Meeting Summaries

DESIGN OF THE NEW “TAMAR” LIFEBOAT,  19^th October 2007

Mr Chaplin began with a brief description of the RNLI, saying that it had 233 Stations around the UK and Ireland, with 300 Lifeboats.  Lifeboats, as well as being able to carry rescued people, are designed to be: safe, self righting, and easily operated by the crew.  They operate from the beach to 100 miles off shore.  The average total of launches in a year is 8000, and 8000 people are saved.  Crews comprise a full time Captain and about seven volunteers; 10% of whom are women, a figure that is rising.

Mr Chaplin had lived with the Tamar Lifeboat design for seven years, from concept to seeing it into service: four stations now have one, a fifth soon will, and two have them on standby.  In 2006 there was a successful trial at Tenby.

Starting in 1997 several models were made and checked in a test tank, No 9 version 3 being chosen: the next year they went to tender, from four firms selecting DML to make the hull; then in 2004 computer analysis led to an improved hull form - and new moulds; by the end of the year they had successfully carried out self righting trials – it takes 6 sec.

In 2001 the Systems and Information Management System (SIMS) was designed, a highly redundant [backed up] electronic set-up with six positions, each with an LCD screen, headset and PC with flash memory [which holds data with power off] giving a full set of controls for: communication, navigation, fire fighting, and marine systems.  Software was optimised, the display style having big on screen ‘buttons’; screens can be independently set for eg: Chart Plotter, CCTV, Radio communication, Machinery information.  Crews are often sceptical of new technology, but after a couple of days trials in 2003 it was liked.  Radio communication near shore is by VHF.  At longer ranges MF is used, for which the aerial needs a metallic ground plane – not easy on a plastic boat.  Satellite links are more expensive – but will probably be used in the future.

Over the years top speed has increased from 8 knots to 18 (Severn and Trent), and now for the Tamar, 25 knots - though 17 knots in bad weather.  In 2002/3 engines were chosen, two 1000 HP, C18 diesels from Caterpillar, which give full speed at 80% power.  They run for about 300 hr a year.  Engine oil heaters are fitted to ease starting in cold weather.

Many Lifeboats are operated from slipways, enabling them to be launched at all states of the tide.  A boathouse at the top of the slipway provides shelter and indoor maintenance for the Lifeboat – though the slipway itself needs maintenance.  However, at other locations a slipway is not necessary and, without its constraints, boat design can be optimised for size and speed, for example, as with the Severn and Trent.  The Tamar is designed to replace the Tyne for slipway launch, and also be suitable for non-slipway use.  It has a ten hour endurance, can take ground (sit on the sea bed without damage to the propellers or rudder).  Ergonomics were designed in conjunction with Loughborough University.  The wheelhouse is the highest part of the boat, with a view all round, though constrained forward by the roof over other accommodation – it could not be made higher because of the 6m height limit of boathouses.  The Tamar has ten survivor seats (and can carry 44 survivors inside, still self righting, or a total of 118 with others on deck).  For situations the lifeboat cannot reach a Y-boat (rubber dingy) is provided aft, with a launch ramp and transom door.

Design was done with industry, while ensuring that the special needs of a lifeboat were met.  It must cater for a volunteer crew with a range of size and capabilities (they only do 1-2 hours per week).  It has to fit boathouse dimensions – it is 16m long, 5m beam, 6m overall height, 1.35m draft and weighs 31.5 ton.  A fibre reinforced hull takes the shocks produced by rough seas.  This has a 2mm inner and outer skin with H80 foam (with individually sealed pores) between: an inch thick for the deck but up to 4 inches for the hull.  The hull is moulded in three parts: either side and the deck & wheelhouse - by vacuum impregnation in special moulds, and cured at 80^OC for 10 hr – then glued together and overlaminated.  An engine hatch is left in the deck.  Each side weighs 9.5 ton, and the upper works 1.25 ton.  The hull is not made as a single piece, partly for ease of manufacture, but because the sides have a tumblehome (wider below deck level) and a multipart mould would be needed with a chance of poor quality at the joins.  Up to three watertight compartments can be flooded before the boat is in danger.  The total cost of a Tamar lifeboat is £2.5m.

The crew seat is similar in design to the ejector seat of an aeroplane.  It was designed with Southampton University, who tested prototypes with dummies.  A damped vertical travel of 8 inches keeps the forces experienced by an occupant below 3g even in the worst weather.  A SIMS terminal can be mounted on the seat, in front of the occupant, to whom it appears to stay still – unlike earlier deck mounted designs.  The RNLI are considering fitting the seat to older lifeboats. 

