How can I build a self-propelled ground vehicle using the Dungeons & Dragons 3.5 edition magic rules as written?

Question

For example, could characters build a simple self-propelled, steerable wagon using either magic spells or magic items to rotate and guide the wheels, with rules as written from Dungeons & Dragons version 3.5 core rulebooks + rules supplements (PHB I and II, DMG I and II, MM, Complete Adventurer, Arms & Equipment Guide, Unearthed Arcana)?

I'm thinking along the lines of transport for the player characters and their stuff (a mini-van or station wagon!), although it certainly wouldn't be a stretch to add ranged weapons to the vehicle to make a tank.

Answer 1

In Arms And Equipment Guide.

Self-Propelled Vehicle: By animating the wheels, steering mechanism, and other moving parts on a vehicle, it’s possible to build a vehicle that doesn’t require dray creatures. Any land vehicle of Large size or smaller can become self-propelled, gaining a speed of 60 feet. It still moves under the direction of the driver and retains its usual maneuverability. Unlike with a normal casting of the animate objects spell, the vehicle does not become a construct and does not gain the ability to fight on its own. Caster Level: 11th; Prerequisites: Craft Wondrous Item, animate objects; Market Price: 132,000 gp; Weigh --

If you want it faster.

Speedy Wheels: This pair of wooden wheels fits most wheeled vehicles, increasing the speed of one so equipped by 10 feet. The wheels must be placed on the same axle to be effective. Regardless of how many speedy wheelsa vehicle bears, its speed increases by only 10 feet. Caster Level: 3rd; Prerequisites: Craft Wondrous Item, expeditious retreat; Market Price: 100 gp; Weight: 20 lb. each.

When limited to Player Handbook only.

Your best bet is finding a spell that propels the vehicle such as a level one halfling sorcerer who sits in a small cart and spams Unseen Servant to push him around. When you get level 6 spells you get animate object, which would be your preferred method. Then you could use craft wondrous item to create the above self-propelled vehicle.

Answer 2

A carriage is either Large or Huge, provides cover while having (or having easily carved) arrow slits and viewports and such, and has good attack stats, hardness 5, and a 60ft move. Animate objects is a core spell (Clr/Bard 6) and can be made permanent. Also, it shouldn't be too hard extrapolate a carriage variant of the Apparatus of the Crab, which uses animate objects as the base spell to give it movement. (Crab-tank link courtesy of Hey I Can Chan.)

Depending on your DM's interpretation of phantom steed, a pair of them (cast "for" the heaviest party member) might be able to pull a carriage until you're high enough level to animate them. Two castings of mount can acquire you two light horses for 2 hours per caster level and can be accomplished by a first level character.

Answer 3

Of Course There is a Way

...and that way is Necromancy, where all magical perpetual motion machines unlive. If you just want a magic-powered transport, hitch skeleton horses to your wagon. That's not what you asked though, and necromancy (of course) has an answer to the exact thing you wanted. Specifically, for "how do I propel something," you will be very hard pressed to do better than the spell haunt shift from Libris Mortis.

Haunt shift permanently converts whatever undead you have lying around into a "haunting presence." You convert a caster-level-dependent amount of hit dice, but nothing with more than 9HD (which is a limitation that matters, because 10HD would give you jet fighters. Which is also possible, but out of scope here).

"Haunting presences" are described in exactly one place: a sidebar on page 6 of Libris Mortis. Haunting presences are where an undead takes up residence in some item or location. We care about items. They can manifest near the item, which is somewhat underwhelming as they are almost impossible to destroy otherwise, but does mean that your car may come with a mandatory zombie butler. More importantly, the haunting presence gets an ability called "Poltergeist," which lets it animate its object's moving parts. What exactly the limits of this are are not well defined, but "a wagon can roll out of the stable" and "a crossbow can cock and fire." The object's movement is limited to how fast the original undead could move in its normal form, and the max object size is huge.

So, what do you do with all that? Here's a six-step recipe for your very own self-propelled wagon!

1. Buy a wagon.
2. Get ready to cast haunt shift, animate dead, and lesser planar binding.
3. Bind yourself up a canoloth (MoP). Or get whatever else; you're looking for fast move speeds and lesser planar binding only goes up to 6 HD. Go crazy. Don't worry about whether you'll be able to bind it though, because next you're going to...
4. Kill it quickly. You don't even need to feel bad; canoloths are waaay more evil than all the goblins you waded through to get to this level.
5. Animate dead the canoloth corpse into a skeleton.
6. Haunt shift the skele-cano-loth into the wagon.

You now have a wagon with a move speed of 50 ft. You have exactly the same control over it as you do over a skeleton created with animate dead, permanently unless you release it.

Obviously you can optimize that a lot more, but the basic version is pretty basic.