This is heavily based on the work of others. 

The Arm, Hook and Hub came from Jensa's design here:
https://www.youmagine.com/designs/adjustable-heavy-duty-filament-spool 
(which in turn came from Thingiverse).

The base is from Cor3ys in this post:
http://umforum.ultimaker.com/index.php?/topic/4498-first-print-straight-out-of-the-box/?p=38596

I modified Cor3ys upper side part to make it longer and include the tube the shaft sits in. The Hub was modified to make the hole larger and to include a longer tube to stabalise the the hub on the shaft. 

I made a shaft to fit - who wants to buy 2 meters of pipe just to get 175mm worth when you can print one! I also made a base for the spool holder and a couple of spacers to position the filament wheel in the center.