Preface:
As technology advanced over the 21st century, and approached the 22Nd, mechanized warfare began to dominate the battlefield. As laser counter measures for defense against long range cruise missiles improved, the conventional way of waging war with ICBMs in the 20Th century became obsolete. Cyber tanks became the wave of the future. Dubbed "OGRE's" they where able to go into a highly hostile and defended area, seize control, and then be able to sit for as long as needed to secure the area. With layers of BPC armor, they could withstand most anything and with flawless non emotional battle logic, they were a living nightmare for commanders of defending city's. The auto-facs that made them became a need for everyday life as well and the factories in ones city were likely targets for rival factions during the years of the "factory states". New means of defending ones factories and command posts where needed. This led to the development of underwater installations. Built and run by the mix of mankind and machine, rival states began installing their nearby lake beds and sea shores with command posts and auto facs. This made them absolutely nearly impossible to infiltrate and destroy, and an Ogre traveling under water was at a disadvantage when trying to take one of them out, as they where not only underwater, but embedded far under the layers of silt as well. the only way in or out of one of the underwater facility's was by underground loco motive train, and the outside administrative depot buildings where strong holds in their own right. And it was in one of these underwater auto facs that a siege train for the destruction of rival states was born. Dubbed the Goliath Siege Engine (G.S.E.), the first ones where little more then a few heavy tank guns on-board beefed up human conducted trains. These eventually gave way to trains conducted entirely by Ogre type brains. As the Ogre brain proved itself time and again in siege after siege of city with the use of its new hardware, the hardware got mass upgrades. When auto facs and command posts went "underwater", a new means of attack had to be made. As it took massive amounts of BPC marines or mobile Howitzers to lay siege to a installation under water, newer ways of transporting and implementing those types of units had to be re-invented. It was the G.S.E. that was eventually chosen for this job, as it was discovered that they were able to infiltrate and or destroy one of these places much more efficiently. It Eventually led to the creation of the true Goliath. nearly 5 miles long, and spanning incoming and out going tracks, it carried a main armament that was akin to the "Dora" of the early 19Th century and more than a few other cars. Able to lob rounds the weight of Mk V power plants up to approximately 12-20 miles depending on the munition, and with increased "bunker buster" rounds as well doing nearly the same damage as cruise missiles, Ogres where called to defend their city's and facs instead of going out to destroy others. It was this creation of the G.S.E. that led to the eventual shut down of all super sentient Ai's world wide in "The Crash of 2100" to debate in secret amongst themselves.
G.S.E.
-INTRODUCTION-
This is an advanced (perhaps Master Level) fan made extension of the games OGRE, G.E.V. and the expansions Shock-wave and Battle-Suit by Steve Jackson Games. This is a one or two player game of a battle between a force defending an underwater CP or auto-fac of an OGRE and other units and a G.S.E (in the basic scenario) trying to lay siege. This is not a stand alone rule set and uses many reference from OGRE, G.E.V. and Shock-wave, and may also include expanded play on the game of Battle-Suit.

Disclamers:

OGRE is a registered trademark of Steve Jackson Games. All rights are reserved by SJ Games. This material is used here in accordance with the SJ Games online use policy.

OGRE/GEV/Shockwave & Battlesuit are trademarks of Steve Jackson Games, and its rules and art are copyrighted by Steve Jackson Games . All rights are reserved by Steve Jackson Games. This game aid/expansion is the original creation of Joshua Matott and is released for free distribution, and not for resale, under the permissions granted in the Steve Jackson Games General Online use policy.

