Using a framework like Rails, instead of just coding everything yourself directly in some sort of programming language, is a trade-off. A framework requires that you do things "it's way", but the payoff is that you can do those things quickly.

But, if your project just won't fit the way of the framework, or you want to reuse your original database tables in a re-write, there's no substitute for coding the thing the old-school way. Chances are you can't make the framework fit your design, ever.

If I tried to rewrite any of the sites I work on using another *language*, but keeping the same database tables, I could. In fact most of the heavy lifting is done in SQL, leaving the scripting language to iterate over returned queries and generate the output.

But the only way they could ever be safely rewritten using a framework would be to throw *everything* away and build from the ground up, redesigning everything with the chosen framework in mind. Anything less would just be begging for pain.