MoreMSTS Conversion With Detail On Valvegear

conversion of msts models to rail3D

1 Some basic points to be aware of

1.1

If the final Rail3D model is to be released for open use then the original model maker (and possibly the skin producer) must be contacted for permission to do release. They should also be acknowledged in the model preamble.

1.2

Locomotives with complete outside valve gear (e.g. Walschaerts) cannot be converted from the msts s file with the motion working as in the prototype. This is due to the way in which msts and Rail3D models animate the various motion rods. In general, motion rods aligned as near horizontal in the L direction for Rail3D will appear close to realistic but rods aligned almost vertically (e.g. expansion link, combination lever and eccentric rod) will have poorly reproduced motion.

The way to correct for this is to have available the original model build file (from tsm, Gmax, 3D canvas) and realign the motion rods in the L direction for Rail3D and with the pivot point of each rod at the left hand end of the rod. This can then be converted to the standard msts s file and from there converted to and Rail3D model in the manner described below.

1.3

Locomotives with simple outside motion (outside cylinders, con rods and coupling rods) can be converted in a reasonable fashion to Rail3D but here again would be enhanced if the original model was built with horizontal motion rods and their axes at the Left Hand end of the rod as in 1.2 above.

1.4

All other models e.g. locomotives with only coupling rods, wagons, coaches, guards vans etc can be converted with ease. Static models (scenery, etc) pose few difficulties.

2. Locomotive Conversion Steps

In the following, unless otherwise stated an lner V2 Class locomotive has been used as an example of conversion nomenclature and convertor output.

2.1 Basic Conversion

Follow the steps outlined in Tweaking ConvertedMSTS Models. However it does not deal with the converting of the valvegear components which are addressed in the following sections.

Valvegear motion is well described in the user manual and in Steam Locomotive Valve Gear. It is recommended that these are read by anyone who is not fully familiar with nomenclature and valve gear operation prior to commencing a conversion.

2.2 The stk File.

The conversion of the msts s file from the msts eng and s files produces a Rail3D stk file. This can be quite lengthy but basically consists of a series of ‘primitives’ at the beginning of the listing, followed by the ‘ normal ‘ Rail3D definitions.

e.g. the opening lines of the conversion are :

		with msts to R3D conversion tool
	 Sub 0 Primitive 0
	Name 60845_v2.0.0
	Millimetric
	Component
	Skin “bw_v202.tga”
	<IndexedTriangleList>
		0,2,1
		3,5,4
		6,5,3
		…
		…
	IndexedTriangleList>
	<VertexBuffer>
		610/5419/1664	1000/0/0	0.231018,0.221924
		610/5511/1524	1000/0/0	0.231628,0.225098
		…
		…
	VertexBuffer>
	[end]
	——  Textures used
		…

Then follow the Rail3D definitions as for example:

	Name V2Loco
	Millimetric
	Length 12660
	Weight	94
	Power	1270

etc.

Then comes a series of Primitives each of which is identified with the original msts part name. This is of considerable help in identifying which motion rod is which.

include 0/6330/0 60845_v2.0.0 main include 0/6330/0 60845_v2.0.2 main include 0/6330/0 60845_v2.0.21 main include 0/6330/0 60845_v2.0.23 wheels3 include 0/0/0 60845_v2.0.4 wheels3 include 0/0/0 60845_v2.0.25 wheels3 [end] Name 60845_v2.mtx.2 Component Millimetric include 0/0/0 60845_v2.0.5 Steam Locomotive Valve Gear).

	e.g. include −6/4060/1040	 60845_v2.mtx.1

	becomes
			wheel −6/4060/979	1880/0 60845_v2.mtx.1		'> wheel3  

	and similarly
			wheel −6/6512/979	1880/0 60845_v2.mtx.2 	wheel1

2.3.2 Pony Wheels or Bogie Wheels

These can be identified in the stk file as wheels11 etc and will have a bogie linked with them - usually Bogie1 for wheels 1x and Bogie2 for wheels2x.

	Name 60845_v2.mtx.5
	Component
	Millimetric

		Wheelbase 1890   bogie1

		wheel −5/−8/−172  959/0	 60845_v2.mtx.6   wheels11
	include 0/0/0	 60845_v2.0.33	 wheels3
		include 0/0/0	 60845_v2.0.4	 wheels3
		include 0/0/0	 60845_v2.0.26	 wheels3

		include 0/0/0   60845_v2.mtx.4  #   Coupling Rod

	[end]

Note that as the wheel is already defined as a wheel motion, a plain include is sufficient for the Coupling Rod and inherits a motion1. Also in this particular model, the rod was already positioned correctly relative to the wheel centre.

2.4.2 Connecting Rod

This has had its include moved to the centre driving wheel and converted to a motion2 as shown below:

	Name 60845_v2.mtx.2
	Component
	Millimetric
	include 0/0/0	 60845_v2.0.5	 wheels2
	include 0/0/0	 60845_v2.0.28	 wheels2
	include 0/0/0	 60845_v2.0.30	 con_rod  

	[end]

In this case it was necessary to lower its placement by 330 to fit it correctly Â trial and error may be required sometimes.

The 2410/1050/2 term is well covered in the user manual and in Steam Locomotive Valve Gear but again it was found necessary to adjust the first two figures in the editor while it was running in Rail3D preview mode in order to get the cylinder entry parallel and looking correct.

