www.compilejava.net

java_3CWIcP.java

import java.lang.Math;


public class SpokedWheelCalculator {
  private static double f (Wheel.Side s, double dd, double da) {
    return s.calculateEffectiveSpokeLength(dd, da) - s.calculateEffectiveSpokeLength(dd, 0);
  }
  
  public static void main (String[] args) {
    final Wheel wheel = new Wheel(new Rim(600), new Hub(60, 20, 16), SpokeType.GENERIC_SWAGED_JBEND_SPOKE, 3);
    final double angleDelta = wheel.getLeftSide().calculateFlangeTwistUnderTorque(2000, 200); // 0.3x Bugatti Veyron peak engine torque
    
    System.out.format("Angle delta = %f rad%n", angleDelta);
    
    final double
      lengthDelta1 = f(wheel.getLeftSide(), -3, angleDelta),
      lengthDelta2 = f(wheel.getLeftSide(), 3, angleDelta);

    System.out.format("dl-3mm = %f%ndl+3mm = %f%n", lengthDelta1, lengthDelta2);
  }
}


enum SpokeType {
  GENERIC_SWAGED_JBEND_SPOKE(200000, 1.8);
  
  private final double
    materialYoungsModulus, // N/mm^2
    mainSectionDiameter;
  
  private SpokeType (double materialYoungsModulus, double mainSectionDiameter) {
    this.materialYoungsModulus = materialYoungsModulus;
    this.mainSectionDiameter = mainSectionDiameter;
  }
  
  public double calculateHookesLengthChange (double force, double length) {
    return force * length / (materialYoungsModulus * Math.PI * Math.pow(mainSectionDiameter / 2, 2));
  }
}

class Rim {
  private final double effectiveRadius;
  
  public Rim (double erd) {
    effectiveRadius = erd / 2d;
  }
  
  public double getEffectiveRadius () { return effectiveRadius; }
}


class Hub {
  public static class Flange {
    private final double
      radius,
      distanceFromCenter; // distance from plane containing centers of rim holes on this side of the wheel
    private final int numberOfSpokes;
    
    public Flange (double radius, double distanceFromCenter, int numberOfSpokes) {
      this.radius = radius;
      this.distanceFromCenter = distanceFromCenter;
      this.numberOfSpokes = numberOfSpokes;
    }
    
    
    public double getRadius () { return radius; }
    public double getDistanceFromCenter () { return distanceFromCenter; }
    public int getNumberOfSpokes () { return numberOfSpokes; }
  }
  

  private final Flange leftFlange;
  

  public Hub (double leftFlangePcd, double leftFlangeDistanceFromCenter, int nLeftFlangeHoles) {
    leftFlange = new Flange(leftFlangePcd / 2d, leftFlangeDistanceFromCenter, nLeftFlangeHoles);
  }
  
  public Flange getLeftFlange () { return leftFlange; }
}


class Wheel {
  // www.compilejava.net doesn't allow inner classes
  public static class Side {
    private final Wheel wheel;
    private final Hub.Flange flange;
    //private final double offsetDistanceToRim; for asymmetric wheels
    private final SpokeType spokeType;
    private final int nCrosses;
    

    public Side (Wheel wheel, Hub.Flange flange, SpokeType spokeType, int nCrosses) {
      this.wheel = wheel;
      this.flange = flange;
      this.spokeType = spokeType;
      this.nCrosses = nCrosses;
    }
    
    
    public double getFlangeHoleAngle () {
      return (2 * Math.PI * nCrosses) / flange.getNumberOfSpokes();
    }
    
    public double calculateEffectiveSpokeLength (double flangeDistanceOffset, double angleDelta) {
      final double
        R = wheel.rim.getEffectiveRadius(),
        r = flange.getRadius();
      return Math.sqrt(
        Math.pow(R, 2) +
        Math.pow(r, 2) +
        Math.pow(flange.getDistanceFromCenter() + flangeDistanceOffset, 2) -
        2 * R * r * Math.cos(getFlangeHoleAngle() + angleDelta)
      );
      // - spokeHoleRadius and account for spoke stretch for material spoke length calculation (a different method)
    }
    
    // for now, assume hub shell has zero torsional stiffness
    //
    public double calculateFlangeTwistUnderTorque (double force, double armLength) {
      final double
        torquePerSpoke = force * armLength / flange.getNumberOfSpokes(),
        forcePerSpoke = torquePerSpoke / calculateSpokeTorqueArmLength(),
        spokeLengthChange = spokeType.calculateHookesLengthChange(forcePerSpoke, calculateEffectiveSpokeLength(0, 0));
      return 2 * Math.asin(spokeLengthChange / (2 * flange.getRadius())); // angle from chord length
    }
    
    private double calculateSpokeTorqueArmLength () {
      final double
        r = flange.getRadius(),
        alpha = getFlangeHoleAngle(),
        flatWheelTangentialSpokeLength = calculateEffectiveSpokeLength(-flange.getDistanceFromCenter(), 0),
        flatWheelRadialSpokeLength = calculateEffectiveSpokeLength(-flange.getDistanceFromCenter(), -alpha);
      return (flatWheelRadialSpokeLength + r) * r * Math.sin(alpha) / flatWheelTangentialSpokeLength;
    }
  }  
  
  private final Rim rim;
  private final Hub hub;
  private final Side leftSide;
  
  
  public Wheel (Rim rim, Hub hub, SpokeType spokeTypeLeftSide, int nCrossesLeftSide) {
    this.rim = rim;
    this.hub = hub;
    leftSide = new Side(this, hub.getLeftFlange(), spokeTypeLeftSide, nCrossesLeftSide);
  }
  
  
  public Side getLeftSide() { return leftSide; }
}