First coal forge build

[Bowland]

Decided to make a portable coal forge for added customer intrest at shows. Never done this before ( I use gas)  not worked on a coal forge for near three decades either - forgot so much!  

This is were I am up to trying to decide on were to divert excess air ( thinking in the horizontal directly in- line with flow? Via a sliding trap that I could pull or push from front end? 

I'm 

The fire pot is roughly a foot square by 6" deep made from.. 5 mm ( sorry I forget the imperial about 3/16?)  

Pipe is 2 1/2 bore.

 

I plan on putting in a heavy floor plate well slotted to heat centrally as this could be adjusted to suit situation?  

The pipe is flanged but I have no clinker breaker. I figured this was overkill? Couldn't I just rod is out down the vertical? 

[Bowland]

I have about a day in it so far and every thing was from my " might come in handy pile" part of my fabrications company.  Flame cut by hand 

The paint is a bit overkill but I want it to start life looking nice ( remember it's for clients to see and I don't want them to know it's scrap pile built) 

The pipe is actually some 5 mm wall chs I had spare and rusted. Is it worth even considering water Cooling?  Not that I have quite figured out how yet!  

[Charles R. Stevens]

Not for a bottom blast forge, it would be over kill. 

[the iron dwarf]

zinc plated bolts that will get hot

plain steel ones would be better

[Bowland]

26 minutes ago, Charles R. Stevens said:

Not for a bottom blast forge, it would be over kill. 

Thought as much   thanks 

11 minutes ago, the iron dwarf said:

zinc plated bolts that will get hot

plain steel ones would be better

The zinc will burn off first proper burn and become plain steel ones 

[Charles R. Stevens]

Vaporized zink can lead to heavy metal poisoning. A day or two in a bowl of vinegar will take care of that. The risk may or may not be that big but why take the chance. 

[Bowland]

I work with this stuff. It's electro plated not galv the quality of zinc is slight and likely creates less hazard than the coal

 More Londoners were killed in a big coal smog post war in one winter than in the blitz of ww2 

Like I say first burn and I expect it will be gone.  It's relative and this forge is for outside use 

Galvanising is far more dangerous ( hot dip)  due to massively higher concentrations and have unfortunately seen the results  this in co- worker in the past.  I have to grind heavy sprue from the hot dip process weekly and I take those risks very seriously

Could we therefore leave this subject of electo plated m10 x 40 bolts? 

[b4utoo]

should it be that deep? Mine is only about 2" deep and works great.....

I ask because If I should make another forge a bit deeper.... if mine is working great would it work even better deeper

[Bowland]

I plan on putting in what amounts to a false floor in from heavy plate.  Deeper can be made shallower but shallow can't be made deeper was the way I figured it 

Learning process for me like I say 

2" sounds shallow but if it works for you why change

[John B]

2 hours ago, Bowland said:

This is were I am up to trying to decide on were to divert excess air ( thinking in the horizontal directly in- line with flow? Via a sliding trap that I could pull or push from front end? 

You need to be able to control the air, so a slide valve is easy to do, and you will need to be able to seal off the bottom of your tube or you will have difficultu cotrolling air flow.

I would suggest making a hinged ash dump as they are easier to use especially when forge is portable

No need to water cool, total waste of time on a bottom blast set up. maybe make a removable plate to fit over the central tube and drill a series of holes or put slots in for the grate.

To control air I prefer to feed from rear with adjusting handle at the side on a ratchet arrangement as this gives repeatability and is less likely to get accidentaly knocked or disturbed when in use, which can be potentially dangerous.

What fuel will you be using? The existing depth should be ok, but for future reference the steeper the sides, the more difficult to remove clinker.

Here are some pictures that may help to illustrate what i mean square tube was used because weld prepping is easier than on round to round.

Look forward to seeing pictures of it working and what you are making in it. Have fun.

[Bowland]

Thanks JohnB and pictures as well! Yeah I was thinking a dump on the bottom. I left enough so I wasn't needing to dump until the end of the session.

