I got a 12 volt relay from radio shack. here is the data sheet http://datasheet.octopart.com/R40-11D2-12-NTE-Electronics-datasheet-55584.pdf
I am trying to figure out if this relay could generate AC (I understand the frequency would be limited to the relay's switch time. )
essentially I am trying to make a H-bridge.
I don't know if the data sheet says but this relay has 2, three pole switches
(I think it is double pole double throw)
thank you for your help.
H-bridges are just four switches. And relays are switches so you can build a h-bridge out of relays.
Whether they will do a good job at that is a different question.
can a double pole double throw relay be used to make an h-bridge?
No, you need 2 single pole double throw relays to make an H-bridge that gives you forward, reverse and stop states.
can a double pole double throw relay be used to make an h-bridge?
Absolutely. Connect the load between the poles and the throws to power / ground.
can a double pole double throw relay be used to make an h-bridge?
See this link for a circuit:-
http://www.thebox.myzen.co.uk/Workshop/Motors_1.html
Building your own H bridges is great to learn about them, but in an application if space is an issue - you're probably better off using an H bridge IC such as the LMD18200 or L298 as these have features such as overcurrent / overtemp protection, seperate enable functions, internal clamp diodes etc.