How to control cell fracture. Object falling into fan blade.

So I have modeled a scene where a an object falls into rotating fan blades. I have all the physics set up in addition to the bullet constraints. However when I animate the falling object I have to uncheck start deactivated to get it to fall. But when I do this as soon as the object hit the fan blade the whole object fractures. What I would like to have is only the pieces in contact with the fan blade facrture. So as the object falls it feeds itself into the fan blade. I have tried key framing it, unsuccessfully. I have tried to figure it out the last two evenings, but I cant seem to get it. I have googled and searched the forums, but its sucha specific thing I am looking for and there is not much for 2.71. Using Physics and simulations, Cell fracture and bullet constraints as search words pull up a pluthra of stuff. But I cant seem to find anyhting that addresses this.

Thank you for your time.

Breaking thinks with the cell fracture tutorial
Part 2 shows you controlling the starting and stopping the object dynamics

There is some add on or function of blender that determines how an object shatters according to marks made with the grease pencil. You could use this to fake it, and just set the fan for non-collision.

There’s an addon called Bullet Constraints Tool that is exactly what you’re looking for!