Before playing this expansion/game aid, become familiar with the games OGRE, and more importantly G.E.V.
Some Shockwave and Battlesuit material background will help as well.
After you are orientated with those games, take out a GEV and Shockwave map, lay them north side up, and make a "lake" in the middle of the two maps. Defending player will be placing a Cp or Admin building(se. shockwave and GSE advanced scenario) in the lake, and the GSE and escort team will enter on and near any rail hex at the edge of either map.
Basic Scenario: This represents a G.S.E. attack on a heavily guarded underwater command post. The defense sets up first. Defending player gets one Ogre Mk III, 20 points of infantry and 10 armor units (se. Ogre/GEV). All point tables stay the same for any and all units (howitzers count as 2 ap's and marines count as 2 ip's etc.) . Defending player takes and places a command post in the lake at least 1 hex from any shoreline or river, and then disperses the rest of the defending units within 10 hexes of the command post, following all GEV terrain and stacking rules for unit placement. No defending units may exceed these starting boundaries. Attacker gets 1 train tile to represent a G.S.E. ST A-1 (se.GEV game and GSE types in GSE), 12 infantry points to start from within the train or GEV-PC's, and 6 Ap worth of GEV type units only. Train will start on the last train track hex of either map at a speed of (2-1)3/4(2-2). And GEV type units will start within the 3 hexes near the trains entrance point along the edge of the map as well, following all stacking limits as per. OGRE/GEV. All units start face up and fully functional.
Victory conditions: All defenders destroyed, and GSE escapes with main howitzer intact; Complete GSE victory. Defending players command post destroyed, GSE escapes with main howitzer destroyed; GSE victory. Command post destroyed, and GSE destroyed, or GSE escapes without main howitzer and Cp destroyed; Marginal GSE victory. Cp not destroyed, GSE escapes with main howitzer intact; marginal defense victory. Cp survives, GSE escapes without main gun, but is not destroyed completely; Defense victory. Cp survives, GSE completely destroyed; Complete defense victory.
Advanced scenario: Play set up is identical to the basic scenario, except (A) the defense gets 30 points of infantry and 20 armor units without exceeding 25% of force being one single unit of armor type(no more then 5 units total of any one kind of armor), and an OGRE IV (again all howitzers etc count as double), and an admin building of sp 60 in place of the Cp; (B) all defense pieces must be set within 9 hexes of the underwater admin building (placement of building is the same as the basic scenario); (C) The attacker will get all the same things except, (1) the ST A-1 will be replaced by the ST C-3 and (2) the train/GEV-PC's will get to carry 15 points of infantry (again marines count double); (D) for a complete GSE win, player must destroy admin building, and the defending OGRE, and escape map with main cannon intact.
Solo play: Solo play is recommended, as this will help one to better "moderate" rules for other gamers wanting to play this extension of the train rules from GEV.
Play balance: Due to lack of mass play-testing, the play balance will not be perfect. And due to many possible alterations of the train, some play balance tooling may be needed. Player beware; The GSE is not a toy, it does its job so well in fact that a new Ogre was needed to be made to combat it efficiently.
Map-sheets: The map sheets that are used are from the GEV and Shockwave sets, one of each. How-ever, if one feels that the 2nd GEV map is needed to balance out play, feel free to extend the other side of the shockwave map with the added GEV map, making one long railway on the northern border from east to west, and start the GSE from the far side of the lake (on the far edge of the 2nd GEV map), and make the victory condition of the GSE must escape from the opposite edge of where it started (exit off the far west edge of the GEV map that is used to make the "lake"). All terrain features for the maps follow the same rules as in the original rules, and all combat factor tables stay as they are except where extended here in.
Terrain and the railway: when a rail hex is destroyed by any unit, place a ruble counter on the corresponding hex and treat as rubble terrain. If a cruise missile or OGRE self destruct is used to destroy a rail hex, place a crater tile on it and treat as a crater hex according to Ogre/GeV rules. When a rail hex is destroyed, a GSE may effect repairs in this way; (A) only the main engines (the outside tiles of the train) may be the first ones to cross a newly repaired tile, as the front and back parts to the train have the equipment necessary to resurface the new rail sets and grade them for travel on board the train; the speed of the train will not exceed (1-0)1 (se. GSE train movement rules below). (B) Infantry are used to make the repairs (se. GSE rail repair rules below). and (C) the infantry car set (one of the outside engine train tiles) is at least 3 hex from the track to be repaired (it will have the cars carrying supplies for the job). No train tile may cross the broken line until repairs are complete. Repairs are not final until a front or back engine crosses the hex completely.
Counters: All standard rules apply to all standard counters, except the train and the command post/admin building. Three train tiles will be used (if you don't have a 3rd make a 3rd), one to represent the front of the train one to represent the middle of the train, and thus the main cannon of the GSE, and one to represent the back of the train. The front or back of the train may be either an assortment of tank guns, small howitzers, missile racks etc. and one piece may be the Infantry cars with infantry/marines on-board, Ap guns/light tank guns for defense and all equipment needed to effect repairs on track.  The train movement, combat and unloading of passengers will go as follows in this expansion. All train pieces are self mobile, and trains may vary by type. 
Extended Cp/Admin building rules: The Cp or admin building will represent an underwater installation that is unfireable upon by any armor units or infantry excepting, (A) howitzer type armor; and (B) marine type infantry. A Cp will have a defense of 6 for combat odds when under water and a 60 Sp admin building with a Defense of 6 when under water also.
Extended Train counter rules: Se. GSE extension on turns, movement, and train types.
Turns: The way turns go is identical to the rules found in Ogre/GEV except;
