Effin mensuration

Statue of Dr Johnson near his birthplace in Lichfield

Statue of Dr Johnson near his birthplace in Lichfield

The learned readers of this site will not need to be reminded of the sapient advice of the late Dr Samuel Johnson:

[…] no man should travel unprovided with instruments for taking heights and distances.

There is yet another cause of errour not always easily surmounted, though more dangerous to the veracity of itinerary narratives, than imperfect mensuration. An observer deeply impressed by any remarkable spectacle, does not suppose, that the traces will soon vanish from his mind, and having commonly no great convenience for writing, defers the description to a time of more leisure, and better accommodation. […]

To this dilatory notation must be imputed the false relations of travellers, where there is no imaginable motive to deceive.

Samuel Johnson A Journey to the Western Islands of Scotland W Strahan and T Cadell 1775

The good doctor would, I think, have welcomed the invention of the digital camera with inbuild chronometer. Equipped with just such a device I arrived yesterday at the first lock on the Royal Canal to witness the lifting of the railway bridge and the passage thereunder of fleets of boats. I thought it would be interesting to record how long each stage took.

I have written before about this bridge: reporting a question by Maureen O’Sullivan TD in October 2013 and another in November 2013 and providing statistics on usage a few days later:

  • only 58 boats went through in 2013
  • the bridge was lifted on seven dates
  • two other scheduled lifts were cancelled as no boats wanted to travel
  • Irish Rail charged Waterways Ireland €1200 per weekday lift and €2000 per weekend lift.

The first 45 minutes

A lift scheduled for early July 2014 was cancelled; yesterday’s lift catered for just two boats, whose passage was assisted or monitored by eight Irish Rail staff and four from Waterways Ireland. Four of the Irish Rail people may have been in training as others seemed to be demonstrating things to them, but that’s only a guess. Three of the WI staff travelled together in WI’s stealth van and operated the first lock; the other, who travelled separately in a 4WD vehicle, visited from time to time. As far as I could see there was no contact between the Irish Rail and WI teams.

The bridge was scheduled to be lifted by 1100.

Before the lift 0945

Before the lift: 0945. The lifting bridge is on the right of the photo

Before the lift 0946

One minute later: 0946. A separate group of workers, perhaps contractors, is going down the west side of Spencer Dock with equipment

Before the lift 0949

Four men still on the bridge 0949

Before the lift 0951

Two minutes later

Before the lift 0956

On the bridge 0956

Before the lift 0958

Still there 0958

Before the lift 0959

One minute later

Before the lift 1006

The bridge 1006

Before the lift 1012

The bridge 1012

Before the lift 1015

The bridge 1015: another person approaches

Before the lift 1020

Six men at the bridge at 1020

Before the lift 1028

A seventh man approaches at 1028

Preparing to lift

The preparation stage, presumably involving the unlocking of some mechanism, took about five minutes altogether.

Preparing the bridge 5 mins 03_resize

One man worked on the far end while another walked to do the same at the near end

Preparing the bridge 5 mins 06_resize

An eighth man, behind the fence on the right, seemed to summon two of the men on the bridge

Preparing the bridge 5 mins 14_resize

They went to this building, which I guess houses the controls for the bridge

Preparing the bridge 5 mins 15_resize

Meanwhile work continued on the bridge itself

Preparing the bridge 5 mins 19_resize

Almost done

Preparing the bridge 5 mins 22_resize

A final check

Preparing the bridge 5 mins 25_resize

Everybody was off the bridge by 1033

Lifting

The lift itself took just over nine minutes; the bridge was up before 1044, in good time for the arrival of the boats.

The lift 9 mins 02_resize

After about one minute

The lift 9 mins 08_resize

Another minute later

The lift 9 mins 11_resize

Another minute (or so)

The lift 9 mins 15_resize

About four minutes have elapsed

The lift 9 mins 18_resize

After five minutes. The sides are clear of the water in which they usually rest; they are dripping on to the canal below

The lift 9 mins 20_resize

Six minutes in

The lift 9 mins 23_resize

Seven minutes

The lift 9 mins 24_resize

The men behind the fence may be controlling the lift

The lift 9 mins 28_resize

Not much further to go

The lift 9 mins 32_resize

Eight minutes

The lift 9 mins 40_resize

It’s up

The bridge up 16_resize

One of the jacks

After the boats passed_resize

Side view (taken after the boats had gone through)

The bridge up 13_resize

Water under the bridge

Boats go through

It took just over three minutes for the two boats to go under the bridge.

Boats approach 12_resize

Cruiser approaches; steel boat visible through the bridge

Cruiser goes through 03_resize

Cruiser about to enter

Cruiser goes through 04_resize

Heads down

Cruiser goes through 06_resize

Half way through

Cruiser goes through 07_resize

Leaving

Cruiser goes through 08_resize

Out

Steel boat goes through 12_resize

Steel boat entering

Steel boat goes through 20_resize

Almost through

Steel boat goes through 22_resize

Looking ahead to the lock

Steel boat goes through 25_resize

Done

 

I did not record the lowering of the bridge, which I presume took much the same time as the raising.

Preparation 5 minutes, lifting 9 minutes, passage 3 minutes, lowering and locking say another 14 minutes: say 45 minutes altogether, allowing some margin. But a large number of boats would take much longer as the rate at which they could move on from the bridge would be limited by the time taken to work through the lock.

 

 

 

5 responses to “Effin mensuration

  1. I hope those fellows in the orange jackets had a good sit down and a rest after all their hard work. A wee cup of tea and a scone, perhaps. Wouldn’t want them to be off work with stress.

  2. Joseph Goodfellow

    Thanks for sharing this. As a mechanical engineer, I can’t imagine why it would take eight IR workers to carry out the lift. There is probably an up button, and a down button, and maybe a little “electrical bridging” on the lines. It is little wonder that IR are always in the red. Lucky for IW the IR guys didn’t take a tea break as it would probably cost another grand!

  3. Dear Sir,
    I am also a mechanical engineer, would you please so kind to explain me explizit how this system works.
    I saw a spindl and a tooth rack. I think the spindl operate a gear and this works on the tooth rack up and town?
    Thank you in advance
    Have a nice say
    RJS

  4. I know nothing about engineering, I am afraid. However, looking at this close-up …

    Pillar close-up

    … I suspect that the motor on top of the pillar is turning a worm drive. Unfortunately I have no photo that looks inside the moving part …

    Moving part

    … to show the workings.

    The lift was made by Somers Railway Engineering, now Lloyds British Somers. It may be similar to this; I understand that problems keeping the four motors synchronised led to early difficulties (now, I think, largely resolved) with lifting the bridge (but should say that I have no idea whether Messrs Buswells were involved). bjg

  5. Dear Brian,
    thank you very much indeed for your very kind help.
    The spindle works the up and down
    Have a nice day
    RJS

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