So, these are some vehicle rules I am working on. If you see any problems, have questions, want to add something, or if I missed something, let me know!
Vehicle Rules Dark Heresy
Example vehicle:
Leman Russ
Bs 42
Front:
Armor: 30 Weapons: Flamer
Side: Armor 26 Weapons: Icantrememberwhatthisweaponis
Rear: Armor 20 Weapons: None
Top: Armor 26 Weapons: Leman Russ Cannon?
Vital parts: Treads (Hit from all sides, 8 structure points,) Engine, (Hit from all sides and rear, 18 structure points,) Gas Tank, (Hit from rear, explosive, 6 structure points,) Crew, (Hit from all sides, 10 structure points.)
Special Rules: Tank, Armored, Transport
For the purposes of size, all vehicles count as Massive
Like biological creatures, vehicles have different parts that you can hit. If you are shooting at a tank, what you hit and how much damage you cause depends on what you can see. Each tank will have different front, sides, and rear armor, and different guns. When you fire a gun at a tank, decide which side of the tank you can see best. That is the side that you are firing at. If you hit, roll a D100.
On a 1-30, a weapon is hit.
On a 31-100, the tank is hit.
Called shots can be made as normal against tanks. If there are no weapons viewable, the tank is automatically hit. Weapons on the top of the tank are visible from all sides. Basic weapons have an armor value of 10 and 4 structure points unless otherwise specified, heavy weapons have an armor value of 15 and 8 structure points.
Causing damage to a vehicle:
When firing at a vehicle, damage is done differently than firing at a creature. Each vehicle has certain parts that can be damaged, with the rest being invulnerable, (relatively,) to harm.
When you hit a gun, if the strength of the hit is greater than the armor of the gun, then the gun takes damage. If the gun has no structure points left, it is destroyed and cannot fire.
When you hit the tank, if the respective armor, (depending on which side you fired at,) must be penetrated. In this case, the attack of the weapon penetrates 1 point, as if it was causing wounds, but the PEN instead penetrates 2 points. Once the armor is penetrated, the remaining damage must be placed. Depending on which side you are firing at, there will be different vital points. (For instance, the tank treads and crew can be hit from all sides, but the gas tank can only be hit from the back of the tank.) Give each target an equal chance of being hit, and roll a D100. The hit target loses that many structure points. If any Vital part of a tank loses all its structure points, the tank is destroyed. If a vital part with the special rule ‘explosion’ loses all its structure points, or any vital part of the tank is loses more than three times its structure points, then the tank blows up, and all models within 2D10 meters are hit with a S10 explosion.
Every type of weapon causes a slightly different result to the tank, however:
Impact weapons cause damage as described above
Explosive weapons cause damage normally, but in addition to injuring the tank normally, however much penetration caused permanently reduces the tanks armor on whatever side was fired at. Halve the damage of the attack and reduce that much armor. (Each point of pen also causes 1 point of armor to be lost.) If the armor is completely removed from that side, the tank is destroyed.
Rending weapons penetrate armor twice as well, (so attack causes 2x damage, PEN bonus stays the same,) but causes half damage to the vital parts.
Laser weapons penetrate armor normally, but their pen is tripled instead of doubled, so AP2 would cause 6 damage instead of 4. In addition, they cause twice as much damage to any vital part with the ‘explosive’ special rule.
Melta weapons are twice as effective in every aspect (damage, penetration, pen bonus,) against tanks, if they are firing at half their range or less.
Here are a few examples of shooting at a tank:
You fire at a Leman Russ in the rear armor with a Long Las that has a hot-shot charge. It is a called shot against the main cannon, and it hits, passing by two points, so it causes 2D10+4 damage, and has PEN4. You roll a 12, for a total of 16 damage. Since the cannon is a heavy weapon, it has 15 armor and 8 lives. However, since the long las is a laser weapon, and the hot-shot charge gives it a total of 4 PEN, 12 of the armor is penetrated by the Pen. The remaining 3 points are destroyed by damage, and the shot causes 13 damage to the cannon. The cannon only has 8 lives, so it is destroyed.
You fire at a leman russ in the side armor with a rocket launcher armed with Krak grenades. You roll an 11 for damage, and add 4, for a total of 15 damage and 6 pen. You then roll a D100, cause damage to the crew. The crew loses 2 structure points. However, since the weapon is explosive, the tank also loses 14 armor on that side, meaning that next time somebody fires at it, it will be at AV 12 instead.
You fire at the front armor of a Leman Russ point-blank with a Melta Gun. Since the melta gun has 2D10+4 damage and 12 pen, it is most likely going to kill the tank. A 9 is rolled for damage, (for a total of 13.) Since the melta gun causes double effectiveness at this range, the 12 pen causes 48 damage, and the 13 damage becomes 26, for a total of 74. This penetrates the tanks armor, and hits the treads. Since the treads only have 8 structure points, and 44 damage was caused to the treads, the tank explodes!
Special rules:
Transport: Most vehicles, but not all, can carry people inside. If the people are inside, they normally cannot be injured, but if the tank is destroyed they each take D5 wounds and pile out, and if it explodes they each take D10 wounds regardless of armor, (toughness bonus still applies,) and appear in the crater, as well as taking damage from the main part of the explosion. Passengers inside cannot normally shoot out of the vehicle.
Tank: If a vehicle is a tank, then it can only be killed by weapons with an pen value of 2 or more, or that explode. Any weapons that do not have 2+ pen or explode cannot damage a tank. (They can, however, damage the guns mounted on the tank.) However, tanks move at half the speed of a normal vehicle.
Open-topped: If a vehicle is open-topped, then the vital parts of the tank can be hit with called shots. In addition, if there are passengers in the tank, they can also be targeted. However, if the tank is destroyed or explodes, the passengers can take an agility test to bail out, and if they pass then they are not injured when piling out. (They are still hurt normally by the explosion, but they do not suffer the damage from leaving an exploding tank.) In addition, 2 passengers at a time can fire out of an open-topped vehicle, counting as being on top.
Armored: Armored vehicles take half damage from rending and impact weapons, as they are designed to be hard to crack open. (AP bonus still applies normally.) However, the armor must be of 30+ to gain this bonus. If a tank has the armored ability and does not have 30+ armor, it does not gain the bonus. If a tank has 30 armor on one side, but the others do not, only the side with 30+ armor gains the bonus.
Fast: Fast vehicles are designed for speed. If a vehicle has the fast rule, and is on terrain that the GM designates as flat, (or road,) it can travel at twice the speed of a normal vehicle.
Skimmer: Skimmer vehicles hover over the ground, and as such count all terrain as ‘flat,’ and gain the ‘fast’ rule at all times.
Walker: Walker vehicles move at half speed, but can be locked in close combat, and thus have Ws and S stats, as well as having a close combat weapon of some sort, most likely.
Moving: All vehicles move 5/10/15/30 unless otherwise specified. Turning 90 degrees costs 1 meter to move. However, they can only fire one gun if they move more than 10m, and cannot fire any guns if they move more than 15m. (If their speed is doubled or halved, then apply the equivalent, so if it was 3/5/8/15 they would move 5m and fire one gun, and 8m would fire no guns.)
Firing: Normally, a vehicle can fire all of its guns. However, it the gun must be able to see its target. Guns on top of a vehicle can fire at all targets, since they can see in all directions, but if they are on the sides, front, or back, they can only see what is not obstructed by the rest of the tank.