This is a modification of this crossbow. 
Print parts from the original crossbow and combine them with these files.
The needed components from the original model are:

• Case
• Cocking rope
• Footpeg
• Bolts (for this version, bolts have to be 33cm long)
• Buttstock (not needed)

Assemble them using the assembly guide in the original crossbow.
For this remix, there are some additional needed parts:

• 4 skateboard bearings
• M5 3030 profile T-nuts
• M3x25 2pcs - for back pulleys
• M3x12 3pcs - front end of the rubber shroud
• M3x8 2pcs - back end of the rubber shroud
• M5x16 3pcs - back pulley mount and rubber shroud mount
• M5x12 2pcs - rubber mount
• M5x10 4pcs - limb mount
• M3x35 2pcs - secondary pulley
• M5x45 2pcs - primary pulley
• Speargun rubber 14mm OD, two pieces of about 10cm (you need to tune the length)

The secondary pulley and back pulleys are assembled by inserting skateboard bearing into printed pulleys.