Curator's Choice: Richard Dunn of the Royal Engineers Museum chooses the Brennan Torpedo

Richard Dunn interviewed by Richard Moss | 05 October 2009
photograph of man standing next to a torpedo

Royal Engineers Director Richard Dunn with the Brennan Torpedo. Photo © Richard Moss / Culture24

Curator's Choice: In his own words... Richard Dunn talks about the Brennan torpedo, an intriguing artefact in the Designated collection at the Royal Engineers Museum.

"This weapon is one of the first wire-guided weapons in the world. It’s one of those unusual circumstances of an overseas invention (in Australia from a very clever inventor) being adopted by the Royal engineers.

By the middle of the nineteenth century we’re moving into the use of electricity for the detonation of underwater fixed mine systems that sappers could detonate under observation from a fort on land.

In those days the enemy was the French and the Russians who were the developing competitor fleets to the Royal Navy.

The Navy realised the Brennan torpedo was a very potent weapon but they couldn’t use it because you couldn’t trail wires off a ship in those days, it would all get tied in a knot. So the Royal Engineers adopted it as a practical weapon and developed it further through the 1870s to become a fully operational weapon by the 1880s.

It was then to be deployed to defend all of the major Royal Navy bases as a secret weapon. All people would know about it was a set of rails sticking out of the wall, or a sluice, going down to the water. However, they practised with it annually in order to see who could do best with it at each base.

In essence it’s unusual for the time because it could be guided. The Whitehead torpedo had just been invented around the 1860s – and this is barely a decade after that. The Whitehead weapon was unguided and self-propelled but it had a depth keeping mechanism to stop it plunging to the seabed or firing out of the water.

photograph of brass propellors

The Brennan Torpedo was powered by two contra-rotating propellors. © Richard Moss / Culture24

This weapon adopted the same device in its forward end to maintain depth. It was not propelled by internal combustion or compressed air but used copper wire wrapped around two drums. The wire was pulled out of the back of the torpedo inside the propeller shaft by steam engines on land in the fort.

An operator on the fort would give instructions just like a director on a control tower or gunnery about left right and the engines down below would speed up or slow down just like the engines on a ship. The wires would then come off faster or slower. A differentiator inside would detect the difference in speed between each drum being unwound and that would be turned into a physical action that would turn the bow and stern rudders to go left and right.

That would lead to contra rotation of the propellers, which prevented the whole torpedo from rotating in the water. It would keep nice and straight and level, speed up, turn left and turn right.

It also has an elliptical section like a submarine or a ship – or a fish. In its time there were other clever torpedo systems being put together but in terms of accuracy it won out.

The way they knew where it was going was the wishbone on the back, which would elevate. In daytime it would have a little white target on it that the operator could see in the distance and at night-time it would have an electric light bulb on it masked from the enemy and powered by a dynamo inside so they could follow it into the target.

As a result the weapon was about 90% accurate at a time when the Whitehead torpedo was between 5 and 10 % accurate. The charge was much bigger than a Whitehead torpedo and the speed about half as fast again. It could have taken out any warship of the time.

photograph of a man kneeling next to a long silver torpedo

© Richard Moss / Culture24

In the 1870s the largest warships around, weighing 10 – 15,000 tonnes, were still quite primitive in many respects. They were heavily armoured ironclads with wooden decking and early types of subdivision inside. They had quite basic watertight bulkhead systems, which a weapon like this would deal with.

Something like this, with a very large warhead and its high speed, would almost certainly lead to a catastrophic breech or worse – a magazine explosion.

However, it never went into action. It did sink a fishing vessel by accident when it crossed its practice grounds - fortunately it didn’t have a warhead on it.

It came out of service in 1906 when there was a big defence review. Gunnery ranges had changed significantly by that time and the self-propelled torpedo had become a much more effective weapon – faster and more deadly. But by that time you still couldn’t stick a wire powered torpedo on a ship – there was no way of doing it physically – wire guided weapons didn’t come back into action until the late fifties early sixties from submarines.

Now of course guided weapons are commonplace, they are either completely detached, self-honing or in the sixties or seventies you would have wire like a fibre optic wire.

What also fascinates me is how it’s a demonstration of technology at a time when one thinks of industrial technology being very much heavy metal, iron, coal – very strong and robust – but quite basic. This is quite a sophisticated concept and it’s clever. It’s very Jules Verne and was ahead of its time."

Watch Richard Dunn talk about the Brennan torpedo.

designation logo with photo of a woman looking at displays

The collection of the Royal Engineers Museum is a Designated collection

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