Chassis

The chassis is the main component of an RC car to which all other parts attach in one way or another. By definition, the chassis is the rigid "plate" that holds together the main components for power, transmission, steering, suspension and radio connectivity. It exists in many shapes and sizes from low-end plastic budget chassis all the way to high-end carbon/graphite chassis.

In the RC community, the chassis term is widely used to refer to the semi-complete or complete base for a car including the chassis plate and all the components for steering, suspension and transmission. A car sold as a complete chassis without the electronic components is known as a roller in opposition to Read-To-Run (RTR) models.

Overview of an RC chassis

An RC chassis is the sum of all parts of an RC car minus the body and radio. It holds several different systems that are attached to the chassis and work together during normal operation of the car.

Overview of the components of an RC chassis (Electric)

The chassis plate(s)

Graphite chassis (lower) plate

The chassis plate is a rigid part that serves as the backbone of any RC car. As a part, it is pierced with holes to attach other parts onto it using screws. A chassis may have more than one plate (an upper and a lower one) as well as reinforcing bars for additional rigidity.

It may be pierced with larger venting holes or have places with less material than others in order to:

• Enhance rigidity or flexibility
• Reduce the weight of the chassis plate and the overall weight of the car
• Allow for parts to protrude below (for example for large spur gears)
• Enhance ventilation of the electronic components
• Enhance aerodynamics of the car

Chassis plates may be made of one or several materials depending on the range of products, the targeted users, the targeted usage and price range. Lower end chassis are plastic or fiber-reinforced plastic while high-end chassis are built in aluminium, graphite or wooven carbon fiber or a mix of those materials.

Each materials has its own strengths and weaknesses. The choice of material will depend on the application the car is intended for. The main considerations for chossing a specifi chassis material are stiffness, weight, durability, cost and availability.

Impact of chassis plate material flex on a car behavior

Depending on the chassis plate material, the overall chassis will have a certain amount of flexibility or rigidity and impact the car's handling. The front to rear suspension stiffness, along with chassis flex, will determine how weight is distributed to each tire during cornering. The suspension stiffness is dependent on the springs, shocks, sway bars and suspension geometry.

If the front stiffness is greater than the rear, the front will tend to lose grip first and the car will experience under steer. If the rear stiffness is greater than the front, the rear will tend to lose grip first and the car will experience over steer. This weight transfer effect is what allows RC drivers to tune the corner balance of their RC cars.

A chassis that is too flexible will twist and the weight will not transfer adequatly to the tires. The amount of twist will be impacted as cornering loads raise. In return, the car will handle differently during high speed cornering than it will during low speed cornering which could be desirable in certain situations if intended. The downside to chassis flex is that suspension adjustments become less effective than with a stiffer chassis. Changing the spring rate one step with a stiff chassis might require a two step change with a softer chassis.

The consideration of chassis flex is true for racing drivers but today's casual hobby cars are designed to be very versatile. Still, considering the application intended for a car is paramount when selecting the chassis plate material.

Plastic chassis

A plastic chassis

Since plastic is durable and inexpensive to manufacture, it is the material of choice for most Ready-To-Run (RTR) kits. Since plastic is injection molded, RC car designers can create complex shapes, limiting the number of parts in a kit while reducing its cost and the price to the consumer.

Plastic offers a low resistance to stress hence plastic chassis are often tub shaped with ribs for extra stiffness and require the most material to achieve an acceptable level of resistance and durability. In general, plastic chassis are the softest and allow for the most flex but they remain the most cost effective.

Fiber-reinforced plastic chassis

Fiber-reinforced plastic has strands of fiberglass or carbon fiber mixed in with the plastic resin. This material looks very similar to ordinary plastic however it is much stronger, lighter and stiffer. It is usually seen as an upgrade to plastic except when a driver needs a chassis which flexes.

Even though fiber-reinforced plastic is stronger than regular plastic, it will not bend as far without breaking and this is even more critical in low temperatures, rendering the material brittle.

Various systems mounted on the chassis

The chassis plate being the backbone of the RC car, various systems then attach to the plate(s) and compose the car chassis. Each one is paramount to the overall behavior of the car. It is the homogeneity of the various systems that makes a car perfom properly.

The transmission system

Transmission gears

The transmission system is a set of components working together to transfer the power generated by the engine or motor to the wheels thus making the car move and keeping it moving. Combustion engine and electric RC cars might have different transmission systems but the purpose and end results are the same.

See the Transmission system article for more detailed information.

The suspension system

Suspension and schocks

An RC car suspension system is a set of components working together to make sure that under normal conditions, all four tires are touching the ground. It allows for optimal stability and handling, sends the car in the direction the driver wants, keeps bumps and potholes in the road from breaking parts or loosening screws and handles all the forces from acceleration, braking, and cornering.

See the Suspension system article for more detailed information.

The steering system

The steering system on an RC car is a set of parts working together to turn the wheels of the car. The steering movement is made possible by an electronic component called the servo (a small electric motor) which transfers its power to the steering linkage mechanism, turning the wheels and the car left or right.

Most RC cars will have front wheels steering but some cars offer 4-wheels steering.

See the Steering system article for more detailed information.

The electronics

An ESC and electric motor

Electronics in an RC car are a combination of electronic components working together to drive and steer the car. They differ between electric and combustion engine vehicles, with an electric vehicle using an electric motor and electric speed controler which are not present in an engine car. The common electronic components in an RC car are:

• The electronic speed controller (ESC): to translate radio order from the drivers into motion for the electric motor
• The electric motor: to power the car in electric RC cars
• The servo(s): to turn the wheel and in engine cars to activate the throttle
• The receiver: to convey the driver's orders from the radio transmitter to the ESC

See the Electronics article for more detailed information.

The radio communication system

Radio transmitter and receiver

The radio communication system of an RC car is a combination of electronic components and devices working together to control a vehicle from a distance. It uses a standalone self-powered radio transmitter that sends radio waves to a receiver in the car. Upon receiving the signal, the receiver transfers it to the Electronic Speed Controler to power the car or to the servo to turn the wheels.

The main components of the radio communication system are:

• The transmitter: usually holds a wheel and trigger to control steering & power then sends it over radio frequency to the receiver
• The receiver: a small on-board device that transfers the radio signal from the transmitter to the servo and the ESC

See the Radio-Communication System article for more detailed information.

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