"Bogeys" container

As of classics 3 and later, you can now specify "permits-sideplay" and "permits-rotation" in the "Bogeys" container.

The default is '0' for sideplay, and '1' for rotation, which matches previous Trainz behaviour. Each is a boolean option (you can set either '0' or '1').

With "permits-sideplay 1", the bogie will follow the track, rather than stay rigidly locked in place at the location of the attachment point on the body.

With "permits-rotation 0", the bogie will not rotate to align itself with the track. This is useful when the wheels being represented are fixed to the frame of the vehicle, and are not mounted on a rotating bogie.

For example, a Tri-Bo locomotive where the centre bogie slides from side to side can be represented like this:

bogeys {
  0 {
    reversed           0
    bogey              <KUID2:xxxxx:yyyyy:zzz>
  }
  1 {
    reversed           1
    bogey              <KUID2:xxxxx:yyyyy:zzz>
   }
  2 {
    reversed           0
    sideplay-permitted 1
    bogey              <KUID2:xxxxx:yyyyy:zzz>
  }
}

a.bog0 and a.bog1 are used for the two end bogies, and will locate the vehicle on the track as happens now. But the bogie attached at a.bog2 in the middle will now follow the track through curves rather than stay firmly riveted on the underframe with it's wheels dangling in mid air.

Another example is a loco with central power bogies, and outer bogies to help traverse curves. The PRR GG1 (wheel pattern 2-co-co-2) is of this type. This can now be represented as follows:

bogeys {
  0 {
    reversed           0
    bogey              <KUID2:xxxxx:yyyyy:zzz>
  }
  1 {
    reversed           1
    bogey              <KUID2:xxxxx:yyyyy:zzz>
  }
  2 {
    reversed           0
    sideplay-permitted 1
    bogey              <KUID2:xxxxx:yyyyy:zzz>
  }
  3 {
    reversed           1
    sideplay-permitted 1
    bogey              <KUID2:xxxxx:yyyyy:zzz>
  }
}

a.bog0 and a.bog1 are used for the main power bogies to locate the vehicle correctly on the track. a.bog2 and a.bog3 are used for the leading and trailing unpowered bogies. These are permitted sideplay so they follow the track.

A two axle rigid frame vehicle can be represented as follows:

bogeys {
  0 {
    reversed           0
    rotation-permitted 0
    bogey              <KUID2:xxxxx:yyyyy:zzz>
  }
  1 {
    reversed           1
    rotation-permitted 0
    bogey              <KUID2:xxxxx:yyyyy:zzz>
  }
}

In this case, each "bogie" would be a single axle. The location of the attachment point will specify how the vehicle is aligned when on a curve, so should be placed at the location of the axle in the 'y' direction.

An interesting case might be a three axle rigid frame vehicle - with sideplay (but no rotation!) on the centre axle. This might be represented as follows:

bogeys {
  0 {
    reversed           0
    rotation-permitted 0
    bogey              <KUID2:xxxxx:yyyyy:zzz>
  }
  1 {
    reversed           0
    rotation-permitted 0
    bogey              <KUID2:xxxxx:yyyyy:zzz>
  }
  2 {
    reversed           0
    rotation-permitted 0
    sideplay-permitted 1
    bogey              <KUID2:xxxxx:yyyyy:zzz>
  }
}

These tags are useful for steam locos too. Consider the pacific '4-6-2' wheel pattern. Looking from the front (a.limfront) end through to the back (a.limback), one way to arrange the bogie attachment points to get the required behaviour is:

a.bog2 - front bogie (the '4' in '4-6-2'). For best results, the attachment point should be the centre of the wheelbase. Use 'sideplay-permitted 1' on this bogie.

a.bog0 - drive bogie (the '6' in '4-6-2'). The attachment point should be circa where the front axle is. Move it back a bit if you have a lot of axles (e.g. 5 or more) in the drive bogie. Configure this one with 'sideplay-permitted 0' and 'rotation-permitted 0' - you don't want it moving around on curves at all! (With 'rotation-permitted 0' there is now no need to locate it at 0,0,0 to stop it rotating).

a.bog1 - an invisible bogie in line with the rear axle of the drive bogie. Move slightly forward if your drive bogie is large (e.g. 5 axles or more). This will make the locomotive body follow the track properly.

a.bog3 - trailing pony truck (the '2' in '4-6-2'). The attachment point should be in line with axle. Use 'sideplay-permitted 1' as with the front bogie.

This will produce the correct behaviour both from the locomotive body and the various bogies.

Using these parameters should mean that even very flexible locos (e.g. a Mallet or Garratt) can be built in a much more realistic manner, and with fewer separate pieces that need assembly in Surveyor.

Random debugging hint

Q: "But I set this feature, and when I go round a corner, my bogie now floats off in some other direction that I wasn't expecting! What is wrong?"

A: Have you by any chance rotated the attachment point by 180 degrees in MAX to get the bogie to appear the other way round, but not set "reversed 1" in the config container for that bogie? These two things together can cause the effect you are seeing. You should also be able to spot this case because your wheels will be rotating the wrong way...