After a tiring mission slipway recovery has to be done, coping with wind, tide and waves while getting the boat back into its boathouse.   Mr Chaplin described how slipway recovery of a Tamar lifeboat is done.  Although keeping to the usual, manageable, size and design, slipways are being rebuilt for the Tamar.  The boat is brought stern first towards the slipway, and secured by ropes to mooring buoys on either side.  Using these it is aligned with the slipway, whence two shore crew throw a bridle which is secured; the 1 ft wide keel has to engage a 2 ft wide centre channel.  The Tamar will take a 90 ton impact.  The boat is then winched up the slipway and onto a cradle in the boathouse - the cradle, with the boat on it drops to horizontal: this makes it much easier to work on the boat, for instance when checking engine oil level.

Despite all the modern technology, lifeboats still carry paper charts, and crews are trained in traditional navigational skills.

MARINE RENEWABLE ENERGY,  16^th November 2007

Professor Dave Elliott spoke to us about the renewable energy that could be extracted from the sea, particularly around Britain which has the best conditions anywhere in the world with 350 TWh per annum (of which it would be practical to use 30%).  Two basic sources are: wave energy, derived from Solar energy (which causes wind, that raising waves); and tidal, due to gravitational effects, mainly Lunar.  The tide is dependable and has been used for centuries in tide mills.  The French built a tidal barrage in 1968 across the Rance in Brittany and use it to drive turbines to produce electricity – very efficiently and more cheaply, though they do not publicise it, than even their nuclear power stations.

He did not favour the Severn barrage proposal, costing £15 bn and developing 8.6GW, but only for an hour or so after high tide.  It would block the entire estuary and have a big impact on the environment, cause silting, and a drastic change to the ecology.  It would only cut national carbon emissions by 1%.  This plus other sites suitable for barrages could develop 15GW.  A variant of a barrage is a tidal lagoon, situated within an estuary - one is proposed for Swansea.

Since water is 800 times denser than air machines are much smaller than wind turbines, most designs operating quite slowly, making them fish friendly.  The tide, as it sweeps round the country, can give continuous power.

Tide current turbine designs are based on an old tide mill which had an anchored pontoon with a paddle turned by the passing tide; though they operate underwater.  Most are to be put in narrow channels with tidal currents of 4–6 m/sec, to provide power on rising and falling tides.  Designs, and many are being tried, are usually mounted on a mast so that they can be raised above water for maintenance (particularly to keep the blades clear of marine growth).  One such is a 300kW machine which has successfully operated for three years at Lynmouth.  At the entrance to Strangford Lough, N Ireland, a 1.2MW a twin propeller turbine is being built.  For slow tidal flows the Hales turbine, with a venturi, is a simple design, many of which could be laid out as a tidal farm.  The Sea Snail is a large, heavy machine designed to sit on the sea bed, without an anchor though it has down force hydrofoils, and a (seemingly small) propeller on top.  In Dublin the Open Hydro is being developed, an annular machine - a hole at the centre surrounded by a rotor incorporating both the turbine and a generator – held between a pair of masts.  Canada is developing a Blue Energy tidal ‘fence’ with wide openings, each containing a slow moving turbine – a 2GW system is destined to go between two islands in the Philippines.  About twenty tidal projects are under test.  Britain has a potential tidal power of 31TWh/annum from thousands of sites around the coast.

Wave power is most plentiful in the N Atlantic, the Antipodes and the SE Pacific (Chile).  The USA could get 10% of their requirements from it.  British wave power potential is about 70 TWh/annum.  Waves are usually present but die down some days after a storm.  Wave power is greater far offshore.

Many machines, in a variety of forms, float on the surface.  The first was the Stephen Salter’s Duck in 1970s, with articulated sections, energy extracted from hydraulic pumps at the hinge points, and designed to work broadside to the waves.  The Osprey, a 2MW machine, followed in 1995 but failed – it sank.  In 2006 the Pelamis – a sea snake - was developed, again with articulated sections but designed to work in line with the waves (giving less power than a broadside design but making it much more seaworthy): a 2.25MW system is being installed by the Portuguese.  The Wells turbine works on in- and outflow but is only 10% efficient.  In Belfast they are developing the Wavebob, a buoy whose motion can be tuned to the wave frequency to maximise energy extraction from a piston tied to the seabed.  The Dutch are trying their Archimedes design with a floating inverted pendulum.  The Danes have developed a ‘wave dragon’ a device with a tank above water level, a simple design which works.  Wavegen is building a 3MW system in Scotland.  The Canadians successfully trialled an Aqua Energy buoy, but promptly afterwards it sank.  In 2000 a 500kW Limpet was installed on land with a long channel to feed in the waves to compress air in a chamber and drive a turbine in a cylinder above.

