Hi, I'm new to forging and just building my first propane forge. It's a big one- about 2500 cubic inches. I made venturi style burners (3 of them), figuring that would work. Problem is, outide the forge they work pretty great, but once installed the flame is very weak and often just oxidizing, even though I can control the amount of air going in. I'll post videos, but here is the info anyways. The burner construction is as follows. Straight from the tank there is a high pressure regulator with a hose that leads into 2 tees in order to split the assembly into 3 branches. At this point the pipes are 3/8, but they lead through 90 degree elbows and reduce into 1/4 to go into the burners themselves. There are ball valves on all three. I threaded the pipe nipples and put it through a bracket which is welded to the reducer on the top of the burner. A disc is threaded onto the pipe so that it can move up and down on top of the reducer in order to control the amount of air going in. At the end of the pipe there is a cap with a 0.035 MIG tip for a jet nozzle. The reducers themselves are 1-1/4 to 3/4, the burner shafts are 3/4 by 8. Currently they are just being held in the forge by 3 pipes welded to the body that the burners just sit in, I'm wondering if I need to make the pipes bigger and just use retention screws so that there is extra space around the burner for air getting into the forge. Here are the videos of the burners outside of the forge, as well as inside. In the videos of the burners installed in the forge, I am using a hair dryer to blow more air into the forge and you can see the flames immediately get better. Any help would be appreciated. Do I need to change to forced air?
https://drive.google.com/file/d/19G5r9ooaupDswwOTEb7V86BOxJCLwvaf/view?usp=sharing
https://drive.google.com/file/d/1I3u6BKHZkke4ReYdSmcobE7I1L23mcue/view?usp=sharing
https://drive.google.com/file/d/1_NdbDASkVa0yWP81iZXV_j_EZYY8fb-W/view?usp=sharing
https://drive.google.com/file/d/1d_ENhJzxfnhyX8lo3VjfN7li14zRJ0JR/view?usp=sharing