mahonrimorian

Hi guys, I'm new here and I've been building a forge for most of last year. Or rather, I spent a few months building it, found some flaws, and then put it on the back burner for a while (get it?). Now I'm trying to fix the errors I made and I'd love some advice. The forge itself is made out of a repurposed propane tank (one of the small ones) with twin burners that I welded to the top. Those burners are made of bell reducers on either side, 4.5"x3/4" stainless pipe nipples, and 3"x1/8" pipe nipples with tweco tips as the nozzles for propane. I also had a butterfly valve between the two burners so I could have an easy shutoff if I needed it, or to otherwise modulate the flow of propane. I think it's a fairly common design, but the issue I found was that when I turned on the burners they would pulse rather than burning smoothly and evenly. I understand that's an inefficient and expensive way to heat a forge so I'm trying to rectify it now. I bought 1.5" to 3/8" bell reducers to replace the 1" to 3/8" reducers I had, and a set of 6"x3/8" pipe nipples to replace the 4.5" ones. My question is this: is there a way to know how long my burner necks should be/what size bells I need in order to make sure it runs smoothly? Or is it more trial and error?