Other uses  Marine power, particularly if far offshore, can be used, for instance, to produce fresh water, or to produce hydrogen by electrolysis.  A tanker could visit as necessary to take either ashore.

Funding  Professor Elliott said that our funding for all renewables is much less than Denmark and Germany (who laugh at us), China and Japan.  For such a well endowed country our record on marine renewable energy is lamentable – it just so happens that our nuclear power programme is effectively mandated by the USA.  Initial government funding was curtailed by Margaret Thatcher; though the present government is providing funds they are only tea money: £50m over four years.  Scotland is putting up £13m.  Although marine renewables are still at an early stage, there is enough data to fit to the standard learning curve and, applying economies of scale, predict future prices.  A 2.5 MW tidal power system, or a 100 MW wave power system could provide power at 2.5 p/kWhr.  At this level we could have 200 MW installed by 2010 (ten times the present figure); and 5000 MW by 2020–5, though if 5–6 p/kWhr were acceptable that figure could go up to 10GW.  This compares with our present capacity of 70GW from power stations (if working).

Members' Evening, 14th December 2007 

Falkirk Boat Lift

Mrs June Mackenzie: Two canals crossed southern Scotland, the Forth & Clyde, and then the Union, running eastwards from Edinburgh through the lowlands.  They were linked by a flight of eleven locks at Falkirk.  The advent of rail and motor transport caused trade to dwindle and both canals were closed in 1930, their courses since being broken by new development.  However, they were given a reprieve as a millennium attraction for boating and walking; with the flight of locks replaced by the iconic lift.

To reach a basin in the lower canal, the upper canal has a half mile aqueduct in the form of a trough supported by piers; each is adorned with a (fibre-glass) arch over the top to match the design of the lift which has two spectacular end supports with a pair of gondolas between.  Boats can leave and enter when the gondolas are at top and bottom with the approriate steel gates opened.  Water levels in each gondola are equalised so the lift can easily be rotated, through 180 degrees, by ten hydraulic motors on a 4m diameter axle.  Gravity should keep the gondolas upright, but this is ensured by support bogies engaging with cogs in the support structure.  Operation takes 15 minutes.

The lift was made in Derbyshire, its sections bolted together (to avoid distortions possible with welding).

Street Furniture

Mr Richard Buchanan: Some street furniture is invisible despite its size and one having to walk round it.  In the early 20^th century cast iron electricity junction boxes were put in the pavement to provide weatherproof housings for joints in mains cables.  Early Woolwich ones had the borough coat of arms cast on their doors, a few still surviving.  One remained on Shooters Hill until it was recently hit by a car (which probably came off badly – such boxes weigh ¼ ton).  It was taken to the Heritage Centre, and replaced by a joint housing below the footway (modern joints are waterproof).

Sewer vent pipes (also known as soil pipes or stench pipes) resemble lamp-posts, though slightly thicker and open at the top.  Most were put in in the late 19^th and early 20^th century.  Several companies made them, together with other cast iron water supply fittings, visible ones being drain covers and drain gratings.  A conservation area on Shooters Hill has two soil pipes by A C Woodrow & Co, which will therefore require maintenance – no doubt eased by modern scientific methods.  Woolwich has a splendid one in Grand Depot Road, by Fredk Bird & Co Ltd.  The need for sewer vent pipes has virtually disappeared with modern cleaning agents.

[Mr Kite added a comment about his erstwhile place of work: as grease laden gasses rose through a relatively cold vent pipe the grease would form a plug, causing the gas pressure to rise until the grease was expelled – messily.]

Also in Woolwich, in a proposed conservation area around the Old and new Town Halls, are drain gratings by R Ginman & Son, Founders, Plumstead, possibly of 19^th Century.  These are unusual in having their slots parallel to the curb.  They are more lightly made than later cast iron designs (modern steel drain gratings are comparable), but are still in good condition.

Timber Shrinkage, Rotting and Seasoning

Mr Jim Lugsden: Freshly cut timber has an outer layer of sap wood, which is removed as it would quickly rot, and heart wood.  Timber is preserved when in [stagnant] wet conditions, an example being bog oak; or if kept bone dry.  Otherwise it is susceptible to fungal attack, unless treated with a fungicide, eg Cuprinol, or painted.  Creosote (a coal tar distillate) is now considered a health hazard, but is used for pressure treating railway sleepers and telephone poles.

Depending on the species seasoning (drying) causes 2-12% shrinkage, with an average of 5%, around the annual growth rings but only half as much across the rings.  This results in shakes (splits) along the length of a piece of timber, seen for instance in a mill in Keston or the Globe Theatre on the South Bank; though shakes are seldom of concern.  Shrinkage also causes a plank cut from the side of a log to warp, the rings tending to straighten; though one cut on the diameter will be fine.   

