The chassis
Probably the most complex issue on the entire vehicle.
Table of contents
- Introduction
- Construction
- wheelbase
- Gauge
- Ride height/neutral position
- Compression and rebound travel
- Caster, camber and track
- Ackermann steering
Introduction
This is where everything comes together. Wheelbase, track width, weight, weight distribution, torsional rigidity of the frame, steering structure. All of these factors play a role even before the chassis has been designed. Then there are things like track, camber and caster.
All of this can be influenced to make the car extremely performant.
After the frame has been built, the wheelbase has been determined and all factors of the frame have been optimized, the next step is to build a functioning chassis.
Disclaimer
The structure of this page is, for the most part, organized according to relevance to building. Please read completely!!!!!!
There are some things that I don't fully address, or even at all. This is because these things are not relevant or cannot be changed in cars.
Construction
There are different types of landing gear types. McPherson, rigid axle and many more. All have advantages and disadvantages. I decided on the double wishbone axle. It is very easy to build, very stable and very adaptable.
Wheelbase/Wheelbase
The wheelbase is the distance between the front axle and the rear axle. This decides how agile the car is at what speed. This will already be the case Frameconstruction determined.
A short wheelbase is recommended for a winding route.
- the car becomes more agile and maneuverable
- but is more difficult to control at high speeds.
A long wheelbase is recommended for a route with long, fast straights.
- the car becomes more sluggish
- but is much more stable at high speeds and is easier to control
I simply based myself on a 1:10 touring car and a wheelbase of 257mm chosen.
The general thing to say here is to start with real RC models. They work and make it easier for us to build the car
Gauge/Track Width
The track width is the distance between the left and right wheels (center). This decides how agile the car is at what speed.
A narrow track width is recommended for a winding route.
- the car becomes more agile and maneuverable
- but is more difficult to control at high speeds.
A wide track width is recommended for a route with long, fast straights.
- the car becomes more sluggish
- but is much more stable at high speeds and is easier to control
I simply based myself on a 1:10 touring car and a wheelbase of 200mm chosen (common: more like 190 mm).
The general thing to say here is to start with real RC models. They work and simplify the construction of the car.
Ride height
The ride height is the same as the neutral position of the chassis. It is the height of the vehicle when stationary with only the load of the vehicle on the chassis.
The ride height is defined by the installation position of the shock absorber and the strength of the spring. The ride height must of course be adapted to the needs of the route or intended use. Below I will go into the different axle parameters such as toe and camber. Very important here, these parameters change when the height of the chassis changes!
Compression and rebound travel
At this point I would like to clarify a few myths from the world of terminal blocks. A good chassis is not defined by a tough chassis, which simply means that the car is fully rebounded in neutral. Of course, a racetrack car needs harder springs for smooth tracks. However, even a racetrack car needs downswing.
Example:
When the car drives through a bump, the chassis should rebound and thus ensure that the wheels are in contact with the ground even in the bump. Especially when there is a strong change in load (for example, suddenly accelerating), the car can swerve in such a situation without making contact with the ground.
When cornering, the car deflects on the outer wheels. If the inner wheels did not rebound, they would lose contact with the ground.
Another myth is that a Lego shock absorber cannot be called a shock absorber. Strictly speaking, it's just a feather. A full-fledged shock absorber consists of a, usually, hydraulic damper and a spring. This damper is there to slow down the up and down movement during compression and rebound and to stabilize the chassis again. In other words, the vehicle absorbs a shock and immediately returns to neutral. Just one spring would cause the car to tend to swing. This would result in a massive loss of traction and the car would be difficult to control!
Correct shock absorber = chassis works correctly
Lego "shock absorbers = chassis rocks
Caster, camber and track
These are the axle parameters that can be changed and have a significant impact on the performance of the car. This is where things get a little tricky, as some parameters influence each other and change depending on the driving situation.
Disclaimer
Some parameters can only be changed to a limited extent and some only in connection with this Wheelhub 110t.
Wheelhub 110T
Only with the Wheelhub 110T do you have the opportunity to influence all parameters.
The default is:
- 2° camber Va and Ha
- -1° single track VA
- 3° single-pure HA
The camber is adjusted depending on the height of the car. Higher means less fall and lower means more fall.
By changing the camber you automatically change the track. That's why I recommend installing adjustable tie rods.
trailing
Caster is the inclination of the steering axis to a perpendicular to the road. To understand, the steering axis is the axis around which the wheel rotates when steering.
A positive caster, the steering axis ends before the vertical, causes the steering to want to return to a straight position by itself. The bike runs much more stable. Another effect we need is that you have a certain amount of camber when steering, which greatly improves cornering stability.
With the space frame you cannot adjust the caster continuously. This is generally very difficult or even impossible.
Strictly speaking there are 3 positions.
- 0° = only relevant for rear axle
- 4° = for the front axle
- 8° = not relevant
In general you can say that the caster on the front axle should move in the range 4° - 5°. It is negligible on the rear axle.
Fall
This is called a fall
angle between the center plane of the wheel and a vertical line to the road. To put it simply, camber is there to compensate for play in the suspension and deformation of the tires when cornering. This ensures that the tires rest on the road with maximum surface area and therefore have maximum contact with the ground.
Spur
The toe angle is the angle between the longitudinal axis of the vehicle and the wheel. The longitudinal axis is an imaginary line through the car from front to back. However, a distinction must be made between individual tracks and overall tracks. The individual track only considers one wheel. The overall track includes 2 wheels on the same axle. The overall track of the front and rear axles also play a major role. If these are set incorrectly to each other, both axles move offset from each other and the car corners differently.
The Wheelhub 110T comes preset -1° on the front axle and 3° on the rear axle. Both values are the single track. I still recommend buying adjustable ones in order to be able to adapt the track perfectly to the vehicle.