The ratchet I get - good idea for sure. Is the danger running with too little air then breaking into the coal or what?  

The two square flanges with the pull out plate for the air choke look good to me.

My plan was always to put in that raised internal floor - what kind of min / max on that as regards the plate thickness? 

Also saw some cast iron heavy grid covers recent and wondered if I might source one the right size or one I might alter?  

Does the airflow still work if it's not centrally focused in the burn pile though? That's what I fear with a grid cover 

Thanks for taking the time, appreciated

[John B]

8 hours ago, Bowland said:

Thanks JohnB and pictures as well! Yeah I was thinking a dump on the bottom. I left enough so I wasn't needing to dump until the end of the session.

The ratchet I get - good idea for sure. Is the danger running with too little air then breaking into the coal or what?  

The two square flanges with the pull out plate for the air choke look good to me.

My plan was always to put in that raised internal floor - what kind of min / max on that as regards the plate thickness? 

Also saw some cast iron heavy grid covers recent and wondered if I might source one the right size or one I might alter?  

Does the airflow still work if it's not centrally focused in the burn pile though? That's what I fear with a grid cover 

 

In practice, you should not get a lot of ash/clinker in the ash dump,(to qualify that it will depend also on the size of the air vents in the hearth base suporting the fire) so you don't need a great volume beneath the air intake,

The ratchet gives a repeatable and secure reference point when the forge is working, if you have a simple pivot on a lever then there is a tendency for it to move when working on the  forge, if the lever is horizontally mounted then not it is a tad better, I just like the directness of the ratchet type, I also have it inside the periphery of the hearth so it is easier to transport and stack if it is going to be portable.

I am not quite sure what you mean by "Is the danger running with too little air then breaking into the coal or what?"

So long as you have air being fed in it will percolate through the fire by the easiest route, if you have a load of clinker in then it will either have a hole through the clinker's centre, or the air will go around the outside edge of the clinker giving the appearance of a good fire, but it will have no 'heart' and you will heat around each side rather than towards the centre where you would expect the hot spot to be. You can usually tell if this is happening as the centre bit of the length of heated bar will be duller in colour thtn the ends of the heat.

Air control is vital, you need sufficient for the job being worked on. You are better off using less air + patience and let the workpiece soak up to the required temperature.The amount of air dictates the size of the fire/heat generated, too much air results in all sorts of problems, eg excessive fuel being used, ash and clinkers attaching to the workpiece giving a poor finish, and needing excessive use of the wire brush or hot file, burning of the exterior surface resulting in 'scabbing', excessive scaling, the metal being hot on the outside but not all the way through, particularly on the larger stock.

The above also partially answers your question re grid covers and centrally focussed. It is also dependant on the size of the grid you are using as this is what holds the clinker, too big and ash and small particles of fuel can fall through also.

"My plan was always to put in that raised internal floor - what kind of min / max on that as regards the plate thickness?" 

If you put in a raised floor ensure the air will not escape around its edges as it can cause fire management problems, as to min/max size of plate to use. There are no guide lines but longevity in use is the problem, personally I would recommend at least 3/8"/10mm thickness preferably 1/2"/12mm  as a minimum for the grid base,

I would also use 6 or 8 holes on a pitch circle diameter of  holes 3/8" diameter  with a central hole of a similar or slightly larger size. This is a proven design.

I would abandon the thought of using a cast iron grid as it can cause more problems than it solves and depending on configuration may be totally unsuitable.

The forge in the picture has a shallow angle base of 6mm (1/4") plate with the tue area made of 10mm (3/8") (or could be 1/2" = 12mm ) The shallow angle allows for easy clinker removal, you just allow the fire to cool and let the clinker coagulate, then slide a slice or shovel along a side and remove the majority of the clinker in one go. Steep sides can be awkward.

What you don't mention is the fuel you are going to use. The abve design can be used for coal or coke.

Hope this helps you a little further on your journey. Have fun

 

[Bowland]

Thanks again. All good stuff John B obvious when thought through but easy to omit on my first build