The base of my Swan

The Stuart 6A of Oxbird

This machine is a compound type, i.e. that the steam passes initially in a first cylinder, smallest, then carries out a second relaxation in the second cylinder, of a larger volume (in direct connection with the pressure of admission), this type of engine is more economic in steam consumption than a traditional twin-cylinder, in which is used only once by cylinder.

The boiler and the machine of Mélusine

Oiler for a Swan

Three pumps on the same Swan

Pipes calculation

This website Give us some informations on that subject, it is more dedicated to the model making, but it is interesting by the way of doing it.

Calculations

A very useful Website
and this one for the réalisation of a boiler, nice job!

Boilers link

Many informations on the boilers, how to calculate and to make them...
on this Website
I have add it in the useful links on the side of the page.

Steam engine: How does it go?

(original description found on the Net)
General information:
A steam engine consists of two distinct parts:
* A boiler whose role consists in producing steam,
* A machine which will use the expansive force of this steam and to transform it into movement.
All the remainder constitutes only one series of objects which are there only in order to improve the total output of the machine or contribute to its good functioning or the safety of control.



In the machine above, we will see the principle of the closed loop and the elements necessary to its realization.

The boiler:


The boiler with thus for role to produce steam. It consists of a closed tank containing of water and the steam. Under this tank, a hearth supplied with coal, gas, oil, wood… creates a sharp heat allowing the creation of steam and to bring it to a sufficient pressure.
The boiler opposite is said to fire-tubes owing to the fact that the heat produced by the hearth passes in tubes around whose is water to heat. Other boilers, said to water tubes, are built in such a way that water circulates in tubes which are heated by hot gases of the hearth.


The machine:


The machine is used to convert the expansive force of the steam into a mechanical force. The steam, while pressing on the pistons, obliges them to move, actuating the crankshaft, by a device of the type rod/crank.
The engine opposite is a triple engine expansion, i.e. that the steam, having been used in a first cylinder will be lost or will not be recycled but re-used in a second, then in a third cylinder. This provision makes it possible to use to the maximum, the resources of the produced steam.


The condenser:


Some machines exhaust the steam used, directly in the atmosphere.
On the machine here above, the steam crosses a condenser, where it will condense to be re-used in the boiler. This process with the double advantage of providing already tepid water to the boiler and of saving fresh water (requirement on the boats sailing at sea.


The air pump:



On the outlet side of the condenser, a particular pump (known as air pump) makes it possible to aspire, at the point low of the condenser, the results of condensation.
These condensed are sent in a cover (tank) to water which is used as reserve plug for the boiler.


The feed-water pump:


Lastly, to close the loop, a feed-water pump, coupled mechanically with the machine, draws water in the cover with water and injects it into the boiler.
Concerned with safety unit if it is, this pump is generally coupled with another pump (with hand on the small units) in order to bearing with any failure.


Propulsion:

The engine can involve either one or more wheels, or a propeller, in order to transmit its power to the boat.
If the wheels had the beautiful share at the beginning of the propulsion with steam, the propeller quickly supplanted, offering a better output and a reduced vulnerability in the event of combat.

The boiler




General information:

The goal of the boiler is to provide steam under pressure to a machine. The principle is thus simple: it is just to heat water.

For that, all the means are good: drink, coal, gas, oil, fission of atoms… in short, all that can burn and thus which is likely to provide heat.

Heat thus produced is communicated to water contained in a closed tank.

In order to optimize the output of the boiler, it is necessary to have the greatest surface of possible contact between the hearth and water, which one calls the heating surface.

The boiler is thus divided into two distinct parts:
The hearth in which heat will be created,
A closed tank locking up water and the steam (the pressure vessel).

The hearth:


The hearth will vary according to the type of fuel.

For a heating with wood or coal, it is necessary to have a grid on which will be placed the fuel and an ash-pit allowing on the one hand the recovery of ashes and, on the other hand, the passage of the fresh air allowing combustion.

For a gas heating or with oil, one or more jets will involve the creation of a torch. The air flow will have, of course, being consequently envisaged in order to avoid an incomplete combustion.


The outer firebox:


The outer firebox exists strictly speaking only on the boilers with light-back, i.e. in which the hot gases follow a way in “S” in the boiler.

It has as a role to recover hot gases, resulting from combustion, and to distribute them in all the tubes constituting the beam of tubes heating (see below).

Surrounded by water, it contributes to the heating surface and this principle makes it possible to prevent that the paroies boiler are not too hot and are likely to put fire at the hull.


The beam of tubes:


The beam of tubes consists of a great number of parallel tubes, connected to each other by two plates to holes.

The hot gases, while passing by the interior of the tubes heat them and thus make it possible to communicate the heat of the hearth to water on a very great surface.

Welded or expanded with the plates with holes, it happens, that one of them bores causing a damage with the boiler requiring its replacement.


The smoke-box:


The smoke-box recovers hot gases at the exit of the beam of tubes to direct it towards the chimney.

Its role is capital in what one call pulling, i.e., the force, generated by a difference in pressure between the hearth and the chimney, which will allow “to draw” hot gases through the beam from tubes.

Its form and the variation of its section since the plate with holes until its outlet in the chimney enters for a great part this calculation.


Water:


The water contained in the boiler must be purest possible in order to avoid a clogging of the boiler.

On a small machine of approximately a horse power, the water consumption (thus quantity of evaporated water) is about 30 to 40 liters per hour. If this water contained 36 grams of salt per liter (e.g. sea water), it would not be less than 1,2 kilogrammes of salt which would be found in the boiler per hour, with the disadvantages which one can suppose.

The level of water will have also to be permanently supervised in order to avoid any risk of explosion. The indication of level is done through a tube out of glass, this indicator must be purged regularly to avoid any erroneous indication.


Steam:


The steam is locked up in the same closed vase as water, but partly high.

It is useful to specify here that only steam must be in this space and that the presence of air must be avoided to the maximum in order to avoid, on the one hand, a fast corrosion of the boiler and, on the other hand, jolts of pressure due to the elasticity of the air.


The steam catch:


The presence of fines droplet of water in the steam makes essential the use of a species of strainer to take the steam in the boiler, indeed, the presence of water is strongly disadvised in the cylinders (its incompressibility being able to lead to a destruction of the machine).

It is the role of the steam catch which will be, most of the time, a simple tube bored of small holes of sufficient numbers in order to spare a passage to the steam compatible with the consumption of the machine.


The gate valve:


The gate valve must be located more close possible of the boiler.

It makes it possible to stop or restore the steam flow supplying the engine.

In certain cases (pipe breakage for example) it will make it possible to insulate the boiler so as to avoid any risk of burns.

The drains which transport the steam are insulated to avoid all losses and also for this still protecting from the burns, because they circulate around the engine, and on a boat which moves one quickly made cling to it!