My new gas forge

[Dunk_c]

Hi

my previous posts showed my old anvil and my first attempts at tool making.  My reason for starting to learn blacksmithing was to make items that I cannot buy easily or at all.  I don't have time for hobbies at the moment so this is all about gaining ability and skills, and items I need.  Anyway, my first gas forge was made from two hollowed out soft kiln bricks and a bernzomatic propane torch and it worked very well.  Size was a problem but I was able to make a few things but only just managed to make these anchors for a new building I need tied down to a wall.  To make things a bit easier I needed s slightly bigger forge:  Ibought a commercially available burner, soft kiln bricks (1400 C) and some ceramic fibreboard (1100 C). I knocked up this forge over the weekend from some scrap metal.

I trialled the burner before finishing the design and was finally able to get a stable burn with wide open throttle and about 7psi, at lower pressure the flame front kept jumping to the forge floor.  The forge volume is about 200 cubic inches and the burner has a 1/2" tube with a heavy duty flare.  Not sure what nozzle aperture is.  Here are some pictures for anyone interested.

 

 

[WayneCoeArtistBlacksmith]

You need to move the ball valve and hose further away from the forge.  A length of copper tubing or black steel pipe long enough to get the ball valve several inches beyond the side of the forge.

It would also help to paint the interior with an infrared reflective product, such as Metrikote or Plistix.

Let me know if I can help you.

 

[Latticino]

Gosh that is a cute little forge.  Very nice fabrication skills, I look forward to see what you will forge based on your attention to detail in the construction of your gasser.  Having the brick slightly overlap the door openings and be replaceable is a sophisticated touch.

In my experience soft brick doesn't respond all that well to forge temperatures and rapid thermal cycling (but I was using some 2300 deg. F brick, so YMMV).  Hope you have better success there than I did.  If anything you may want to put a skim coat of high temperature refractory coating on the brick before you put on the IR coating that Wayne recommends (at least on the brick directly opposite the flame).

[Dunk_c]

20 hours ago, WayneCoeArtistBlacksmith.c said:

You need to move the ball valve and hose further away from the forge.  A length of copper tubing or black steel pipe long enough to get the ball valve several inches beyond the side of the forge.

It would also help to paint the interior with an infrared reflective product, such as Metrikote or Plistix.

Let me know if I can help you.

 

Thanks for the suggestions.  If the heat is getting to the valve by conduction then presumably it would need quite a few inches of extension. If the heat is getting to the valve and tube by convection then presumably lagging would be a solution.  Any ideas? - probably both play a part.  Wish we had easy access to the refractory materials in small quantities here in Oz.

6 hours ago, Latticino said:

Gosh that is a cute little forge.  Very nice fabrication skills, I look forward to see what you will forge based on your attention to detail in the construction of your gasser.  Having the brick slightly overlap the door openings and be replaceable is a sophisticated touch.

In my experience soft brick doesn't respond all that well to forge temperatures and rapid thermal cycling (but I was using some 2300 deg. F brick, so YMMV).  Hope you have better success there than I did.  If anything you may want to put a skim coat of high temperature refractory coating on the brick before you put on the IR coating that Wayne recommends (at least on the brick directly opposite the flame).

Thanks for the nice comments.  I tried to leave a 5mm brick edge all round but my plasma cutting skills let me down a bit on the backside.  The checker plate is quite thin and during the first burn the heat escaping around the brick at the backdoor cause the metal to buckle; had to bend it back and add a piece of angle iron as a strengthener.  The porch is to deflect heat away from the air intake and was also added after the firt run.  So not so much planning as fault fixing!  You may be right about the soft brick as my first micro forge cracked rather quickly.  However, I drilled out the brick centres and the wall thickness was greatly reduced.  Hopefully this will fair better, and I will not be forging every weekend for a while, so I could still get some mileage out of it.  I chose bricks also because high temperature refractory board is either hard to find or too expensive.  I would apply a lining but these items are also not readily available in OZ in small quantities.  While I do not intend to do any welding, I do have a scrap sheet of stainless steel I was going to cut to shape as a floor just to protect the brick from heat, abrasion, but  not particularly for borax.  Would that be of any benefit?

[MonkeyForge]

When I had my burner pointed downward into my forge it would usually remain cool while running but act as a chimney when I switched the gas off, it would then get hot quickly.I have heard of this chimney effect occurring during operation as well, feeding combustion gasses back into the burner. Others might heve more experience with the straight down configuration you use. Al in al that is a pretty little thing you built.  

[Dunk_c]

Thanks MF.  Goeje Avond ( Dutch wife!)

