RC dragster chassis


If you choose to build you’re own chassis for your dragster, you need to take into account a number of important issues.


-Weight
-Stiffness
-Possibility of assembly
-Torsion


Weight of Rc drag racing chassis



The weight of the chassis of your dragster will naturally affect the performance. Building as light as possible is one of the priorities. Construction should however be solid. It is better to build solid and slightly heavier than too have a light build and have problems at the slightest bump.



Carbon Fiber Plate


With a chassis made of carbon, weight will not be a problem. Carbon Fiber Plate is inherently very light and stiff. This makes it ideal for a chassis / bottom plate. Virtually all modern rc drags have a carbon chassis. Of course you can remove as much carbon from a sheet as you want but do not start right away. First see how rigid things are when all components are mounted and assess whether you have sufficient stiffness. Carbon is stiff but in longer pieces it will be pliable.



Aluminum


With a chassis made of aluminum, you will soon notice that aluminum when overused is clearly heavier than carbon. For this reason, in most cases, as much aluminum as possible is removed to save weight. Aluminum will exhibit, at sufficient length, flexibility but is clearly less resilient than carbon. Once you bend the material you may throw it away because straightening is not an option.



Stiffness of a chassis


Stiffness in a chassis can be achieved by using a combination of carbon fiber and aluminum plate or using corner profiles and tie rods.
If you have looked at several chassis made by a number of different manufacturers you will see that the aim is that the profiles are perpendicular to the base stand. This can be in the middle or on the sides. Placed in the middle you will sometimes have enough when using 1 profile and save weight but you will need to divide other parts (battery, receiver, and servo) to the left and right side.
The option on the sides of the chassis gives more freedom but will result in more material. A final option is to use a so-called "double deck" this might be the best way to achieve the best of both. The attachment of a "pull rod" may in some cases be a solution to several problems at once.
Both with a rod as well as a deck construction you can catch the problem of sagging / bending and get the desired stiffness. A second advantage of these two structures is that the forces that the "engine mount" performs on the chassis are better distributed through the chassis. You will not get with this construction to put excessive force on the connection between the base plate and motor mount.



Possibility for the mounting of components on a chassis


Whether you've chosen a carbon fiber chassis, an aluminum chassis or maybe a combination of both, there are several components to be fitted on the chassis. Depending on the component there can be considerable forces released during the explosion of the acceleration. Parts that are really part of the chassis, such as parts that increase the stiffness, tension rods, and engine mount etc. should really just be bolted on the chassis. If possible go through the chassis. Aluminum can be relatively easy and precise drill and tap. Carbon is easy to reshape with iron tools. Fixate parts through the carbon fiber with bolts that may or may not end in the component that needs to be mounted. Do not try to glue or paste parts. Use screws that can be recessed into the base so you’ll keep clearance and the bottom remains smooth.


Rail chassis


Another option for a light and rigid chassis construction is a so called "Rail chassis".
Using this method, two carbon plates are placed vertically next to each other and connected with aluminum components. Its clear that the carbon plates in this construction can`t bend in the horizontal direction. The stiffness is achieved by the aluminum compounds. The only problem that may occur is torsion. Assembly of the various components on a rail chassis also occurs by screwing through the carbon. On the example beneath of an A51 EVO Sidewinder chassis (pro mod version) you can see what this means.

Pro stock rc dragster rail chassis

Torsion


Torsion forces will only exist if you mount the engine in the longitudinal direction of the chassis, or if you choose to use a drive with differential.

In the case of a longitudinally mounted engine, the engine body (the engine as a whole) will start to rotate because of resistance due to the shaft which is driven. These torsion forces ensure that the chassis (with insufficient rigidity) will be lifted on 1 side which in turn ensures that you will have a warping car. The solution can be found in the placement of both engine and transmission in a torsion-free housing. This is an expensive and material demanding solution. You make will make it so much easier on yourself when you just place the engine across the chassis.

Torsion may occur in the chassis with the use of a differential. In this case, it has nothing to do with the placement of the motor, but with the upward force exerted by the wheels have on the chassis. If the differential does what it is made for and is not blocked it can occur that one of the drive wheels does not have enough grip or just one more than the other. At that point, that side of the chassis will be pushed upward more than the other side and thus cause an undesired curvature in the chassis. This effect is reinforced by the wheel with the most grip which will even push forward harder because of the extra weight on that wheel.


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