We all know, chassis designing is not a day job and is very crucial for performance, stability, durability and strength of the car. Chassis (for beginners) is the bare-bone of the car. The most basic and most crucial component to which all other components of the car, like suspension, body panels, engine, front and rear fender assembly and everything else is integrated, which makes it also a specification dependent design component, meaning, to design it, you must already have all the specification sheets and a basic chassis idea in your head. And, the best way to design a good chassis to fit your all components is to start with a cube of a definable length x width x height and roughly start adding components into it. Well, in this series of chassis design I'll start from the basic of it and will take you through types of chassis, types of loads on chassis, contributing factors to chassis design, chassis design, stress and torsion analysis methods and finally Computational FEM.
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Well, for the starters, we always need to remember one thing during chassis design, the higher the ground clearance, the reduced will be the stability of the car; thus, the COG always need to be at low as possible. Now, there are many layouts of chassis designs which are:
1) Ladder: This chassis is the most basic chassis design with good stress load capability but lacks torsional bearing capacity completely. The design is very simple, it used a uni-planar parallel shafts joined with each other using cross-members just like in a ladder and hence the name. The parallel shafts and cross-members are responsible for all load bearing capacity and all intersection points are the high stress regions, one should not reduce the load bearing capacity at these regions by adding holes.
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2) Backbone: In simple words, it is opposite of ladder design when it comes to functioning. The backbone design is targeted towards reducing high torsional profile where the front and rear axle are connected with each other using a single multi-sectional solid/hollow rod which removes the torsional forces off the vehicle.
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3) Body-on-frame: It is the most appreciated chassis design after unibody chassis design, every car manufacturer has used this design in every vehicle at one point or another. The body on frame design is very similar to ladder design but it takes into account components like center of gravity and torsional force very seriously. The design includes elongated parallel shafts for more reduced stress profiles and added reinforcements on intersections to reduce the torsional force profile. The benefit of the design is that body is mounted on the frame which reduces sprung mass and also reduces COG.
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4) X-Frame: A perfect fusion of ladder and backbone chassis design. The system looks into both stress and torsional profiles on the design. The design includes 2 parallel rods connected diagonally with X structure starting from front axle to rear axle. The design increases the surface area as to reduce stress profile and because of X intersextion, the torsional capability is increased.
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5) Unibody: It is the most popular and advanced design which is specially designed for mass production and the whole process is carried out on a single piece of material from which material is then reduced to get the required shape. The designs are designed in softwares like CATIA V5 and they are of industry standards, because of mass production, CNC machines are used for the process. The design is carefully designed with regular updates with analysis using Computational FEM softwares like Ansys, Hypermesh etc.
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6) Monocoque: The easiest way to understand monocoque design is to think yourself as you don't have bones and you are living because of strength of your nerves. The monocoque design doesn't have a designed structure but the body panels serve as the load bearing components. The design was high unappreciated due to obvious reasons and presented very poor results against stress and torsional analysis. One might easily confuse monocoque with Unibody, the difference is that, the Unibody design incorporate structural components that works as frame.
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7) Spaceframe: Spaceframe chassis design is considered as the best design for prototyping and is highly popular in motorsports because of two reasons, first: the design is made of hollow narrow pipes of small lengths; second, it corresponds to pyramidal shape which is considered as strongest in dissipating force over the entire structure. The array of such shapes completely disintegrate torsional and lateral forces from the structure and the design shows best restrain towards car crash test.
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8) Stressed member engine: One can also say it as minimal chassis design or frameless chassis design. The system is most popular for bikes and engine plays the major role in deciding the stress and torsional profile of the design. The design mounts the engine and make it the force bearing component. Also, it is made sure that COG of the vehicle is as close to engine as possible for best stability and control over the vehicle.
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9) Subframe: The subframe chassis design is best for innovation in the field of chassis design, the chassis is essentially divided into more than 1 component and each component may/may not be independent of each other. Subframe designs are most popular for kit cars and Do It Yourself Cars. Also, since each component is independent, one can easily do changes in the chassis to reduce stress and torsional forces as per the requirement.
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10) Superleggera: Ring the bells? Superleggera or in Italian, "light weight" is a special division of chassis design which incorporates materials like carbon fiber rods, titanium pipes and other innovative components to increase strength of the design while reducing the weight of the car. Many high end vehicles like Lamborghini Murcielago/Aventador, Aston Martin Vanquish and many more have special superleggera editions.
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Thus, in this article we discussed about various chassis design and their characteristics from which one can opt for making his/her own design, in upcoming articles we will start explaining different types of loads that are found in vehicle and then stress analysis methods.
hie guys,i am trying to design a braking system similar to abs,on a miniture locomotive,mounting a speed sensor on the axle for a feed back,is it possible.any advice will be greatly appriated
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