I have the community to thank for many design features.  I searched the net and picked up ideas from what people had shared online. The vertical burner configuration was one I found on some commercial sites (farriers forges for example) so thought there must be some merit (or more likely economy of manufacture).  I had read about he chimney effect also.  Wrapping a kitchen fire blanket around the top vertainly protected the valve from the head radiating from the top of the burner with choke closed off.  I think I may have to get an extension to move the valve away.  The burner designer tells me he had not inte ded it for this tupe of configuration but it certainly seems to work quite well.

[Dunk_c]

1 hour ago, Dunk_c said:

Thanks MF.  Goeje Avond ( Dutch wife!)

I have the community to thank for many design features.  I searched the net and picked up ideas from what people had shared online. The vertical burner configuration was one I found on some commercial sites (farriers forges for example) so thought there must be some merit (or more likely economy of manufacture).  I had read about he chimney effect also.  Wrapping a kitchen fire blanket around the top vertainly protected the valve from the head radiating from the top of the burner with choke closed off.  I think I may have to get an extension to move the valve away.  The burner designer tells me he had not inte ded it for this tupe of configuration but it certainly seems to work quite well.

Sorry about terrible spelling.  Also, 1093 Celcius Dupli Color High Heat auto paint can take the flames without burning.  Touch stuff!

[MonkeyForge]

No apology needed  . I am thinking to use high temperature paint on the next build. The one I have now is a bit like the knives I make: It needs to work, then I can refine as my skill grows. Curious to see your future forgings. Oh and it will be noon here in half an hour

[Latticino]

7 hours ago, Dunk_c said:

While I do not intend to do any welding, I do have a scrap sheet of stainless steel I was going to cut to shape as a floor just to protect the brick from heat, abrasion, but  not particularly for borax.  Would that be of any benefit?

If you will reach any appreciable temperatures I would not hold out any great hopes for the scrap of SS.  It will be better than nothing, but there is a reason you don't see the interior of forges lined with steel...   A piece of high alumina kiln shelf will be much better, if you can get one from a ceramic supply house.  If nothing else try to source some refractory furnace cement used for furnace repairs.  This is a common hardware store item here in the states, is typically rated up to around 3,000 deg. F, and can be applied in multiple thin coats with a brush (thin with water).

Another option for dealing with the chimney effect is to just remove your burner assembly each time you shut down the forge.  Kind of a PIA, but could save the ventauri section from long term damage.

[Dunk_c]

5 hours ago, Latticino said:

If you will reach any appreciable temperatures I would not hold out any great hopes for the scrap of SS.  It will be better than nothing, but there is a reason you don't see the interior of forges lined with steel...   A piece of high alumina kiln shelf will be much better, if you can get one from a ceramic supply house.  If nothing else try to source some refractory furnace cement used for furnace repairs.  This is a common hardware store item here in the states, is typically rated up to around 3,000 deg. F, and can be applied in multiple thin coats with a brush (thin with water).

Another option for dealing with the chimney effect is to just remove your burner assembly each time you shut down the forge.  Kind of a PIA, but could save the ventauri section from long term damage.

Thanks, That would be why my Google searches came up blank!   The refractory mortar available to me from the hardware store is only rated to 1000 C, for pizza ovens only.  I'll use nothing until I come across a small amount to paint on as you mentioned.  when I bought my kiln bricks I asked about shelving ans was told it would not take the heat.  I have seen people using high alumina tiles but no idea where single items can be sourced.  Tile would need to be thin so as not to reduce the forge height too much.  Every year I visit a foundry for work, some of what they coat their crucibles with might be good.

 

 

 

[MonkeyForge]

I got my kiln shelf and also the zirconium silicate and kaolin clay for kiln wash at a pottery supply. earlier experiments with brick and that coating where semi successful. I did not have a frame to hold them together. I imagine they might last longer if something holds them. Pictures below are experiments. Don't build them, This is just me testing the burner and coating.

 

[Dunk_c]

Just an update:

New picture showing gas valve extension tube added to reduce temperature of the valve (as suggested, it worked). Also showing refurbished bernzomatic mini forge, now on refractory board with proper torch holder (previously used too much wood in build, that eventually turned to charcoal!).

Using a cheap eBay thermocouple, the chamber tempersture only reaches 850-900 Celcius (steel is bright orange to my eye at 7psi) but I was able to straighten out a Pandrol-type rail clip with a large hammer.  Might try higher psi to see if temp will rise.  Forearm injured from long-screwing some timber so cannot get stuck into a project at the moment.