Seasoning is dependent on usage; shrinkage starts as the moisture content is reduced below 26%: 20% prevents decay, 18% is suited to exterior work, 16% for garden furniture, 14% for unheated indoor conditions, 11% for a heated building or 8% if near a radiator.  Kiln drying is necessary for a very low moisture content, and is much quicker than air drying which can take a year per inch of thickness.

For an environment that may be wet suitable species include Oak and Greenheart, but not Beech or Ash.

NANOTECHNOLOGY, from Watching Single Atoms to Home Pregnancy Tests,  18^th January 2008

Professor Aeppli introduced the nanometre by a comparison of the familiar: the earth’s radius is 10 000 km (10⁷m), ones hand is 10cm (10^-1m) wide, and reducing size by the same ratio again gives a nanometre (1nm = 10^-9m).  Fingernails grow about a nanometre per second.  Red blood cells are micron sized (1ìm = 10^-6m), the diameter of the DNA helix is 25nm.  A hydrogen atom is 0.1nm.  At smaller scales still one moves into the realm of high energy physics.

Nanotechnology is about manipulating, measuring and characterising things at that scale.  Semiconductor fabrication started at a scale visible by eye, but as integrated circuits came in it shrank, allowing more copies of a circuit to be printed onto a silicon wafer.  Semiconductor processes now achieve nm dimensions.  This represents a top down approach: while micromolecular chemistry is bottom up, with 19^th century roots.  Carbon in its familiar forms of coal, diamond and graphite has been joined by newly discovered forms such as buckyballs.

Semiconductor processes are typically carried out in clean rooms (down to 100 particles per cu ft) with operators in fully enclosing suits.  Vapour deposition machines, with evacuated to 10^-11 torr, are capable of adding individual atoms (a picture of such a machine showed two cylindrical chambers surrounded by a large agglomeration of pumps, measuring and control equipment and their interconnections).

Characterisation of a surface at nm dimensions uses the same principle as the gramophone, with an arm holding a head.  The arm is made from silicon, bulk material etched away to leave a thin cantilevered beam, with a stylus on the end.  This is moved over the surface by a piezo-electric drive, and vertical movement of the stylus is measured using a laser and photodetector.  If the stylus is replaced with a magnetic head magnetic domains can be studied; or an electrostatic head can show electrical properties.  A microscope of this type is relatively small (not a room filler) and cheap at £10k.  Another type of machine is the Scanning Tunnelling Microscope, capable of resolving a single atom – on a prepared surface in a high vacuum.

In order to visualise it, nano-scale design has to be computer aided.  Professor Aeppli showed a computer model of silicon with bismuth added: the bismuth bonded at the surface, bridging between silicon atoms - pointing the way to fabricating bismuth wiring on silicon.

Commenting on the principle that the most successful work is not the most obvious, Professor Aeppli mentioned computer hard drives, in which an arm with a magnetic head scans tracks on the disc.  By making the head smaller tracks can be closer and more data stored.  He gave an estimate of £10bn as its contribution to the world economy.  Another example in the medical field, his main interest, is the home pregnancy test.  In this nano-sized latex spheres coated with an appropriate hormonal antibody will, in giving a positive result, react and coagulate so that when passed through a filter they are caught and nano-particles of gold included in the test mixture are then sufficiently concentrated to show up - pink, as they are so small.  This too contributes to the world economy, by freeing up the medical facilities needed for other, much longer, tests (which are less reliable) and by removing the embarrassment of telling friends and family if the result is negative.

In the medical field the drug companies need to improve their rate of producing new drugs, and in the longer term there are aims to: customise drug delivery for all; improve point-of-care productivity; and improve the quality of life and economic viability for a rapidly ageing population.  Nanotechnical procedures can help.

Osteoporosis is an area where study of the bone surface at nm scale is leading to a better understanding of the problem, which is more prevalent in older women.  A latex tip on a microscope beam is used.  The surface can be gently “hammered” to test the strength of the bone, and also tested to find the proportion of calcium.  Previously the best that could be done was X-ray analysis of much larger samples, the results being of average conditions over an area containing a large array of atoms.  Much of this work resulted from the study of astronauts after long periods of weightlessness.  Bone growth needs mechanical simulation.

Another area of medical concern is the superbug – such as MRSA which is resistant to antibiotics.  Even the last resort antibiotic, which attaches to and breaks open the cell wall, has been breached.  A microscope made with a silicon block that has several beams is used as a weighing machine: the tips of individual blades are coated with drugs to be tested, with one neutrally coated as a reference.  The bacteria are introduced, and the deflection of the blades is measured, the greatest deflection, possibly 95nm, showing the drug to which the bacteria attach best.

