You might have seen various vehicles that are made up of Lego blocks. People have made an F1 car and a Bugatti Chiron out of Legos. These blocks which are usually bought for children could also be used to explain complicated things. Here, is a video uploaded by Beyond the Brick on Facebook that explains a 4×4 system very easily.
In the video, we can see a chassis of a car in which an electric motor has been joined. The vehicle is given a task to climb a 20-degree slope. The vehicle is able to climb a bit but then the front wheels start to lose traction and start spinning. This happened because the vehicle is front-wheel drive. Then the person adds four-wheel drive by giving it a rear differential and a drive shaft that carries power to the rear wheels. Now, the vehicle is able to drive up the slope quite easily.
The person increases the slope angle by 20-degrees. So, now it is 40-degrees. Despite having a four-wheel-drive drivetrain, the Lego vehicle starts losing traction after climbing for a bit. The solution to this is more grippy tyres which you can also call off-road tyres. The person upgrades to the tyres of the vehicle and immediately there is a difference. The vehicle is able to climb up the slope once the tyres were changed.
Then the person increases the slope angle to 50-degrees. The vehicle immediately failed as it tried to climb up but as soon as the rear tyres touched the glass, the vehicle flipped over. This happened because of the weight of the battery or in real life, it would be the engine. To counter this, the person shifts the position of the battery under the floor instead of being on the floor. Due to this, the centre of gravity decreases significantly. The vehicle did climb up half of the slope but then it started slipping.
This was happening because of a lack of torque. The person then lowers the gear by removing the small gear sprocket and replacing it with a larger one. A larger gear sprocket means that it would rotate less and will provide more torque. This is what you can call the low range gearbox in the internal combustion engine vehicle. Once, the change is made the vehicle is able to go up the slope.
The person then increases the slope to 60-degrees. The vehicle starts the climb but as soon as the rear wheels come in contact with the slope, the front wheels lift up and is no longer in contact with the ground. This happens because the wheelbase of the vehicle is too short. Once the person increases the wheelbase then it is able to climb up the slope.
Finally, the person increases the slope to 63-degrees which is quite steep and the vehicle is not able to climb. He tries various ways like decreasing the weight and adding more wheels. But the vehicle is not able to climb. So, he decides to cheat a bit by sticking a double-sided tape on the tyres. Then the vehicle is able to climb the slope.