Transcript – Boulton and Watt

Drawing of the Boulton and Watt engine
Drawing of the Boulton and Watt engine.


Transcript – Boulton and Watt
By Debbie Rudder

The Powerhouse Museum’s most valuable object. I’ll start off by saying - what is it? It is the world’s oldest rotative engine. Full stop. No ifs and buts. It’s the oldest one that was made to produce rotative motion. Before that, most steam engines were used for pumping water. They only produced a reciprocating, an up and down, motion.
This one, and a few before it, which have now disappeared from the face of the earth, produced rotative motion.

What did the engine do in its working life? It worked in Whitbread’s Brewery in London. The drive wheel was used to turn another wheel and that was used to turn a series of shafts and other gears that would operate the equipment in the brewery. There were some rollers for grinding the malt. There was an Archimedes screw to lift up that ground malt and take it to the vat. There was a pump to pump water to that vat. And there was also a hoist that lifted up bags of malt from the yard into where they could be ground. 

Not only that, but in its early days, this engine also had a pump hanging from the big beam and that pump went to a well in the outside yard of the brewery and pumped water up into a big tank on the roof. And of course that water was used for the operations of making the beer.

So, an amazing engine – 15 horsepower, did all these things. Today you wouldn’t think 15 horsepower could do very much at all. Other engines of this sort were used to drive all sorts of machinery. And basically they replaced horses. This one replaced a team of horses because the brewery was in London and it wasn’t near a river for water power. It didn’t have a good source of wind for a windmill. So it used horses.

But horses were expensive to maintain. Basically what these sorts of engines did was to make it possible to have factories in cities. Anywhere people wanted them. To run them cheaply. It was cheaper to pay an engineer than it was to pay for food for a team of horses.

What’s good about this engine is that you can actually see a fair bit about its workings, whereas with a modern engine there’s not an awful lot to see. Start off with the cylinder. Now hidden inside that cylinder is a piston. And a piston is basically a smallish disc, maybe that wide or maybe in some places that wide – but it’s just a disc that fits very neatly inside the cylinder.

How it worked was the steam pushed that disc up and then it pushed the piston down. It pushed it up and down. You can see the valves on the side of the engine being operated by the rod hanging off the big beam overhead. And that opens some valves that are hidden away inside the chest on the side of the cylinder. And those valves admit the steam to do the pushing up, the pushing down and the draining away of the steam when the stroke’s finished.

OK. As that piston moves up and down that makes the big beam above the engine rock like a see-saw. And at the other end of the beam we have another rod called the connecting rod, or con rod, that turns some other gears down here called the sun and planet gear and they turn the output shaft around.

The whole point of the engine is not all this train of mechanism; the whole point of the engine is to use the energy in that steam that’s pushing the piston up and down to turn the drive wheel. Now when you look at the engine, the most obvious feature is the huge flywheel. The flywheel is impressive but is not as important as the drive wheel. The flywheel just maintains the momentum. If you watch the engine driver start the engine, he needs to give that flywheel a bit of momentum to get it going.

Once it’s going it’ll keep going because of the energy stored in the flywheel. But the drive wheel, the toothed wheel that’s behind the flywheel, is the one that was used to drive equipment in the brewery where this engine worked for 102 years.

People often say this engine is the beginning of the industrial revolution. It’s not really the beginning. There were, as I said before, there were engines before. And some of those engines were actually used to pump water from below a water wheel to above it. So you could get rotative motion indirectly from using a steam engine.

But this one really made it possible – it accelerated, if you like, the industrial revolution - it made it possible for the innovations that were happening in other industries, particularly textile industries, to be harnessed to be used in a big factory.

People moved to cities. It changed people’s working life. Later steam engines made it possible to run equipment on farms. So again, it accelerated that move to the cities. So, a major step.

The other important thing about this particular engine is it embodies all four of James Watt’s innovations that made these engines such a success.

The story is that he was an instrument maker in Glasgow. And he was given a model steam engine to fix. So if anybody tells you that James Watt invented the steam engine – no – he was actually fixing one that was of a type invented in the early 18th century.

