Electric cars are quickly outpacing their counterparts, internal combustion engines, they appear to be the future of the auto industry. By the way, all the big names in the auto industry are heavily investing in electric vehicles with Volkswagen being the most ambitious one among them, planning to spend over $30 billion by 2023.
The electric car is evolving from its counterpart, after ditching the internal combustion engine, giving birth to electric vehicles, we have seen in the past that the internal combustion engine in traditional cars is replaced by an induction motor and a battery pack, so what is the next big difference between internal combustion engine (ICE) and electric vehicle (EV)?
Henceforth, here is a question that piqued my mind recently, do electric cars use gears at all? Electric Cars do not have gears and the reason why electric cars do not have gears is that electric cars use an electric motor (induction motor); furthermore, electric motors produce a very high initial power and torque at a very low (RPM) revolution per minute.
So you do not need to start it in first gear to put it in motion and it also has a wide range of RPM as a result of that it does not necessarily need second and third gear. But let us explore the longer version of the answer or the hard way of answering this question. We will begin with:
Why do we even need gears in a car anyway?
Think of this problem this way, when a kid wants to ride a bike, he/she has to stand up; and then to pedal it, but once he gets that extra push he can now sit and coast along on the bike smoothly, that initial push needed to get the bicycle moving from inertia is the work of the gear, gears are very important in machines they help provide better speed and torque when needed.
So what exactly is torque, because we will be using this term more often from now on. Torque is simply a form of force, the only unique thing about this form of force is the direction it acts and its effects on bodies.
It acts perpendicular to the axis of the object and causes a rotation of the object, just like opening a door, when you push the door it tends to rotate
Let’s take into account what happens in an internal combustion engine; just like we have above, so we have power coming from the piston connected to the crankshaft, in this case, our crankshaft is the driving gear, the movement of the piston up and down will rotate the crankshaft (driving gear), the crankshaft is connected to the transmission consisting of four gears.
Gear ratio =
We have four driven gears labeled as (first, second, third and fourth) with teeth (20,15,10,5), our driving gear is called X and it has 10 teeth
First gear ratio= 2:1
Second gear=1.5:1
Third gear=1:1
Fourth gear=1:2
Why do we need the first gear?
To understand this we need this equation
Engine torque × gear ratio = output torque
The engine torque is the power generated from the pistons, which is fairly constant, it does not change but our gear ratio, however, changes.let’s assume an engine torque of 50 N
In the first gear, we will have the greatest output torque of 150 N, this is why we need the first gear to get the vehicle in motion. Another question you may ask is:
Why not just stay in first gear?
We could stay in first gear and drive around town but that will be counter-effective because of the redline. When you check your car speedometer in the dashboard, you are going to see some marking on the speedometer in red ink, now that’s your redline, all engines have different redline value, and the redline refers to the maximum number of RPM the engine can take before things start to go kaboom!!!.
The redline is determined by factors such as friction, components in the engine, stroke, etc.
Furthermore, another reason why you can not just coast in first gear is because of the absence of speed, the engines output power is given as
P=T × W
Where T = torque and w = angular speed of the shaft.
So by using different gear ratio, we can vary torque and angular speed, since the relationship between torque and angular speed is inversely proportional
As we have in any transmission system of an internal combustion system and as described above, the first gear is the biggest, here it has the highest number of teeth (20) and the largest diameter, therefore it produces the highest torque but the lowest speed.
While the fourth gear in this instance is the smallest gear with a ratio of (5) but has the highest speed, staying in first gear you will be trading speed for torque. Gears help the driver to manipulate angular speed and torque, to ensure a smooth driving experience.
Do electric vehicles need gears?
Now that we have understood why the internal combustion engine needs gears to operate, because:
- Low starting torque
- Low initial speed
- Presence of redline, that limits operation in first gear
- Design and efficiency of the internal combustion engine
Let’s go back to why electric cars need gears or why they do not need them.
Why electric cars do not need gears
Point of correction here, electric cars do not need G.E.A.R.S. they need one G.E.A.R. No mechanical machine can output power without the help of gears. Electric cars, unlike their internal combustion engine counterparts, use one gear.
If you have ever been inside an electric car like the tesla model S, jaguar i-pace, Chevrolet bolt EV, Audi e-Tron you will notice they only have something that looks like a knob.
This knob is similar to what you have on automatic cars but unlike automatic cars, you don’t get a gearbox that operates different speeds. You will only see drive to move the car forward, reverse to move the vehicle backward and neutral to park the car.
Some might add additional setups (such as eco or sport mode) that don’t change the way the transmission operates but only changes the throttle sensitivity. Once you zoom off inside an electric car you will notice that as you accelerate and decelerate you do not experience the feeling of shifting gears, it’s just a smooth ride to wherever you are going.
This happens because of the absence of a gearbox that comes with gears numbering one to four or six in some sports cars that use an internal combustion engine they need only one gear to operate. How this is achieved will be discussed further, below
Why electric cars need one gear?
Unlike internal combustion engine that needs multiple gears to reach it tops speed, electric cars can achieve this same feat faster and easier using a single gear, how an electric car is able to do this seems to be the next 8th wonders of the world right? Well, you do not need to be a rocket scientist to understand how an electric vehicle does this, let’s begin.
High starting torque
Firstly, electric motors are able to produce very high torque at low RPM; such as 0 or 1 RPM, to know how this is achieved we need to understand how an electric motor operates. The battery pack in an electric motor supply current to the motor which sits in between two large magnets.
These currents flow through the electric motor and it generates a force to rotate the armature of the motor according to the Flemming left-hand rule. The more current is applied to the armature the faster the motor it’s going to spin, as the driver matches the acceleration pedal the faster the motor spins, but this motion causes the production of something called back-EMF.
According to newton; for every action, there is an equal or opposite reaction, this back emf opposes the supply of voltage from the battery and tends to slow the motor, the net force output by the motor is now reduced, but with no back EMF present when a car starts, high torque is produced
If you ever look at a torque curve for an electric motor you will notice that at the beginning, maximum torque is produced which continues for a very long time, and then start to decrease steadily. The region all of this happens is a very wide band.
This happens because most electric cars use induction motors, which is very efficient in outputting power and high torque from startup due to less moving parts, so friction is greatly eliminated.
The torque/speed EV (electric vehicle) graph is different from that of an internal combustion engine when you look at it, you will notice internal combustion engine have low starting torque and limited or small RPM band range on its graph.
To sum everything all, electric cars need only one gear:
- They produce a very high initial torque
- They are efficient across a wide range of RPM ( torque/speed graph)
- they are a high revving
All this eliminates the need for a multiple gear system since an electric car produces high initial torque for start-up, and it can easily reach top speed without hitting redline, internal combustion engines generally have redline around 6000 to 8000 RPM.
Although some Formula One racing cars that use internal combustion engine boast of redline value around 10000 RPM. This still does not measure up to the 20000 RPM of electric cars such as the Tesla Model S, fossil powered cars still have a long way to go to catch up.
Will there ever be a multiple gear system in an electric car?
We have seen some automakers tuning electric cars by putting a manual gear system, such as Renault Formula One car and the Genovation GXE. But this will defeat the purpose of having a manual gear system fitted into the car because electric cars do not stall, therefore electric cars do not need a multiple gear system.
The presence of a multiple gear system in an electric car will only increase the complexity of the car, add more weight to the car and increase moving part thereby increasing friction, All in all, an electric car only has one gear and multiple gears will only make it inefficient.
