Counterweights in Engines and Trees

Lime tree seed arrangement

Before James Watt invented the steam governor in 1788, boilers had a habit of blowing up when there was too much pressure inside them.

The way steam boilers work is that a source of heat outside the boiler heats the water inside the boiler. The water turns to steam, which escapes. And the force of it escaping powers a piston or a wheel or anything.

The problem is that the increase in pressure can burst the boiler before the operator can open a valve to release the pressure and bring it back within the limits that the boiler can handle. And even if the operator can control the boiler, the changes in pressure causes the boiler to slow down and speed up.

What was really needed was something that would react very quickly and accurately to changes in pressure, and release just enough pressure and not too much.

Watt’s steam governor solved this problem in an elegant way. it’s a simple mechanism whereby some of the steam that escapes does so through a screw mechanism and the screw turns faster under greater pressure. Two little weighted balls attached to the thread, move out further from the central axis by centripetal force and open the valve and release the pressure a little. As the pressure goes down the two little balls collapse nearer to the central thread.

Here’s a snap of a beam engine with the steam governor highlighted.

steam governor in a steam engine

So the boiler is self regulating. It doesn’t depend on an operator to open a valve. Instead, the governor reacts quickly and exactly, and the engine runs at a steady speed.

Lime Fruits

So now to the photo at the top of this post that shows the fruit or seed arrangement that falls from a lime tree.

The leaf-like top part has a twist along its length like in an aeroplane propellor. That causes it to rotate as it falls, and the rotation causes the arrangement to carry further that it would otherwise as it falls from the tree.

But that is not all.

Below the propellor there are two little balls containing the actual fruits or seeds. They hang like a split counterweight. And when the ‘propellor’ spins, they spin as well, causing the whole arrangement to spin faster and travel still further from the tree.

And that caused me to wonder whether the two little balls move further apart from one another by a tiny amount as it speeds up? Just like the Watt steam governor.


By the way, limes are hermaphrodites, meaning both the male and female reproductive parts are contained within one flower. They also have a very strong perfume at this time of the year, a light floral smell that by its sheer quantity is quite heady when you are passing a mature tree.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: