GURPS Mechanical Artillery

All of the following weapons are built at TL3 levels, though their stats remain unchanged whether they are built anywhere from TL1 to TL4. They are constructed with the design rules from GURPS Vehicles 2nd Edition, with Erratta dating to November 20, 1996.

Explanation of Variables

• ST: The Strength of the mechanical atrillery piece. All Mechanical Artillery pieces are rated for a certain ST.
• Malf: The Malfunction number of the weapon, essentially the number that the effects of a critical failure happen. 'Crit' means only on a regular critical failure.
• Wt is Weight in pounds.
• Vol is Volume in cubic feet.
• Cost is, of course, the machine's cost in $.
• WPS, VPS, and CPS are Weight Per Shot [lbs], Volume Per Shot [cf], and Cost Per Shot [$], respectively.
• Crew is the crew required to load and fire the weapon, including the gunner.

Spring-Powered Stone-Throwers

Torsion Powered Stone Throwers:

The 'Onager' as listed in GURPS Vehicles 2nd Edition Weapons table is an ST 100 stone thrower. Its damage should be listed as shown here.

The 'Onager' as listed in GURPS Vehicles 1st Edition would be, converted in terms of projectile weight, an ST 300 stone thrower.

The 'Heavy Onager' from GURPS Pre-Industrial Architecture (Available at the GURPSNet FTP site) is apparently inconvertible by these rules.

ST	Malf	Type	Dam	SS	Acc	1/2D	Max	RoF	Wt	Vol	Cost	WPS	VPS	CPS	Crew	HP
50	Crit	Cr	8d+7	30	2	220	270	1/35	500	10	5800	5	0,1	2,5	2	30
100	Crit	Cr	13d+13	30	2	240	300	1/50	2000	40	8800	10	0,2	5	3	75
150	Crit	Cr	18d+18	30	2	270	330	1/61	4500	90	13800	15	0,3	7,5	4	125
200	Crit	Cr	23d+23	30	2	290	360	1/71	8000	160	20800	20	0,4	10	5	200
250	Crit	Cr	28d+28	30	2	320	400	1/79	12500	250	29800	25	0,5	12,5	7	250
300	Crit	Cr	33d+33	30	2	340	430	1/87	18000	360	40800	30	0,6	15	8	400
350	Crit	Cr	38d+38	30	2	370	460	1/94	24500	490	53800	35	0,7	17,5	9	400
400	Crit	Cr	43d+43	30	2	390	490	1/100	32000	640	68800	40	0,8	20	10	500
450	Crit	Cr	48d+48	30	2	420	530	1/106	40500	810	85800	45	0,9	22,5	12	600
500	Crit	Cr	53d+53	30	2	440	550	1/111	50000	1000	104800	50	1	25	13	600

Counterweight-Powered Siege Engines

ST 500 stone throwers have decent 'Finger of God' potential. St 1000 stone throwers have 'Fist of God' potential. ST 5000 stone throwers have 'Left fist, Right Fist, and Left Knee of God' potential. I can't imagine anybody bothering to build a stone thrower much stronger than ST 5000.

The 'Trebuchet' from GURPS Preindustrial Arcitecture, converted by projectile weight, is an ST 1000 stone thrower.

All Counterweight Engines posess the following statistics:

Malf: Crit; Type: Cr

Torsion-Powered Bolt-Throwers

All torsion-powered bolt-throwers are of the double-armed variety.

The Ballista, from GURPS Vehicles 2nd Edition, is an ST 50 bolt-thrower.

