Pickup Truck (Scratch-built)
The scratch-built truck (Sometimes referred to as a "NASCAR truck" or pickup truck racer) is a circuit racing vehicle that resembles a pickup truck, but in fact uses a tube frame like NASCAR Stock Cars. It is an offshoot of the NASCAR Stock car racing, and shares much in common with stock cars.
The scratch-built pickup truck is characterized by a tube frame chassis with a high horsepower engine mounted at the front which drives the two rear wheels. The suspension design and chassis place the truck very close to the ground for the lowest possible CG (Center of gravity). The chassis is covered with formed sheet steel bodywork that gives the shape of a pickup truck. A rear spoiler provides downforce.
UK Racing is through a spec manufacturer only and the NASCAR truck series is prohibitively expensive for an amateur racer, but the type is included in our race car types because of its potential future in local racing. This type of vehicle can be raced in the top-level of Autocross/Solo.
Racing events are held on oval and road course circuits in the USA and UK.
Pickup Truck (Scratch-built) Contents
|Power and Weight Stats|
|Horsepower (Typical Range)||450-700|
|Race Weight (Typical Range)||1611-1679 kg
Design and Construction
Race Car Models of This Type
NASCAR Truck, Pickup Truck Racer (UK), Autocross
Build Your Own Scratch-built Pickup Truck
Due to the scratch-built nature of these pickup trucks, the designer should be knowledgeable in handling, chassis, suspension, powertrain, aerodynamic and safety design. These six major areas of the truck design work as an integrated unit and the designer must have an understanding of how changes to one area affect the others. Much of the design work is iterative, meaning re-designing areas based on new changes to another area. After the iterations are completed, the design will be complete and optimized.
Weight Distribution: Typically the front will be heavier in front/rear weight distribution due to the front-engine configuration. However, most engines are set back between and slightly behind the front of the front wheels, giving a more favourable weight distribution that is almost balanced. Left/right weight distribution is adjusted depending on the type of circuit. The lowest CG possible within regulations.
Suspension: Maximizing the contact patch of the tires with good suspension geometry is of key importance.
Suspension, wheel and tire weights (Unsprung weight) affect the compliance of the suspension, which in turn affects handling, so keeping all these components as light as possible is an advantage. Springs and dampers (shock absorber) must be matched to the suspension geometry and calculated forces.
Front suspension utilizes unequal length a-arms. Rear suspension utilizes live axle configuration.
The suspension pickup point locations impact the chassis design.
Chassis: The chassis is very close to a NASCAR stock car—A tube-frame chassis with some triangulation. Designing torsional rigidity into the chassis will give predictable handling as the chassis will not twist unduly affecting the suspension performance.
Powertrain: Weight distribution is heavily impacted by engine position, so placing it as far back as permitted and safe as part of a near balanced weight distribution is preferred. Intake, Cooling and exhaust need to be considered in relation to chassis design, bodywork and aerodynamics.
Aerodynamic: Front air dam and rear spoiler are used to generate downforce. Using airflows to perform a function (i.e. cooling) while using the flow for another purpose (say downforce) reduces the drag penalty over using two separate flows. The brakes in current designs are cooled with intakes at the front of the truck. Cowl induction at the base of the windshield provides a pressure boost for air going to the engine. Depending on regulations, more opportunities may exist.
Safety: The chassis of the scratch-built pickup truck integrates a substantial crash/rollover safety cell with racing seat and racing harness. Fuel safety is provided via a fuel safety cell while fire protection is provided with an integrated chassis firewall. Front/side/rear impact protection is usually provided by stock car-like tube structures integral to the chassis.
If you intend to race under a sanctioning body, always read and understand the regulations of your chosen racing class before designing or building any race vehicle.
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Ensuring the chassis is dimensionally accurate and straight is important as flaws in the structure will create handling issues via misaligned suspension. The use of a solid, flat and level build space is important. Jigs are often used in this case to ensure that structural tubing stays in alignment during welding/brazing.
The builder should have solid joining and metal working knowledge and skills when fabricating the chassis/rollcage/suspension. While mild steel (1018/1020) is very forgiving, some metals are best welded using a specific method (mig/tig) and some require heat treatments before and following welding to restore their toughness and strength.
Most parts for a scratch-built truck can be purchased as racing components via NASCAR suppliers. For lower power/budget trucks, aftermarket companies may offer more economical, yet durable components. The ultimate cost depends on the path chosen.
The chassis cost to fabricate will be primarily felt in tools and materials and especially effort.
As the truck is scratch-built, there will be significant effort in design and construction. There is however, an equally great satisfaction and sense of accomplishment at being one of the few people in the world who have built their own race truck from the ground up!
Tires and fuel probably form the single largest consumable expense along with engine rebuilds and body repairs.
Transportation and Support Equipment