Before I begin actual design procedure of chassis for RC cars, I want to throw some light on its basic concepts. And in this chapter you will get information about material selection, design procedure and different analysis of design. After completion of this chapter you will be able to design your own chassis with ease.
The chassis is a main component of the car, it's like a skeleton of human body; it holds other parts together and provides stability to vehicle. A good design of chassis assures proper stability. Chassis is the main and complex structure of the modern automobiles on which the engine, axle assemblies, transmission, steering mechanism, brakes, and suspensions are mounted in a proper manner, so that it can assure proper weight distribution on wheels as well as on chassis. This combination of the body and frame performs a variety of functions. Such as absorbing of reactions, that are generated from vibrations of the engine and axle, receives the reaction forces of the wheels in acceleration and braking, absorbs aerodynamic wind forces and road shocks through the suspension.
Material selection
The material selection is a very important step and plays a crucial role in design, Its proper choice can make your car an engineering marvel. So choose appropriate material for chassis, such that it must be lite and good at strength. There are different options available, such as the carbon fiber, plastic materials, metal sheets etc. And among those we choose aluminum metal sheet of 2mm thickness for fabrication in our project.
Following information about aluminum sheet helps us to make decision.
Following information about aluminum sheet helps us to make decision.
1. It is easily available material and less costly.
2. It has great stiffness property.
3. It will not need any pre /post processing operations as in case of carbon fibre.
4. Melting point is high, about 660.32 °C. As the engine is mounted over it, will heat the chassis.
5. Since it is smooth, and easy to give any shape by using simple and easy tools, such as profile cutter.
6. It has got good tensile strength of about 90MPa that is more than sufficient for fabrication of chassis for RC cars.
7. And density of about 2.7 x 103 kg/m3. That makes it lighter metal, and most appropriate for RC cars.
Following is a photograph of metal plate that is used for fabrication of chassis.
Design concept:
During designing period of our own chassis, we studied different kinds of chassis, such as integrated chassis, tubular chassis etc. So on referring them, we came to the conclusion for fabrication of the integrated chassis, and following are concluded points those helped us to go for it.
1. It is easy to fabricate within a time.
2. It has more strength compared to other kinds of chassis.
3. It provides the good stability to vehicle.
4. It is less fragile in case of crashes.
Following are some pictures of standard chassis which are referred by us.
Just by choosing an appropriate material and giving it your desired shape will not contributes for good design. Instead it’s a complex procedure, includes lot of mathematical calculations and trials. So before going to fabrication process please make sure that your design is mathematically correct. It includes stress, strain, shears force and bending moment analysis, but I am not going to explain them here. For this purpose lot of softwares are available in market such as CATIA V5, Pro E etc if you are a student, then you can get them from your collage for free, we used CATIA V5 for designing of our RC car chassis.
During process of design we created and analyzed 4 different chassis as shown below and all fall under same category i.e. integrated chassis. Following is figure of our first conceptual chassis.
Chassis 1
This is our first design. It is quite simple, and we got this idea by referring 4 wheel skates, if you are a beginner then a skate can help you a lot to get good design Ideas. But we drop it only because of its weight. Just have a look at a figure given below and you will definitely get good concepts about design.
Skate
Chassis 2
This is improved version of Chassis 1. But our project needs little bit extra space.
Chassis 3
This appears to be a good design. But during analysis we found several flaws, such as weaker points that are vulnerable to severe damages specially during jumps, its weight is below desired, complex to fabricate etc.
Chassis 4
This is our final design and fulfilled all our expected needs. One more thing I want to clear i.e. we are not inventors or discoverers of this chassis. We just applied a reverse engineering methodology and redesigned a chassis that we bought from a Mumbai based vendor for our first race. If you are new to term reverse engineering let me explain. It is a process where you have to develop a product from scratch by taking reference of existing one. And in the end you will get a marvel that is far more superior to previous. If you still need more information about reverse engineering then only Chinese can explain it in far better way.
Following is a figure of our final design of chassis that is drawn using CATIA V5.
Fabrication of chassis:
There are lot of options available for machining of chassis; such as laser cutter, profile cutter, by hand using Hacksaw blades etc. But material used is an aluminium sheet that is soft metal. So we used the profile cutter to give desired shape. A typical profile cutter looks like as shown below and we used it for our project.
Mounting different parts on a chassis is a crucial process and for this you have to consider various analysis reports such as shear force, bending moments. In our project we did all those processes.
These reports really helped us to mount different parts on chassis in such a manner that assures uniform weight distribution of parts on chassis. Once decision is made then we used drilling machine to make holes and counters on it, to mount parts and screw them together. Finally we used bench vice to bend certain parts as per our design. In below photograph you can see layout of chassis on plate before fabrication.
Following is a photograph of chassis taken after complete fabrication.
Our chassis dimensions are as follows.
1.
Length: 38.5cm.
2. Width: 14.5cm.
3. Thickness: 2mm.
4. weight: 210gms
This ends this topic, and I hope this information will definitely help those friends, who are beginners to world of RC cars. If you have any doubts and suggestions, then please mail me at bpr890@gmail.com .
Thanks and Regards