// starts encoders
 public DriveTrain() {
   leftEncoder.start();
   rightEncoder.start();
   gyro.reset();
   Preferences p = Preferences.getInstance();
   if (!p.containsKey("DriveTrainShootLimitVoltage")) {
     p.putDouble("DriveTrainShootLimitVoltage", kDefaultShootLimitVoltage);
   }
   if (!p.containsKey("DriveTrainQuickTurnP")) {
     p.putDouble("DriveTrainQuickTurnP", kDefaultQuickTurnProportion);
   }
   if (!p.containsKey("DriveTrainQuickTurnDeadband")) {
     p.putDouble("DriveTrainQuickTurnDeadband", kDefaultQuickTurnDeadband);
   }
   if (!p.containsKey("DriveTrainReverseDirection")) {
     p.putBoolean("DriveTrainReverseDirection", kDefaultReverseDirection);
   }
 } // end constructor
 // starts encoders
 public DriveTrain() {
   leftEncoder.start();
   rightEncoder.start();
   gyro.reset();
   Preferences p = Preferences.getInstance();
   if (!p.containsKey("DriveTrainShootLimitVoltage")) {
     p.putDouble("DriveTrainShootLimitVoltage", kDefaultShootLimitVoltage);
   }
   if (!p.containsKey("DriveTrainQuickTurnP")) {
     p.putDouble("DriveTrainQuickTurnP", kDefaultQuickTurnProportion);
   }
   if (!p.containsKey("DriveTrainQuickTurnDeadband")) {
     p.putDouble("DriveTrainQuickTurnDeadband", kDefaultQuickTurnDeadband);
   }
   if (!p.containsKey("DriveTrainReverseDirection")) {
     p.putBoolean("DriveTrainReverseDirection", kDefaultReverseDirection);
   }
   if (!p.containsKey("LeftEncoderRatio")) {
     p.putDouble("LeftEncoderRatio", 4.875);
   }
   if (!p.containsKey("RightEncoderRatio")) {
     p.putDouble("RightEncoderRatio", 4.875);
   }
   if (!p.containsKey("Encoder_kP")) {
     p.putDouble("Encoder_kP", 0.05);
   }
   if (!p.containsKey("OutputMin")) {
     p.putDouble("OutputMin", .2);
   }
   if (!p.containsKey("DistBuffer")) {
     p.putDouble("DistBuffer", 1);
   }
   if (!p.containsKey("Gyro_kP")) {
     p.putDouble("Gyro_kP", 1 / 18);
   }
   if (!p.containsKey("AngleBuffer")) {
     p.putDouble("AngleBuffer", 4.5);
   }
   if (!p.containsKey("AutoDist_0")) {
     p.putDouble("AutoDist_0", 0.0);
   }
   if (!p.containsKey("AutoDist_1")) {
     p.putDouble("AutoDist_1", 0.0);
   }
   if (!p.containsKey("AutoDist_2")) {
     p.putDouble("AutoDist_2", 0.0);
   }
   if (!p.containsKey("AutoDist_3")) {
     p.putDouble("AutoDist_3", 0.0);
   }
   if (!p.containsKey("ShiftWhenTurningThreshold")) {
     p.putDouble("ShiftWhenTurningThreshold", 0.5);
   }
   if (!p.containsKey("ShiftWhenTurningDelay")) {
     p.putDouble("ShiftWhenTurningDelay", 1.5);
   }
 } // end constructor