Second Life Railroad/SLRR standards

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Revision as of 14:28, 24 August 2010 by Stryker Jenkins (talk | contribs) (→‎SLRR track standards: added Tetriary Guide to Guidance prim alternatives)
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Description

Second Life Railroad uses a basic railway track for vehicles to run on. On this Page you find the measurements and information associated with the railway track. The SLRR was originally designed to work under the prevailing conditions in SL. No formal standards for its design were ever published until now. Many changes have occurred in SL since that time, and there is work underway to establish formal standards to guide Resident rail content creation for use on the SLRR. This work was started on the 18th of August 2010 during a LDPW led Railway Brown Bag meeting with the Rail community.

The SLRR is made up of specific prim sizes and names. The standards here are general measurements taken from in-world and put on the Second Life wiki pages.

In the future a description of an open source scripts will also be made available here and some objects like the rail tracks are made available at the "Mole Mart".

If you have a different idea about the standards as described here you can use the Talk page to add your comments, idea's and suggestions. Please don't add them in this text.

Open Access

Since 2005 the SLRR has been operating. First with Linden Lab automated trains and later with trains build and operated by SL Residents. Already many Residents have personal trains they use on the SLRR. SL Residents can operate trains on the SLRR, much as anyone can operate a car on the roads in SL. In addition, some Residents have used the SLRR track gauge to build drivable railroads on their private lands.

Different train builders came up with a variety of train types with different propulsion methods. The SLRR Track standards have not changed much over the years and train builders found ever better ways to make their trains run on the SLRR.

Component information

Guidance

Guidance is the actual way the vehicle "knows" where the track is and uses it to steer itself.

The existing system, Collision Guidance, involves a non-phantom (invisible) center rail, called Guide. The trains running on these tracks use this rail as a physical steering mechanism. A vehicle linear motor pushes the vehicle and collisions with the rail steers it.

Other vehicles use a sensor and target system to steer (Sensor Guidance), so collisions are unnecessary.

Control

Control is the way the rail network as a whole works safely while sharing the rail resources among consists.
Currently (12-2009) there is no such system in place.

Many people have suggested a control system on the public SLRR is not a good thing. Other say it is best to have a system that tells if there is on comming trafic on the track. And ohter residents suggest a full control system like on Real Life railroad tracks. On the Talk page you can voice your opinion about this subject.

Gauge

Gauge is the width of the actual vehicle / track combination.

This is not very important, as it is for appearance only, but it would be good to have a standard that builders can use.

Railbed

Railbed is the actual track design.

There are presently:

  • Flat - cheap for prims, does not look so good, good for sliding on.
  • 3-D phantom - costs more prims, looks good, good for sliding on.
  • 3-D non-phantom - costs more prims, looks good, creates a visible gap (the Havok Clearance of 0.1 meter) between sliding prims and rails.

Standards

SLRR track standards

(information based upon measurements taken from the original tracks made by Eric Linden.)

  • Gauge:

The inside edge-to-edge distance between the rails.

Size: 1.96M 
  • Railbed:

To construct the Railbed (e.g. Gravel bed) you place a prim on a flat surface and set the measurements and attributes as given below. The length of the track is set in this example to 10.00 meter, but this can change according to your needs.

prim size:        prim rotation:
 x = 8.322         x = 0
 y = 10.00 *       y = 0
 z = 0.686         z = 0

prim attributes
- Prim name: Atoll Railroad Section or SLRR Alternate Route **
- Taper set to x 0.40
- Taper set to y 0.00
- NOT Phantom
- Material: Glass
    • The name Atoll Railroad Section is used for main section of track and SLRR Alternate Route is used for pass-tracks and spurs.
  • Track:

To construct the track (the actual rails themselves) you need to place 2 prims directly on top of the already constructed Railbed. And place them 1.96/2 (0.98m) left and right of the center of the Railbed. Do not forget to make the prims Phantom, so they don't interfere with the train wheels. The length of the track is set in this example to 10.00 meter, but this can change according to your needs.

prim size:        prim rotation:
 x = 0.173         x = 180
 y = 10.00 *       y = 0
 z = 0.198         z = 0

prim attributes
- Taper set to x 0.50
- Taper set to y 0.00
- Phantom
  • Loading Gauge:

The clear width (from the centerline) and height (above the Guide) should be as follows:

  width = 4 meters for straight track and cars under about 20 meters length; 4.5 meters if longer cars are expected
  height = 8 meters for normal passenger and freight equipment; 9 meters for double-stack containers

Long cars on sharp curves will require expansion of the loading gauge.
A nice Resident might wish to take a test run along the right-of-way and check for violations (Michael Linden) / Info shared (Stryker Jenkins).

  • Guidance:

To construct the Guidance place a prim on the Railbed and raise it 0.15 meter up. And apply a full transparent texture to it. Next name the prim 'Guide' The length of the track is set in this example to 10.00 meter, but this can change according to your needs.

prim size:        prim rotation:
 x = 10.00 *       x = 0
 y = 0.5           y = 0
 z = 0.5           z = 0

prim attributes
- prim name: 'Guide', 'Alternate Guide' or in special cases 'Tetriary Guide'
- NOT phantom
- Material: Glass

SLRR track curves

Curves in the SLRR tracks are made using shortened sections of the standard (straight) track. There is currently no fixed data on how tight a curve can be (a.k.a. the radius).

Out of experience can be derived that a radius should be very wide to have the trains pas at any significant speed. Tighter curves tend to de-rail trains that use the center 'Guide' to steer.

To make curves use straight sections with a

length of 5 to 9 meters

and angle them no tighter then

15 degrees, but more typically 2-6 degrees

from each other. Using the center of the guide as a pivot point.

SLRR track Sim crossings

Border crossings are always tricky in SL. A much used method to improve this is to over lap the 'Guide' prim (2 in the same location more or less centered near the border).

Then to Link 1 of those doubled up prims to the next 'Guide' prim on one one sim. And to link the other doubled up prims to the next 'Guide' prim on the other sim. Making sure that the doubled up prims is the 'child prim' and the prim completely over the sim is the 'root prim'.

SLRR track switch (concept)

Having the ability to switch from one track to the other is an essential part of any rail network. This can be done in many different ways. It depends on the type of guidance used to make the train move along the tracks. But also on the type of trains that use the system.

On the following page we discuss a concept of how a semi automated switch point could help users switch track. LDPW is working on a switch. The way this is operated or how it will look is still unknown.

SLRR buffer stop

At the end of a railway line we often find a Buffer. These are put there to prevent trains running of the track.
In SL this also exist in many way shapes and forms. Sensor driven trains can look for an object named

Buffer stop

Depending on the way the scripts in these trains work the sensor driven trains know when to stop and even to turn around when they encounter such an object. An other method that is commonly used is to turn sensor driven trains around when they no longer "sence" the presence of more "Guide rails". Most Physical trains rely on drivers to stop in time and turn around their train.


Source

The above information was collected by the Virtual Railway Consortium (VRC) Tuliptree (107, 131, 30) with the help of Stryker Jenkins, Moundsa Mayo. Qie Niangao and Kitto Flora.

Additions where provided by Jer Straaf and others associated with other Railway related group.

Linden Lab is currently the "operator" of the SLRR track. The SLRC collected existing data for these wiki pages but did not set any standards. They evolved over time as Linden Lab employees constructed the Second Life Railroad.