*SetTorsionSpring() - single torsion spring
Sets the properties of a torsion spring. \
Syntax
*SetTorsionSpring(spr_name, TYPE_k, TOKEN_k 
                                      TYPE_c, TOKEN_c 
                                      f, l)
    Token
- LIN
 - Enter a value for: k and c
 - CRV
 - Use a Curve to represent the torsion spring behavior. See Comments.
 - SPL3D
 - Use a Spline3D to represent the torsion spring behavior. See Comments.
 - EXPR
 - Enter a solver expression that represents the torsion spring behavior.
 
Arguments
- spr_name
 - The variable name of an existing torsion spring.
 - k
 - The stiffness coefficient of the torsion spring.
 - c
 - The damping coefficient of the torsion spring.
 - f
 - The load on the torsion spring when it has a particular angle.
 - l
 - The angle of the torsion spring when it has a particular load.
 - curve_name, AKIMA|CUBIC|LINEAR|, QUINTIC, `indep_variable`
 - When using curve data, a curve, an interpolation method, and an independent variable must be specified, where curve_name is the variable name of an existing curve that represents the force characteristic, the interpolation method can be set to AKIMA, CUBIC, LINEAR, or QUINTIC. The indep_variable is the solver expression representing the independent variable along which the force curve is characterized.
 - spl3d name, AKIMA|CUBIC|LINEAR| QUINTIC, 'indep_var1', 'indep_var2'
 - When using spline3d, a Spline3D entity, an interpolation method, and two independent variables must be specified, where spl3d_name is the variable name of an existing Spline3D entity that would represent the force v/s two independent variables. The interpolation method can be set to AKIMA, CUBIC, LINEAR, or QUINTIC. indep_var1 is the solver expression for the first independent variable. indep_var2 is the solver expression that represents the second independent variable.
 - `expression`
 - An expression for the torsion spring token.
 
Example
*Point(p_bar_mnt_left,  "Bar mnt left")
*Point(p_bar_mnt_right, "Bar mnt right")
*Body(b_bar_left,     "Bar left",	   p_bar_left_cg)
*Body(b_bar_right,    "Bar right",     p_bar_right_cg)
*TorsionSpring(tspr, "Torsion spring", b_bar_left,
                                       b_bar_right,
  				   p_bar_mnt_left,
  					   p_bar_mnt_right)
*SetTorsionSpring(spring_uca, 1.000e+02,	0.000e+00, 
		  	    0.000e+00,	3.500e+02)
*TorsionSpring( spr_tbar, "Torsion bar", 
			                 b_upr, b_lwr, p_upr, p_lwr)
    
*SetTorsionSpring(spr_tbar, `-POLY({ spr_tbar.AZ }, 0, 0, 10, 30)`,
                            1000,
                            0,
                            0)
    Context
Comments
To specify non-linear properties for the force in any direction, a solver expression, curve data, or spline 3D data can be used. When using solver expressions, Templex syntax is used and all variables are enclosed in braces {} and the rest is treated as literal.
The QUINTIC interpolation method is supported for MotionSolve only.