ST	Malf	Type	Dam	SS	Acc	1/2D	Max	RoF	Wt	Vol	Cost	WPS	VPS	CPS	Crew	HP
20	Crit	imp	2d+3	20	6	400	500	1/22	32	0,64	1600	0,25	0,005	2	2	5
30	Crit	imp	4d	20	6	410	510	1/27	72	1,44	3600	0,56	0,011	2	2	8
40	Crit	imp	5d+1	20	6	420	530	1/32	128	2,56	5056	1	0,02	2	2	12
50	Crit	imp	6d+2	20	6	430	540	1/35	200	4	5200	1,6	0,032	3,2	2	16
75	Crit	imp	9d+2	25	6	470	570	1/43	450	9	5700	3,5	0,07	7	2	27
100	Crit	imp	12d	25	6	480	600	1/50	800	16	6400	6,3	0,13	12,6	2	40
125	Crit	imp	14d+2	25	6	505	630	1/56	1250	25	7300	9,8	0,2	19,6	2	60
150	Crit	imp	16d	25	6	530	660	1/61	1800	36	8400	14	0,28	28	2	70

Greek Fire Projector

All Greek fire projectiors recieve an Armor Divisor of (5), meaning that unsealed personal or vehicular armor has its DR divided by 5 when hit by a Greek Fire Projector. On the up side, the PD of armor is doubled vs. this damage.

Greek Fire shots do the listed damage every second for 10d seconds to the target, and won't go out unless completely smothered (Just dumping on water won't do it). Thus, they tend to be very likely to kill PC's (as if anything else in this article isn't)

Light, Medium, and Heavy apparently apply only to the range and size of the Greek Fire thrower.

Type	Malf	Type	Dam	SS	ACC	1/2D	Max	RoF	Wt	Vol	Cost	WPS	CPS	Crew	Shots	HP
Light	14	Spcl	1d(5)	10	3	1,5	2,1	1	150	3	750	4,25	0,5	1	20	13
Medium	14	Spcl	1d(5)	10	3	2,5	3,0	1	275	5,5	1375	4,25	0,5	2	20	19
Heavy	14	Spcl	1d(5)	10	3	3,0	4,5	1	525	10,5	2625	4,25	0,5	3	20	30

Notes

As in Vehicles I, all these weapons are assumed to have DR 5.

I'm also toying with a house rule that postulates that 80% of the required loaders for Counterweight Stone-Hurlers do nothing but contribute their ST for loading, in terms of pulling back the armature. As such, they can be replaced by draft animals numbering (Average ST of Draft Animal)/10.

Vehicles 2nd Edition also made no difference between single-armed and double-armed stone- and bolt- throwers. My suggestions (all untested house rules):

1. Single-Armed stone throwers cannot be mounted inside a vehicle body. They must always be placed in Open mounts. Double-Armed stone throwers can be placed, well, anywhere.
2. Double-Armed torsion-powered mechanical Artillery uses two skeins of fiber, one for each arm. As such, they need to be 'tuned' from time to time to keep the projectile firing straight forward. For every day that a torsion-powered artillery piece goes unused, its Acc number drops by 1. Once Acc drops to 0, then impose a further to-hit penalty of -1 to a maximum of -5.

In a particularly hot, cold, or humid climate, double the rate at which the above penalties accumulate.

Greek Fire Bombs

Greek fire Bombs are earthenware jugs hurled by stone-throwing mechanical artillery for the purpose of delivering the flammable substance at a far better range than the Greek Fire Projectors are capable of doing.

Start with the Weight per shot (WPS) of the stone-throwing mechanical artillery piece. From that, find the Diameter (D) of the Greek Fire Bomb in millimeters.

D = Cube root (WPS x 75.000)

Radius = 0.00057 x D x D
Cost = $50 x WPS
VPS = WPS/33

• Anything hit by the Greek fire bomb takes Kinetic damage, equal to half the damage that would have been delivered had the round been solid. If it hits anything solid, it then shatters,splashing Greek fire all over the place.
• Any object in half the burst radius is considered hit, and covered. It takes damage as above, 1d per second, persisting until 10d seconds have passed, or the fire is completely smothered. Unsealed DR is divided by 5.
• Anything in the outer half of the burst radius is considered hit on a roll of 3d vs the Size Modifier+5, and suffers the same effects.
• Anybody stupid enough to walk through the area of effect suffers the effects of walking through fire as discussed in the Basic Set.