Breast cancer tumours can be detected by injecting a radioactive dye and measuring the radiation.  A much safer method, developed between London and Houston is to inject a dye containing magnetic nano-particles and use a magnetic detector.

Professor Aeppli commented that the London Centre for Nanotechnology was small in international terms, but said there was an exciting future for Nanotechnology.  He mentioned the artificial nose, where the shape, chemistry and vibrational resonances of a captured molecule were all important for recognition – which needs a high vacuum.

    Training of Guide Dogs for the Blind,  15^th February 2008 

She explained that guide dogs are now bred by Guide Dogs for the Blind, their favoured breed being curly haired retrievers - crosses of Golden Retrievers with Labradors.  They inherit the gentler nature of retrievers with the intelligence of labradors; also a black coat which sheds less hair, a much appreciated characteristic.  The Charity is the largest breeder of guide dogs, with 250 brood bitches, each producing four litters, from 50 stud dogs.  At any one time there are a thousand puppies, and there will be 5000 working dogs.  The dogs usually retire at nine years old; most owners having a succession of dogs through life.  Border Collies have been used, but their herding instinct can bring problems.  Nor are scavenging dogs used, or ones who might run after balls.  David Blunkett, when the lighting in the Houses of Parliament failed, said his guide dog (curly coat/labrador) would lead them out – and did.

At six weeks guide dog puppies are placed with Puppy Walkers, with whom they live until they are a year old.  During this time they are taken everywhere, to shops, on transport (though not on escalators), even to pubs, to familiarise them with people and the world they will work in.  There can be difficulties, such as shiny floors, doors that open away or towards one, or revolving doors.  Some basic training takes place: the puppy walker always holds the lead in the left hand; and by ten months the puppy will have been taught left from right.

Ms Marchese has been a volunteer puppy walker for some time, Turner being her 16^th.  Now she also works for the Charity.  Puppy walkers, and others who board dogs during their training, have to live within 40 miles of a Guide Dog centre; they have to have a garden; and be prepared not to go out without the puppy for more than three hours.  When she started she had some basic training.  Monthly visits by a supervisor ensure that the puppy is suitable, and that no bad habits creep in.  Guide dog puppies are generally given the same access to shops etc as guide dogs, though they do not have this as a legal right and it is best to ask; corner shops cannot always cope.

At one year the puppy is taken to the Charity’s training centre at Woodford Green.  Here each dog is matched with a Trainer.  A brown harness is put on for each training session, and over the next six months the dogs are trained to act on 40 recognised commands.  One of these is ‘busy’, a toilet instruction to be followed in the garden before going out (Police dogs respond to ‘empty’).  They learn to judge whether widths are sufficient for their owner as well as themselves – for instance between a shop’s advertising board and the edge of the pavement, or by road works; and heights - beneath an overhanging branch of a tree or an awning.  When crossing a road they are trained to signal the kerbs and cross at right angles to the road (no short cuts – the blind are fit).  They also learn to lead their owner up and down stairs – at rising steps the dog puts its front paws on the first step and stops, the owner feeling the signal – just before downward steps the dog will stop and lie down.  They learn to avoid obstacles, some of the worst being: uneven pavements; litter; sales boards; wheelie bins; bicycles lying on the pavement; parked cars (in narrow roads); overhanging hedges; and for the dog’s paws, or fur if signalling by lying down: broken glass and chewing gum.

Guide dogs are neutered, the bitches after their first season, the dogs spayed at nine months.  Over three quarters become guide dogs, some of the others going on to a disabled person, the Police, or as sniffer dogs for the Customs.  The best dogs are selected to guide deaf and blind people (who will have red band on their arm or their white stick).

At 18 months the dog is assessed, both for its abilities and nature; and matched to a potential owner.  This matching fails in no more than one percent of cases.  Another four month’s training, suited to the needs of the future owner, is then carried out by a District Team.  The dog is boarded out.

When trained the dog meets the owner, and gets its yellow harness, marked on a large label “Do not distract me, I’m working”.  One for whom this is their first dog will need training in the 40 commands, something an older person will take longer to master (partial sight can be helpful – only 4% are totally blind).  This may be at home but will often be done at a selected hotel, for three weeks – of hard work.  An owner having a replacement dog will soon take to the new one.  A photograph of the dog with the new owner is sent to the puppy walker – often leading to a continuing friendship.  Thereafter the owner will be visited every six months, to ensure all is well and no bad habits are forming.  The youngest a blind person can have a guide dog is at 16 (though two 14 year olds have done well).  When placing dogs priority is given to replacements; a first time owner may wait up to a year for a suitable dog.  Retired dogs may be kept by owner, but will usually go on to live with an elderly person for whom they make ideal pets.