-Attacker first movement faze, all gev's and infantry move, all normal rules for disabled units is dealt with, train decides what speeds to use for the turn, and moves if needed at half its total top speed (round up). (ex. if the train is moving at the speed of 3/4, and wishes to stay at 3, the first movement faze it will move 2 and on the Gev faze it will move 1. ex if the train is moving 3/4 and wishes to go from 3 to 4, the first movement faze move 2 and on gev faze move 2. ex. If the train is moving 3/4 and wishes to slow from 3 down to 2, move 1 on the first turn and 1 on the GEV faze. ex. if the train is moving 0/1 and wishes to slow from 1 to a stop (to fire its main cannon or unload passengers), move 1 on the first faze and then stop on the GEV faze, train may not fire its main cannon until the next turns fire sequence. ex. if the train is stopped and wishes to move to 1 hex per turn, it sits still the first movement faze, can then fire its main gun, and on the second movement faze move 1 hex.
 So in retro aspect look at a train tile, the movement faze looks like this; 3/4 now i have taken it and extended that to go according like this;
 (0-0)0/1(0-1), (1-0)1/2(1-1), (1-1)2/3(2-1), (2-1)3/4(2-2). Max speed on train types will vary. 
The speed of 1 is considered to be the speed for necessary resurfacing/grading during repairs of track, and for safe movement over repaired tiles and thus is very slow movement. The extended use of Gev type movement for the train is to represent that the train is moving during the whole turn and not just on a first movement faze.
-GSE attacking team fires, train may fire any weapons besides the main gun while in movement and may only fire the main gun when at a stop. GSE May unload Infantry's if stopped.
-GSE attacking team takes second movement faze, and as exemplified above, moves the train if necessary.
-Goliath Missile round, If fired, Hits; damage dealt with.
-Defending team first movement faze
-Defending team fire faze
-Defending team second movement faze.(GEV's)
Multiplayer Sequence: If more than two players are present, and more maps are used, use all multiplay sequencing as found in either Ogre or GEV. Any players with a GSE shall follow turn sequencing for the train as above.
Movement: As stated in OGRE / GEV, the movement factor on a tile is the number located in the top right hand corner of the tile. However due to the lack of functional rules for the train as provided in the GEV rule set, the train shall use different rules for movement. As stated above in the "turn sequence", the train will divide its max speed chosen for a round, and move half (round up) the first movement faze, and move the remainder during the GEV movement fase. 1 is the only speed that will permit a train to move once a turn. If the train has a max speed of 5 chosen at the beginning of the round, it can not move 3 hex, and then on the GEV faze move  just 1 hex (unless its been rammed successfully during the combat fase's). Train speed reduction, addition, or equalization is chosen at the beginning of the train conductors turn according to the last factor from the last round of play. The only way to slow the train by any player once speed is set is to ram the train (se. ramming below). A Train may only move as fast as its weakest link, And also only along a train track hex.
Stacking: All stacking rules as found in GEV are to be used. However the train is still a non stack-able piece, and any other unit, excepting infantry types, may not pass over or be stacked on a train tile, unless it be an attempt at a ram(se. ramming below). If any armor piece(including GEV) is on a rail hex and the train is going over that tile(s) at a speed greater than /1(0-1) or (1-0)1/ , a roll for ramming will proceed for each piece obstructing the trains path(including stacked units).
Infantry stacking and the GSE: The train may be traveling with infantry/marines onboard at the start of a game. The units inside the train may not be unloaded until the train is at a full stop for one whole turn. After the whole turn has gone by, the units loaded with in may depart, stacked if needed to limits, to the left and right sides of the train tile that was chosen as the infantry cars. Infantry/marines may "hitch a ride" on a train going by as long as it is a friendly train. Hitching a ride is done in this way; (A)the infantry unit to be jumping on the train moves into the train tile as it is going by at a speed no greater than (2-2)4/ , or /4(2-2). (B)Units that have hitched a ride may fire as normal, units carried within the infantry cars may not fire until unloaded. (C)No more than 3 units of any type of infantry may hitch a ride on any single train tile, all train tiles may be used by infantry in this way(even the main gun tile), and (D) No infantry types hitching a ride in this manner may disembark off the train tiles at a speed greater then what is used to "hitch" (max speed per turn 4).
Movement for Extended Ram rules in over-run combat, and train ramming: (1)As stated in GEV rules, ramming may take place during a movement phase. However my official rules did not have a roll chart that would help resolve this. Expanded rules on armor vs. armor ramming are as follows; (A) during movement fase, before over run combat proceeds, if one armor unit moves onto a hex occupied by an enemy armor unit, and the armor unit has any movement points left to use, the player may choose to use one of the movement points left to try and "ram" the other armor unit before the "over-run" starts. The other player may also use any movement points to "ram" back, but the player doing the original overrun gets first ram roll in an over run combat situation. (B) Player "Ramming" rolls one D6 each time a ram is used in over-run. On the result of a natural 1, the ramming players unit is disabled permanently, on the result of a natural 6 the unit getting rammed is permanently disabled. Any other result ends in the ramming and to-be-rammed unit just "wheeling around each-other,and overrun may proceed as normal. (C) Once an armor unit is disabled in this way, no more rams may be dealt as it would be ineffectual. Once a unit is permanently disabled in this way,the unit left may choose to leave the hex if it has any movement points left. A permanently disabled unit in this way is permanently disabled, as it just got major damage to whatever tracks/ wheels that move it. (D) This is for smaller armor units only ( non OGRE units), follow the rules in the original rule sets for ogre vs. armor ramming, and ogre vs. ogre ramming. GEV's and infantry of any kind may not be subject to rams and they may not ram during over-run. (2) Armor units ramming the train and vice verse'; any armor unit that trys to ram a moving train or getting rammed by the train, no matter what speed its going is destroyed at 6-1 odds but if the unit was of a Tank type (Lt. tank, Hvy, Sp.Hvy) the max speed of the train for the round will be slowed by 1. Only the OGRE may try to ram the train properly, but the OGRE will take severe damage to treads and weapon systems, if not being destroyed by the process. The train will also take massive damage as well, this will all depend on the speed of the train and Ogre movement points used to ram as follows; (A) The train will take 10 Sp of damage to movement points (se. train types) per 1 point of movement speed divided equally among train tiles (depending on train types) that are linked in chain; ex. if the