He realised when he was fixing this model that there were some inefficiencies in its operation, so he did a whole lot or experiments with steam to understand steam and to work out why this engine was inefficient. And then it occurred to him, once he’d worked out what was happening in this series of models he’d made, was that in previous engines the steam had been condensed to create a vacuum inside the cylinder. And the condensing step was done in the same working cylinder. So in every stroke the steam heated up the cylinder and then a jet of water cooled down the steam - and also cooled down the cylinder. So on the next stroke the steam had to heat up the cylinder some more as well as doing the actual pushing of the piston and creation of the vacuum.

So he said ‘Ah-ha – what if I put the condensing step in a separate place.’ So his first and major invention, major patent, was the separate condenser which you can see here. Well, you can’t see the condenser but it’s hidden away in the big tank you can see underneath the cylinder. And that really made his engines a lot more efficient than previous ones.

The next innovation, in order of looking around the engine, we can see here is the parallel motion mechanism, which connects the piston rod to the end of the beam. If you can imagine the piston rod going up and down but the end of the beam is moving in an arc. Earlier engines had a chain running between the two. And that was OK if the atmosphere was just pushing the piston down. But once you want to push the piston up as well as down, you need a solid link between the two. Lots of methods were tried. But parallel motion was the invention of which Watt was most proud. It was a very canny bit of inventing and it made it possible for that piston rod to go almost straight vertical while the beam was going in an arc.

The next invention you can see as you move around the engine is the governor. The governor is an early feedback mechanism. It’s not the first feedback mechanism that people invented. Of course in nature there are feedback mechanisms.

Somebody else had invented a very similar one to this. It was used to keep the spacing of the millstones in a windmill just right. So, Matthew Boulton, Watt’s business partner and also an inventor of note himself, noticed this mechanism in a windmill that he’d visited. He came back and said to James Watt: ‘I’d like you to invent a similar mechanism that will stop our engines from running too fast.’

There’s a belt attached to the output shaft of the engine, and that belt goes directly to the governor. When the engine starts to go too fast, the balls of the governor will swing outwards. That pushes a little linkage up above that. And that pushes a linkage across to the main inlet steam pipe to the cylinder and that reduces the amount of steam flowing through that pipe. And therefore the engine will go more slowly.

OK, we have the last of these four amazing innovations that James Watt and his co-workers put together – and that is the sun and planet gear. There’s some debate still about whether it was actually James Watt’s invention or his assistant, William Murdoch’s. Both claimed it was theirs. Maybe they came across it independently. We’re not sure. What we do know is that Matthew Boulton also contributed to the final form of that mechanism. But the reason they invented that sun and planet gearing was somebody else had patented the crank as it applied to steam engines.

And the other big question people want to ask about this engine is how did it get here. The story is that this museum in its first formulation as the Technological, Industrial and Sanitary Museum in Sydney had only just been set up in the 1880s when this engine was decommissioned.

One of the trustees of the Museum, Professor Archibald Liversidge of Sydney University, was in London at the time, and he heard the engine was being – probably bound for the scrap heap. And he asked could it be donated to the museum in Sydney. And they said yes, as long as you set it up and use it for educational purposes.

When they were packing up the engine at Whitbread’s Brewery, they decided they’d better chop the fly wheel in half. This was because it was an awkward thing to handle
and they were worried that if they didn’t actually carefully break it in half, that it might break in transit. So of course the rim of the fly wheel is made in sections anyway so they just had to unbolt that. But the big boss, the central part of the fly wheel, was actually drilled across.

It was put back together again at the old museum site in its own separate engine house. Later, in the 1920s or 30s, an electric motor was attached to it just to turn it over so that people could see it in motion. It wasn’t until the 1980s that it was actually restored to steaming condition.

There’s one more really important thing I want to say about this exhibition – and that is that it’s not just the engine. If you go behind the engine, and see about the life of Boulton and Watt and their other contributions to industry, and there are some interactives back there that explain parallel motion, the sun and planet gearing and the governor.

So those who are able to make their way upstairs will be able to enjoy that, plus they’ll be able to see parts of the engine close up.