Jump to content


Photo
- - - - -

Electric Kiln Design: 'bucket' Or 'box' Preference?


  • Please log in to reply
28 replies to this topic

#21 Mart

Mart

    Advanced Member

  • Members
  • PipPipPip
  • 283 posts

Posted 02 August 2013 - 04:41 PM

 

 

 Circular design is a huge waste of staking space.

It's is easy to imagine why. Just draw a circle with a diameter of 10 and now draw a square with a edge length 10

 

Do you make square bowls? No. Does the heat from the elements stops at the corners? No.

That is why the "bucket" kilns are more efficient than the "box" kilns.

(And that is why everybody should be obligated to take a science class while in school!)

 

 

I throw them square... no, those are actually cubes. Yes, I throw cubes <--This was a joke ;)

 

LOL, you kinda proved my point, actually.  You see, the corners of a rectangular shelf are perfect for posts (or pots, if posts are in the middle). But when you add posts to a round shelf, what happens then, Mr SleepingInGeometry? ;)

Cheers!



#22 jrgpots

jrgpots

    The hands can express the soul

  • Members
  • PipPipPip
  • 524 posts
  • LocationHurricane, Utah

Posted 02 August 2013 - 05:04 PM

 

My big oval doesn't have removable rings. too bad.
Rudy Autio had an electric hoist he used to lower his large vessels into his top loader.
I love that idea.

The front loader does look like a back saver. Thanks Neil for that explanation.

Marcia

Not only a back saver, but a gut saver.  I have to hang over the edge of my classroom L&L, to get things loaded into the bottom.  My feet sometimes come off of the surface I am standing on.  It probably looks a little precarious, and I've had students ask, "What would happen if you fell in?"  They seem to thing, that I would be consumed in fire, like if I fell into a pit containing a mixture of lava and acid.  I tell them, "If I fell in, I would have to fall in hard enough to cause me to squeeze all the way in, the lid would have to close and magically lock behind me, someone, who knows how to use the control panel would have to start the kiln, and I'd have to be incapacitated long enough, that I didn't try to get out, before the heat/ electricity would kill me.  So basically, nothing would happen more than me looking like an idiot, as I struggle to push myself back out."

 

Stories of Hansel and Gretel come to mind.  The evil witch potter loading his kiln is kicked into the hot bowels of the consuming kiln's fire... More details at 10:00.

 

I have seen a homemade kiln made from a "bucket" style.  The kiln had been cut in half along the midline vertical plain and hinged.  I don't know how the bricks were stabilized.  Half of the kiln swung open like a front door.  Has anyone else seen this type?



#23 Claypple

Claypple

    Advanced Member

  • Members
  • PipPipPip
  • 261 posts
  • LocationReno, NV

Posted 02 August 2013 - 07:31 PM

 

 

 

 Circular design is a huge waste of staking space.

It's is easy to imagine why. Just draw a circle with a diameter of 10 and now draw a square with a edge length 10

 

Do you make square bowls? No. Does the heat from the elements stops at the corners? No.

That is why the "bucket" kilns are more efficient than the "box" kilns.

(And that is why everybody should be obligated to take a science class while in school!)

 

 

 You see, the corners of a rectangular shelf are perfect for posts (or pots, if posts are in the middle). 

 

Take, e.g. an electric element as long as 100cm. If you put it in a square shape, you will have a kiln with the surface of 625 sq cm. (25x25=625) If you put it in a round shape, it will give you a circumference of the kiln of 100cm, which is equal to a circle with the diameter of:    100 : 3.14 = 31.847 cm.    Then the radius of this circle will be 31.847 : 2 = 15.9 cm The area (surface) of the round kiln then will be: 15.9 x 15.9 x 3.14 = 793.8 sq cm.

Now compare the numbers: Square kiln: 625 sq cm. Round kiln: 793.8 sq cm. 

Since the amount of electricity/energy going through the 100 cm electric element is the same in both round and square shape, the round kiln will be 27%more efficient.

 

By putting the posts in the corners you are simply "smoothening" the corners to more round shape. You are actually doing opposite to "squaring the circle", but there is always a lot of available space in any kiln for the posts between the bowls.



#24 Mart

Mart

    Advanced Member

  • Members
  • PipPipPip
  • 283 posts

Posted 03 August 2013 - 10:36 AM



 



 



 



 

 Circular design is a huge waste of staking space.

It's is easy to imagine why. Just draw a circle with a diameter of 10 and now draw a square with a edge length 10

 

Do you make square bowls? No. Does the heat from the elements stops at the corners? No.

That is why the "bucket" kilns are more efficient than the "box" kilns.

(And that is why everybody should be obligated to take a science class while in school!)

 

 

 You see, the corners of a rectangular shelf are perfect for posts (or pots, if posts are in the middle). 

 

Take, e.g. an electric element as long as 100cm. If you put it in a square shape, you will have a kiln with the surface of 625 sq cm. (25x25=625) If you put it in a round shape, it will give you a circumference of the kiln of 100cm, which is equal to a circle with the diameter of:    100 : 3.14 = 31.847 cm.    Then the radius of this circle will be 31.847 : 2 = 15.9 cm The area (surface) of the round kiln then will be: 15.9 x 15.9 x 3.14 = 793.8 sq cm.