train is moving 4 max, with two tiles total in the link, and an Ogre rams it with a "2 step" movement , the train will take 60 Sp of damage to its movement factor (40 for the trains movement and 20 for the Ogres movement) possibly destroying/derailing the train parts with each piece taking 30 Sp in damage to movement factor. (B) In the same sense of things, the Ogre that has done that ram above, will take the same damage to its own movement factor (60 points), and instantly roll at 2-1 odds for each weapon platform left (including Ap turrets). This is at any speed of either and any units, even if the train is stopped and the Ogre rams with one movement point. (C) The train will slow down as according to to whatever Sp it has lost to movement points, if it even survives. If the train is slowed to 0 (but not already at full stop) by a ram, it is of course derailed/destroyed. (D) If the Ogre survives with any movement points left, they are not usable until its next movement faze. (E) The train will keep moving at whatever max speed is left for the rest of the turn, if it can still move and did not get derailed. (E) Only Ogre Mk III's and larger can be used to do this, smaller Ogres count as Tanks during the train rams(and get crunched). (F) Gev's and infantry can get out of the way of a train if they have any movement left, and use it immediately. (G) Any unit may be at the mercy of a train ram, even friendly ones.
GSE Train combat(expanded rules on train rules from GEV 3rd ed. case numbers 6.05, 6.135, 6.138, 6.139, 6.14-6.142): 
6.05: The train has now become its own scenario, as a GEV before it and an OGRE before it. For train attacks, treat a train as if it's it's own unit, as the above units are. This said, use the rules found in GEV 3rd ed. in the case number 6.05, but make the one exception that if the train parts are unhitched from a link (a train with more then one tile), and if one piece is destroyed that's out of link, the other cars are unaffected. All train piece parts are self driven and may run themselves bereft of other train tiles, train types may vary, and a train type may end up having as many as 3 sets of cars...
6.135, 6.138, 6.139: As above in ramming rules, if any unit other than a powered infantry type attempts an overrun on a train moving or not, it is counted as a ram, the GSE has a brain and even if stopped it can move just slightly to ram a unit in the hex its trying to overrun (not to mention the mass of firepower onboard). Powered infantry of the opposing side may be used to attempt to sabotage the train as in over run combat, but the infantry units attacking the train in this way may not exceed the tiles max unit strength of 3/1 per train hex. Infantry must deal overrun combat on any Ap turrets on the train tile they are trying to sabotage before going for any other parts of the train cars or Sp. Once a train tile is bereft of Ap turrets to defend its self in this way, and then the infantry are free to take turns as normal. The train will be pretty much harmless to the infantry onboard, and other outside units (such as GEV's) must take shots at them in the normal way, using spillover rules on the train the infantry are "stealing" as if it was an Ogre. Attack and defense of infantry and Ap turrets are doubled during this over run. Only a friendly infantry unit may commence proper overrun again on the invaders of the train. In Over run on the train treat the train as if it was an Ogre in all ways, being an "X" result is all that can destroy a component or damage Sp. After an above overrun has finished, proceed with the turns as normal.
Goliath Missile Cannon Combat:
When the Goliath cannon fires, use a cruise missile counter from Shockwave for the shot that has been fired. Place it on the train link that fired it (either hex) and keep it in place, and wait for the proper sequence of events before aiming it at your target, dealing all damage as proper during that time. Shots aimed for ground level not only make the damage for gun that was fired, but also leave a crater in the hex they hit (unless a hardened building is in that hex and withstands the damage), and do shockwave damage as if an Ogre had destroyed itself (se. Ogre on self destruct). A Goliath Missile cannon may shoot once every 3 turns, and only if stopped the previous movement fase and for the fire fase. A train may move after it fires on the preceding movement fase for that turn.
6.14-6.142: As in the CRT tables found in the previous games, use all effects as for all units, with exceptions as found above for the train. When spillover fire effects the train, treat all "D" results as N/E. Only an "X" may damage the train as if it was an Ogre, the same shall be in effect for any and all Overrun combat. When a train or howitzer is firing its Goliath cannon/ missile cannon at an underwater/underground facility, treat the building as if it had a defense value of 6, and only an "X" may make damage effects on the building(an "X" destroys a simple Cp). Infantry/marines may try to "overrun" an installation(but no other attacks), and I have based battle suit games on this premise. That's the only way I can see it being done, as they would be swarming with internal defense systems and security drones, if an entrance was made evident.
Infantry making repairs on train track: Infantry may make repairs to train track that is broken if there is a Truck, Hover Truck, or Train link within 1 hex of the track to be repaired. Repairs are done in this way; (1) during the players first movement fase, the player moves an able infantry unit of strength no more then 1/1 onto the damaged track. (2) the player declares that they are going to attempt to repair it. (3) Player rolls D6's, according to the damage done. Numbers shown is amount of turns it will take to repair the track. (4) Player places the die(dice) that was rolled, with the number rolled showing, on top of the infantry unit making repairs in the track hex. (5) Each turn that goes by, one point is removed from the dice, making them show the next number down. (6) When no numbers are left to take off the dice, the repairs are complete and the infantry can move off the tile.
The damage chart for damaged/broken track hex and dice to be rolled for repair time is as follows;
Rubble track hex: 1d6
Broken bridge track: 2d6
Crater track hex: 3d6
Bridges are not allowed to become craters. Effects may not be added together. Infantry must remain in the hex to be repaired at all times (this is the only time a unit may enter a crater hex). Trucks, Hover Trucks, and/or Train links carrying the needed supplies must remain within 1 hex near the infantry for the first turn of repairs only, they may move again after this turn is up.
Ending a Game: Outlines for victory conditions are found in the Basic and Advanced scenarios. However feel free to make your own train, and make your own battles for it.
Train Types, Train type explanations, Further options for Trains, Counting Armor point total for a train, and building your own GSE:
Train Type Examples:

