Friday, 18 February 2011

World's biggest 3D Jigsaw?

A bold claim maybe but a big puzzle nonetheless. My engineering volunteer team Andy and Gill found these rusting cast iron leviathans stored outside whilst auditing, apparently in no particular order but next to other bits of machinery including a press, a rolling mill and a couple of large boilers. The first image appeared to be a lineshaft with a set of pulleys and two flywheels, not a common arrangement. The second picture shows, hidden in the undergrowth, a large cast iron disc with rubber inserted around the rim and a central square sockle hole. The third picture seemed to be two curved arms with bearing rests at one end. After Gill and Andy brought the audit sheets back and i was trying to reconcile what we found with accessioned items I had several trips down to try and figure out the puzzling bits and pieces and see if i could work out what they were part of. they certainly didnt seem to be part of the same thing.

I decided to have a closer look at the press because we had identified it as a blanking press made by Greenwood & Batley of Leeds. It was used at the Royal Mint in Haverfordwest but I still couldnt work out how all the bits could be part of it.

I couldnt see any power source for this press, it had no motor or pulleys for belt drive, and the other thing that struck me was the sockle on the top of the screw thread, which was square. taking measurements showed that it fitted the hole in the centre of the disc with the rubber inserts perfectly. this still seemed odd though, a horizontal flywheel? and what was the rubber for? I measured the outer diameter of the disk and then took a closer look at the gap between the two flywheels on the lineshaft - again, it fitted perfectly. and then a metaphorical lightbulb lit up and i realised how the press worked and how the pieces fitted together. The two curved arms fitted on the flat rectangular sections at the top of the press, they supported the lineshaft with the two vertical flywheels whilst the other flywheel fitted horizontally between them on the top of the screw, creating what is known as a friction drive. The leather inserts would give enough adhesion to allow the disk and the screw to be driven downwards to press out the coins or blanks but once slipped out of gear it could be skidded back into its original by the lever mounted near the sockle. Using a friction drive meant that the press screw could move in two directions without having to invest in a complex gearing system or reversing the power source, and it turned out to be a very common and still used drive for screw presses.

As an added bonus I looked up Greenwood & Batley screw press on Google and found this, the very same press in action at the Royal Mint!

Thursday, 10 February 2011

Keeping the Balance: a 2500 year old coin

The oldest coin that I’ve had the privilege to look at in the numismatic collections at Leeds Museum Discovery Centre has been preying on my mind since I first saw it several weeks ago, waiting to be photographed in its drawer.
This tiny coin is only 12 mm across, much smaller than a five pence piece, and much thinner too when you feel it. What first intrigued me about the coin was its ambiguous antiquity – its card label said “?5th century BC” – and I was struck by that. I had never (knowingly) held anything as old, and I have been thinking a lot more about where this piece came from how it ended up here. What makes the piece even more interesting to me are the animals shown on the obverse: a goose and a salamander. The goose is turning its neck round so it can look at the salamander and the Greek capital letter Η (theta).

A little research at told me that this coin is of a type that was produced at a town called Eion between 500 and 480 BC and is called a trihembiol.

Eion was a town in western Thrace that had been established as a trading post by Persian traders in the sixth century BC. Under Athenian expansion in the fifth century BC, Eion was seen as a strategically important port and soon after 476 BC the Persians had been removed and Athenian settlers arrived.

What is most relevant to our numismatic understanding of the piece comes from this tussle between Persian and Athenian powers. The quality of a coinage is based on its weight and on the fineness of the metal and these small coins from Thrace fitted both Athenian and Persian weight and fineness standards so could be used for trade with both commercial powers. Persian coins weighed around 3.85g; fractions (quarters of Athenian staters) weighed between 3.6–4.4g. The trihembiols still retained their own local identity through the distinct iconography on them.

The foundation of the city of Amphipolis by the settled Athenians put paid to the coinage and indeed the city of Eion, and by 440 BC it was uninhabited.

What is unusual about these trihembiols is that they are often found pierced with a hole so that they could be worn and are found, not just in the area near Eion, but across southern Thrace. Were these coins kept by people who came from Eion, unable to be used as currency, but perhaps carrying an apotropaic power of their own?

Just as the salamander balances the goose in the coin design, so too this fascinating local coinage of ancient Greece kept the balance between two major empires who were vying for control of the city. Producing this currency meant allegiance did not have to be formerly asserted to either power and at least a semblance of independence could be maintained. From this you can imagine the day-to-day lives of people using three different currencies with the threat of war constantly looming.

What began as curiosity becomes a quite melancholy window into the past.
Accession Number: LEEDM.N.2010.0004.0030
Author: Lucy Moore, Leeds Museums and Galleries Intern 2011