WHAT YOU TORQUEIN’ WIT? – EV Gear Reduction and Driveline Setup

EV Gear Reduction and Driveline Setup

Unlike internal combustion engine (ICE) vehicles, the vast majority of EVs on the road today do not have a multi-speed transmission. Almost every OEM electric vehicle currently produced, including Teslas, BMWs, Rivians, and the Ford Mach E, use a single speed transmission that provides gear reduction from the EV motor(s) to the driveline or axle. The fact that EVs can operate effectively with a simple single-speed transmission is a sign of an extremely capable and efficient electric powerplant. Electric motors provide consistent torque throughout a massive RPM band, all in a small and power-dense package.

Gear reduction uses mechanical advantage to trade speed for torque. An electrical motor may spin at 8,000 rpm and put out 200 lb-ft of torque without gear reduction. However, if you mate that motor to a single speed gear box with a gear ratio of 2:1, the output of the system will be 4,000 rpm and 400 lb-ft of torque. Total power output is the product of speed and torque, so power is not reduced in the system, but is merely applied in a different way.

Now, while many EVs use gear reduction, you can also maintain an existing manual transmission, use a two-speed transmission, or explore a number of other options. That’s why the focus of this article will be, what is gear reduction… and… do I need it in my EV?

While gear reduction is an excellent way to take advantage of an electric motor’s potential, it’s not right for every build. There are a few factors you will want to consider when determining if gear reduction is right for your build.

• How will the gear reduction affect the top speed of your vehicle?
• Will gear reduction fit within your project’s budget?
• Do you have the space to forgo gear reduction?
• How will the efficiency of your daily drive be affected by gear reduction?
• Do you want a smooth/effortless driving experience or a more interactive driving experience (using a manual transmission)?

Let’s dive into each question, below.

01. How will the gear reduction affect the top speed of your vehicle?

Depending on your electric motor’s max RPM, your tire size, and differential gear ratio, the top speed of your vehicle will change. If the gearing is too high or low in your differential, a torque box may not lower the final drive ratio enough or may lower the drive ratio too much. Use the calculator at legacyev.com/pages/top-speed-calculator to find if a torque box is right for you.

02. Can your build afford gear reduction (or afford to skip on it)?

If you plan to use a manual transmission for your build, you will want to make sure your transmission can handle the torque of your new motor. You will also need to source adapter plates, new flywheels, and clutch plates. In some cases, you might even need to source an entirely new transmission for the vehicle. Comparatively, a torque box does add anywhere from around $3,000 to $5,500 in cost to your build.

03. Do you have space to forgo gear reduction?

Gear reduction takes up ___% of the space on an average transmission, allowing more room for batteries. If your build is planning on using a large battery pack and space is tight, gear reduction will add much needed room for more batteries.

If your build is planning on using a large battery pack and space is tight, gear reduction will add much needed room for more batteries.

04. How will the efficiency of your daily drive be affected by gear reduction?

EV motors have an optimal operating efficiency for their individual RPM band, as you can see in the efficiency curve for a Hyper 9 motor in the figure here. Depending on the gearing in your EV, optimal efficiency will occur at different speeds. To find the optimal operating efficiency you can use the maximum RPM efficiency of your motor in the top speed calculator below to find what speed is best for efficiency in your EV.

05. Do you want a smooth/ effortless driving experience or a more interactive driving experience (using a  manual transmission)?

If you plan to use a manual transmission you may allow for a more interactive driving experience, but you will also want to ensure you are comfortable locking gears that you will no longer need (often 1st and/or 4th). Often when building a manual EV, the motor can spin through first gear so quickly it becomes only useful for doing burnouts. This can create a somewhat clunky driving experience but for those that enjoy a more interactive drive, it may be the right fit.

Building an EV may seem like a complex undertaking at first glance, but once you understand new technology, it’s actually much simpler than its combustion counterpart.

Building an EV may seem like a complex undertaking at first glance, but once you understand new technology, it’s actually much simpler than its combustion counterpart. Understanding whether gear reduction is beneficial to your build is just one small step towards successfully building your own EV. To understand how to install your own Torque Box or simply understand more on the intricacies of your own EV build make sure to check out the next issue of EV builders guide and read more about Legacy EV’s certified technician program on pg. ___ of this issue.

FREQUENTLY ASKED QUESTIONS

What are some fundamental parameters, aside from the electric motor, that affect an electric vehicle’s performance?

Key Factors Influencing Electric Vehicle Performance

When considering the overall performance of an electric vehicle (EV), there are several crucial elements beyond just the motor itself. Let’s delve into some of these fundamental parameters:

1. Gearbox Ratios

The choice of gearbox can have a substantial impact on an EV’s ability to handle different terrains. A mechanical gearbox allows the vehicle to increase torque applied to the ground, which enhances its capacity to manage steep inclines effectively. Including “reduced gears” in an electric vehicle significantly boosts its ability to conquer challenging climbs.

2. Tyre Selection

The selection of tyres plays a pivotal role, affecting vehicle performance by approximately 5%. This includes traction, efficiency, and handling. Opting for tyres specifically designed for electric vehicles, such as those from manufacturers like Michelin or Bridgestone, can optimize performance and reinforce overall driving experience.

3. Tyre Pressure

Often overlooked, maintaining proper tyre pressure is vital for maximizing range and performance. Incorrect pressure can detract approximately 5% from the vehicle’s efficiency. Regular checks and adjustments ensure optimal contact with the road, reducing resistance and extending the distance the vehicle can travel on a single charge.

How does the torque of an electric motor compare to that of a combustion engine in terms of efficiency and performance?

Unlike internal combustion engine (ICE) vehicles, the vast majority of EVs on the road today do not have a multi-speed transmission. Almost every OEM electric vehicle currently produced, including Teslas, BMWs, Rivians, and the Ford Mach E, use a single speed transmission that provides gear reduction from the EV motor(s) to the driveline or axle. The fact that EVs can operate effectively with a simple single-speed transmission is a sign of an extremely capable and efficient electric powerplant. Electric motors provide consistent torque throughout a massive RPM band, all in a small and power-dense package.

Electric motors excel in delivering immediate torque, a stark contrast to combustion engines, which must reach a specific speed to unleash their full torque potential. This immediate torque availability is a key reason why electric cars often outpace their petrol or diesel counterparts in standing starts.

Moreover, electric vehicles boast impressive efficiency rates, with some achieving up to 88% efficiency. This high efficiency translates into better energy utilization, making EVs not only powerful but also environmentally friendly. However, it’s worth noting that while electric motors are highly efficient, the energy stored in their batteries is typically less than that found in a standard petrol car tank.

This efficiency and performance combination makes electric vehicles an attractive option for those seeking a balance of power and sustainability.

How does energy storage in electric vehicles compare to that in traditional petrol cars?

The energy stored in electric vehicle batteries is less than the energy capacity of a conventional petrol car’s fuel tank, indicating a limitation in range for electric vehicles compared to traditional petrol cars.

What is the efficiency of electric cars compared to combustion engine cars?

Electric cars are highly efficient, achieving efficiencies of up to 88%, which is significantly higher than traditional combustion engine vehicles.

How does the torque delivery of electric motors compare to that of combustion engines?

Electric motors deliver torque instantly, providing immediate power from a standstill, whereas combustion engines must reach a certain speed to achieve peak torque, often making electric vehicles quicker off the line.

What is the torque of an electric vehicle and why is it important?

Unlike internal combustion engine (ICE) vehicles, the vast majority of EVs on the road today do not have a multi-speed transmission. Almost every OEM electric vehicle currently produced, including Teslas, BMWs, Rivians, and the Ford Mach E, use a single-speed transmission that provides gear reduction from the EV motor(s) to the driveline or axle. The fact that EVs can operate effectively with a simple single-speed transmission is a sign of an extremely capable and efficient electric powerplant. Electric motors provide consistent torque throughout a massive RPM band, all in a small and power-dense package.

