# CVT transmission for an electric motor

• Ayrity
In summary, the conversation discusses the design of a small and lightweight continuously variable transmission (CVT) for an electric car. The CVT must be able to switch between on and off states without variable speeds from the motor. The car must complete a race of 312 inches with a top RPM of 4040 and torque approaching 0. The graph of torque vs RPM has two parts with different equations for when RPM is less than or greater than 1248. The problem lies in representing a smooth change between the infinite gear ratios and determining the time it will take to cross the finish line. The diameter of the drive wheels is 3 inches. The conversation also touches on using a CVT with an electric motor and the possibility of using
Ayrity
Hey everyone, i am trying to design a small and lightweight cvt (continiously variable transmission) for an electric car that can either be on or off, no variable speeds from the motor. I am having trouble representing the math of the transmission. I have to have the car complete a race of 312 inches, the motor has a top rpm of 4040rpm, and at that rpm torque approaches 0. the graph of the torque vs rpm is piecewise in 2 parts with the following equations when rpm<1248 then torque=-0.0019*rpm=23.3 and also when rpm>1248 then torque=-0.0075*rpm=30.3

anyway, my problem is that i don't know how to represent a smooth change between the infinite gear ratios and relate that to how much time it will take to cross the finish line (312 inches later). obviously i am starting at a velocity of 0, and an rpm of 0. this should give me a torque just as the motor starts to move of 23.3 ounce-inches. i know i want to minimize time, and maximize velocity. i think i have to use an integral to represent the cvt, but I am really turning around in circles here. oh and by the way, the diameter of the drive wheels is 3 inches. please can anyone help me out here?

Power = torque * RPM

Graph it out and Pmax ~= 2000RPM

So you bascially have two conditions to figure for:

A) 0 RPM to 2000RPM at the maximum practical gear ratio as the torque falls from 23.3 to 15.3 and the maximum ratio is used to minimize the acceleration needed to the moment of inertia of the engine/CVT plus the smallest acceleration of the car.

B) A steady 2000RPM for Pmax and the gear ratio changes to hold it there over time.

Both should be similar and near linear lines on each side of the inflection point of 2k RPM, its basically a matter of power/mass to find the resultant acceleration.

hows the electric car going?

I'm also thinking of using a cvt with an electric motor. I'm planning on using two eteks or two perm motors on a motorcycle with the Comet 94c torque converter (that's what they call their cvt). I'm wondering how I can set it up so it will have torque at 0 rpms and also allow me a higher vehicle top speed when the motor reaches top rpms. Any advice? I figure there's some springs and weights or something in the cvt to adjust and also the gearing on the rear wheel. I don't have it all yet to try but want to make sure it's possible first. I've heard of it being done. Youre doing it I imagine.
thanks
john

Im wondering why you are using a DC motor and not an AC motor with a VFD/Inverter? I am correct on the use of a DC motor right (the ON/OFF remark)

Pease check:

www.warko.it

Electric engines need different rate transmission as IC engines, for this reason Ac motors with inverter is not enough!
If correctly designed it will be big and heavy (and energy expensive) compared with the correspondent motor+CVT.

## 1. What is a CVT transmission for an electric motor?

A CVT (Continuously Variable Transmission) is a type of transmission system that allows for smooth and seamless shifting between gears without the use of traditional gear ratios. In an electric motor, the CVT system adjusts the speed of the motor by continuously varying the gear ratio, resulting in a more efficient and smoother driving experience.

## 2. How does a CVT transmission work in an electric motor?

In an electric motor, the CVT system uses a set of pulleys and a belt or chain to continuously adjust the gear ratio. As the speed of the motor changes, the CVT system adjusts the position of the pulleys to maintain an optimal gear ratio for the driving conditions. This allows for a more efficient use of energy and a smoother acceleration.

## 3. What are the benefits of using a CVT transmission in an electric motor?

One of the main benefits of using a CVT transmission in an electric motor is its ability to provide a smooth and efficient driving experience. The continuously variable gear ratio allows for optimal use of energy, resulting in improved fuel economy and reduced emissions. Additionally, the lack of traditional gear shifting means less wear and tear on the motor, resulting in a longer lifespan.

## 4. Are there any drawbacks to using a CVT transmission in an electric motor?

One potential drawback of using a CVT transmission in an electric motor is its higher cost compared to traditional transmissions. The complex design and technology involved in a CVT transmission can also make it more difficult and expensive to repair if it were to malfunction. Additionally, some drivers may not be accustomed to the different driving experience of a CVT transmission.

## 5. Is a CVT transmission necessary for an electric motor?

No, a CVT transmission is not necessary for an electric motor. Electric motors can also use single-speed transmissions or direct drive systems, which do not require shifting between gears. However, a CVT transmission can provide benefits such as improved efficiency and smoother driving, making it a popular choice for electric motors.

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