GSE ST A-1: 30Sp, Max Movement(MM) speed; 8(4-4), Ap cost total 83
Light Goliath Missile Cannon (12/2-12, D3)
-0
15 Goliath missile cannon shots:
-00000 00000 00000
2 Main Battery Super HVY Tank guns (6/3, D3)
-00
2 Secondary Mobile Howitzer Battery's (6/6, D3)
-00
1 Infantry Cars (D3)
-0
14 AP (1/1 against infantry or D0 units only, D1)
-0000000 0000000
30 Sp (D3)
-00000 00000 MM drops to 4 (2-2)
-00000 00000 MM drops to 2 (1-1)
-00000 00000 MM drops to 0; permanent stop/ destroyed


GSE ST B-2 : 72Sp total (2 train tiles, 36Sp per tile) Max Movement speed per train tile 6(3-3); Ap cost total 163
First Train tile set:
4 Tank Missile Racks (D3)
-00 00
20 Missiles (4/3)
-00000 00000
-00000 00000
4 Main Battery HVY Tank cannon (4/2, D4)
-00 00
6 secondary LT Tank cannon (2/2, D4)
-000 000
3 Infantry Cars (D4)
-000 
16 AP turrets (1/1 vs. Infantry or D0, D1) 
-0000 0000 0000 0000
36 Sp (D4)
000000 000000 MM drops to 4 (2-2)
000000 000000 MM drops to 2 (1-1)
000000 000000 MM drops to 0; Permanent stop/ destroyed
Second Train tile car set:
Heavy Goliath Missile Cannon (14/4-14 D4)
-0
15 Missile Cannon Shots
-00000 00000 00000
1 Main battery Super HVY Tank cannon (6/3, D4)
-0
2 secondary Mobile Howitzer cannon (6/6, D4)
-00
1 Infantry car (D4)
-0
16 AP turrets (1/1 vs. Infantry or D0, D1)
-0000 0000 0000 0000
36 Sp (D4)
000000 000000 MM drops to 4 (2-2)
000000 000000 MM drops to 2 (1-1)
000000 000000 MM drops to 0; permanent stop/ destroyed

