Dave steam 6 (newcomen)(44)

A series of lessons

by David C

Dec 2010

Steam Engines

Part 6

The piston

What I like about history is that

there are so few straight lines in it.

A fellow can be trying to solve a

particular problem in one part of

the world, and he comes up with a

solution that is picked up by

another inventor in another part of

the world, working on a problem

that has absolutely nothing to do

with what the first fellow was

working on. …

– EXCEPT that they have exactly

the same answer.

What I like about history is that

there are so few straight lines in it.

A fellow can be trying to solve a

particular problem in one part of

the world, and he comes up with a

solution that is picked up by

another inventor in another part of

the world, working on a problem

that has absolutely nothing to do

with what the first fellow was

working on. …

Now something like this happened

to a Frenchman named Denis

Papin, who invented this thing in

the 1690s. This is a pressure

cooker.

Now something like this happened

to a Frenchman named Denis

Papin, who invented this thing in

the 1690s. This is a pressure

cooker.

You put food into the container and

then fill it to the brim with water.

Then you seal it very tightly and

light a fire underneath it.

The water heats up and wants to

boil, but it can’t because there’s no

room for the steam to expand into.

…so the water stays liquid even

though the temperature has risen

higher than the temperature at

which water normally boils.

The water heats up and wants to

boil, but it can’t because there’s no

room for the steam to expand into.

The result is food that has been

cooked at very high temperature;

very tender and cooked quickly.

…so the water stays liquid even

though the temperature has risen

higher than the temperature at

which water normally boils.

The water heats up and wants to

boil, but it can’t because there’s no

room for the steam to expand into.

Papin’s invention made him quite

famous for a time.

Papin’s invention made him quite

famous for a time.

But what’s important here is that

this is a container loaded with

boiling water under pressure.

A thing like this could blow apart

and injure someone.

Papin had to keep the lid screwed

down very tight to resist the

tremendous pressure that built up

inside it.

Papin’s invention made him quite

famous for a time.

But what’s important here is that

this is a container loaded with

boiling water under pressure.

A thing like this could blow apart

and injure someone.

I can imagine the thing leaking

from time to time, and steam

shooting out the top, and Papin

trying very carefully to push the lid

back down again without scalding

himself.

I can imagine the thing leaking

from time to time, and steam

shooting out the top, and Papin

trying very carefully to push the lid

back down again without scalding

himself.

It was probably this experience that

got Papin to thinking that maybe

this tremendous pressure could be

used for something else.

Papin set up an experiment

that looked kind of like this:

You put some water into a

brass cylinder and drop this

odd-shaped thing inside.

It’s a disk with a kind of a

handle on it.

The disk is ever-so-slightly smaller than the diameter of the cylinder,

which means that a tiny bit of water will squish up the side of the disk

and allow it to slide up and down without letting any air in or out.

Papin set up an experiment

that looked kind of like this.

You put some water into a

brass cylinder and drop this

odd-shaped thing inside.

It’s a disk with a kind of a

handle on it.

Now if you heat the cylinder,

the water will boil and expand

and push the disk up.

When the disk has gone up

as far as it will go, you lock

it in place so that it can’t

come down again.

Then you cool the cylinder down.

You can do this efficiently by

pouring water over it..

The steam collapses back into

water, which occupies only a

fraction of the volume of the steam.

That means there’s an awful lot of

nothing above the water; a vacuum.

The piston will want to get down

to the water surface again,

…really fast, because there’s

60km of atmosphere pressing

down on it, which is really

heavy.

The piston will want to get down

to the water surface again,

But before releasing it, Papin attached a rope to the top of the piston handle, and

ran it over a couple of pulleys so that he could hang a heavy weight on the other

end.

So when he released the piston, it

slammed down immediately to the

water surface and lifted the heavy

weight off the floor.

That weight was 27 kg.

That’s the weight of a

not-so-small child!

In effect, Papin had shown

how to lift a heavy weight off

the ground by boiling a kettle!

Papin knew he was on to something significant,

but wasn’t really sure where to go next.

He wrote some scientific papers on the

subject, and suggested a few ideas, but

none of them inspired a rich-financier to

sponsor any further work.

However, there was one

Englishman, a fellow named

Thomas Newcomen who

knew exactly how to get rich

using Papin’s invention.

You see, the important part of Papin’s invention was this part here;

the brass cylinder with a sort of disk-shaped thing inside it.

Today we call it a piston.

You see, the important part of Papin’s invention was this part here;

the brass cylinder with a sort of disk-shaped thing inside it.

Today we call it a piston.

You can make the handle go up

by letting steam in through one

of the vents.

You see, the important part of Papin’s invention was this part here;

the brass cylinder with a sort of disk-shaped thing inside it.

Today we call it a piston.

You can make the handle go up

by letting steam in through one

of the vents.

And you can make the handle

come down again by letting

steam out of the other vent.

You see, the important part of Papin’s invention was this part here;

the brass cylinder with a sort of disk-shaped thing inside it.

Today we call it a piston.

You can make the handle go up

by letting steam in through one

of the vents.

And you can make the handle

come down again by letting

steam out of the other vent.

… and if you really want the handle

to come down fast, pour water over

it to condense the steam first.

Mr Newcomen installed

Papin’s invention in the

middle of this monstrous

structure. Can you see it?

Steam goes into the piston

chamber and makes the

handle go up

… which causes the

balance beam at the top to

tilt so that the cable on the

left goes down.

Steam goes into the piston

chamber and makes the

handle go up

You can make the balance

beam tilt the other way by

pouring water over the

piston and condensing the

steam into water.

You can make the balance

beam tilt the other way by

pouring water over the

piston and condensing the

steam into water.

You have to open and close

the two valves at just the

right times to make it work.

Now, if you have a bucket

on the end of the cable on

the left, you can use it to

scoop water out of a mine.

Better yet, put a long tube

on it and you can siphon the

water out of the mine.

Now, if you have a bucket

on the end of the cable on

the left, you can use it to

scoop water out of a mine.

?

But the great thing is that

you can put anything on

the end of that cable, and

use it for things that’ve got

nothing to do with mining.

?

But the great thing is that

you can put anything on

the end of that cable, and

use it for things that’ve got

nothing to do with mining.

That’s what triggered the

Industrial Revolution.

End

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