Hi, I’m Mike De Greasley…. Now I’m not an Historian or an Archaeologist,
but I do tend to carry out a lot of historical research as a Graphic Artist, 3D GCI Developer
and Documentary Video Maker. During the course of 2014, I’m gathering material
for a project I’m working on — to produce an Independent video production entitled:
The Salt Revolution. Richard Trevithick — born in Tregajorran
Cornwall in 1771 — He became a British Mining Engineer and Inventor. He was the first to
develop a high pressure steam engine and the first to build a full scale working railway
steam locomotive. All modern-day working reproductions and museum
exhibits of Trevithick’s steam locomotives are based on a few known surviving drawings
— in particular — the 1804 Pen a Darren and the 1805 Wylam Colliery models.
I created this CGI model from a set of drawings from this website and downloadable as a pdf
file. In spite of not being a steam engineer or
for that matter an enthusiast — as part of the main Salt Revolution production I am keen
to learn about the early development of steam engines and how they were literally the driving
force behind the industrial revolution. So let’s start by getting stuck in to the
belly of the beast. And what we see is boiling water and pressurised
steam….. Hidden within is a horizontal steel tube and sealed steel tank. This tank is known
as the firebox. And it does exactly what it says on the tin….
Inside is where coal is burned to heat up the box which in turn boils the water and
generates the steam. However, there is a little bit more to its
design. The burning coal or fuel is contained within its own compartment and rests upon
a metal grate through which the ash falls. The hot air and smoke is drawn through the
firebox and up into the chimney stack. Above the firebox, we can see this horizontal
cylinder — and if we have a look inside that ….
Now as I have already mentioned, I am not a steam engineer, and while the plans for
this engine are top notch, clearly naming each piece and giving a broad outline of the
mechanics involved, I did have some fun reverse engineering this section for demonstration
purposes — so let’s take a closer look. This is the cylinder and valve chamber. It
has a sealed plug at this end which also rests in cylinder support bracket.
Let’s also put this part in cross-section so we can see it all.
This divider splits the tube into two sections — the Piston Cylinder and the Valve Chamber.
Here we have the Piston Head — firmly connected to the Piston Rod which runs through the centre
of the structure. And here we have the valve — which if you
watched my other video on the Newcomen & Watt steam engines is a more refined version of
the plug tree. The valve’s already shown here in cross-section
and we can see that it has a central bore of the same diameter as the piston rod — however,
it also has a core bore of a slightly larger diameter. And that accommodates this raised
collar which is fixed firmly to the piston rod.
Well those are the main components… now let’s see it in action.
That’s all well and good — but it’s missing something. STEAM….
Like most things under pressure Steam is desperate to find an escape route.
And our cylinder actually provides it with the start of one — but one which compels
it to follow a course of Trevithick’s design. Here we can see a series of coloured tubes
attached to the cylinder — Now I’ve arranged these slightly different for the purpose of
this demonstration but technically they’re in the correct positions.
Here we have our Active Steam Inlet pipe and I’ve colour coded Active Steam as Blue.
And here we have the Exhaust Steam Out Pipe and the Exhaust steam is shown here as being
mauve. I found there’s a trick to following this.
Here – Active steam is constantly flooding into the tail section of the valve chamber.
And in the mid-section of the valve…. exhaust steam is finding its way out of the chamber
. Now there is still a lot going on here but
we can see that it’s the backwards and forward movement of the valve which is controlling
the alternating flow of steam through the piston cylinder….
With the valve in this position — Active steam can’t escape through this tube because
it blocked by the head of the valve. But it can escape through this tube and begins to
flood into the head section of the piston cylinder.
Meanwhile — the way is now open for the exhaust steam in the tail section of the Piston Cylinder
to be expelled to the valves exhaust chamber and finally out through the exhaust pipe.
With the valve now in this position — the configuration has changed — furthermore – a
space has been created between the head of the valve and the cylinder divider.
A space into which Active steam can now flood into through this unblocked tube — where
— it finds it also had an exit route through this tube into the tail section of the piston
cylinder. Meanwhile — the state of this tube has now
changed to allow exhaust steam to be expelled to the valves exhaust section and finally
out through the exhaust pipe. And that basically describes one cycle of
Richard Trevithicks pressurised steam locomotive engine.
And as for the exhaust steam — well that finally escapes up the chimney stack with
the smoke from the firebox. Richard Trevithick died penniless in 1833