Author Topic: Sawed off cupola (Read 242585 times)

vtsteam · « **Reply #75 on:** June 05, 2013, 02:15:03 PM »

The bracket and bolt welded in place.

vtsteam · « **Reply #76 on:** June 05, 2013, 02:17:37 PM »

Cupola with lid swung out of the way, and showing the lever extension. Might be a little long, but depending on how hot that furnace and lid is, might seem a little short!

We have rain predicted for the next three days, so that should slow things down a bit.

Rob.Wilson · « **Reply #77 on:** June 06, 2013, 11:48:31 AM »

Looks like your getting close to the finishing line Steve

I like the lid lift arrangement

Rob

vtsteam · « **Reply #78 on:** June 06, 2013, 04:35:37 PM »

Thanks Rob!

Luckily the rain held off today, and I was able to work on the belt clamp.

First I cut up another piece of that pallet to make brackets:

vtsteam · « **Reply #79 on:** June 06, 2013, 04:40:24 PM »

Then welded two of the brackets to the furnace base:

vtsteam · « **Reply #80 on:** June 06, 2013, 04:45:35 PM »

Then I bent a strap out of 1/8" x 2" and welded the other two brackets to that:

vtsteam · « **Reply #81 on:** June 06, 2013, 04:49:51 PM »

The strap and base before adding the barrel:

vtsteam · « **Reply #82 on:** June 06, 2013, 04:53:49 PM »

And the barrel bolted in place:

vtsteam · « **Reply #83 on:** June 06, 2013, 05:00:31 PM »

The furnace mostly finished:

vtsteam · « **Reply #84 on:** June 06, 2013, 05:12:03 PM »

Because the welding was finished, I moved the cupola up to where it will be tried out. I live on steep ground, so I wanted to get it up there before it started to rain because even the tractor won't make it in mud. We have heavy rains predicted for 2 days. It is supposed to clear up Sunday.

The next job is filling the lid with refractory. I found some lightweight fire brick given to me many years ago by a friend who was rebuilding a kiln. The lid will be quite heavy, since it's 4" thick, so I thought I'd break these up into chunks and plaster them into the mix to lighten it up.

I'll leave a 1" thick layer of pure fireclay and sand as a hot face, since these brick aren't rated at as high a temperature, I believe.

vtsteam · « **Reply #85 on:** June 06, 2013, 05:21:48 PM »

I had a 1/4 bag of fireclay that was in a storage area that was recently flooded with an inch of water. The clay was probably a perfect consistency for making pottery, but poor for mixing with sand to make refractory!

I spent about an hour kneading in sand by hand, then switched to the riddle and put it through that twice using a firebrick as a muller. That was a lot of work!

Finally it seemed to be mixed and stick together reasonably well. I covered it and put it aside, even though I really wanted to ram up the lid. But with rains imminent, I knew that firing it wouldn't protect it, since I couldn't cover a hot lid with plastic sheet, and I could imagine trying to save the whole thing at night in the rain. Bad idea. So, uncharacteristic patience for me -- I put the furnace aside until Sunday.

vtsteam · « **Reply #86 on:** June 09, 2013, 05:46:18 PM »

It's Sunday finally, our one day of sun predicted before we return to rains until Wednesday. Couldn't get much done because of a retirement party for a friend and neighbor this afternoon, but did work on the lid.

Here is the bare metal ring and some scrap reinforcing:

vtsteam · « **Reply #87 on:** June 09, 2013, 05:48:41 PM »

Cutting up soft firebrick with an old pruning saw (never worked well on wood). Cuts quite easily. The bottom of the lid was rammed up first with about 2 inches of refractory before adding the brick:

vtsteam · « **Reply #88 on:** June 09, 2013, 05:50:03 PM »

Checking the brick for fit. The spray can is there to provide a form for the exhaust hole.

vtsteam · « **Reply #89 on:** June 09, 2013, 05:55:37 PM »

The fire brick was mortared in place with premixed "refractory cement" mixed with Perlite. I had both left over for a few years from other projects. Neither is a super high temp product, but I hope that the 2" of fireclay and sand refractory below will keep the upper portion of the lid within a reasonable temperature range.

