Sawed off cupola

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You can see the two separate connections for the tubes here at the tee fitting at the bottom of the pitot. Both are connected to a U-shaped tubing gauge with colored water in it. A ruler is located in the gauge to judge the relative heights of the water on each leg of the U. The difference between the two heights is a measure of the pressure that the pitot tube is sensing. For a furnace this is called blast pressure. And traditionally, in this country at least, it was measured in "inches of water column". This can of course be converted to any measurement system.

BTW if you want a great converter for your computer -- look up Josh Madison's "Convert" online. It's free software. I use it constantly.

(Just checked it -- unfortunately It doesn't calculate inches of water column, but you can add that in its custom tab and then it will in future. 1 inch water column = .00249 bar = .0361 PSI)

Actually, most texts on cupola furnace operation use inches of water column -- so it's usually unnecessary to convert to anything else. And its easy to make a guage if you have a ruler graduated in inches.

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Okay, back to the cupola.

Salvaged materials: a steel packing crate for a tractor mounted chipper. A few pieces of cutoffs from a galvanized fence top rail. A piece of bent semi flattened 2' pipe I found somewhere.

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I cut up some of the crate with a grinder and cut the fence rail with the bandsaw. I put the tube into a container of muriatic acid to get rid of the galvanizing.


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Cut to length and mitered some pieces of angle iron.

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Welded them together.


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Ground it.

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And started to put legs on. Got two welded and two tacked by supper time.

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[Rob.Wilson]

Lookin good Steve  ,,, were is your tapping hole ? 

Rob

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Thanks Rob.

The tapping hole 's on the right side, low down, you can't see it from this angle. It doesn't have a spout yet. I had been using it as a tuyere when I melted aluminum as a crucible furnace.

The cupola tuyere is on the left where the elbow is -- it was formerly plugged. There is no wind belt on this small furnace.

Today I cut out the bottom of the furnace. I just used a stick to do that -- the stainless is very thin -- I measured .020 on the drop.

I started to make up a new bottom -- I don't have much for sheet steel, but found an old disk shape that was almost exactly the right size -- the OD was 17", perfect. But the hole was 6" dia. and I needed 7"

So I found a circle cutting attachment I made for my torch several years ago and took a strip of steel and tacked it across the hole to give me a center point. Then I punched the center.

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Here is the circle cutter assembled to the torch.

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And the hole it cut.

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I decided to make the drop door. I don't have much height to work with -- I wanted to keep the cupola low. And since the max melt is 10 lbs (I hope) the height of a ladle is probably going to be only about 6".

Anyway, It occurred to me that the door might be better as the traditional double doors seen on much larger furnaces, to keep them short when in the down position.

Also, I only had two pieces of 3/8" plate available. one was too narrow for a single door, but wide enough for a double, so I tacked my wider plate to it and put the tacks right where the circle centers would be. Then punched them.

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And cut them out.

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Cut up some water pipe for hinges and welded two sections to the doors.

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And welded the other hinge barrels to the bottom plate. The wavy edge on the left is just an old upside down garbage can I was welding on. My welding table. Some day I'll have a better one...

I need to turn some better fitting pins than the 5/8 all-thread here. It was time to quit for the day.

[Rob.Wilson]

  Doors turned out well Steve  me thinks I may be loosing  the race 


Rob

[Mayhem]

Best pull your finger out then Rob!

[Rob.Wilson]

Best pull your finger out then Rob!

  I no Darren    , must admit I am looking forward to seeing Iron flowing from Steve's furnace 


Rob

[Mayhem]

I want to see both in action, so I know which one to copy 

Just think - if you finish yours Rob you can cast a new mill instead of spending all that time trying to get your Chester square - or is that a sore point 

[Rob.Wilson]

You planning on building cupola Darren ?

  No the Chester mill is all all nice and square now , I will probably still fined something to moan about on it further down the line   


Rob

[Mayhem]

Its in the back of my mind Rob - along with hundreds of other projects, many of which may never see the light of day.  I still have to finish off my babington burner and then get my furnace built. 

The burner worked fine when I had it set up on retort stands with a gravity drip feed to see if it was plausible to actually build.  Since then there have been little problems crop up with progressing it to a self contained unit with an oil pump and sump.  Now that winter is upon us and the fire bans lifted, I can play a bit more with it.  Once it is running I'll start on the furnace and see how it performs.

If there is any interest in it, I'll start a thread on here when (if) I get the kinks ironed out...

[Rob.Wilson]

Aye Darren  get a tread started 


Rob

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Rob, you know I'd be happy if you poured first. But the friendly cupola wars is a great motivator to actually get the darned thing done, for me. Maybe we'll pour on the same day. That would be cool!

Well, it just started storming so I quit for the day. Here's what I did:

Welding the hinges on really warped up the 1/8" plate, so I weighted it down and clamped it to the base to keep it flat while I welded it in place.

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I welded the disk on. I wanted to avoid more distortion, so I didn't continuous weld it on, but put two welds per angle section. Then I ground the tops of the welds down flush with the plate. Not pretty, but it was flat.