[3.5] My players, gnomish engineering, and tricked out transportation

[Kabump]

My players are in the process of getting a custom build carriage for themselves. One of them is playing a spoiled noble type char and he insists in needed for the group. Everyone seems to think its a good idea, myself included, after hearing what he wants to do with this. Think spy car in D&D, build a collapsible crossbow on top, drop grease spells out the back, a rack of magic missile wands in front, and other stuff while powered by magic, needs some engineering skills to fit into the cart (as my DM interpretation). My plan is to allow them to do this, but SLOWLY and over time, and telling them they need to get to LARGE TOWN X, where they can find a skilled gnome engineer to do all of this. My question is this: is my decision to say what they are asking for require gnomish engineer justified? And as such, what kind of time/money requirement are we looking at? Right now all they have is the custom made cart, nothing fancy right now, as they are just level 4. Im just wanting general thoughts people might have on this, as I frankly am not sure where to go with all this. My 3.5 source books are limited, but if you know any I could look through, one of my players has a quite extensive collection. Any ideas/thoughts/concerns are appreciated!

[AstralFire]

3.5, IMO, handles vehicles horribly for the most part. The Apparatus of the Crab (SRD)/Kwalish's Apparatus (DMG) is terribly overpriced, for example.

I wouldn't bother pricing it:
1) It adds to the group's strengths as a whole
2) Hard to go mano-a-mano and utilize the carriage at the same time, so dungeon crawls aren't affected
3) 's cool
4) They can't sell it - most people with the money won't be interested, most people without the money, are er, without the money.

If you want to know costs to build, then I'd just glance at the special material tables, use the pricing for each magic spell cast as in the SRD under services, and add a misc. labor cost of 100 to 500g for attaching any individual part, depending on how complex it is.

Time? I'd say a week should do it for what you have listed, +1 day for every major upgrade from that point on.

[Kabump]

Seems reasonable. They aren't anywhere that they can get anything but the cart right now, so this is something I want them to have to wait a little bit to get, make it that much cooler when they do get it. Thats why I wanted them to get different pieces at different times, just seems more rewarding that way, but perhaps thats my opinion :) My plan is to come up with some sort of cool chase sequence for them, both before they get the goodies, then give them another one once they have their additions, just so they can get to use all the neat stuff they put the player time and PC money into making. Hell, one of my players is even taking to making diagrams of the carriage, complete with different views :)

[Mephit]

The arms and equipment guide has a chapter on vehicles. Not sure wether it's any good though. :/

[AstralFire]

The arms and equipment guide has a chapter on vehicles. Not sure wether it's any good though. :/

It's not. Most of it's overpriced or overly technical without being very usable.

An Ornithopter for... what was it, 4,000 GP? I mean, really?

[Prometheus]

I had a group with a vampire that carried her coffin in the false bottom of a wagon pulled by horses. I gave them the very basic of it for what the PHB it costs to buy a wagon, and set of horses. Of course, no one wants to ride in that so its extra for a top, permanent magic items, luxury seating, etc.

My group later wanted it to be tricked out with stuff like that, and also increased hiding for the coffin, so they had to seek out the one place on the map that can help them with it and when they got there the person to do the job wouldn't take cash. They had to do a favor for favor type thing.

Be especially mindful that there are some places that this wagon just can't go (caves, heavy forest, and some mountain passes). In the mean-time, players have to either secure it at a town, leave it out in the open, or have someone there to gaurd/alert them (this last one worked out better when they gained a goblin slave and a goblin refugee to their party). Most of the time I said whatever solution they had worked out perfect, but sometimes messed with them (in a poor area the food had been looted but nothing else, one time they left it alone a horse walked off. etc) Make it simple enough that you don't waste game-time on logistics, but complicated enough to make things interesting.