ADAMS/Chassis offers several options for twist beam rear suspensions.
Twist Axle, Trailing Arm, Axle Attachment and Spindle Compliance options are explained in this document.
The explanations of these twist axle options are described below.
2-piece twist axle has a left and a right twist axle parts. These left and right parts are connected by "FIELD" statements. These axle parts are conneced to trailing arm parts by "BEAM". The user has to define BEAM statements in the "CustAdmText" Tab of the subsystem file. The following is the example of these BEAM statements:
R E A R T W I S T A X L E F I E L D S FIELD/52,I = 35295,J = 35396, CRATIO = 1.0E-08 FIELD BTW L & R TWIST AXLES ,KMATRIX = 1.154582E+02 , 1.542750E+00,-3.299564E-01,-2.565903E+02,-5.435790E+03, 9.227785E+04 , 1.542750E+00, 9.740945E+03,-2.232566E+00, 9.166660E+05,-6.793570E+01 ,-7.803890E+02,-3.299564E-01,-2.232566E+00, 1.134659E+02,-9.083015E+04 ,-2.085445E+00, 4.021194E+02,-2.565903E+02, 9.166660E+05,-9.083020E+04 , 1.878283E+08,-8.830405E+02, 4.053620E+05,-5.435790E+03,-6.793570E+01 ,-2.085415E+00,-8.830370E+02, 1.080241E+06, 4.342619E+06, 9.227785E+04 ,-7.803890E+02, 4.021194E+02, 4.053620E+05, 4.342619E+06, 1.073457E+08 , LEN = 0, -1600, 0, 0D, 0D, 0D FIELD/53,I = 35396,J = 35295, CRATIO = 1.0E-08 FIELD BTW R & L TWIST AXLES ,KMATRIX = 1.154582E+02 ,-1.542750E+00,-3.299564E-01,+2.565903E+02,-5.435790E+03,-9.227785E+04 ,-1.542750E+00, 9.740945E+03,+2.232566E+00,-9.166660E+05,-6.793570E+01 ,+7.803890E+02,-3.299564E-01,+2.232566E+00, 1.134659E+02,+9.083015E+04 ,-2.085445E+00,-4.021194E+02,+2.565903E+02,-9.166660E+05,+9.083020E+04 , 1.878283E+08,+8.830405E+02,-4.053620E+05,-5.435790E+03,-6.793570E+01 ,-2.085415E+00,+8.830370E+02, 1.080241E+06,-4.342619E+06,-9.227785E+04 ,+7.803890E+02,-4.021194E+02,-4.053620E+05,-4.342619E+06, 1.073457E+08 , LEN = 0, 1600, 0, 0D, 0D, 0D B E A M to A X L E BEAM/0005,I= 35261,J= 36152 L TWIST AXLE BEAMT to ARM , LEN = 589.965462, IXX = 3237.5, IYY = 204750, IZZ = 4650, AREA = 45 , EMODULUS = 2.06832E+05, GMODULUS = 79551, CRATIO = 1.0E-08 BEAM/0006,I= 35362,J= 36253 R TWIST AXLE BEAMT to ARM , LEN = 589.965462, IXX = 3237.5, IYY = 204750, IZZ = 4650, AREA = 45 , EMODULUS = 2.06832E+05, GMODULUS = 79551, CRATIO = 1.0E-08
Note that in the above statements, if spindle compliance is turned on, a spring pod is created. In that case, BEAM/0005 and BEAM/0006 should connect "TWIST AXLE BEAM" and "SPRING POD" (instead of "ARM"). Thus, markers have to be changed accordingly.
3-piece twist axle has three axle parts: left, right and middle axle parts. Left and right twist axle parts are connected to trailing arms by "BEAM" and connected to a middle twist axle part by "SPHERICAL" joint and "BUSHING".
For this option, a user can define a number points on a twist axle and a twist beam axle is created. Each small parts are connected each other by "BEAM". Twist axle and trailing arm are connected by a "FIXED" joint.
(2) Trailing Arm option "2" (2 piece arm) has to be selected. Other options are not allowed.
(4) "twst_axs_angle" and "arm_axs_ang" are properties such that users can change the orientation of Z-axis for BEAM statements. The following pictures explain these angles. The default of these variables are 0 deg. which points z-axis to upward (the same as the global z).
For this option, the user has to select "2 pc arm" option. If the user wants to use 1 pc arm option, it is suggested to use "2 pc arm" option with very stiff beam parameters for arms.
For this option, a trailing arm and a half of twist axle are constructed as one part. Left and right axle are connected by a "SPHERICAL" joint and a "BUSHING".
(2) Trailing Arm option "3" (1 peice arm+ half axle) has to be selected. Other options are not allowed.
Depending on the twist model selected, various properties and parts will be available via the property editor to modify the data. Some examples are shown below:
Four trailing arm options are available.
Two axle attachment options are available. Axle can connects to either a spring pod or an arm.
Spindle compliance can be turned on and off by a construction option.
When a spindle compliance is off, a twist axle and a camber adjuster are connected by a rev. joint and a spindle and a camber adjuster are connected by a rev joint. If a model does not have a spindle (for example, an old twist.aft does not have a spindle part), a toe adjuster is created between a wheel and a camber adjuster. The user has to be careful for the following things:
(1) If using a beam twist axle and there is a panhard rod in the model, a spindle compliance has to be turned on.
(2) Axle attachment option has to be 2 (Arm) when a spindle compliance is off.
When a spindle compliance is on, there are a ball joint and a bushing between a camber adjuster and a spring pod. A spring pod is always created when choosing this option. If a hub compliance is on, a spindle and a hub compliance are connected by a ball joint and a bushing. If a hub compliance is off, a spindle and a hub compliance are connected by a fixed joint. A dummy hub compliance is created in *.adm file whether or not a hub compliance is on or off.