roll gradient!  If the spring settings you have chosen mean that the car already has a stiffer roll gradient then a little blue exclamation mark will appear – hover the mouse over it to see an explanation.

The TLLTD, or total lateral load transfer distribution is a measure of the handling balance of the chassis.  The roll bars main function is to tune how much weight transfer in roll is split between the front and rear wheels.  Make the front wheels work harder to induce understeer and make the rear wheels work harder to induce oversteer.  In general a value 5% forward of the front/rear weight distribution is used for racy cars.  The further in front of the CofG, the more the chassis wants to understeer.  The further aft, the more it wants to oversteer. A value equal to the front/rear weight distribution would give you a neutral but unstable car with no natural tendancy to keep the front wheel ahead of the rear ones on the limit!  The definition of TLLTD is not consistent.  MoTeC have a consultant who promotes the concept of the 'Magic Number' and deprecates TLLTD - in fact they refer to it as the relative roll resistance of the antiroll bars alone, not so terribly useful.  Despite the marketing hype it would appear that their magic number is merely what everyone else calls TLLTD!

It may not be possible to achieve the handling balance you require with roll bar settings.  If so a little blue exclamation mark will appear.  Hover the mouse above it to read the explanation.

Two factors outside carFactory's control can make any effort you put into this screen worthless.  If your roll centres migrate wildly or if your mod uses a .tbc file with unusual settings.  Do check that the mod uses a tyre (.tbc) file that does not defy the laws of physics :-)

Generator

Creates an entire .pm file and snippets for the .hdv file. At the moment the fuel tank and driver head are arbitrarily located.

Don't forget to use the Estimate button, or to enter your own values for the car's inertia settings.

The .hdv snippets should be inserted into the [SUSPENSION] and [FRONTLEFT] etc. sections of your .hdv file.

If you based the car on an existing mod, the wheel and spindle settings will have been copied verbatim.