I've messed with coal forges since '99 and my experience is similar to this.I know I am going to get some flak from this post, but here goes anyway.
So called Clinker Breaker at the bottom of firepots. Is it really a clinker breaker?
Just look at the one in your own forge, does it stick up into the firepot far enough to actually break up a clinker?
Probably not. If you stop and think about it and look at some of the information from old publicatios, you will find it referred to as a tuyere, blast gate or ash gate.
Due to the shape of their construction they were made to be used to control the amount of air entering the bottom of the fire, and could be manipulated to have a small center fire, a large fire with more air, or a fire off to one side.
The Trinagular ones, with one of the V's corners is pointing down will give you a nice small even fire in the pot. If you rotate it to so that one of the V's is pointing to one side, you will get a little larger fire. If you rotate it so one of the V's is pointing up, you will get a really hot fire.
The round ones with a slot in the center have the pivot rod offcenter. With the slot pointing up and the highest side up, you will get a nice small condensed firel. Rotate the slot to the side and you get a little larger fire, Rotate it so the highest side is down and you get lots more air around the sides and also up thru the slot for a large fire.
When you rotate this so called Clinker Breaker during a heat, what are you actually doing?
You are getting rid of the fine ash and small clinkers at the bottom of the firepot.
You more than likely have at some time removed a Doughnut Clinker from your firepot, did you happen to notice that the center of the doughnut is open from the air blast shooting up thru it. The clinker material (impurities and residue from burnt iron) forms around the air inlet automatically being pushed to the side by the force of the air. Occassionaly if you are using exceptionally dirty coal when and the clinker has built up sufficient to overpower the air blast (2 to 5 Oz of pressure) the fire wil more or less quit and/or you idle the fire for a bit and the clinker molten ooze flows over the air hole , and upon restarting, you get no air. if you stick a straight poker down into the center and lift you get a good fire for a little bit.
No matter how much or vigorously you rotate the air gate, so Called clinker breaker it doesn't do any good.
forges with a plate with slots and no air gate/so called clinker breaker are high suseptible to clinker choke is what I call it when the clinker restricts the air to your fire.
Side Blown or Back Blown forges do not suffer this problem as the clinker just pools or congregates at the bottom of the fire in front of the tue or Tuyere iron.
I have been wanting to post this for some time now, finally got it off my chest so to speak.
Now let the ranting and raving and name calling begin, but before you do just stop and reread this post and think about your own forge and forging experience.