Now compare the numbers: Square kiln: 625 sq cm. Round kiln: 793.8 sq cm. 

Since the amount of electricity/energy going through the 100 cm electric element is the same in both round and square shape, the round kiln will be 27%more efficient.

 

By putting the posts in the corners you are simply "smoothening" the corners to more round shape. You are actually doing opposite to "squaring the circle", but there is always a lot of available space in any kiln for the posts between the bowls.

 

 

 

This picture looks like a test for a color blind :) but it's not. This is a quick Qcad drawing of our imaginary kiln, using 100 xyz long coil

 

2n1ao0x.png

 

Here is the legend:

Blue outer square - wall for our imaginary kiln

Red - 4 coils, each 25 xyz long

green circle - bucket kiln wall (100 cm circumference for the coil)

White square with 4 white circles - kiln shelf with 4 posts

Yellow circle with green lines - round kiln shelf with 3 posts (small yellow circles)

 

Square shelf has approximately 22% of more stacking space, while surrounded by that same 100 xyz coil.

 

PS! Pleas, do not take this personally. As I have said before, I sometimes miss the nuances of English language and can sound a bit harsh :) It is not my intention.



#25 Claypple

Claypple

    Advanced Member

  • Members
  • PipPipPip
  • 261 posts
  • LocationReno, NV

Posted 03 August 2013 - 10:51 AM

You sound very nice, no harshness at all. I like your diagram, too, but the round kiln would not be inside of the square one. (See theorems for "squaring the circle" ). That is your main mistake.

 

What you drew would be very important if you had only one huge bowl/platter you had to place on one shelf. The reality is we are all stacking multiple, different size objects, so there is plenty of room for the posts in between of them.

 

You have a very good point, but only if your work is a very large round  bowl or platter that hardly fits into the kiln.



#26 DAY

DAY

    Advanced Member

  • Members
  • PipPipPip
  • 160 posts

Posted 03 August 2013 - 12:21 PM

I currently load a pair of 7.5 cu ft 'bucket' kilns about six times a week. (same height as the 10 cu ft) I don't have any health issues doing the job. I am 5'8", 30 pounds overweight, and 72 years old.



#27 OffCenter

OffCenter

    Advanced Member

  • Members
  • PipPipPip
  • 1,372 posts

Posted 03 August 2013 - 03:12 PM

I enjoyed that debate, Claypple and Mart. Thanks.

 

Jim


E pur si muove.

"But it does move," said Galileo under his breath.

#28 Mudslinger Ceramics

Mudslinger Ceramics

    Advanced Member

  • Members
  • PipPipPip
  • 113 posts
  • LocationAustralia

Posted 07 August 2013 - 06:53 AM

Thank you all for the replies.

 

Thank you Neil for the engineering explanation, was enlightening......had thought the 'box' shape would be easier to build but apparently not!

 

Realise that car, trolley or tunnel kilns would be very different as they are usually used in high volume, architectural or industrial type applications and other than some raku kilns I have not seen gas fired 'bucket' ones.

 

My curiousity was mostly about the 2 designs for comparable size kilns.....the kilns as was said, that go into homes, basements, small/ medium size studio situations or into teaching environments.

 

It appears that manufacturing costs and the consquential retail price are the main reason for the top loading preference in the US, which is ironic because our front loaders are about 25-30% more expensive than a comparable top loader here yet we seem to prefer front loaders anyway!

 

I have 2 front loaders in my studio. I also have 2 small portable kilns that fire from our Australian 240V/10amp domestic plugs that I take with me in the car....hey!! painters have portable easels for location work.....I have a portable kilns!........(use them to test found clay deposits while on holidays)

 

The hexagonal one is great for tumble-stack bisque firing or a few small things for glaze but it does seem to me to be less space efficient for glaze firings than my portable 'box' kiln so found the 'debate' between Mart and Claypple interesting........thanks Mart for the diagram!! (I really am a visual learner).

 

jrgpots....have just seen the 2 part open bucket design you mentioned on our main manufacturers site, it's called a 'split tube' furnace...... new to me!!!

(http://www.tetlow.com.au/used-a-reconditioned-furnaces)

 

 

thanks all,

Irene


Mudslinger Ceramics :   www.mudslingerceramics.net

 

'Don't worry about your originality. You couldn't get rid of it even if you wanted to.

It will stick with you and show up for better or for worse in spite of all you or anyone else can do.'

                                                                              - Robert Henri


#29 jennifer arthur

jennifer arthur

    Newbie

  • Members
  • Pip
  • 8 posts
  • LocationCairns, FNQ,Australia

Posted 08 August 2013 - 04:21 AM

I really battle to load the front loader at tafe. Being a little vertically challenged trying to hold the half kiln shelf up and place it is a strain on shoulders and back, not to mention nervewracking.
I think from these comments I'm going to go for a top loader. thanks everyone.






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users