model rigged inside unreal editor

rigging the vehicle

Roamer model is based on the scorpion so load it into the unreal editor and use middle mouse drag to get the size of the wheels. 

45/10 = 4.5

Create a cylinder in trueSpace with the same diameter scaled by 1/10.  The PSK exporter scales by 10.  Scale the model till the wheel size matches.  The PSK exporter will mirror the mesh on the Y axis, so use the mirror tool on the mesh across the Y axis.  Next freeze the transforms of the mesh to set the scale to 1 and the rotations to 0.
before mirrormirrored and frozen
before and after mirror and transform freeze 

freeze transform script

Scorpion joint placement

bone layout
Roamer skeleton - side view shows extra bones for the steering wheel and the door

Build skelton with the default joint spread set to 180,180,180
Start skeleton in the front view drawn vertically top to bottom centered more or less on origin.  Exit the skeleton tool and reset the matrix on the Skeleton node and on the Skeleton_root node inside the Skeleton node.
This process makes the first joint of the hierarchy relative to the origin in position and orientation.
Name the bottom joint, "MyJoint" and rename the bone to "MyBone".  These names are required by the exporter.
Now build the rest of the skeleton from the top joint.  The top joint will act as the root joint for the skeleton.  The joints can be perfectly centered in the wheels by using the object snapping script.

click this line to get the object vertex snap script

joints before leaves
initial joints before the leaf joints are added
wheels where snapped to the center using the script

The wheel joint has an extra joint to form a bone for skinning.  Use the extra joint to align the wheel joint z axis.  Place the extra joint above the wheel joint then rotate the wheel joint until it's rotations are close to 0,0,0.  This will make the z axis up and the x axis point toward the front of the vehicle.  The joint orientation script makes this process simpler.

click this line to download the joint orientation script

It's best to start using the script at the root joint, "Main_Root", and work towards the ends of the chains.  The scene view makes it easy to select the joints.

orient before
Main_Root joint before orientation

orient after
Main_Root joint after orientation(rotations set to (0, 0, 0))
note that Z points up and X points towards the front of the vehicle
the tires will have the same orientation

The joint names for the wheels were set to match the names used in the Scorpion.  "F_L_Tire" for the front left tire etc.  However, the left and right sides are reversed because of the mesh being mirrored earlier.  So the front left will be on the right side of the model.  The child bones of the joints are given the same name as their parent joint with a "Bone" postfix.  "F_L_Tire" joint would have the child bone named "F_L_TireBone".  This naming is required by the PSK exporter.  The joint names at the end of the chains don't matter. 

joint naming
joint renamed - notice front left is on the right side of the vehicle

child bone naming
corresponding child bone name

I later found that the gun_rotate joint was needed for proper eye placement.  In fact the whole process would have gone smoother if I had recreated all the joints used in the Scorpion.  The carDoor was originally named door, but the unreal import changed it's name.
Export the bone names for the Scorpion from ued to save some typing and avoid errors.

Scorpion bone names

remove all weights from MyBone,  set first bone Main_Root to chassis, front right wheel

steering wheel and door
Unreal requires triangulated meshes, so triangulate the mesh.
Skin the mesh to the skeleton and then use weight paint to set the values.
I named the resulting actor to SK_VH_Roamer.

1. Select the bone
2. Use the convert skin weight to soft selection tool
3. Choose a point edit selection mode(painting, rectangle, lasso, soft selection etc)
4. Make a selection then choose select connected to get entire piece(like a tire)
5. Choose convert soft selection to skin weight tool. Right click for options and make sure replace mode is chosen.  If not select replace mode and run the tool again
6. Right click to exit point edit mode and return to weight paint mode

Repeat for each bone.
Remove all weights from the bones that have no influence including "MyBone".  All of the vehicle body is assigned to the first bone in the skeleton after MyBone.

import export panel
click this image to get the unreal import export script and plugin.

Export a PSK file to SK_VH_Roamer.psk
Make animations and export psa files - each animation will have the same internal name and can be renamed after importing into unreal editor. 
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