Testing our own oil-filled watch to destruction

In an expriment worthy of Wilf Lunn, we find out if a £10 Casio can do the job of an expensive diver’s watch

IN OCTANE 207 we featured the Sinn UX Hydro oil-filled diving watch, a serious piece of kit cut from a slug of specially hardened German submarine steel. It’s certified to the standards in DIN 8310 for waterproofness, and Sinn says it’ll descend to 12,000m without any fuss. That’s deeper than the Mariana Trench.

When we wrote about the Sinn, we mentioned that we’d made an Octane version. We took a £10 Casio F-91W, removed the caseback, and submerged it in a small dish of silicone treadmill oil for long enough to make sure the oil had fully penetrated and that there were no air bubbles. Be warned: you will need a lot of kitchen roll – the silicone gets everywhere – and there will be some leakage, so don’t wear it with your linen suit. Then all we needed was a tester to see if our resin-cased Casio – or ‘Casioil’, if you like – could survive at the sort of depths that scare far posher watches.

Mr John Hogan, editor of SuperBike, put us in touch with a pal of his – let’s call him Wilbraham, or Will for short – a professional saturation diver (not that there are any amateurs). He was happy to oblige and took our £10 F-91W down with him on his next assignment. Will is not only a watch enthusiast, but also spent a previous career as an Army diver with a line in underwater bomb disposal. He sounded like just the man for the job.

Sat-divers work between a pressurised living chamber on a surface vessel, a diving bell that acts as a lift to get them down to the job, and the seabed. They need to spend the entire campaign at the same pressure as the depth they’ll be working at. That means the surface team has to equalise the pressure in the living chamber with the diving depth, a process called ‘blowdown’. And that was our watch’s first test. Will wasn’t taking any chances, putting the watch in a transparent bag should the in-case oil have made a bid for freedom.

It’s worth pointing out that saturation diving – working on a pipeline 200m underwater in zero visibility and breathing heliox – is no-one’s idea of fun. As Will points out: ‘Good viz and solid bottom are like Willy Wonka golden tickets.’ It’s a properly hostile environment.

Will had taken our Casioil on a 15-day job covering ‘diagnostics on hydraulics and electrics and changing out a couple of subsea command modules (they provide the comms link from platforms to wells). Good viz, hard bottom, no complaints.’ A golden ticket!

The Octane watch team stood by anxiously, waiting for news. W hen it came, it was positive. ‘Good news is the watch survived blowdown,’ wrote Will from inside the chamber, with a pic showing our F-91 next to a depth gauge registering 200ft of pressure. There followed a sigh of relief, and a celebratory beer was opened to mark the passing of the first test.

There are two things a watch needs to do to survive a dive: keep the water out (rather obviously) but also resist the pressure at depth. At sea level, the pressure is just under 15psi. Your car tyres are probably around twice that. At 200ft, Will and our watch were under around 100psi, well outside its design spec.

The next message from Will explained that the dive might be going on for longer and – crucially for the Casioil – deeper. The plan was to descend to 120m.

Things were, unsurprisingly, taking their toll on our £10 diving watch. As Will relayed: ‘I think there’s a leak.’ Fortunately, it was oil escaping under the pressure rather than water getting in. Will was still worried though: ‘Doubt I’ll take it in the water as it’ll drown over six hours. I’d rather send it back home in relatively one piece.’ We explained that the Octane budget could bear a £10 loss in the name of science and a decent story.

So Will took it on his next excursion out of the diving bell into 112m of water and nearly 180psi, attached to his harness. He takes up the story: ‘The first three hours were fine – if it was going to fail because of the pressure, it would have failed then.’ Our Casioil was thus a proper, professionally tested diving watch!

The next update was not so good: it was a picture of a very dead F-91. Will explained: ‘I think it suffered “a knock” when I was climbing over a structure. Would you like the remains repatriated?’ We assured him we would.

So our humble Casioil survived most of what the sea could throw at it, despite being designed for nothing more stressful than the local municipal baths. Its remains now have pride of place on the Octane watch desk.

Right, from top On Will’s wrist and ready to dive, dive, dive; all looking good at 200ft of pressure; then prepped for a bigger test; and finally... the Octane Casioil becomes a desk ornament.