I hoped that the refractory cement would provide a better bond to the brick and steel. It contains sodium silicate and fireclay and some kind of non-asbestos fiber. Sticky stuff.

I hoped the perlite would help lighten the lid (as would the insulating firebrick).

Guess we'll find out.

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vtsteam · « **Reply #90 on:** June 09, 2013, 05:58:05 PM »

Cooking the lid:

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Rob.Wilson · « **Reply #91 on:** June 10, 2013, 11:55:26 AM »

Nice work Steve

You must be dam close to a test run

Rob

vtsteam · « **Reply #92 on:** June 10, 2013, 01:01:12 PM »

Not too close yet Rob. I need proper tuyere attachment, patching lining (it's taken a beating with all the metal work and moving), make pouring shank, need to mix iron molding sand, make ingot molds, make blower /motor assembly, test fan output, make skimmer, line ladle, make more charcoal, break up and clean iron pieces, get weights for flasks, figure out a ladle heater. Seems like there's a never ending list ! And it will be raining through Wednesday. I'm going to guess a week 'til I get a nice hot ladle full of slag!!

vtsteam · « **Reply #93 on:** June 10, 2013, 08:47:31 PM »

Decided as long as it was raining today I'd take an hour drive down to a town in Massachusetts that has a pottery supply business, and buy some silica sand. It's getting hard to find, and expensive for the real stuff because of health concerns.

They had the pure stuff in #60 mesh. I had read a recommendation for #70 from Stewart Marshall, but 60 was all they had. So I bought 200 lbs of it and trucked it back. Brought plastic bins with me to keep it dry.

I'm going to use Ironman's mix of 85% sand, 7.5% Bentonite, 3.5% coal dust (I might have found a source for some coal I can pulverize -- but can I substitute charcoal dust?), and 4% water.

Ironman's video:

(Ironman, if you read this, is this greensand composition by weight or volume. I'm assuming weight. Thanks!)

Swarfing · « **Reply #94 on:** June 11, 2013, 03:04:47 PM »

Vsteam not sure about your side of the pond? but a good source for silica sand is the stuff they use for brushing in between block paving. Here it is qute fine and i use it with good results

ironman · « **Reply #95 on:** June 11, 2013, 08:38:51 PM »

vtssteam It is by weight. The coal dust burns and slightly lifts the metal of the sand to give it a smooth surface. Coal dust may be hard to find so you could use other things that burn ie. sawdust or wheat flour.

vtsteam · « **Reply #96 on:** June 11, 2013, 09:23:54 PM »

Thank you Swarfing, I will look into that for silica sand.

Ironman, would powdered charcoal work? That would be easy to get/make. I'd prefer not to use other things like flour and sawdust that can decompose.

I could carbonize sawdust -- I have quite a bit of that from my homemade sawmill.

awemawson · « **Reply #97 on:** June 12, 2013, 03:46:53 AM »

Recalling something I read in one of my early foundry books, I think the coal is added to stop 'blistering' where the sand fuses to the cast. If I remember correctly the coal dust breaks down forming a gas layer that cushions the sand from the metal. Also improves surface finish.

If the above is correct powdered charcoal wouldn't work as the gases have already been driven off.

vtsteam · « **Reply #98 on:** June 12, 2013, 07:45:56 AM »

Thanks awemawson, I think the gas involved is CO2 or CO so any of the above might work.

awemawson · « **Reply #99 on:** June 12, 2013, 09:48:40 AM »

Google "why is coal added to foundry sand" There are many references to the coal partially burning and off gassing organic compounds - here is one on wikipedia

http://en.wikipedia.org/wiki/Molding_sand

My feeling is charcoal won't work as the majority of the organic stuff has been driven off in the making process.

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Author Topic: Sawed off cupola (Read 242585 times)

Rob.Wilson

Rob.Wilson