2.4.3 Piston Rod

This is attached to the Connecting Rod at its opposite end to the wheel. As the Piston Rod moves in the same line as the Connecting Rod, half the work is done. The motion2 call can be placed in the Connecting Rod component as shown:

	Name 60845_v2.mtx.8
	Component
	Millimetric

	include 0/0/0 60845_v2.0.12    piston_rod 

	[end]

Again the user manual and in Steam Locomotive Valve Gear gives guidance on the derivation of the parameters.

2.4.4 Eccentric Rod

This is a bit more tricky. It is attached to the eccentric crank on the centre driving wheel and it was essential that the motion2 call was from that wheel.

Name 60845_v2.mtx.2 Component Millimetric include 0/0/0 60845_v2.0.5 wheels2 include 0/0/0 60845_v2.0.28 wheels2 include 0/0/0 60845_v2.0.30 con_rod motion2 1100/180/30 1561/1100/2 60845_v2.mtx.9 Steam Locomotive Valve Gear) on how to calculate the 1561/110/2 term, although some adjusting will be necessary to get it to look right.

2.4.5 Expansion Link

This was one component that had to be completely changed in the msts model prior to conversion. It needs to have its pivot point at the bottom and its L axis up the link:

It is attached to the remote end of the eccentric rod by trial and error again. The documentation advises on how to calculate its pivot point on its location bracket on the locomotive and may need slight tweaking:

	Name 60845_v2.mtx.9
	Component
	Millimetric

	include 0/0/0 	 60845_v2.0.14	'> eccentric_rod

	motion3 110/1560/40 0/8224/1659	 60845_v2.mtx.14   Expansion link

	[end]

2.4.6 Crosshead Link

With Rail3D, it is best not to make this a motion component, but attach it to the Connection Rod assembly:

	Name 60845_v2.mtx.8
	Component
	Millimetric

	include 0/0/0 60845_v2.0.12   piston_rod  

	motion2 1000/2410/0  1735/1050/2	 60845_v2.mtx.10	 xhead_link  
	motion3 50/430/−220 0/9200/1618 60845_v2.mtx.11  #  Combination lever 

	[end]

2.4.8 Radius Rod

This is connected to the Expansion Link and the top of the Combination Lever. In Rail3D, the wisdom is to connect it to the Expansion Link, either as a fixed component or as a motion2, depending on how the msts model modelled it. If a motion2 is used, then it should be attached to the Expansion Link at its pivot point on the locomotive frame.

2.5 Outside Cylinder Locomotives

Models of this type only need to use the general descriptions presented in sections 2.3 and 2.4 (up to and including 2.4.3). It may be that the motions produced in Rail3D are not as good as they might be due to the msts s file. Hence, if the original tsm etc file is available then adjustment of alignments will correct this.

2.6 Inside Cylinder Locomotives

Models of this type only need to use the general descriptions found in section 2.4.1 with completely satisfactory results.

2.7 Coaches and Wagons

These models only need to be modified in respect of pony wheels - section 2.3.2. See also the relevant section in the user manual on Bogies.

Most wagons do not have bogies hence they can be converted in the same way as set out in 2.4.1 ignoring the Coupling Rod motion.

2.8 Static Models

A simple example of a static model conversion from an msts s file is that of a static milk churn.

The initial conversion from the s file (no eng file is used in msts) in reduced form is as follows:

	 Sub 0 Primative 0
	Name bw_churn.0.0
	Millimetric
	Component
	Skin “bw_chrn.tga”
		<IndexedTriangleList>
			0,2,1
			…
		VertexBuffer>
	[end]

		 Assembly 
			bw_chrn.ace

		Name bw_churn
		Millimetric
		Length 0

The file will have the xxx.stk format. This needs to be changed to xxx.stc, i.e. a scenery file.

The additions needed to the stc file take the form of includes for each of the Primitives identified in the leading part of the conversion. This simple model only has one -

	——  Textures used
	 additional line needed in the stc file

	[end]

If the stc file and the associated bmp / tga files are then place in the scenery folder and the scenery index rebuilt the model will be available for placing in the Rail3D route as described in the user manual for scenery placement.

3. Further Considerations

By the modular nature of building models in Rail3D additions can be made to models with ease. Examples of this approach can be found in the use of different liveries on the same model build, the placing of loads into wagons so that a variety of loads can be depicted.

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3.2 Liveried Wagons etc

Different liveries can be attached to a basic wagon by changing the reference to the skin in the assembly part of the wagon file. An example of this can be found in the listing for the two lms Brake vans (lms Brake Vans.zip) which have been uploaded to the files/stock/wagons area of Yahoo Railway3D Group.

4 Locomotive Units

Locos and tenders are usually set as a composite unit and can be called as such in Rail3D.

For the lner V2 the stk file contains the conversions for both the Locomotive and the Tender. These are then combined into a unit as follows:

	Name V2
	Description	Ex-lner Class V2 Locomotive and Tender in br livery
	Credit Brian Walker for the original msts model and R Darling for the conversion to Rail3D

	Unit V2Loco&V2Tender

	[End]

5 Numbered / Named Units

This is explained in the users manual under the heading ‘ Gricer’ Mode. An example of numbering is as follows:

	Number       801–983        60%03d
	Â
	fill 1355/1710/1905 1355/−25/1905 1355/−25/2305 1355/1710/2305 0.0.0 $ <$number 1 255.255.220 256.65 72 arial>

6. Conclusions

It has been found that with a few modifications of a msts model prior to conversion, a Rail3D locomotive with the msts valvegear working to the same standard as starting from scratch can be produced satisfactorily.

Thanks are due to Brian Walker for his patience with RussellÂs suggestions during our experimentation with his model and to Mark Goodspeed for his help in putting Brian Walker on the correct path with frequent questioning of Âhow do you….?Â

18 December 2006

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