New Cosplayer! How do I make Qrow's sword?

[Tryfarce]

Hey all.

First time cosplayer, long time fan. I'm looking for some help in constructing a functioning sword wielded by Qrow in the show RWBY. I'll include a gif below, but essentially it's a sword that turns into a scythe, an I want the transformation to be done with as little effort as possible. Like, 3 button presses. I figure I'll have to hollow out some foam for the blade and keep the mechanics in there, but that's as far as I've gotten. Is this even possible? I have 0 experience in mechanical work, so this is all foreign to me. Any help would be stupendous! Thanks!

Here's a link to a gif of the transformation (too big to post):
http://rwby.wikia.com/wiki/File:Qrow_Scythe.gif

BTW, I'm not looking for the handle to be automatic; I'm just focusing on the blade right now.