function clearEfficiencyResults(num)
  {
    for ( numItems = 1; numItems <= num; numItems++ )
    {
      elementName="ec"+numItems+"efficiency";
      document.forms['efficiencyForm'].elements[elementName].value="-";
    }
  }

  function calcRubberEfficiency(num)
  {
    speed=document.forms['efficiencyForm'].speed.value;
    load=document.forms['efficiencyForm'].load.value;

    if( isNaN(speed) || speed < 0 )
    {
      alert('You did not enter a valid number for speed');
      document.forms['efficiencyForm'].speed.select();
      return;
    }
    if( isNaN(load) || load < 0 )
    {
      alert('You did not enter a valid number for load');
      document.forms['efficiencyForm'].load.select();
      return;
    }
    speed=speed*1.0;
    load=load*1.0;

    for ( numItems = 1; numItems <= num; numItems++ )
    {
     item_sd="ec"+numItems+"sd"; // Static deflection
     item_ml="ec"+numItems+"ml"; // Max load
     item_df="ec"+numItems+"df"; // Dynamic factor

     static_deflection=document.forms['efficiencyForm'].elements[item_sd].value*1.0;
     max_load=document.forms['efficiencyForm'].elements[item_ml].value*1.0;
     dyn_factor=document.forms['efficiencyForm'].elements[item_df].value*1.0;
    
     dist_freq=speed/60;
     deflection=(load/max_load)*static_deflection;

     nat_freq=(1/(2*Math.PI))*(Math.sqrt(9.81/(deflection/1000)))*dyn_factor;
     e=Math.round((1-(1/((Math.pow(dist_freq/nat_freq,2))-1)))*10000)/100;

     elementName="ec"+numItems+"efficiency";

     //calculator = "calculator"+numItems;

     if ( e < 0 || e > 100.0 || load > max_load )
     {
       document.forms['efficiencyForm'].elements[elementName].value="n/a";
//       //document.forms['efficiencyForm'].elements[calculator].src="images/spacer.gif";
     }
     else
     {
       document.forms['efficiencyForm'].elements[elementName].value=e;
       //document.forms['efficiencyForm'].elements[calculator].src="images/calculator.gif";
     }
    }
  }

  function calcSpringEfficiency(num)
  {
    speed=document.forms['efficiencyForm'].speed.value;
    load=document.forms['efficiencyForm'].load.value;

    if( isNaN(load) || load < 0 )
    {
      alert('You did not enter a valid number for load');
      document.forms['efficiencyForm'].load.select();
      return;
    }
    if( isNaN(speed) || speed < 0 )
    {
      alert('You did not enter a valid number for speed');
      document.forms['efficiencyForm'].speed.select();
      return;
    }
    speed=speed*1.0;
    load=load*1.0;

    for ( numItems = 1; numItems <= num; numItems++ )
    {
     item_ml="ec"+numItems+"ml"; // Max load
     item_sd="ec"+numItems+"sd"; // Static deflection
     item_sc="ec"+numItems+"sc"; // Spring constant

     static_deflection=document.forms['efficiencyForm'].elements[item_sd].value*1.0;
     max_load=document.forms['efficiencyForm'].elements[item_ml].value*1.0;
     spring_constant=document.forms['efficiencyForm'].elements[item_sc].value*1.0;
    
     dist_freq=speed/60;
     deflection=(load/max_load)*static_deflection;

     nat_freq=(1/(2*Math.PI))*(Math.sqrt(9.81/(deflection/1000)));
     e=Math.round((1-(1/((Math.pow(dist_freq/nat_freq,2))-1)))*10000)/100;

     elementName="ec"+numItems+"efficiency";

     //calculator = "calculator"+numItems;

     if ( e < 0 || e > 100.0 || load > max_load )
     {
       document.forms['efficiencyForm'].elements[elementName].value="n/a";
       //document.forms['efficiencyForm'].elements[calculator].src="images/spacer.gif";
     }
     else
     {
       document.forms['efficiencyForm'].elements[elementName].value=e;
       //document.forms['efficiencyForm'].elements[calculator].src="images/calculator.gif";
     }
    }
  }