Tracing the development of steam engine


I must again open with an apology for lack of recent columns, but medical problems and other things here at home have absorbed a lot of my time and energy.

I decided I would reprise some earlier work on the steam engine, a form of which is the star of most of our shows.

Very early years

The history of steam engines as we know them begins in the mid-1600s, which appears to be an interesting period both politically and scientifically.

The scientists of the day — Englishman Isaac Newton; Denis Papin, French Huguenot; Christiaan Huygens, Dutch; Rene Descartes, French mathematician; Robert Boyle, English scientist; and the Italian Galileo — seemed to communicate a lot with each other and travel freely to each other’s countries.

Hugyens seems to have proposed the cylinder and piston idea, which led to the production of such a device in 1690 by Papin, and soon after on a workable scale by Thomas Newcomen in England as a mine pump.

Papin, who lived and worked mostly in Germany and England, also built a “steam digester,” which was a type of pressure cooker, and he gets credit for the invention of the safety valve.

Giant leap

At this point, we take a great leap to the development of the steam engine as we know it, with the invention of the crankshaft, valving setups, and James Watt’s double-acting cylinder.

Newcomen’s engine or pump was a walking beam structure, slow and massive, often six strokes a minute. Its motive force was atmospheric air pressure with the steam creating a partial vacuum under the piston by condensation. It was massively inefficient, but it did the job required, so was a copied success. Cheap coal was a big factor in its success.

Thank you, James Watt. Perhaps the biggest contribution the engine made was when a model given to James Watt failed to perform.

Watt must have had good powers of observation and an analytical mind and was among the forefront of those who were coming to understand the true nature of heat as energy. He diagnosed the problem as the need to alternately heat, then cool, the cylinder and invented the separate condenser — a separate cold cylinder connected by a valve to the hot or power cylinder.

This saved enormous amounts of the heat needed, but they were still using only two or three pounds steam pressure. I have never read what caused Watt to decry higher pressures, but perhaps an unrecorded accident was involved. Certainly, lots of tragic failures happened.

Someone else had a patent on the simple crank, so Watt’s solution was the “sun and planet” gear arrangement. He also closed the top of the cylinder so the steam pushed the piston both ways, getting something like double the work from the machinery.

The great improvement in efficiency and saving of coal allowed the Watt design to drive Newcomen engines out of the market.

His business partner, Matthew Boulton helped to set up to manufacture and install engines. Their success is probably one reason Watt is so well remembered today as the primary inventor of the steam engine.

Next steps

Enter two engineers who used higher pressures of the order of 50 PSI — the Englishman Richard Trevithick and the American millwright Oliver Evans. It appears that they had correspondence, but not enough of it survives to credit the correct inventor for some of their ideas.

Both made engines powerful enough and small enough to be portable, in carriages for Trevithick and boats for Evans.

Now we are up to the point that steam power could be applied to most any field where a prime mover was needed, including agriculture.

Single cylinder machines mounted on their own boiler were put on wheels and made portable. As they got bigger and heavier, the idea of making them self-moving gave rise to our favorite toy — the steam traction engine.

Actually, Trevithick built a couple self-propelling carriages, including one on rails, but they were not agricultural machines and their development was a dead end.

Amphibious dredge

Evans’ contribution was a self-propelled steam dredge he called Orukter Amphilobus. It was truly amphibious, as it moved on the street and launched itself into the river and kept on going.

It was also a dead-end project, though some of Evans steamboats traveled some of the rivers around Pittsburgh.

Since the technology was new, at least one blew a boiler because the operator didn’t know he had to keep enough water in the boiler.

Some barn steam engines were used in England for stationary threshing, but the portable engine was a later development in the mid-1800s when early threshers were also on wheels.

Some early attempts at self-propulsion involved chain drive, but it was rarely a great success and soon gear arrangements were being designed.

Short-lived designs

One early setup was a bevel gear on the crankshaft driving a ‘slanting shaft’ to the rear wheels. It was built by license by Russell, Aultman-Taylor and others. Russell appears to have used it for only a couple years, but Aultman-Taylor used it for quite a few years and some of them are still around at shows.

Regular gear and clutch arrangements soon became the normal setup and were built roughly from 1890 to 1925.

Most traction engines depended on the boiler as the frame for all the machinery, but a few like Frick had an actual frame separate from the boiler.

Also, the double under-mounted engines like Avery and Twentieth Century had frames as the boiler was on top.

Odd man out

Most companies had their specialty or oddity. For instance, Huber engines always used return flue boilers and most other companies like Minneapolis, Russell, Avery and a few more made some return flue engines along with standard style.

It seems strange to me, but in England, it appears no traction engines were built that way even though large Cornish and Lancaster boilers with as many as three tubular furnaces were common in factories and larger ships.

A few traction engines and numerous small tandem rollers used vertical boilers with fire tubes, but they had to be handled carefully to keep water from rising into the engine.

A couple oddities arise here, namely Westinghouse, with a cross water tube boiler very similar in construction to the boilers in Sentinel steam lorries or trucks in England built by Alley & McKlellen.

Engine features

Now we need to talk about the actual mechanical features of the engines. We have mentioned single cylinder engines as being the most common type, their only drawback being the ‘dead centers’ at each end of the stroke.

It doesn’t matter how much pressure the boiler sends to the cylinder, if there is no angularity to the crankshaft to cause torque or turning force it will not run. This is most commonly remedied by using two cylinders working on cranks at 90 degrees to each other so that when one is on dead center the other one is at maximum torque position.

Plain “D” slide valves are the most common, but with higher steam pressures they consume an excessive amount of power to run the valve. This is mostly taken care of by using some sort of balanced valve which takes some of the pressure off the back of the “D”.

The ultimate answer here is the piston valve where the D becomes a spool and there is no unbalanced pressure on the valve at all. But they are more complicated to make and machine so a lot of “plain valves” were used right up to the end.

In the USA, only Reeves advertised the compound style of engine where a small high-pressure cylinder exhausts in a larger low-pressure cylinder — double expansion gets more work out of the steam.

Cross compounds

Cross compound engines had the cylinders parallel to each other, but Port Huron, Russell and Minneapolis and a few others used tandem compounds with both pistons on one rod, one ahead of the other.

Cross compounds were common in England and Europe where efficiency was more important. They are easy to spot on films showing two different diameter cylinder heads or covers. Most of the British companies made them, along with singles.

A different development here was Burrell’s single crank compound, which was accomplished by connecting both piston rods to one crosshead casting from which a single connecting rod goes to the crankshaft.


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