When going out the owner must know the route –the number of kerbs to be crossed, and which shop along a parade to go in – tactile maps are available, and much is now being marked in Braille – signs and buttons on traffic lights, busses etc.  Greenwich is good.  Underground stations can be difficult (Green Park is worst) as lifts have to be used (though one dog had special boots for escalators).  If crossing a road at ones bus stop is too difficult it can be better to use the next stop.  A sighted person offering help is asked to present their left elbow, and to warn of kerbs etc.

Ms Marchese showed some aids promoted by the Royal National Institute for the Blind including: a talking clock/watch; a liquid level indicator to hook over the side of a cup which bleeps when the liquid reaches the hook; a cheque book guide (a template marking spaces to be filled in); shaped buttons for different coloured clothes; a pocket Brailler (a diary sized folding metal frame with 24 x 7 holes on the front, each backed by a six hole array on the back, used with stiff card and a stylus.

Finances are odd: when taking a dog the owner is charged 50p – originally 10/- in 1931 when the Charity started.  The cost, however, averages £10 per day, amounting to £40 000 per dog over its life.  Administrative costs within the Charity are 2% of their income.  Much comes from owners who are happy to pay more, and from legacies.  There is a ‘Sponsor a Puppy’ scheme at £5 per month; and a ‘Name a Puppy’ scheme for a single £5000 payment – this is for a locally walked puppy, with regular news updates.

INVESTIGATION OF ENGINEERING EQUIPMENT FAILURES,  14^th March 2008 

Mr Dean first explained how his career had developed after obtaining a Mechanical Engineering Degree in 1970.  He began at BICC in Erith, where he worked on 400 kV oil filled cables, and the design of power connectors used in coal mining.  He described the laying-up process for making these cables; as the cable core was drawn through the winding machine, bobbins would be spun in opposite directions round it, forming braided layers of paper tape, successive layers being of different widths of tape.  When filled with oil this gives a very reliable insulation – cables designed for 40 year life have been rerated for 100 years; the only difficulty is having trained staff to terminate them.

He was involved with on-line partial discharge (PD) monitoring.  Partial discharges show insulation breakdown - at very low levels these are acceptable, particularly in an oil filled cable where oil should flow into a damaged spot and restore the insulation resistance.  At higher levels they spell trouble.  Applications he dealt with were mainly with HV cables, and associated equipment, and were in the oil and gas industries, petrochemicals, transport, power generation, distribution and transmission – all having high value installations.

The aim of investigating engineering equipment failures is to find out why a failure occurred, then using this knowledge to: avoid it happening in the future; save lives; establish liability; and reduce losses.  The investigation must be financially justified – not doing it just for academic purposes, but so that it pays for itself with demonstrable savings.  These can come from improved design, procurement, maintenance or operating practice – and deciding when refurbishment is worthwhile.  All evidence should be examined, not just the physical state of the failed item but condition monitoring records and failure records; and taking eye witness statements.  The mode of failure, whether mechanical, electrical, chemical (eg corrosion), and/or thermal is determined and the root cause found.

Investigation can start with something as simple as a magnifying glass, but go on to use electron microscopy, chromatography, microanalysis, etc.  Computer modelling and finite element analysis play a part.  The ERA works in conjunction with University College, London,  Southampton University and Surrey University.

The ERA is contracted to do all fault investigation for the National Grid, and is called in by many other industries when fault investigation requires special expertise.  They are involved with air craft accidents.

Mr Dean cited several failures.  Coated steelwork could fail after an impact – which could create a gap in the coating, letting in water, that causing corrosion, leading to the propagation of cracks – the root cause would be put down to poor maintenance.  Most damage to HV cables is due to them being dug up – a sharp edged break in the sheath exposing the insulation, leading to progressive breakdown accelerated by the generation of ozone.

Ships were traditionally made with steel plates riveted to the fames – if a crack developed in a plate it would stop when it reached the edge.  During WW2 Liberty ships were of all-welded construction, not always of good steel – cracks could just keep propagating right round the hull…  The Alexander Kieland oil platform failed when it was taken into too cold waters.  The MV Kurdistan similarly failed with oil, heated to reduce its viscosity, inside its hull plates when it sailed into cold water.  There can be cargo failures, due to vibration from the engines or low frequency wave action – which can be determined by examining a fracture under a microscope and looking at the pattern of striations, caused by the growth of cracks - a few microns apart in the sample he showed.

He handed round a blade from a turbine, with a magnifying glass to view the crack which was forming at the root in the ‘Christmas tree’ dovetail which held the blade in.  He said that although aircraft engines were very reliable, land based variants of such turbines were less so.  If a blade did come off it could either burst through the side of the casing or go through the turbine causing more destruction.

