How to build a copy of the Franklin's bell
A quick run around google suggests that all you need is a rod that is above the house and a wire down to the bells. The rod and wire must be insulated.

Don't use it anywhere important (say, your house.)  

If the long rod is grounded, then the bells won't work.  

If the rod isn't grounded, and lightning strikes, then your bell device will conduct the current down closer to the house and ground.  

You will have made your house into a better target for lightning.  

A lightning strike might set your house on fire.  

Lightning won't have any trouble jumping the distance from your bells to the ground, but will make an awful mess doing so.