Forge welding, how to see when it's ready?

[Frazer]

Torbjorn is a member here and has been known to pop in from time to time. His username is Tubbe.

[DennisCA]

Re: torbjörns forge, he had a video where he demonstrated it and gives measurements, depth 52mm or almost exactly 2":

 

[anvil]

First, I want you to know I hold him in high esteem. 

Next, I have no reason to change what I stated above.

The fabricated forge at the beginning of the vid looked to be about 4" deep. 

Notice the size fire he has near the end of the vid. That's about the max you can get with that forge setup. That is a small fire, and the size will limit the size and amount of iron you can work. You can with coke use that size firepot in conjunction with a couple of castable refractory bricks about 4" high and a bit longer than the firepot. The thickness should be such that when they are face to face, both bricks being a bit more than half the width, cover whole width of the firepot +. If you do this, you can have a coke fire that can be very narrow and open it up to get your 4" of coke under your work and 2" above.

Please understand I'm not saying you can't use a firepot of what ever dimensions you choose and you can make it work. I am saying that for a given coke and a given blast it will take x amount of coke to consume y amount of O2. And, the dimensions I gave fill the bill for basically a one man shop any time in the history of burning coke.

Finally, and I think I've given this advice to you before,,, go up to his shop and offer to work for him on a per job basis for free or perhaps room and board.

Second to that, just go to his shop, knock on his door and ask him the same questions you ask here,,, get it first hand 

I've never known a smith who would turn someone away if he makes an attempt to come to me and asks for advice. Personally for me, My policy is to take the time unless I'm dealing with a deadline. Even then, feel free to stay and watch and I'll answer your questions 

[DennisCA]

Torbjörn lives in another country from me, it's not realistic for me to visit him. I did ask Torbjörn directly though and he said most firepots in sweden he'd seen where of his size, he did say he'd use bricks to make it bigger if needed, though that rarely seemed to be required. I am guessing the clinker breaker and fan must have an effect too, if it spreads the air widely instead of a concentrated blast for instance and if the fan is on the low pressure side.

At any rate for me it's mostly intellectual curiosity I use a side blast for now so not really relevant. I've thought about building a bottom blast, but maybe I'll stick wi th the side blast, it's nice not to have to think of fishing clinkers all the time.

I was looking at this blueprint if I were to try make a bottom blast as it seems proven, but I have a lot more in fabrication equipment than most so I was thinking of a real clinker breaker and not a grate then. Or a bullet grate, that looked like a nice design, so clinker was shed around the air intake in a donut form.

http://magichammer.freeservers.com/fabricated_fire_pot_by_bob_patri.htm

I've not had time to do more forging the last few days since I've been hewing logs for my shed / smithy build and I got a load of lumber so I can start putting up the walls. I modified the tuyere so it aims downwards now, that's my next test.

[Frazer]

Hey Dennis, in the spirit of trying something new I decided to give this a shot and share what seemed to work reasonably well for me. I'm not great at explaining things concisely so I took some pictures along the way to (hopefully) save myself some typing.. You will have to pardon the poor image quality.. My phone was not made for taking nice, pretty pictures.

I stared with a piece of 1.5"x0.25" (~ 40x6mm) flat stock and upset each end to ~8mm.

Then I scarfed each end

Then I put a slight taper where the scarf is (to help make blending a little easier), ground out the fishtail, and prettied things up a little.

 

Don't be me and measure things wrong and then mess up your scarves trying to fix it... Normally at this point I would just start over, but since I didn't actually need this ring I just went with it. I did not clean up the surfaces prior to welding and I followed my normal welding procedure that I described earlier. I'm not saying my way is right. The other fluxing/cleanup suggestions certainly can't hurt to do. I'm just describing what I did.

Here's my setup. Even with my pointy Soderfors there just wasn't enough wiggle room in there for me to use the horn so I used my bridge/flat bick/"whatever you want to call this thing" that I made out of a couple Unit V railroad anchors. I did dress the sides and face so they were a little more square. I used my little "welding hammer" which is just a 24oz (680g) ball peen hammer that I turned into a stubby straight peen. I find it to be very handy for tacking things together and blending scarves, but you could do the same with any hammer. I also used my 2lb rounding hammer toward the end.

 

 

Regarding your fire, I think you have gotten some great suggestions. Hopefully they work for you. The big thing that I tried to remain aware of was that I have two pieces overlapping each other. Therefore, no matter how I orient the ring, one side is always going to be exposed to more heat than the other. It is very possible to start burning the outer layer before the inside layer has come up to a welding temp. The lighting in my shop is relatively consistent so I am looking for a very bright yellow.

In the early stages of your weld it is just as important to know when to start hammering as it is to know when to stop. If you're not at a welding heat, then stop and heat it back up again. I usually brush and flux every 1-2 heats depending on how I feel about the way thing are going.

Once you are welded most of the way, a straight peen followed by a rounding hammer is great for smoothing out what's left of that that seam. However, that seam should be your primary focus throughout the the weld... OR you can take a texturing hammer and give the whole ring a wood-like, hammered appearance which could hide little lines like you see in the first picture and might even look pretty cool.

 

Ok, so it's not all sunshine and rainbows. My earlier mistake ended up making for a great example of a refined scarf vs an unrefined one. Because the toe of the one of the scarves was hiding in the corner, I couldn't get in there to work it into the ring. So the one on the outside is nice and blended in while the other has a huge seam.

 

Hopefully this is helpful for you. Good luck.

[anvil]

Nice forging and a good demo.

Dennis, When I suggested you go see him, i remembered your answer from before. Lol,All things are relative. when you live where I do, Im far away and you guys are danged close. So Im glad you called him. 

A last suggestion. You are coming to a decision based on little experience. The important thing is to increase your experience. Why dont you do What was done in the second vid and put a red masonry bricks on top of the air inlet and add two more on each side of your air source and try it? Cant cost much. Then play with both ways until you are comfortable with both types? 

[Irondragon Forge ClayWorks]

11 hours ago, DennisCA said:

I was looking at this blueprint if I were to try make a bottom blast as it seems proven,

Yes, the Bob Patrick firepot is definitely a good one. I have used two forges at ESSA that have them and they work very well. Better than some of the commercial ones I have used.

[Frosty]

I made a bottom blast similar to Mr. Patrick's but used free exhaust pipe from a local muffler shop that services semis as well. I use hole saws to "cut the 2" to match the 4". I use an exhaust flap cap for the ash dump. Originally in increased the counter weight but it's not necessary. Flap caps clamp to the pipe and are available in all the larger sizes. 

I have a piece of probably 5/16" plate drilled with 5/16" holes for the air grate. It all just bolts to the bottom of the forge table, being a duck's nest forge there is no fire pot. 

I made a bar air grate based on Glenn's description and like it a LOT more. In my version I bent 3/8" round in 3, hair pin bends. I folded it over 1/4" strap to space the bars. Each leg is about 3" long. 

This air grate just drops over the opening in the top of the tuyere and is held in place by the salvaged fire bricks clay that makes up the table. 

Clearing clinker is as easy as sliding the rake over it, if I have to pick at something the openings are long and smooth so I can put the point of the fire rake in the opening and slide it along. Crud just pops off or through fast and easy.

Frosty The Lucky.

[DennisCA]

Thanks for the detailed walkthrough Frazer, though I haven't had any free time the last few days, busy framing walls right now

[Frazer]

No problem. Let us know how it goes when you get around to it.

Oh, and you my good sir can call me Ferdinand. 

Edit: aw... you fixed it.. It was funnier the other way.

Edited July 13, 2021 by Frazer