Hi I have built one for my workshop like in this thread 
https://permies.com/t/29052/rocket-stoves/builds-experimental
 I used old red bricks for the batch box and stacked more around the bottom barrel for some mass.
 It as been going for about a week and I'm well pleased, the work shop is 30X35 foot.
 The cost apart from the time, about a day, was nothing.