RC Viper ACR - Hardware & recuperation
I decided to explain step by step all the technology used in my last project - RC Viper ACR, and the first is hardware and ERS. So, let’s take a look at what we have here.
This model is first and for some time the only one of its kind, but it does not mean that it will be parked somewhere on the shelf. If we have a race car, we do not leave it in the garage but we drive it. That’s why I had to depend on the selection of the chassis and I used all my knowledge about the construction of racing cars. For this project I decided to use the chassis from 3Racing, namely Sakura Sport XI. On front-wheel drive, I chose a fixed axis instead of the differential. It is for this reason, that when we have one wheel in the air on differential, such as when we are passing apex, it spins more quickly, a second wheel that touches the road slow down, which take the car from the ideal track route, in some cases it may end up twisted into hours. The fixed axis ensures a better drive of the front axle. On rear wheel drive is applied differential with variable stiffness. The rear axle is contrary to the front seated higher, like on the F1 car as the RB12, to transfer the overstrain on a particular side of the model and thus to prevent wear of the rear wheels.Front and rear axles have installed the stabilizers, which means that between the left and right wheel is a physical connection. The pressure at a one suspension is transferred to a second,
extinguished axle vibrations and reduces the risk of tipping over when cornering at high speed. In cornering, the car winds through the stabilizer to the top of the bend and then transfer the center of gravity, reducing understeer and allows faster trips. To this also helps the mentioned construction of the rear axle. Chassis assembled like this ensures, that the model is perfectly balanced, it has a perfect distribution of power and keeps track. The used materials are FRP, aluminum and plastic. The final weight is 416 grams, which is very little to the similar chassis in 1:10 scale.
Motor - Turnigy 5200kv
Esc - Turnigy 120A
Servo - Carson 5Kg low-profile
Reciever/Transmiter - Carson Reflex Wheel Pro LCD 2.4Ghz
Battery - 3S Turnigy Grapheme (grapheme increases the flow of electrons, thereby increasing discharging currents)
With the combination of the electronics and the chassis model can reach speeds up to ~200 km/h and an acceleration from 0 to 100 km/h time is under two seconds.
On this model I chose body of the Dodge Viper SRT10 ACR. Several iconic cars have stopped production in 2016, for example Ferrari F40, Scion, Mitsubishi Evo and last, but not least - Viper. Viper was one of the last cars with pure atmospheric V10 engine and rear-wheel drive, without hybrid systems, electric motors, but nevertheless it holds the track record at many circuits. Production was discontinued due to new safety regulations, but also partly in order to avoid Viper this new hybrid era. I think it’s a shame, the car with potential such as Viper could be much faster using the latest recovery system and electric motors. Viper was my dream since childhood, that is why I decided to use it for this project, I wanted give a Viper kind of homage, that I think it deserves. The body manufacturer is Matrixline, it is made of Lexan, the colors are from Tamiya, body is an replica of the Viper 2010.
RPI electrical connections
Systems in the car are managed by RPI Zero, a small but performance-sufficient computer. It is supplied by an external powerbank. The RPI is connected to Wi-Fi module, to the reduction of the WGA to HDMI + 3.5mm jack for audio, GPIO pins used to control electronics are connected to the interconnecting board, which galvanically separate RPI from the rest of the electronics. Galvanic isolation provide optocouplers, only thing, which is not galvanically separated, is the signal for the servos.
The main thing, in which everyone is curious - Energy recovery system. In recent years, the automotive industry focused on electrification. Hybrid vehicles as well as fully electric cars seem to be the future of this industry. Energy Recovery System is used to capture excess kinetic and thermal energy and converting it into electrical energy. Then it is stored in batteries. In this model, the ERS is used to charge the battery for light and aerodynamics mechanics. Energy is derived from several influences on the model - under braking, when passing inequalities and from the surplus heat from the engine.
During braking energy is obtained via the MGU-K system, similar to one used in Formula 1. In the real cars is stepper motor connected to the crankshaft, so when we brake it slows down and simultaneously generates electricity. In this model is servo, which is secured to a small electric motor. Thanks to air brake, I had a program in which I needed to add a code to move the servo while model is braking, so it stoke electric motor to belt-drive before the rear differential. In this way we can capture some of the energy, which would otherwise be unprofitable.
Passing inequalities evolving’s suspension movement. Audi came last year with the concept for converting this motion into electrical energy by using the MGU. This model has similar system, which is used on the rear suspension, on each side is mounted small electric motor, which capture this movement energy. Model is in scale 1:10, road is not, this means that asphalt is not entirely smooth, suspensions constantly oscillate and generate electricity.
The most powerful part of the recovery in this model is the heat recovery. Here I used a Peltier module. This component can be found mainly in the refrigerators. When it is passing current, one side of the module heats and the second cools. We have used this property upside down. The engine heating up one side of the module, on the other is a passive-cooler and a fan. The hotter the engine is, the greater is the difference in temperature on the module, so it generates more electricity.
In this model are also few fans for cooling, whether motor, ESC, ERS as well as for the air flow. These fans are powered from recovery, but can also generate their own energy. Even the fan is a motor that can generate energy from kinetic movement. When air flow increases in model, fans will get to the point, where they do not need power to spin, but the air rotates them. At that moment, the appliance becomes a generator.
Energy produced via the ERS is used to power the cooling fans, for lights and servos, or it is stored in batteries. First we had to used the diodes bridge as a rectifier for each electric motor. Then we bring together all these rectifiers in parallel in order to increase the current, stable voltage keeps us Peltier module. To this involvement we have appended fans, also parallel. Finally, we connected in parallel rechargeable battery. So, fans can be powered from the battery, but at the same time they protect it from surges generators. To the battery we engage diode against short-circuiting and stabilizer L4049v5, which stabilize output to interconnecting board to 5V 1A.
Quite simple, isn’t it? Stay tuned and have a nice day!