Tide recorder ?

[Andy Freeman 1Participant @andyfreeman1]

[Andy Freeman 1Participant @andyfreeman1]

Today I went on a tour of RRS Discovery, a National Environmental Research Council ship that was visiting Liverpool. Some fascinating underwater probes, submarines, autonomous torpedos.

One thing that interested me was what I think is some kind of tidal chart recorder. Has anyone seen one of these. The instrument is powered by a small motor.

If all the cams are fixed, surely it would always repeat the same trace on the paper?

More photos in my album

Edited By Andy Freeman 1 on 07/10/2016 19:49:15

[SillyOldDufferModerator @sillyoldduffer]

I think that's a tide predictor. I remember a version with more wheels on a TV programme that I think came from Belfast. My memory is awful though.

Dave

Edited By SillyOldDuffer on 07/10/2016 20:02:01

[Neil WyattModerator @neilwyatt]

That's a very basic one

Each cam is driven at a different speed, but it looks like only two cams on that one have belts.

They use one's that have many different inputs for creating tide tables, there's a great wikipedia article, I'll see if I can find it.

Neil

[Neil WyattModerator @neilwyatt]

Here you go,, this one has a mere ten components!

en.wikipedia.org/wiki/Tide-predicting_machine

Neil

[Neil WyattModerator @neilwyatt]

Or this article about 'Old Brass Brains' that will compute up to 37 factors!

en.wikipedia.org/wiki/Tide-Predicting_Machine_No._2

<edit>

Ha! We Brits have one that uses up top 42 factors!

http://www.ntslf.org/about-tides/doodson-machine

Neil

Edited By Neil Wyatt on 07/10/2016 20:17:24

[John HaineParticipant @johnhaine32865]

Adds Fourier components to predict tides. Vital for D Day apparently, as well as for general coastal navigation that needs tables for every significant port. You can get software to do it now, but not so much fun.

**LINK**

[SillyOldDufferModerator @sillyoldduffer]

The tides depend on the sun, moon and the rotation of the earth. So what are all those wheels needed for?

This is going to be yet another thing that's more complicated than I thought it was…

Dave

[Geoff TheasbyParticipant @geofftheasby]

There are many cycles, of differing periods, all superimposed. Sometimes they cancel out, sometimes they coincide and build an extra-high peak. (Spring and Neap tides)

Geoff

[Neil WyattModerator @neilwyatt]

Posted by SillyOldDuffer on 07/10/2016 20:53:28:

The tides depend on the sun, moon and the rotation of the earth. So what are all those wheels needed for?

This is going to be yet another thing that's more complicated than I thought it was…

Dave

Lots of small things affect the tides and they are mostly location specific, such as the tide 'bouncing' back down an estuary. In the Solent the tide goes in and out four times a day…

Neil

[SillyOldDufferModerator @sillyoldduffer]

Reading about it I see that the tide is a 20000km long wave with the world rotating underneath. Thought about that way the flow of water could get really complicated whenever it hits a coastline, goes through a narrows or up an estuary.

It is more complicated than I realised. Clever blokes those Darwins!

Dave

[Dave MartinParticipant @davemartin29320]

Posted by Andy Freeman 1 on 07/10/2016 19:48:24:

Today I went on a tour of RRS Discovery, a National Environmental Research Council ship that was visiting Liverpool. Some fascinating underwater probes, submarines, autonomous torpedos.

One thing that interested me was what I think is some kind of tidal chart recorder. Has anyone seen one of these. The instrument is powered by a small motor.

If all the cams are fixed, surely it would always repeat the same trace on the paper?

More photos in my album

Edited By Andy Freeman 1 on 07/10/2016 19:49:15

Andy – as other have said, I think its a simple tidal predictor. If you're in the Liverpool area, you may have heard of the Proudman Oceanographic Laboratory at Bidston, that housed the Doodson tidal predictor.

Dave M.

[Ady1Participant @ady1]

The wind speed and direction affects the tides, any sea currents affect tides, the air pressure like a big low or a big high over an area affects tides.

I used to calculate them in the 1980s as part of my trade and it's a very inexact science, no doubt they are better at it today with pooters but there's always a degree of guesswork and interpolation

[Ady1Participant @ady1]

There was a very interesting BBC program about the Germans missing some huge opportunities from high tides in London during WW2, the city was basically at the mercy of the sea if anything had failed during a big one

If they had bombed Londons tidal defences just prior to these tidal events it would have been far more effective than anything the Dambusters managed to achieve

There's an article about their work here

Most of the tube system and large areas of London could have wound up submerged

Edited By Ady1 on 08/10/2016 00:15:35

[Neil WyattModerator @neilwyatt]

Posted by Ady1 on 07/10/2016 23:52:24:

The wind speed and direction affects the tides, any sea currents affect tides, the air pressure like a big low or a big high over an area affects tides.

I used to calculate them in the 1980s as part of my trade and it's a very inexact science, no doubt they are better at it today with pooters but there's always a degree of guesswork and interpolation

Don't spoil the illusion that wheel number 42 really makes a difference

N.

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Ady1 on 07/10/2016 23:52:24:

any sea currents affect tides,

Surely it's the tides that determine the currents, at least away from fast flowing rivers?

Tides cannot be calculated exactly. Recordings from tide stations over many years are subjected to Fourier analysis to determine the coeficients to use in the predictions. The predictions don't take into account weather related effects but they can be estimated fairly well.

Russell

[Enough!Participant @enough]

At least you know when it comes in on this side, it goes out on the other side.

[Andy Freeman 1Participant @andyfreeman1]

Thanks all for the interesting replies. Lots of links to investigate further.

Dave Martin, I know the Proudman Oceanographic Laboratory well, living only about a mile from it! It has been vacant for many years now and only last week the building was sold. The new owners hope to turn it into some kind of 'Art hub / centre'

I need to find out if the original Doodson Tidal predictor is on display at the Liverpool Museum. I don't remember ever seeing it there.

[John OlsenParticipant @johnolsen79199]

Ocean currents like the Gulf Stream are independent of the tide. They have eddies either side which could make a difference to local tide levels on nearby land masses. I suspect it would only be minor.

John

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