You have Infinite intensity dont you? He explains how in there. It is quite simple. I have made 4 dumbells really cheaply.
if you want to make it go to a junk yard they have all different sorts of pipe there and take wat you want or just go to a metal selling place
Relentless, Take one of you dumbell plates to the hardware store and get them to cut a pipe for you that fits with the weight plate (and the length you want it). Buy some hose clamps and a baseball grip (for a handle). Use the hose clamps to kepp the weight plates in place (2 for inside collars 2 for outside collars).