I would like to see a ramped up micro controlled version of this metal smelter. It is a duel fuel setup which starts out with propane and after warming up converts over to waste oil. There are several things that could be automated or just monitored.
Monitoring:
Heat temp inside (very handy when dealing with different types of metal and saving fuel)
Air fuel mix (maybe a old sensor from a waste oil burner could do this)
Fan speed (There not only is a compressed air line running the burner for the waste oil suction but also a extra air source to help with the fuel mix)
Automation:
This could be setup to run off its own power using a thermoelectric generator and a startup battery.
Automatic fuel cut over: The propane side is only to warm up the body of the torch and if you could monitor the temp of the torch (separate from the internal temp of the smelter) after it reaches operating temp it could shut off a valve and open the oil valve.
In a very advanced version with lots of research it could be setup to control the air/fuel mix. This could vary based of which fuel you want to monitor since the propane would mix differently than the oil. But since the oil is going to be the primary fuel during the melting process they I believe it would be the preferred choice.
Thanks for your time I know this is a little different than what the channel usually works with but maybe you could think of a way to incorporate the control side of this into something else without making it just for a metal forge.
