Calculating the Speed of a 3500 RPM Motor for a Pedal Go-Cart

Introduction

When setting up a pedal go-cart, one of the most critical aspects to consider is the speed at which the go-cart will move. This depends on several factors, including the motor's RPM, gear ratio, and the physical dimensions of the wheels and chain. Given the specifics of your go-cart project, we can help you understand how to calculate the expected speed and ensure a safe and efficient ride.

Motor Specifications and Gear Ratios

The power of the motor is a crucial factor in determining the speed and acceleration of your go-cart. However, the exact speed is difficult to determine without knowing the specific motor's power rating. Assuming a powerful enough 3500 RPM motor, the gear ratio is key. A typical bicycle gear ratio is around 1:3.5, which is the opposite of the 3.5:1 used in rear differentials of rear-wheel-drive cars.

For a 3500 RPM motor with a gear ratio of 3.5:1, the calculations are as follows:

3500 RPM (motor) times; 3.5 (gear ratio) 12,250 RPM for the drive wheels Wheels with an 8-inch diameter have a circumference of approximately 25 inches or 635 mm.

Potential Speed Calculation

Using the above information:

12,250 RPM times; 635 mm/revolution 7,743,750 mm/min (or 7,743.75 m/min) 7,743.75 m/min divide; 60 132.4 m/s (approximately 480 km/h or 300 mph)

However, this calculated speed is dangerously high for a go-cart. Safety must always be the priority. A typical bicycle chain and drive system would not be sufficient at this speed. A much more powerful motor, on the order of 100-120 hp, would be required, which is impractical for a pedal go-cart. Therefore, a more reasonable setup is necessary.

Reasonable Gear Ratio and Speed Calculation

Applying a more practical gear ratio, say 1:3.5 on the bicycle style gears:

3500 RPM (motor) divide; 3.5 (gear ratio) 1,000 RPM for the drive wheels Assuming 8-inch diameter wheels with a 635 mm circumference:

The speed calculation would be:

1,000 RPM times; 635 mm/revolution 635,000 mm/min (or 635 m/min) 635 m/min divide; 60 10.58 m/s (approximately 37.5 km/h or 23 mph)

Realistic Setup and Safety Considerations

For a reasonable setup that still provides a thrilling experience, a 1-2 HP motor would be sufficient. Ensuring that the go-cart is equipped with substantial and reliable brakes is paramount.

The wheel diameter plays a critical role in the calculation of the speed. Therefore, it is crucial to measure and record the exact diameter before setting up the go-cart.

Conclusion

Calculation the speed of your go-cart involves several steps, including motor power, gear ratios, and wheel dimensions. A 3500 RPM motor can provide impressive speeds, but practicality and safety should be the primary concerns. A more reasonable setup will help achieve both fun and safety. Always prioritize safety measures, including adequate brakes, and follow local regulations for recreational vehicles.

Keywords

pedal go-cart, RPM motor, speed calculation