GSE ST C-3 126 Sp total (42 Sp per train set) Max Movement per turn 5 (3-2);  Ap cost total 174
First Train Car/Tile Set: 
3 OGRE Missile Racks (D3)
-000
15 OGRE Missiles (6/5)
-00000 00000 00000
5 Main battery HVY Tank cannons (4/2, D5)
-000 000
2 Secondary LT Tank cannons (2/2, D5)
-00
1 Infantry car (D5)
-0
18 Ap Turrets (1/1 against infantry D0, D1)
-000000000 000000000
42 Sp (D5)
0000000 0000000 MM drops to 3 (2-1)
0000000 0000000 MM drops to 1 (1-0)
0000000 0000000 MM drops to 0; Permanent stop/ destroyed
Second Train tile set:
Super Heavy Goliath Missile Cannon (20/6-20, D5)
-0
15 Sp Heavy Missile cannon Shot
-00000 00000 00000
1 Main Battery Mobile Howitzer Cannon (6/6, D5)
-0
4 secondary Lt Tank Cannons (2/2, D5)
-0000
2 Infantry Cars (D5)
-00
18 Ap Turrets (1/1 vs. Infantry or D0, D1)
-000000000 000000000
42 Sp (D5)
0000000 0000000 MM drops to 3 (2-1)
0000000 0000000 MM drops to 1 (1-0)
0000000 0000000 MM drops to 0; permanent stop/ destroyed
Third Car Set:
2 Main battery Super HVY Tank cannons (6/3, D5)
-00
6 Secondary Lt Tank Cannons (2/2, D5)
-000 000
9 Infantry Cars (D5)
-000 000 000
18 Ap Turrets (1/1 vs. Infantry or D0, D1)
-000000000 000000000
42 Sp (D5)
0000000 0000000 MM drops to 3 (2-1)
0000000 0000000 MM drops to 1 (1-0)
0000000 0000000 MM drops to 0; permanent stop/ destroyed

