Welcome to the Online Presentation of RaceSim

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Masses Input

The chassis is a seven-degree of freedom model (pitch, yaw, roll translations front and rear plus chassis twist). The inputs are sprung and unsprung masses and inertias. Go to extras-mass calculate to calculate CG’s and inertias from lumped masses.

Chassis

Input basic chassis dimensions and characteristics. Note torsional free-play term. Not necessarily desirable but often present. If values such as chassis torsional damping and/or free-play is unknown,input zero and the calculation will continue without these parameters.Input Steering characteristics. Frame heights function is for calculation of dynamic ride heights at 4 user defined points on the chassis.

Independent Kinematics

The suspension kinematic is described by a wheel displacement versus orientation line/curve e.g. camber versus bump travel etc.Non-linearity is described by a quadratic equation. Go to extras-parabola to assist with curve fitting and equation determination.Input roll and pitch center static position and linear or nonlinear movement versus wheel displacement. Input camber and toe compliance versus loadings. All inputs are for each wheel independently.

Live Axle

Select a solid axle for front or/and rear left and right corner. Like the independent suspension the solid axle kinematics describes a wheel displacement versus orientation line/curve

Springs

Select front-rear, left, right or middle unit.Input spring, helper spring, bump stop stiffness and stroke. Use parabola tool for quadratic (nonlinear) curve fitting.

Dampers

Input five force versus speed data points for bump and rebound for each suspension damper, import directly from Roehrig dyno or contact D.A.T.A.S. Ltd. regarding import of damper dyno data into RaceSim.Shaft friction may be modeled and there is a linear coefficient output for use with critical damping calculations.

Anti Roll Bar

Input front and rear (linear or non-linear) roll stiffness and/or damping – at the wheel.

Tyre

The tire characteristic is basically described by high and low vertical load, longitudinal and lateral friction (force) and self-aligning torque versus slip angle curves. Corner Stiffness is used to define the initial gradient and a maximum and a constant value to describe the typical digressive characteristic. Toggle between lateral, longitudinal or aligning torque to view respective curves. Pacejka data may be imported and the calculation will be driven by the Pacejka curves.

Vertical damping, hysteresis angle (response), ellipse factor (combined long./lat. force), rolling resistance (friction) and camber stiffness (thrust) help to detail characterize the tyre. Growth with speed is essential for aerodynamically (ht. sensitive) influenced vehicles and for maximum RPM. The temperature model is to assist the user to characterize the tyres, and to enhance the manufacturers data.

Engine

Select engine orientation, rotational direction and drive split.The engine (drive train) is defined by a DIN power verses RPM curve, with modifiers for driveline efficiency, dyno conditions verses current ambient, traction control and response – e.g. turbo lag. Imput off throttle torque (engine braking) and select advanced engine model if required.

Advanced Engine model

Input dyno conditions. Input models for airbox pressure correction, torque and injection maps.Input model for the effect of the exhaust gas on the vehicle external aerodynamics. Input inertia for each gear.Back to Engine window.

Select the type of gearbox – CVT, optimum shift revs (to peak torque at the wheel), static shift revs (to shift rev limit) or individual shift revs. Define number of gears, shift time (gear change/engine cut duration) and driveline efficiency per gear.

Gearbox

Input tire circumference from the tyre model. Gear ratio variations may be selected from the previously inputted drop down dialog boxes and the speed/RPM graph overlaid or redrawn.Numerical data may be viewed by pressing the view data button and scrolling between data sets.

Brakes

Are defined by a maximum torque value front and rear (therefore including the brake balance), with a modifier for ABS and/or rear pressure reducing valve (rear brake limiting). Select balance finder for display of calculated dynamic brake balance.

Differential

Separate or combinations of front, rear and center diffs may be modeled as a plate (Salisbury) type or a viscous – or a hybrid plate/viscous combined. Select RPM ratio of the output/input shaft for live axle if appropriate.

Aerodynamic

The Aero properties of the vehicle are defined by lift (downforce) and drag coefficients at a reference ride height and speed. Variations in coefficients with ride height and speed may be inputted as a linear change or as a non-linear (quadratic) for non-V squared variation. Again use the extras-parabola tool to help determine the quadratic equation.A variation of coefficients when in the slipstream of a vehicle ahead may also be modeled. Select ‘more’ button for variations of coefficients with roll, yaw and wall proximity.The offset drag positions are related to the vehicle CG for wind yaw effects.Select ‘with aeromap’ to load an aeromap of coefficients verses front and rear ride heights.