He showed a picture of the stator of a very large motor, as used to propel a cruise ship.  This has slots on the inside of a cylinder in which conductors, wound with an insulating tape, are inserted; at the ends the conductors are ‘laced’ to stop them moving under operating stresses.  Eventually the lacing can fail, leading to chafing and an insulation failure; a repair will be tried, at least to get back to port - bypassing the failure and making as good as practicable.

Oil filled transformers are normally very reliable – but failure can give rise to a dramatic explosion.  For indoor use cast resin insulated transformers are now used; less reliable but safer.  Tap changing transformers enable the output voltage to be set within a desired range; Mr Dean passed round the tap changing parts of one that had failed – it had been designed for off load adjustment but was regularly used on load – arcing each time and forming pyrolitic carbon from the insulation, covering the parts - he warned us not to open the packet if we wanted to keep our fingers clean.

Another item he passed round looked like a lump of rusty iron dug from the ground.  It wasn’t – it was the remains of a copper cable from an uninterruptible power supply - whose load had developed a short circuit causing the mains to trip out, leaving the battery feeding it until the battery blew up.  By then the cable had melted, and destroyed the concrete floor it was set in.  The battery had had no fuse.  Close up one could see the lump had copper in it.

Much smaller, but still hazardous for the tenant, was a failed residual current device (RCD - nowadays one has several domestically in a distribution box instead of mains fuses) where the plastic casing showed electrical tracking in the form of a tree on an inside surface.  It had come from an unheated lean-to shed on the side of a block of flats, where residents often piled sacks of refuse awaiting collection – this prompted a comment from the audience about how the corrosive juice from an orange one was eating could get anywhere.  In 2006/7 a study of 600 RCDs showed that 3% failed to operate when an out-of-balance current between live and neutral of 30mA was applied (30mA is low enough not to cause heart failure if passing through the body).  Manufacturers recommend that RCDs are regularly tested – but how many of us test our own at home?

MOTOR VEHICLE AERODYNAMICS, Friend or Foe ?  18^th April 2008 

Mr Huntington began by saying that he had worked in the motor vehicle industry for 31 years, and is now in charge of climatic test facilities at a major development site in Essex.  In explaining his title, he said that air flow was a friend by providing a means of cooling the engine, brakes and, nowadays, air conditioning; but a foe in resisting motion. 

Although a general talk, he took illustrations from recent development work on motor vehicles.  He showed a diagram of the main factors that influence the aerodynamics of a car.

He gave two basic equations for the forces a car has to contend with:  Drag Force, F_D ;  and  Rolling Force, F_RO :

F_D   =  C_DA(ñ/2)V²     where         C_D  is Drag Coefficient,  A  is the frontal Area,  ñ  is air viscosity,  and  V  is velocity;

F_RO =  fmg                                       f is coefficient of Friction,  m  is vehicle Mass, and  g  is gravitational constant.

                                                         For a typical car:  C_D = 0.3 – 0.5 ;  A = 2 m² ;  m = 1000 kg ;  f = 0.02

In reality conditions are more complex, but they show that while the Rolling Force is (fairly) constant the Drag Force increases with the square of velocity.  In fact the Rolling Force does rise because the energy used in deflecting the tyre where it touches the road is proportional to the rate of wheel rotation.  Both are low at town driving speeds, but drag increases dramatically on the motorway.

To be effective a car should be less than 11% of the area of wind tunnels (23 sq m) used for aerodynamic testing.  Even so a car’s drag coefficients can be wind tunnel dependent.  High speed testing is typically at 120 km/hr.  Smaller wind tunnels are used for thermodynamic (cooling) tests.

A low drag coefficient - that of a brick is 1 - depends on vehicle shape.  Losses arise from displacing air at the front, causing high pressure, and recombining at the rear at a low pressure.  Drag can be reduced by such methods as having an over crowned roof, or a having a low speed lip below the front bumper and reducing the ride height.  Slipperiness helps too, avoiding protruding edges.  The drag coefficient can be calculated from the design shape by Computational Fluid Dynamics, but even on a modern computer it is an over-night job, so wind tunnels, where modifications can be tried relatively quickly, still have their place.  Initial testing is done with quarter size models (produced by machining a plasticine block with a wooden skeleton), replicating the underbody as well as the upper parts.  Strips or pads of material can easily be affixed and the effect seen.  Later tests are done with full size models, anchors placed just behind the wheels where they do not affect results.  To save the number of tests, wing mirrors of different types to the left and right of the model can be compared on a single run.  One way of seeing this is to inject smoke; sometimes using a ten slot ‘comb’ giving parallel trails to show the flow round an edge – even a small increase in the edge radius can significantly reduce losses.