Explanation of train types: When looking at a train type, read the name of it, ex. GSE ST B-2; the GSE is the name of the unit, "ST" stands for Siege Type, the "B" is the engine, weight, armor class type (Light, Heavy, Super Heavy), and "2" denotes the length of the train in tiles. In retro spec you would call a GSE ST B-2 a 3 mile Heavy Siege Train.

"A" Trains are light and fast. Hit and run is it's code of operations."A" Trains are on a single set of track. An "A" class train will have a Defense of 3 (D3) for all parts of the train except Ap turrets. This train may not exceed the length of two train tiles. An "A" train may have the following cars in link per tile of train;

Any Tank gun chassis (super heavy, heavy, light) as cars,
Mobile Howitzer Cars,
Goliath Missile Cannon of the Light grade,
Infantry cars.

"B" Trains are the bigger brother to the "A" trains. Also spanning just single set of track, "B" trains are used more for securing an area, as well as assaulting Installations. Slightly more armor and weapons exchanged at the cost of speed, a "B" type train brings fear to the battle field. This train may not exceed the length of two train tiles as well.This train type has a total unit defense strength of 4. "B" Types of trains may have the following cars in the train sets;

Tank Missile rack cars,
Any Tank Gun turret as cars,
Mobile Howitzer cars,
Goliath Missile Cannon of the Heavy grade,
Infantry cars.

The "C" class of Train is a class of its own. This beast spans two sets of track, sports the largest grade of Goliath Cannon, and has by far the most armor and weapon cars. This train is also the longest of all train types and may be up to three train tiles long. With a heavy armor class of D5, this train is also the slowest of them all because of of all this.  "C" class trains may carry the following cars in a train link;

OGRE Missile rack cars,
Cruise Missile rack cars,
Any Tank chassis cars,
Mobile howitzer cars,
The Super Heavy grade Goliath Missile cannon,
Infantry cars.

No Train type may connect to another train type (An "A" train may not link to a "B" and so forth). All Train types may only have, and must have, one Goliath Missile cannon of its own grade. Goliath Missile cannon grades are not interchangeable between train types.

How to make a train: This is a some what of a simple process, and would be best done by the steps below.
1: choose the type of train to make (A, B, or C)
2: choose the length you want your train to be according to type (A and B can be up to two tiles, and a C train may be three tiles long).
3: start with the outlines above in train types to familiarize ones self with each trains movement, defense factors, Sp units, and most importantly the amount of Ap turrets per train type.
4: Using the number of Ap turrets as "Train Car Points", per train type and per train link, choose from the list below the arms or amount of infantry cars you wish it to haul and stay within your "TCP" range. It is important that you do not exceed this amount of "points" per train link, as well as staying with only one Goliath Cannon per train type, as it would make the custom train type morbidly unbalanced.

Super Heavy Goliath Missile Cannon (20/6-20) costs 10 TCP
Heavy Goliath Missile Cannon (14/4-14) costs 7 TCP
Light Goliath Missile Cannon (12/2-12) costs 3 TCP
Cruise Missile Racks (se. Shockwave expansion) costs 4 TCP each 
      *1 Cruise Missile per rack, racks count as 8 Ap for Ap totals*
OGRE Missile racks (6/5, D3) costs 3 TCP each. *5 missiles per rack*
Mobile Howitzer cars (6/6,) cost 2 TCP each.
Super Heavy Tank turrets (6/3) cost 2 TCP each.
Heavy Tank turrets (4/3) cost 1 TCP each.
Tank Missile racks (4/3, D3) cost 1 TCP each. *5 missiles per rack*
Infantry cars (no attack until loaded cars unload) cost 1 TCP each.
*Each Infantry car may carry a 1/1 unit of Infantry per car*
Light Tank turrets (2/2) cost 1/2 a TCP each.
Each Train must spend 2 TCP for the front engines.

