An updated/revised consolidation on a number of other older post about building a natural gas or propane forge ( To be proofed again as time allows)
—-Disclaimer: I’m an idiot, putting my words into any actions is an absolute form of neglect. Any reader is responsible for their own safety and should not consider me an expert—
When building a forge: Insulation type, internal forge shape and dimensions, burner style and size are all important.
Notes on burners and forge pairings:
*Orifice* size and pressure, affect flow volume and gas velocity. Regulate the pressure and change the size of the *burner fuel vent hole* (*orifice*) to match the internal volume of the forge. Flow affects **aspiration** in this case “natural aspirated”; atmosphere is drawn into the burner body by the speed and volume of the fuel. Increasing the fuel increases the draft/suction/aspiration effect; but too much too slowly and you won’t have enough room in the path of travel for outside gasses to enter and mix effectively. You want the air and fuel to mix inside the burner and ignite inside the forge. Often forges without a well designed burner run fine when up to heat but not so well warming up due to erratic or improper gas travel inside the burner tube and during the transition from burner to forge.— Many little things happen that we can’t observe directly when tuning a forge/burner; but there are signs and symptoms. Look listen and feel. Trial and error will teach you if you’ve got the ***tools*** (***knowing how it works***).
After plumbing in some sort of regulation- then figure out how to reduce or increase the orifice size. As a start (weld/hi-temp braze/drill) or adjust the size of the forge and size of the burner tube depending on your needs and operating expense. To prevent accidents (I feel obligated to say this even if you must know I’m an idiot.): Keep a pilot light going during testing and never let flammable gases build up in a constrained or restricted area — At least these are my poorly educated guesses. I seem to be on the right path and have ****safely**** (****to a degree that my luck hasn’t run out and neither myself nor my property has been greatly damaged****) made and used a handful of forges since this publication in it’s original form. One of these opinions might be a step in the right direction for a reader. (<-again see the disclaimer)
Fabricating the shell/forge body was filled with bad ideas and potential chances at bodily harm (cutting open a container that once held flammable gasses and dealing with galvanized steel)- but with the help of a good friend we managed to both accomplish the task physically unharmed. Any psychological (pyrological?) damage is irrelevant and probably pre-existing:
A ceramic fiber blanket was cut and fitted as insulation for the forge. Then a castable refractory was applied for health (loose ceramic fibers are not good for you) and durability.
The final step not photo’d was brushing on a thin white high temp and UV reflective coating to improve temperatures and fuel efficiency.
In this video you can see the forge at welding temperatures and learn a bit about pattern welding: