/////////////////////////////////////////////////////////////////////////////
//
// javascript source code for the rotor head calculator at:
// http://www.natew.com/frames.cgi/heli/calc/html.BladePhysics
//
// Nate Waddoups, 14 April 2001
//
/////////////////////////////////////////////////////////////////////////////

var rPi = 3.1415926535;

function SolveForPull (form)
{
  var rBoltRadius = form.elements["BoltRadius"].value / 1000;
  var rBladeLength = form.elements["BladeLength"].value / 1000;
  var rBladeWeight = form.elements["BladeWeight"].value / 1000;
  var rWeightPlacement = form.elements["WeightPlacement"].value / 100;
  var rRPM = form.elements["RPM"].value;

  var rTipRadius = rBoltRadius + rBladeLength;
  var rTipCircumference = 2 * rPi * rTipRadius;
  var rTipSpeed_MPS = rTipCircumference * (rRPM / 60);

  var rMassRadius = (rBoltRadius - 0) + 
	((rBladeLength) * rWeightPlacement);
  var rMassCircumference = 2 * rPi * rMassRadius;
  var rMassSpeed_MPS = rMassCircumference * (rRPM / 60);

  var rAcceleration = (rMassSpeed_MPS * rMassSpeed_MPS) / rMassRadius;
  var rCentrifugal_N = rAcceleration * rBladeWeight;

  var rRotorArea = (rTipRadius) * (rTipRadius) * rPi;
  var rRotorArea = Math.round (rRotorArea * 100) / 100;

  form.elements["TipSpeed"].value = rTipSpeed_MPS * 1.943846560876;
  form.elements["Centrifugal"].value = rCentrifugal_N / 4.45;
  form.elements["RotorArea"].value = rRotorArea;
}

function TipSpeedToRPM (form)
{
  var rBoltRadius = form.elements["BoltRadius"].value / 1000;
  var rBladeLength = form.elements["BladeLength"].value / 1000;
  var rBladeWeight = form.elements["BladeWeight"].value / 1000;
  var rWeightPlacement = form.elements["WeightPlacement"].value / 100;
  var rTipSpeed_MPH = form.elements["TipSpeed"].value;

  var rTipRadius = (rBoltRadius - 0) + (rBladeLength - 0);
  var rCircumference_M = 2 * rPi * rTipRadius;

  var rTipSpeed_MPS = rTipSpeed_MPH / 1.943846560876;
  var rRPM = (rTipSpeed_MPS * 60) / rCircumference_M;

  form.elements["RPM"].value = rRPM;

  SolveForPull (form);
}

function CentrifugalForceToRPM (form)
{
  var rBoltRadius = form.elements["BoltRadius"].value / 1000;
  var rBladeLength = form.elements["BladeLength"].value / 1000;
  var rBladeWeight = form.elements["BladeWeight"].value / 1000;
  var rWeightPlacement = form.elements["WeightPlacement"].value / 100;
  var rCentrifugal_Pounds = form.elements["Centrifugal"].value;

  var rMassRadius = (rBoltRadius - 0) + 
	((rBladeLength) * rWeightPlacement);
  var rMassCircumference = 2 * rPi * rMassRadius;

  var rCentrifugal_N = rCentrifugal_Pounds * 4.45;
  var rMassAcceleration = rCentrifugal_N / rBladeWeight;

  var rMassSpeed_MPS = Math.sqrt (rMassAcceleration * rMassRadius);
  var rRPM = rMassSpeed_MPS * 60 / rMassCircumference;

  form.elements["RPM"].value = rRPM;

  SolveForPull (form);
}

function SolveFromArea (form)
{
}

/////////////////////////////////////////////////////////////////////////////
// EOF.  Stop reading here ->