5: On a piece of paper, start near the bottom corner and make the Sp chart, with the Ap chart above it, as they appear per type.
6: Build the train car by car, following step #4 above and write down each car as you would if you were to replace the train parts as found in the GSE examples. Use all movement factors, defense factors and such as found in each example.

Ex. If a "B" train has 16 Ap turrets, it has 16 TCP, 2 TCP are used automatically for the engines per link, and that leaves 14 TCP to distribute for weapons. Remember that your train type must include at least one train link with a Goliath Missile cannon for it's type. 

Train Options: 
Option 1: If one is now familiar with building a train, then an alternate means of damaging the train may be used. This is a type of "spill over fire" that effects the trains Sp at large whenever a major weapon system or infantry car is destroyed. If one wishes you may take the proper TCP from the tables above, and when one of the weapon systems in the list is destroyed, minus the TCP for the unit from the train links Sp. Ap cannon destroyed in this way will count as minus 1 point for each one destroyed from the Sp for the train link. The engines may not be the targets of such attacks. This may not always destroy a train. Most times some Sp will be left and the train will still be able to move and even ram, even with all parts missing.
Option 2: If one is so willing, if a train has any weapon systems left, but no Sp with which to move, you don't have to count it as destroyed. Continue to use weapon systems until none are left.
Option 3: Self destruct; In order to avoid capture of a Goliath Missile cannon by the other side,If five or more of its shots are left, it may detonate them. This will make a double effect of a self destruct for an OGRE unit as found in Ogre/Gev self destruct rules. The only thing that is not doubled is the crater. A train with less then the required shots left to do the above may do a normal self destruct using all normal self destruct rules for an OGRE. A train piece that self destructs leaves a crater tile in the train track hex it was in at time of detonation.
Option 4: Track repairs; se. Infantry repairing the tracks above in movement. It's your choice how you let repairs go... but I tried to make a fine example.
Option 5: If one is so willing (or scared of the big cannon rules) a basic seige train may be made, ommiting the rule that a GS missile cannon must be used in creation. However, if this is done the train is not a true GSE and will only be called by the middle and last names only (ex. ST A-2 not GSE ST A-2). It is also recomended that if this is done, a new scenario should be used. Perhaps the Combine is rushing a full load of INF's to a front line position... and they get ambushed; the possibiltys are rather endless.
Counting up the Armor points of a train type: 
1: count up the amount of all total attack points, Each missile added individually,
2: add the amount of Sp for the train,
3: Add infantry cars at 1 point for each car in the link,
4: Add together any other links alone, and use the strongest train link total for the train as the Ap value of the units as a whole.

Israels OGRE Mk VII
The GSE ST C-3 was known to have done so well, that Israel began to fear it may come for them next someday soon. Everything was put forth to create something just in case of this. Heavily aided by the Combine during the 15 years it took to develop, at its completion, it was dubbed the Mk VII and finally fielded in the year 2099. It was so well hidden, and so deadly when it appeared, that it was truly a surprise in the infamous "Battle of Mecca" in 2106 when there where survivors left after the battle to tell of it.

MK VII
1 Laser defense system (exception to Sp for lasers, Defense of 3 to be used in place of Sp for lasers. Follow all preceding rules on lasers for a short laser tower as found in Shockwave)
0
2 cruise missile racks (D3)
00
4 on board cruise missiles (for damage/range etc., se. Shockwave)
00 00
2 main battery (6/6, D3)
4 secondary battery's (3/2, D3)
10 Anti personnel (1/1 vs. Infantry, D0's only; D1)
00000 00000
48 TRACK units M1 
0000 0000 0000 0000 
0000 0000 0000 0000
0000 0000 0000 0000 Movement drops to M0

Only two missiles can be fired per turn, according to missiles left onboard. Missiles fired follow all Shockwave rules. If a missile rack is destroyed with a missile in it, Roll D6 at 1-1 odds; a result of "X" means the Ogre is destroyed, and a shockwave that of a self destructing Ogre  ensues. If a missile rack is left, and at least one Missile is onboard, it is assumed it can be fired.
(notes: The author of this would like to thank the following; Steve Jackson, and all the ones that helped him to make OGRE/GEV what it is today, and continue doing so. I, the aurthor, will take full credit for playtesting this work.)