# An Engineer in Wonderland – Cunning power transmission

Thinking about waterwheels the other day reminded me of a power transmission scheme that I happened across while cycling in Cornwall.

Question:
Given a waterwheel on one side of a hill, and a pump on the other, how do you power one from the other?

Now I could come up with all sorts of schemes involving pulleys and chains, hydraulic pressure, and rotating shafts in tunnels.

None of which are as simple and elegant as one at the Wheal Martyn china clay mine (pictured).

No longer in use, although the mine is still active, the power is transmitted by a series of linked horizontal rods, each running on a couple of rollers.

Connected to a crank on the waterwheel, which does still work, the rods oscillate back and forth a metre or so.

Tension from the far end – probably both ends as the rods are draped over a hill – stops the train buckling.

At the pump end, as I remember, the motion is converted to vertical by a quadrant, from where rods drop it down to pumps in the mine sump.

I suspect there are some counter weights on this bit somewhere.

The only real friction in the transmission system comes from the rollers.

There is obviously a lot of momentum to overcome in accelerating and decelerating the rod train, but the sinusoidal drive helps with this, I assume.

Clever.

‘Alice’

alice@electronicsweekly.com, or reply in the box below

(Picture – ‘Wheal Martyn entrance‘ by madnzany, under Creative Commons Attribution licence)

## Related Tech News

1. July 11, 2008 09:23

The momentum of the rods is not a problem since thay are driven by a crank.
Compare the pistons in an engine. It takes exactly the same transfer of momentum from flywheel to piston while the piston accelerates from zero to peak speed as is transferred from piston to flywheel while the piston speed falls from peak to zero.
To get the whole picture you may need to see the sinusoid as an infinitely variable lever.

2. Martin Hill
July 10, 2008 14:22

Greetings:
This mode of energy transport was used all over the North Pennines for getting power from a ‘stationary engine’ (steam) to where it was needed – to the current mine workings. There were often two reciprocating rods, 90 degrees out-of-phase. The beauty of the system was that it was (relatively) simple to move the destination – the (wooden) trestles holding the rollers could be moved quite quickly, and the shafts had junctions every so often to allow for de-coupling. You can still see the remains of the power line by Cow Green Reservoir in County Durham – and a number of photographs of the system still exist.
Cheers
Martin

3. July 10, 2008 12:17

The famous Laxey Wheel on the Isle of Man uses this same principle on quite a large scale.