Understanding the concept of torque in electric vehicles is essential to appreciate why these machines are not just efficient but also powerful. Torque, in simple terms, is the force that allows the electric motor to propel the vehicle by imparting thrust to the wheels. This force is pivotal because:

• Acceleration: Greater torque means faster acceleration, giving electric vehicles a significant edge in performance, especially noticeable in quick starts.
• Hill Climbing: Torque determines the vehicle’s ability to handle steep inclines without losing power or speed.

Electric vehicles boast the advantage of delivering maximum torque instantly, unlike combustion engines that require a build-up to reach peak torque. This immediate availability enhances both the driving experience and the vehicle’s responsiveness.

In summary, the seamless blend of consistent torque across a wide RPM range and the ability to deliver it instantaneously underscores the superiority of electric motors in modern vehicles.

What is driving torque in an electric vehicle and how does it affect vehicle performance?

Unlike internal combustion engine (ICE) vehicles, the vast majority of EVs on the road today do not have a multi-speed transmission. Almost every OEM electric vehicle currently produced, including Teslas, BMWs, Rivians, and the Ford Mach E, use a single-speed transmission that provides gear reduction from the EV motor(s) to the driveline or axle. The fact that EVs can operate effectively with a simple single-speed transmission is a sign of an extremely capable and efficient electric powerplant. Electric motors provide consistent torque throughout a massive RPM band, all in a small and power-dense package.

Driving torque in an electric vehicle is the thrust generated by the electric motor that propels the car forward. This torque is a crucial factor in determining the vehicle’s acceleration and ability to manage challenging terrains. Unlike combustion engines, which need to reach a certain speed to deliver peak torque, electric motors deliver torque instantly. This instant torque is one reason why EVs often outperform traditional vehicles in quick starts.

Gear reduction uses mechanical advantage to trade speed for torque. An electrical motor may spin at 8,000 rpm and put out 200 lb-ft of torque without gear reduction. However, if you mate that motor to a single-speed gearbox with a gear ratio of 2:1, the output of the system will be 4,000 rpm and 400 lb-ft of torque. Total power output is the product of speed and torque, so power is not reduced in the system, but is merely applied in a different way.

The performance benefits of electric motors are notable when it comes to towing capacity and acceleration. Greater torque means more force is available to the wheels, translating into quicker acceleration and the ability to tackle steep inclines with ease. This capability underscores the efficiency and power of electric vehicles, making them a formidable choice for both everyday driving and demanding conditions.

What are the differences in torque between an electric vehicle and a combustion vehicle?

Unlike internal combustion engine (ICE) vehicles, the vast majority of EVs on the road today do not have a multi-speed transmission. Almost every OEM electric vehicle currently produced, including Teslas, BMWs, Rivians, and the Ford Mach E, use a single-speed transmission that provides gear reduction from the EV motor(s) to the driveline or axle. The fact that EVs can operate effectively with a simple single-speed transmission is a sign of an extremely capable and efficient electric powerplant. Electric motors provide consistent torque throughout a massive RPM band, all in a small and power-dense package.

Electric vehicles deliver very high torque at low revs, offering impressive acceleration capabilities. This is due to their ability to maintain torque over a much wider rev range compared to traditional combustion engines.

Key Differences in Torque and Efficiency

• Higher Acceleration: The instant torque allows EVs to outperform many combustion vehicles in terms of acceleration.
• Mechanical Efficiency: With less gears and more mechanical efficiency, EVs streamline power delivery, reducing energy loss.
• Motor Efficiency: Electric motors boast an efficiency of approximately 88%, significantly higher than the 40-50%efficiency of traditional heat engines. This high efficiency translates into more effective torque usage, making EVs more energy-efficient.

These features highlight why electric vehicles are increasingly preferred for their performance and environmental benefits. As technology advances, these differences continue to widen, redefining the expectations of modern transportation.