Aeromap

As an alternative to manually inputting the aerodynamic coefficients, an aero map chart of lift/drag/balance verses front and rear ride heights may be imported. Press ‘plot’ to view a rotational 3d plot of each function.Back to aerodynamic

Setup Calculation

Define time steps to optimize calculation time verses resolution – or use defaults shown in on line help file.Reduced time step at brake or throttle allows one to increase resolution in these critical areas. Input lap sim reduced lateral to model non optimum usage of lateral tyre capacity. Input lap sim reduced brake/throttle to model late braking and therefore late accelerating driver – or the opposite .Steering torque limit may be set to prevent torque feedback being in excess of the drivers’ capability.Set overall (global) grip and ambient conditions.Set check balance to modify the effect of longitudinal weight transfer on grip. Set reduce segment boxes to modify the track map graphical display – or use defaults.Select ‘logging file setup’ to edit channeldetails.

The track map may be created manually segment-by-segment using the track editing boxes – or more usually by importing (ASCII) data of speed and lateral acceleration from a data logged lap. The imported track map may be manually edited – for example to modify the segment local grip &/or banking (track camber) to match real and simulated minimum corner speeds &/or elevation profile to correctly match longitudinal acceleration.

Lap Simulation

Automatic matching (to imported logged data) of corner banking or local grip may be selected from the drop down dialog box. Set wind conditions, start speed and gear ratio per segment. Set the level of simulation (include/exclude heave, pitch, roll, steering) from the drop down dialog box.

Result Channels

Load file. Select channels to view – approx. 65 channels from a possible c.90.Edit the channel trace color, scaling, add/delete/ replace files, delete lines (channel trace) for clarity.

Result Graph

Match simulated lap to actual logged lap and display simulated data.Manually move the curser over the trace line and view data in curser window.Press right mouse button to zoom in on trace line - zoom off. Select dots on – and zoom to view data points.Select print if required. Note this matched lap of Spa in less than ideal grip conditions shows a 2’ 26.85” lap time and a throttle lift at Eau Rouge. Now use RaceSim to evaluate the effect of increasing aero downforce

Modify Aerodynamics

After the lap matching is done, modify the model and predict what the effects are. Here for example with an increased wing setting, and therefore increased lift (and drag) coefficients

Compare Graph

Despite lower top speed and time loss on longest straights, the overall effect of Increasing aero from Low to Medium downforce improves lap time by 0.55 seconds to 2’ 26.30”. Simulation predicts more throttle opening and higher minimum corner speed in Eau Rouge. A good result for qualifying, although one would have to consider the overtaking scenario for the race.

Transient Simulation

Select starting speed and end time (run time).Select run by pilot and adjust throttle and brake slide bars for conventional driveline and brake torque effects – or deselect run by pilot for manual input of acceleration (drive) and deceleration (brake) torque directly into the drive shaft/brake caliper for pure kinematics effects analysis.Select any steering input. Define wind conditions. Define track surface bumps and/or kerbs using the editing boxes. Define track banking and lateral curvature.

Dynamic ride height

Calculates the vertical displacement of the vehicle due to aero effects (downforce), either at a selected single speed or through the speed range. This enables the user to predict the dynamic ride heights (and therefore the potential touch condition) at maximum speed, and thus accurately set the static ride heights.Input speed and press calculate.

Advanced 4 post

A stand alone tool, simulating a 4 post rig vertical excitation, to calculate grip reduction due to vertical stiffness configuration. The calculation considers the stiffness and damping configuration of the vehicle, and the output is based on tire contact patch load variation at user selected modes and conditionsSelect desired mode and conditions and press calculate.

Run assistant

Enables the user to run a batch of up to fifty simulation runs, and therefore have a productive lunch break.

Result Animate

Load file, view real time (or slower) steering, braking, throttle activity.View gear position, speed, RPM, lateral and longitudinal accelerations, force vector direction and magnitude and wheel loads – all dynamically.

Mass Calculate

This tool calculates CG’s, inertias and mass distribtution for 7 lumped massesBack to slide masses input

Parabola

This tool helps to find the coefficients for a quadratic polynomial to fit nonlinear real curves.Back to KinematicBack to SpringsBack to Aerodynamic

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