Ben Franklin Potbellied Stove - Pretty obvious invention. Why not invented earlier?

[astro]

Per the citation below Ben Franklin invented this take on the fireplace and it was improved by a David Rittenhouse.

My question is that, in hindsight, this seems an incredibly obvious thing to invent and the mid 1700s seems a kind of a late date for someone to catch on that this was a better way to heat a room than an inefficient fireplace. Assuming that all the brillant English and German inventors of the time were not idiots, why wasn’t a central radiant stove done in the 1600’s or even earlier. It seems so…well…obvious. Was iron casting technology not up to snuff?People didn’t understand about wasted heat or practical efficiency? Why not earlier? What was the crucial insight or confluence of circumstances that the mid 1700’s contained that allowed for it’s conception and implementation, that earlier centuries had not?
The Franklin Stove

Franklin also conceived the mid-room furnace, the “Franklin Stove.” In those days rooms could only be heated with a fire in a fireplace, which by definition was set into a wall. Franklin knew that, since heat radiates from a fire in all directions, a fireplace was inefficient. So he built a cast-iron furnace that could be placed in the middle of a room. The heat it generated spread out in all directions, and was also absorbed by the furnace’s iron walls, so that the stove provided warmth even after the fire went out.

However, Franklin’s design was flawed, in that his furnace vented the smoke from its base: because the furnace lacked a chimney to “draw” fresh air up through the central chamber, the fire would soon go out. It took David R. Rittenhouse, another hero of early Philadelphia, to improve Franklin’s design by adding an L-shaped exhaust pipe that drew air through the furnace and vented its smoke up and along the ceiling, then into an intramural chimney and out of the house.

[Guy_Propski]

astro–it’s easy in hindsight to say that ANY invention was obvious, from the wheel to the PC. Keep in mind that the vast majority of humanity are pefectly content to do things they way they do because “that’s the way we’ve always done it.” It’s the small number of individuals that wonder “why?” that come up with inventions.

If you visit the Ben Franklin Museum here in Philadelphia, you can see that Franklin was constantly thinking up little gadgets like the stove. He also invented the combination ladder/chair, a tub with a reading desk, a portable secretary (a travelling desk, that is), and so on.

[slortar]

And he wasn’t necessarily the first…he was just the first to have written it down. I think I’ve seen designs in other cultures which used a similar concept.

[Squink]

A fire, in a house, outside a fireplace :eek:
That’s preposterous. You’d just end up burning down the house !
What a stupid idea. I hope Franklin had the sense not to waste too much time on it.

It is extremely hard work to go against ones preconceptions of how things should be done in order to determine how things could be done.

[toadspittle]

I’m fairly certain that masonry stoves, which could be argued to be at least as effective and efficient as an iron stove, were developed earlier by Europeans (Germany comes to mind…). Let me look.

[toadspittle]

Here’s a good cite:

http://www.bartleby.com/65/st/stove.html

Early Stoves
As early as Roman times stoves made of clay, tile, or earthenware were in use in central and N Europe…Scarcity of fuel made an economical heat-retaining device necessary, and these primitive stoves, built of clay, brick, tile, or plastered masonry, became common in the Scandinavian countries, Holland, Germany, and N France. Some exquisitely colored and glazed tile stoves, dating from the 16th and 17th cent., show traces of Moorish influence. In Russia large brick stoves formed a partition between two rooms. Because of the very long flue, which wound back and forth inside the structure, these could be heated for some hours with a small amount of light fuel.
_
Iron Stoves
A cast-iron stove made in China before A.D. 200 has been found, but it was not until late in the 15th cent. that cast-iron stoves were first made in Europe…
Dutch, Swedish, and German settlers of the American colonies, especially those of Delaware, Pennsylvania, and New Jersey, brought with them five-plate stoves or molds for casting them. Iron founding began c.1724 in America, and old forges or foundries have left records of five-plate stoves sold in 1728 as Dutch stoves or, less commonly, carved stoves. These continued to be made until Revolutionary times, when they were superseded by the English, or 10-plate, stove, which stood free of the wall and had a draft or fuel door. These 10-plate devices could cook and warm at the same time and replaced, in part, the large masonry baking oven, usually built outside the house.
The Franklin stove, invented in 1743 and used for heating, was the ineal descendant of the fireplace, being at first only a portable down-draft iron fireplace that could be set into, or before, the chimney. …

Sounds like just one of many innovations and possibilities along the way.

[Fear_Itself]

Minor nitpick:

The Franklin Stove is not the same thing as the Pot-bellied Stove

[astro]

*Originally posted by Fear Itself *
**Minor nitpick:

The Franklin Stove is not the same thing as the Pot-bellied Stove **

That Franklin Stove in the link looks like it’s sitting inside a fireplace. I thought the Franklin Stove was a “mid-room” stove per the description not a fireplace insert type of thing. How is that stove in the link going to provide “mid-room” central radiant heat? Is it in a wall between two rooms?

[ftg]

Note that bricks are made from clay which is plentiful and cheap. Iron was not really common or cheap in those days. E.g., a plough was still mostly wood with only an iron edge or stake at the front. Many tools, even shovels were all wood. A lot of things became possible that weren’t before once iron started to become available in progressively larger (and cheaper) amounts.

Masonary fireplaces are fairly decent at distributing heat thru the building it’s in if centrally located. It’s heat loss up the flue that is the real issue. Second is amount of fuel to get it hot enough for cooking, etc.

[racekarl]

The franklin stove did sit away from the wall, but not really in the middle of the room. Nor was it “pot bellied” as FI pointed out.

The stove worked by convection. Below the fire was a duct that led to a series of air chambers behind the fire. Hot air and smoke rising from the fire rose in front of the chambers and then was directed back down the other side before it went up the chimney. Hot air then left the chambers via side vents at the top to be replaced by more cold air drawn in from the floor. In effect, the franklin stove is sort of a heat exchanger.

The two links have diagrams to make this a little more clear.

American Heritage Dictionary diagram

look halfway down this page

[racekarl]

So to expand the answer to the OP’s question, the Franklin stove is quite a bit more sophisticated than simply a big iron firebox sitting in the middle of the room.

It relies on relatively complex thermodynamic principles, which were just at that time beginning to be understood. Keep in mind that the Montgolfier brothers were just at about that same time figuring out that heat rises and could lift a balloon.

[astro]

*Originally posted by racekarl *
**The franklin stove did sit away from the wall, but not really in the middle of the room. Nor was it “pot bellied” as FI pointed out.

The stove worked by convection. Below the fire was a duct that led to a series of air chambers behind the fire. Hot air and smoke rising from the fire rose in front of the chambers and then was directed back down the other side before it went up the chimney. Hot air then left the chambers via side vents at the top to be replaced by more cold air drawn in from the floor. In effect, the franklin stove is sort of a heat exchanger.

The two links have diagrams to make this a little more clear.

American Heritage Dictionary diagram

look halfway down this page **

Thanks for the link. It’s much clearer now. I have to admit that I had combined the Franklin Stove and the potbellied stove as one in my idea of the stove he had invented. .