One expects cooling air to flow through the radiator, past the engine and out under the car.  But in front of the radiator is a cross member on which the front bumper and a noise shield are mounted; if just squared off it could mask half the radiator – it needs to be rounded off at the rear: behind the radiator is the engine, which if too close will cause the air to recirculate, even back through the radiator; shielding round the fan can help.  The engine bay can be tested using a perspex bonnet, and using tufts of wool on chicken wire to show the air flow – often with surprising results.

Acoustic performance (noisiness) is tested in an anechoic wind tunnel with a microphone mounted at the focus of a parabolic dish.  Noise can be generated at the grille, cowl, wipers, A-pillar, antenna, mirrors, B-pillar – anywhere the air can whistle round.  Road noise is minimised by having double isolation – the wheels and drive on damped sub-frames, with different resonant frequencies.  Mr Huntington showed the improvement gained by raising the cowl (at the rear of the bonnet) so that air flow rose above (the parking level of) the wipers and did not go through them.

This led on to window soiling – tested in a rain wind tunnel using a fluorescent dye in the droplets.  He showed how water wiped from the windscreen could run up it between wipes, annoying the driver.  This too was cured by raising the cowl.  Another test showed how an initial mirror design caused an eddy behind it, which threw out droplets onto the side screen at just the area the driver needed to be clear to see the mirror – no good, particularly with muddy droplets - a revised design worked.

Steaming up is tested by putting a steam generator in a car and using the heated screens and air conditioning to see how quickly it is cleared.

Mr Huntington closed with some remarks on car design, saying how fashion could go against economy.  Narrow tires are better than wide ones, low vehicle heights are better than high, and shapes seldom have as good a drag coefficient as they could – 0.3 is good nowadays, though lower figures can be obtained.

Thames Defences,  16^th May 2008 

In telling us about the defence of the Thames Estuary from flooding, Ms Hill, of the Environment Agency (EA), said she would give us the facts behind the fiction pedalled by the media.  The film “The Flood” showed a 4m tsunami overwhelming London – the Thames estuary could not propagate such a wave, instead it would spread out and flood large areas of Kent and Essex.  However, later scenes in the film, showing the flood level if the Thames defences were breached, had been made in consultation with EA and were correct.  (After the film more visitors came to the Barrier.)

The Thames has flooded in the past, roughly once per generation, notably in 1009, 1236, 1663 (recorded by Pepys), 1928, and 1953 - just not often enough for there to be much awareness.  Ms Hill showed a photograph of the river wall by the Trinity Alms Houses, constructed nicely in brick in 1879, raised later in the century, then again in 1928, and again (with concrete) in 1953.  A 1976 surge did not overtop it.  In 1983 the Barrier was built at Charlton, with an expected 50 year life, and studies virtually stopped.  Flood warning sirens disappeared, as did several flood gates.

However, since the 1990s the EA has been working to understand the Estuary, producing a draft Flood Risk Management Plan in 2000, to be followed by a policy for government appraisal in April 2009, and finalisation in January 2010.  Their remit is from Teddington to Shoeburyness-Sheerness, with 300 km of walls and embankments.  The barrier was closed for the 100^th time in March this year and another nine times since.  There are several other gates downstream, for instance at the Rivers Lee, Roding and Darent, which have to be operated in concert with the Barrier.

The Thames Estuary 2100 project is to produce a Plan for the next 100 years.  SE England is sinking at about 2mm per year, as Scotland is rising after the loss of the weight of ice during the last ice age.  The global high tide level is rising, currently at a similar rate.  There are changes too in the estuary, with more people living there – there are 24 000 properties in Thamesmead, the lowest 6m below high tide; coastal squeeze is causing a loss of mud flats and salt marsh – there is a legal requirement to replace such habitats.  Present defences were to give protection to a once-in-1000 year event up to 2030 (though overly pessimistic forecasts mean they should last longer).  There are three basic threats, which could coincide:     Mean Sea Level Rise;      North Sea Surges;       Increased River Flow (Rainfall up river).

She postulated a level of acceptable (if undefined) risk, to the flooding of property - or services that others on higher ground depend on, such as an electricity supply (even water is electrically pumped), hospitals etc.  Doing nothing would soon give an unacceptable risk; a grand gesture such as a Shoeburyness-Sheerness barrage would not be worth the cost, effort or environmental upheaval for many decades.  A planned series of relatively small interventions should suffice.  A 1.5m increase in barrier protection is possible with over-rotation.  The Barrier is only operated at low tide, minimising mechanical stress; when up it lowers the upstream peak level by 1.5m.