Chassis for a car is analogous to the skeleton for a human body. Chassis, also known as ‘Frame’, is the foundation structure of any car that supports it from underneath. The purpose of the chassis is to bear the weight of the car in its idle and dynamic states. Given that, most people don’t get to choose the chassis of their car and many may not really care about them as much.
What Is a Chassis In Car?
The chassis is a car frame that has a function as a support for the engine and passenger car body. This chassis is usually made of iron or steel with a certain composite.
“Chassis” is a term that should be used to refer to the load-bearing part of a car’s frame. It is the horizontal section of the vehicle that connects other components of the structure together.
The chassis is a set of mechanical components that make it possible to transfer power from the drive unit to the wheels. Moreover, the components used in this part of the vehicle‘s design have quite an impact on the car’s driving behavior. The chassis includes several systems that play a key role in the operation of the car: braking, steering, drive and suspension systems.
The Chassis has the following functions.
- Supports or bears the load of the vehicle body
- Provide the space and mounting location for various aggregates of vehicle
- Supports the weight of various systems of the vehicle such as engine, transmission etc.
- Supports a load of passengers as well as the luggage
- Withstands the stresses arising due to bad road conditions
- Withstands stresses during braking and acceleration of the vehicle
Chassis Basics
Probably the largest part of your vehicle you aren’t familiar with, the chassis forms the basis for the rest of the vehicle. Without it, there’s no place to mount the engine or the wheels and nowhere for you to sit, but we’re talking about more than the frame, if the vehicle even has one!
Basically, the chassis is everything that’s needed to make the car move:
- Frame or Unibody – Everything else attaches to this, the strongest part of the vehicle.
- Suspension – Control arms, springs, struts and shock absorbers provide for directional stability and a comfortable ride.
- Steering – Steering gear controls vehicle direction.
- Engine – Provides motive force to get your vehicle from place to place.
- Transmission & Drive Shaft – Steps down engine rotational force to a more manageable speed.
- Differentials – Splits transmission output left and right, sometimes forward and back, to balance differing wheel speeds based on turning and traction conditions.
- Drive Shafts & Axles – Transmit torque to differentials and individual wheels.
- Wheels & Tires – Transmit torque to the ground.
- Brakes – For when you need to stop!
In the beginning, all vehicles were body-on-frame construction or body-on-chassis. After building the chassis, the body would be dropped on top of it. The body is basically a shell that bolts to the car chassis. Then, the doors, roof, windows, seats, carpets, airbags, dash, instrument panel, controls for the transmission and steering, air-conditioning, radio, and cup holders are added.
Types of Chassis
The following are the types of chassis:
- Ladder Frame Chassis
- Backbone Chassis
- Monocoque Chassis
- Tubular chassis
#1. Ladder Frame Chassis.
Named after the shape it replicates, the ladder-frame chassis is one of the oldest chassis types. This chassis is characterised by two long heavy beams that are supported by two smaller ones.
Its quality of being easily manufactured not only made it contemporarily popular but also eased the way for its mass production. Since ladder frame chassis is significantly heavy it’s usually used for vehicles that transport heavy material.
Advantages
- Easier to assemble as parts can be easily put in.
- The construction method makes it quite tough.
- Easier to fix as parts are not permanently attached.
Disadvantages
- The ladder chassis has a weak torsional rigidity making it bad for cornering.
- Heavyweight makes it not ideal for sports cars or hatchbacks.
#2. Backbone Chassis.
Similar to the ladder frame chassis, the backbone chassis is also named after the shape it reflects. The hollow rectangular cross-section and a cylindrical tube passing through it connecting the front and rear suspension, like a backbone. The cylindrical tube surrounds the driveshaft. You can find backbone chassis in one of the most popular cars, Skoda Rapid.
Advantages
- Due to its construction, the half axle has better contact with the ground when off-roading.
- The driveshaft is covered by the chassis makes it more likely to survive off-roading.
- The structure has good torsional rigidity allowing it to withstand more twist than ladder chassis.
Disadvantages
- The driveshaft repair is complicated if it fails as the main chassis covers the entire shaft which makes it necessary to open it.
- The manufacture of backbone chassis is quite expensive which increases the cost of cars it is in.
#3. Monocoque Chassis.
Monocoque is French for ‘single shell’. This unibody frame is named after its structural outlook. The monocoque frames were firstly used in ships, next in aeroplanes, and manufacturers took quite a while to find them pertinent for cars as well.
A monocoque is like an endoskeleton of a car crafted by fitting chassis and complete basic frame in a single unit. Monocoque chassis is the most popularly used chassis as of now given its number of advantages over the other two types of chassis.
Advantages
- It’s safer than both the other chassis due to its cage-like construction.
- The chassis is easy to repair as well.
- It has superior torsional rigidity.
Disadvantages
- The chassis is obviously heavy as it’s both the frame and chassis as one single entity.
- Producing it in small quantities is not financially feasible and thus it cannot be used for cars that are not mass-produced.
#4. Tubular Chassis.
A three-dimensional derivative of ladder chassis, Tubular chassis are mainly used in performance cars given their excellent safety. Rarely seen in passenger cars, tubular chassis is much stronger than ladder chassis and they popularised the utilization of stronger structure underneath the doors to accomplish more consolidated strength.
Advantages
- Better rigidity compared to other chassis in the same weight.
- Offers the best weight/rigidity ratio allowing the car to be lightweight while being strong.
- Best choice for race cars due to lightweight and better rigidity than other chassis.
Disadvantages
- Tubular chassis are complex structures and cannot be made using autonomous methods.
- Tubular chassis are time-consuming to build and cannot be mass-produced.
- Not feasible to be used on passenger cars.
- The structure raises the door which makes it difficult to access the cabin.
What Is the Difference Between A Chassis And A Car Platform?
A platform is another term you may encounter in the context of the lower part of a vehicle. However, it is a much more ambiguous term than frame or chassis.
When talking about a car platform, it is difficult to point to a specific part of the car, since it is a whole set of common structural, design and manufacturing features shared between different brands and models.
Car platforms are developed primarily to reduce manufacturing costs. By standardizing certain features of a vehicle, expenses can be minimized, as well as the time it takes to release a finished product onto the market.
A platform includes many components, only one of which is the chassis. In addition to it, car components such as the frame, suspension, drive unit, exhaust system or transmission can be standardized. Each manufacturer adapts its car design to these elements, if necessary, making appropriate adjustments to components that allow for it.