Fire pot jig

[Martin Pansch]

Between my own, helping others out and host a poor man's coal forge workshop a few years ago I must have made or helped someone else make about a dozen firepots. Mostly out of 1/4" plate because I seem to come across a lot of 1/4" "crebble." Back when all I had to cut it was a sawzall the cutting took the longest. Once I got my demon saw cutting them out took no time but welding with a small oxy/acetylene rig took the most time. Now that I have a nice MIG welder the time sink has been, remarkably, trying to set all the pieces together before tacking them. We would try to hold everything in place with bricks, tape, whatever we had lying around. It sometimes took 15 minutes putting the puzzle together sometimes only to have it fall apart when you got the MIG gun close (almost like it could tell...) Since most those times we were only making one or a few it didn't seem worth it to do anything more permanent. Now since I making a number of them for the Guild loaner library plus I am scheduled to do another poor man's forge workshop in the spring I finally got around to building a fixture to hold all the pieces in place.

firepot jig.JPG (525.16 KiB) Viewed 7581 times

I made it out of wood for speed and ease of getting the angles right (my miter saw can shave off a little wood easier than I can remove a sliver of steel). Since it will only hold the pieces for a few quick tacks I am not too worried about it burning up.

firepot jig with template sides.jpg (468.75 KiB) Viewed 7581 times

Just cut the pieces to size, slap them in, tack it in place, and pull it out. Should help do it faster and keep the whole thing square easier. This second photo shows how the notches in the side are for allowing me to clamp the grounding cable on the piece somewhere out of the way.

Now back out to the shop to whip out a couple.

[Martin Pansch]

After posting photos of the fixture I went up to the shop and started laying out and cutting out firepot pieces with my demon saw. I have a bunch of odd arc pieces of 1/4" plate I got for free-ninety-nine.

Cutting out firepot pieces

cutting out fire pot pieces.JPG (483.47 KiB) Viewed 7572 times

Depending on how accurate I was cutting them out they either fit really well in the fixture or with just a small gap. Easy enough to weld up. This photo is too far out to see if there is any gap.

Firepot pieces and fixture

Fire pot pieces and fixture.JPG (410.67 KiB) Viewed 7572 times

I cut pieces until the saw needed a break and decided to tack some together. My spool of MIG wire feel and cracked when I took it off last time so it took a little wrestling to get it to behave and not snag. By the time I took care of that and had dinner I ran back out to the shop and tacked 5 pots together.

5 firepot tacked together

5 firepots tacked together.JPG (427.7 KiB) Viewed 7572 times

Then the mosquitos started getting gamey so I called it a night. Next time I'll finish up the pots and start on the forge bodies themselves. I'll probably just work on 3 of those at a time as those are all the blowers I have at the moment.

[wayne.olson]

Nice Job Martin!
Wayne

[Darryl Ponder]

That sure beats my using masking tape to try and hold the whole thing together while I tacked it!

Darryl

[Martin Pansch]

I got a little more work done on the loaner forges. I finished welding up the seams on the fire pot, burned a hole into the bottom of the fire pot, and started making the tuyere parts. I used 3" square tube from a stash Al Olson scored for the Guild and some 1/8" sheet from Derrick Phillips for the plate to bolt on to the fan.

Fan and tuyere.JPG (157.18 KiB) Viewed 7459 times

It is square tube and I burned a square hole in the bottom of the pot. I have only ever seen round holes in the firepots but I have a theory that this is done because the pots were made of cast iron and these corners would likely be stress points and crack. I don't think this would be a problem in mild steel. I don't -think- the square hole will have any bad effects on the hot spot when in action. I won't know until they fire up.

In the past I have made the tuyere bolt on to the bottom of the fire pot but for these I welded them on. It saved a lot of time and I figure if these things need work in the future I have a angle grinder and cut off wheels.

Tuyere and forge top.JPG (105.78 KiB) Viewed 7459 times

I laid one of the fire pots out on a 28" circle of 1/4" plate, again from my brother's shop, and chalked out the opening. I cut the fire pot opening using a plunge cut with my metal cutting circular saw. The pot and tuyere drop right into the hole without the fan bolted to it.

I still have to put legs on them and weld a 1/8" thick lip around the perimeter of it, both using some excellent steel from Jim Erickson. I got an idea for the legs that I think will work out well. I also need to wire up the fan, probably putting a switch on the fan casing itself to avoid having to worry about quick disconnect options for the wires. The fan will get an intake damper and I need to weld some 1/2" round rods as a grill into the bottom of the firepot. I hope to have at least one test fired this weekend.

[Martin Pansch]

I had a chance to get the legs attached. I used round pipe on the last round of forges but I ran out of pipe in my stash. What I do have enough angle iron from Jim Erickson to put legs on 7 forges. I just had to figure out a slightly different way to secure and adjust them. I found some scrap square tube in my stash that the angle just fit in. I cut 6" pieces of that, chopped a hole in one of the angles and welded a 1/2" nut in there.

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Close up of angle iron leg.jpg (94.52 KiB) Viewed 7433 times

I canted the sockets in so no one should catch a thigh on a bolt head. I thought about welding 4" of 1/2" round bar to the bolt heads to allow easy tightening but I figured the people borrowing it can take the responsibility to find a wrench.

I welded the 1/2" rod to the hole in the bottom of the fire pot to make slots. I didn't take any pictures of that because, hey, it is just slots.

Loaner forge almost complete.jpg (115.12 KiB) Viewed 7433 times

Only thing left now it to wire the blower using one of the cords Herb Fick saved for me, put a damper on the fan and cut a piece for an ash dump.