Remote Control Boat Speed Calculator (added thrust )

To add thrust calculation to the boat propeller calculator, we need to know the propeller's pitch and diameter. The formula for thrust is:

thrust (in pounds) = (0.5 x air density x (pi/4) x diameter^2 x pitch x RPM^2) / (792000 x gear ratio)


  • air density is the density of air, which is approximately 0.002378 pounds per cubic inch at sea level
  • pi/4 is the conversion factor from circle area to blade area
  • diameter is the propeller diameter in inches
  • pitch is the pitch of the propeller in inches
  • RPM is the rotational speed of the propeller in revolutions per minute
  • gear ratio is the gear ratio of the boat's transmission

Here is an updated PHP code for the boat propeller calculator with the addition of thrust calculation:

<!DOCTYPE html>
	<title>Boat Propeller Calculator</title>
	<h2>Boat Propeller Calculator</h2>
	<form method="post">
		<label for="diameter">Propeller Diameter (inches):</label>
		<input type="text" name="diameter" required>
		<label for="pitch">Propeller Pitch (inches):</label>
		<input type="text" name="pitch" required>
		<label for="rpm">Motor RPM:</label>
		<input type="text" name="rpm" required>
		<label for="gear_ratio">Gear Ratio:</label>
		<input type="text" name="gear_ratio" required>
		<label for="throttle">Throttle Setting (%):</label>
		<input type="text" name="throttle" required>
		<label for="density">Air Density (lbs/in^3):</label>
		<input type="text" name="density" value="0.002378" required>
		<input type="submit" name="submit" value="Calculate">

			$diameter = $_POST['diameter'];
			$pitch = $_POST['pitch'];
			$rpm = $_POST['rpm'];
			$gear_ratio = $_POST['gear_ratio'];
			$throttle = $_POST['throttle'];
			$density = $_POST['density'];

			// Convert throttle percentage to a decimal value
			$throttle_decimal = $throttle / 100;

			// Calculate speed in miles per hour
			$tire = 6; // Tire circumference in feet
			$speed = ($rpm / $gear_ratio) * ($diameter * M_PI) * $pitch * 60 * 0.0000113636 / $tire;

			// Calculate thrust in pounds
			$thrust = (0.5 * $density * (M_PI/4) * pow($diameter, 2) * $pitch * pow($rpm, 2)) / (792000 * $gear_ratio);

			echo "<p>At $throttle% throttle, the boat will travel at approximately <strong>" . round($speed, 2) . "</strong> miles per hour and produce <strong>" . round($thrust, 2) . "</strong> pounds of thrust.</p>";


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