OH... a few other thoughts on that subject would there be a gp cost associated witht that? would this result in the average steamborg carrying around a mass of spare parts? how heavy would replacement parts have to be per hp repaired?
am i overthinking this?
I think you're overthinking it.
In my campaigns, I'd just leave it at that if we decided to use the rule, but some people like more detailed rules.
I'd say that a lot of the repairs wouldn't necessarily require any spare parts. They could simply be a matter of reconnecting this thingamajig, or hammering out some dents, or pulling arrowheads out of intake valves...that sort of stuff.
As an optional addition to this optional rule, you could say it costs something like 1gp or 5gp pr 10gp or some other arbitrary number like that per hp, and each pound of spare parts will heal 1hp or 2hp or 5hp or some other arbitrary number like that. But I'm thinking that this sort of damage is in many ways cumulative cosmetic damage that doesn't seriously affect the operation of the steamborg's systems and as such doesn't really require any expensive specialized parts. I think to damage a steam power or artificial part enough so it doesn't function would require a specific attack such as sunder.
As sort of a compromise between the "no cost/no spare parts" version and the "cost/spare parts" version, you could say it's possible to jury-rig repairs in the field for no cost and no spare parts (you can temporarily fix the damage by cutting out the frayed part of the cable and duct taping it back together, for example)...then make them pay the GP cost when they get back to town to get permanent repairs.
Then if you wanted to do something really cool for steamborgs who run around all the time with jury-rigged repairs, instead of having them lose the hp again after a certain amount of time, you could come up with some disease-like rules where they start making saves and losing stats.