Calculation

Selecting the right motor for your vehicle involves considering several factors. Here are some calculations and considerations you need to make:

1. Determine the total weight of the vehicle: Measure or estimate the total weight of your vehicle, including passengers, cargo, and any additional equipment. This weight is typically measured in pounds (lbs) or kilograms (kg).
2. Calculate the desired acceleration: Determine the desired acceleration performance of your vehicle. This can be subjective and depends on factors such as the vehicle’s purpose, desired speed, and terrain. Higher acceleration requires more torque from the motor.
3. Calculate the required tractive force: Tractive force is the force needed to move the vehicle forward. It is calculated using Newton’s second law of motion: Force = mass × acceleration. Convert the total weight of the vehicle to mass (kg or slugs) and multiply it by the desired acceleration to obtain the required tractive force. Tractive force = Vehicle mass × Desired acceleration
4. Consider the rolling resistance: Rolling resistance is the force that opposes the motion of the vehicle’s tires on the road surface. It depends on factors such as tire type, tire pressure, and road conditions. Rolling resistance can be estimated using empirical formulas or obtained from tire manufacturers. Add the rolling resistance force to the required tractive force. Total force = Tractive force + Rolling resistance force
5. Determine the wheel radius: Measure or estimate the radius of the vehicle’s wheels in meters (m) or feet (ft).
6. Calculate the required torque: Torque is the rotational force produced by the motor. To calculate the required torque, multiply the total force by the wheel radius. Required torque = Total force × Wheel radius
7. Consider the motor efficiency: Motors have an efficiency rating that indicates how effectively they convert electrical energy into mechanical power. Take into account the motor efficiency when selecting a motor. The efficiency is usually expressed as a percentage. Usable torque = Required torque / Motor efficiency
8. Determine the desired top speed: Consider the desired top speed of your vehicle. This will help you select a motor with an appropriate power output to achieve the desired speed.
9. Consider other factors: Apart from the calculations mentioned above, you should also consider factors such as available space for the motor, voltage requirements, cooling requirements, controller compatibility, and cost.

It’s important to note that these calculations provide a starting point for selecting a motor, but other factors such as motor type (DC, AC, brushless), motor characteristics (speed-torque curve), and specific application requirements should also be taken into account. Consulting with a motor specialist or engineer familiar with electric vehicle systems can provide valuable guidance in selecting the most suitable motor for your vehicle.

Calculating wheel torque in off-road vehicles involves considering several factors such as engine torque, gear ratios, transfer case ratios, axle ratios, and tire size. Here’s a step-by-step guide to help you calculate wheel torque:

1. Determine the engine torque: Start by finding the torque output of your vehicle’s engine. This information can typically be found in the vehicle’s specifications or technical documentation. Engine torque is usually measured in pound-feet (lb-ft) or Newton-meters (Nm).
2. Account for drivetrain losses: The torque measured at the engine is not fully transmitted to the wheels due to drivetrain losses. These losses can vary but are generally estimated to be around 15-20% for most vehicles. Multiply the engine torque by the drivetrain efficiency factor (1 – drivetrain loss percentage) to get the torque at the transmission output. Torque at transmission output = Engine torque × (1 – Drivetrain loss percentage)
3. Consider gear ratios: Determine the gear ratio of the transmission. This information can be found in the vehicle’s specifications or transmission documentation. Multiply the torque at the transmission output by the gear ratio to obtain the torque at the transfer case output. Torque at transfer case output = Torque at transmission output × Gear ratio
4. Account for transfer case ratios: If your off-road vehicle has a transfer case with multiple gear options (e.g., high range and low range), you need to consider the transfer case ratio. Multiply the torque at the transfer case output by the transfer case ratio to get the torque at the axle input. Torque at axle input = Torque at transfer case output × Transfer case ratio
5. Consider axle ratios: Determine the axle ratio for each axle in your off-road vehicle. The axle ratio can usually be found on a tag or plate attached to the axle housing. Multiply the torque at the axle input by the axle ratio to obtain the torque at each wheel. Torque at each wheel = Torque at axle input × Axle ratio
6. Account for tire size: The torque at each wheel also depends on the tire size. Larger tires can effectively reduce torque at the wheels due to the increased mechanical advantage. This is because the larger tires have a greater circumference, requiring more torque to turn them. However, if your off-road vehicle has a gear-driven transfer case or differential, the tire size effect is minimal.

By following these steps and considering all the relevant factors, you can calculate the estimated wheel torque for your off-road vehicle. Keep in mind that these calculations provide an approximation, and there might be additional variables and factors specific to your vehicle that could affect the actual wheel torque.