Ultra minimal propane forge advice

[ymber]

I'm looking to build a very small, light, and cheap forge that I won't be keeping for long. I want to forge small mild steel pieces and try lower temperature metal casting. I saw this design and it looks quite interesting and very easy. Reading the burners 101 thread though I'm concerned about inadequate airflow keeping temperatures down from a lack of oxygen in the flame in that design because there is so little ventilation. Does it look like that would be a problem for it? I'm also curious what torches people use for these kinds of designs and what fuel efficiency is like in them. The TS8000 he's using in the video is hard to come by in this country and way more expensive than it is in America if you can get one at all.

[Mikey98118]

No. The real problem you will encounter is the brass flame nozzle of the air/propane torch MELTING, if you aren't very careful. If you spend a little more money for a torch with the usual thin stainless steel flame tube, it won't melt, but also will not last more than a few hours use inside this forge, before oxidizing away. From there, you can ether upgrade your torch with stainless steel additions to the flame tube, or remember your original desire for cheap and temporary. My bet is that, once you have built your little forge, you will want to keep it working. So, I recommend that you have a look at page 13 of the burners 101 thread.

[Mikey98118]

To be clear, you don't need to change the thin stainless steel flame tube, until it degrades; that is when you must decide whether to keep to your original plan, or upgrade the flame tube

[ymber]

So you reckon the design is workable if I make a custom steel flame tube for the torch?

[Charles R. Stevens]

Mike wrote the book, literally. Take his suggestion and read page 13 of the burners 101 sticky. 
after that you will be surprised at the amount of help you will get. You doing a little home work encourages  the curmudgeons to help more than standing around with your beak open expecting to be spoon fed. Not that I think that is what you are doing but I am speaking as much to you as to any lurkers present and future

[Mikey98118]

2 hours ago, ymber said:

So you reckon the design is workable if I make a custom steel flame tube for the torch?

Yes, but you don't have tore make the entire flame tube; just add a couple of parts over it.

[ymber]

If you get rid of most of the torch tube and just leave the threaded section to mount the Mikey burner on does that mean the only thing the original torch is doing is supplying propane to the burner assembly? That would mean that just about any propane fueled blowtorch would work the same once it's refitted with a 1/2" Mikey burner, right? The design for the 1/2" burner in the book looks ideal for what I need.

[Mikey98118]

Only if you want to make a canister=mount Mikey burner. If you simply push an outer tube over your torch's flame tube, you can greatly slow down the oxidation of the end of the thin walled flame tube; perhaps enough to need nothing further done to your torch, since you state that you don't plan to use it much within a forge. If you end up using the forge more than originally intended...at that point you would need to add a spacer ring and flame retention nozzle on the tube. You have time to work out a proven solution to your problems, step by step as they occur, and you can find the methods for doing so found in the Burners 101 thread. You can even ask me, since they should prove of interest to others

[ymber]

This burners thing is a real rabbit hole. I'm looking at the Amal atmospheric injector designs some people run now and they're promising but I'm not sure about running one without a big propane tank. A Mikey burner on a blowtorch might still be my best bet. I'll see what I can build and report results.

[Mikey98118]

You started off discussing a very small forge. Obviously, the smaller the forge the smaller the burner (or burners). Small burners must be made more carefully than larger burners. If you are thinking about Amal burners, have you decided on a much larger forge, and just forgot to mention this? Or are you supposing that you can simply turn it down very low?

[Mikey98118]

A burner's turn-down range is a function of how thigh its mixture flow reaches. I don't think an Amal burner can be turned down a great deal, without producing a weak flame.The output of an air-gas burner double for every pipe size that is increased. You began by figuring on what is equivalent to a 1/4" burner. 1/4" is half the output of a 3/8" burner, which is half the output of a 1/2", which is half the output of a 3/4"...see where this is going?

[ThomasPowers]

I've used a "1 soft firebrick forge" with a cheap plumber's propane torch for small work and hot forging fine silver.  It's probably about as minimal a small forge as you can get.  I didn't even get the converter to run  the torch off a BBQ bottle.  I had the torch proped up so that the brass tube did not enter the firebrick but just aimed the flame cone into it.   (Windchill of 20 degF below zero and I needed to do some forging for a project so I made the 1AFF and worked in my drafty basement---100 year old house with a fieldstone foundation and way too much outside air infiltration. Did all the nails for my mastermyr chest and then a lot of hack silver.)

[Mikey98118]

Some guy is even selling this kind of forge, with torch, on the Net. It seems to work well enough, short term. How well the torch holds up long term is another matter; or perhaps I'm just being fussy. One of those pesky decisions people must decide for themselves?

[ymber]

Tim Gunn on here had promising results with a burner built around an Amal injector in a small diameter forge. I reckon a 1/2" injector burner would be workable in a small can forge. It's mostly something I'd be interested in for a future build when I've got enough space to build something permanent. The reason I'm still leaning towards a Mikey burner is that it runs off a blowtorch so the system can be smaller and more self contained than an Amal burner and fuel supply for it. Fuel efficiency is also a concern when I'm going to be running this on really small propane canisters.

[Mikey98118]

Later on, a canister-mount burner can be hooked up to a refillable propane cylinder by use of a speciel hose, which is normally used for camping stoves.