An Internet Guide To Constructing Your Own Race Car.

 

Design Approaches

Now that you have studied and understood, it is time to consider the way to approach the designing of a car.

Firstly, the design process for a race car is linear, that is, each step is followed in succession. However, being as there are a million different ways to build things, the designer is quite often forced to consider other components which relate to the area being designed. For example, when designing the suspension of a car, you inadvertently affect the structural shape of the car's chassis in and around where the suspension will mount. Therefore, it is wise to construct the suspension first, keeping in mind the requirements of the things the suspension affects.

Secondly, the design process demands a fair bit of estimation and compromise. Juggling performance, safety, efficiency and cost are what it's all about. This is where you want specifications ready to assist you in putting the pieces together.

Before You Get Started

Computers, mostly PCs, are incredibly useful tools for race car design. A good, but optional investment is solid modeling software. Numerous companies make it, with very few selling below $5000. The lowest cost, value packed package is probably TurboCAD Solid Modeler. This software enables the designer to create virtual models of each part, in whatever required detail, and to create assemblies and finally a whole car. Sometimes training is required, but the picture it gives is as complete as it gets. For those with a smaller budget, there are still 2D and 3D CAD programs to fit any budget.

Other useful software also includes annotation and information recording/categorizing. Free tools are available for creating a simple database of information concerning your design.

The Race Car Project Steps

The chart below illustrates the major steps in designing and eventually constructing a car. (See explanations below) The design steps are discussed in more detail below.

Research Of And Viability of Intended Class of Car is there to put a reality check into place before any work is done. There are many levels of motorsport and it is important that you understand the technical difficulty of the class you have chosen. Formula 1 is not a good place to start. Also consider the cost. Anyway, ask people racing in your intended class for help and you will probably get it.

At this stage, it is wise to do a scale sketch of the car, in simple side, front, rear and top views. Assuming you are designing for an existing class, there will be plenty of examples of other's work, and your car's shape won't change much from the others.

Information and Specifications Gathering is the step where you must go out and source the parts for your car. Whatever you cannot buy, you must fabricate, and 9 times out of 10 it costs more to fabricate, so off-the-shelf will result in lower cost. Fabrication does have it's advantages in that it allows for absolute control and optimization, an important feature in looser rule classes.

Whatever the course of action for a particular part, it is important to know the dimensions, weight, and features that apply. Catalog or record these figures for later reference. Collect brochures, and any other product information suitable--the internet has a wealth of companies offering specs and catalogs.

Use a checklist of parts that the car will need, and collect several examples to chose from when dealing with race-critical parts. This checklist will be used later when design requirements meet available parts

Rough Part Selection can be accomplished by first verifying that each of the available part models can do the job. If one can't, it's eliminated. Then, on the second go round, considerations such as space (volume) required, weight distribution characteristics, and aerodynamics can be evaluated and parts which don't fit can be eliminated. Repeating this process will usually get you down to 1 to 3 possible models. Always save your data. If requirements change somewhere else on the car, it may make a part you eliminated, feasible once again.

The part selection process is somewhat simplified if you use your earlier sketches of the car as templates on which to draw the "spaces" occupied by each part on the checklist. Alot space, according to your research, keeping in mind weight distribution (Front/rear/left/right), safety, aerodynamics, and all the other effects the part has depending on placement. Work out several different layouts if you like, and consider later servicability.

The Preliminary Design is where you translate the pictures you created above into a physical layout. You must focus on connecting all the parts, with small particulars like nuts and bolts left out of the picture, except where suspension and driveline are concerned. The idea at this stage, is to get a starting point. Then, you can use that baseline later when the REAL design work begins. It is a good idea to use CAD or Solid Modeling software for these tasks, as they are easily revised.

Part Re-Selection or Re-Design is the next step. When you study your preliminary design, you should evaluate it for it's acceptability in terms of performance, safety (think impacts from all four sides, and rollover) and efficiency (how well it works for it's weight and size). If there are conflicts in the design, or areas that can be improved, make the change, but keep a baseline copy to go back to if the idea didn't work.

The Final Design is not really the final design. Actually, it is the complete design. This is where you pull out the drafting paper (hard work), or start your solid modeling package (easiest). The goal of this design is to assemble the entirety of the parts you have in the design into a cohesive car. If suspension geometry wasn't considered prior, it is your last chance to consider it without redesigning. The saying "Built from the ground up" is true. No race can be designed without starting at the rubber contact patches, and working toward the chassis.

To simplify life, Final Design Testing can be done if you have the right software. These tools consist of Finite Element Analysis (FEA) to test tortional and structural rigity for chassis, Fluid Dynamics to test aerodynamics, and even tools that allow for ergonomics testing. They are generally costly, but can be very helpful.

Assuming everything has gone well, the Final Design Refinement and Completion will consist of small changes and verification that all parts work together, do not bind, etc. At this stage, it should be clear where every bolt goes, and how many bolts there are in the car. If it's not clear, then you need to complete your final design. More often then not, this will mean going back to research some more to find solutions to problems or shortcomings.

Construction, Preliminary Testing, Car Analysis and Refinement and Future Development notes are planned for the future.

The Race Car Design Process

Outlined in the table below is order in which major components of the race car can be designed, and some of the related aspects you will need to consider (There are many more than what are shown!)

Order of Design	Component	Considerations
1	Tires/Wheels	* Wheel appropriate for application * Tire appropriate for application * Wheel matches the hub/rotor * Available rotors and calipers are appropriate. * Unsprung weight is acceptable
2	Hub/Rotor assembly, Wheel bearings, spindle, Uprights ("At the wheel" suspension)	* Hub/Rotor appropriate for application * Same for bearings/spindles * Upright/knuckle design * Suspension geometry design * Loads affecting these components
3	Suspension wishbones/axle shafts, housings	* Strong enough for application * Aerodynamics for exposed wishbones * Mounting positions on chassis
4	Shocks/springs/anti-roll bar	* Shocks/spring/anti-roll bar appropriate for application * Mounting considerations * Leveraging (pivot) considerations and mounting * Spring/damping rate appropriate for travel, adjustability, vehicle weight, etc.?
5	Steering	* Steering ratio * Left/right wheel movement (Toe in/out) through suspension travel * Mounting location on chassis
6	Driver cockpit	* Strong, intrusion-preventing safety cell for the driver * Good ergonomics for controls and seating. Good visual field * Pedals/Steering wheel positioning correct for driver * Position for weight distribution * Appropriate steel tubing, bend radius for roll bar. * No protrusions that could cause injury to driver
7	Driveline	(This step could arguably be with suspension and steering, as it guides motor placement, if that course is preferred) * Determined torque handling for chassis * Mounting of differential * Driveshafts/Chain * Path of driving force not a wild angles * Proper materials used in high stress drive shafts/half shafts
8	Engine placement and mounting	* Determined torque handling for chassis and mounting positions * Exhaust clearance and temperatures * Fuel and air delivery * Cooling system proximity * Weight distribution * Transmission placement/weight
9	Fuel Cell	* Positioned as far away from driver as possible * As close to center of gravity longtitudinally and laterally, but as close to the ground as possible vertically * Relative position to engine * Fuel pump or delivery * Safety level (Degree of protection) appropriate * Mounting in chassis * Refuelling opening is located away from driver
10	Electrical/Engine Management/Battery	* In accessible location, for maintenance * Relative close position to engine * Battery located anywhere, but use for weight distribution
11	Front chassis	* Chassis structure focused on handling forces generated by suspension mounts and steering * Addresses safety, preferably through extended crumble zone(s). well ahead of the driver's legs.
12	Driver Safety cell Chassis	* Chassis structure focused on handling forces from side, frontal, and rear impacts as well as rollovers. * Anti-intrusion panelling to protect driver * Position for weight distribution
13	Rear chassis	* Chassis structure focused on handling forces generated by suspension mounts, as well as driveline torque * Addresses safety, via impact zones, or at least prevents engine intrusion into cockpit.
14	Bodywork	* Light as possible * Aerodynamically attains goals of design * Optimizes air flow allowed by class rules

There are quite a few more. The point however, is that the more you understand about the car you are designing, the more you will consider when designing.

You will notice that the suspension is first in the design areas, then the engine, cockpit, electrical, and safety concerns are addressed. Finally, the chassis is designed around the requirements created before it. Each aspect listed above can be thought of as requiring you to consider every other aspect further down in the list. So, to select the tires and wheels, you must consider the entire car's dynamic requirements right through to aerodynamic shape.

Two final words of advice. First, know the properties and parameters of what you are designing by consulting racers in your intended class. Second, understand the fundamental workings and physics affecting your race car. Combine the two, and you will understand what needs to be where in your car, and how strong everything needs to be to hold out for that chequered flag!

Move on to "Starting From The Rules" >>