Coffee Cups, a Cauldron and Containers

Gavin Turk told  a newspaper [sadly, behind a pay wall] about a day in his life. He was one of the original Young British Artists and is a busy man employing several people. We learned about some of his past work. There were the 1000, signed sheets of paper each just marked with a ring from a cup of tea. Then there were the bronze casts of bite-marked, polystyrene cups painted to look real. He also took a single bite out of lots of Rich Tea biscuits (because, he said, of his interest in ideas about identity and how he could manipulate his image and name) signed each one and then sold them for £25 each.

The Lad looked up at the very moment after reading this piece. A shipping container on a lorry passed by the window.

Arbitrary Container
Engineers designed Containers like this one.

The conception, design and value of the container were different to Turk’s works. The concept and design of the container has transformed international commerce. That transformation, without exaggeration, is equal to the change from the stagecoach to the High Speed Train. That has changed the World. If you want to discover more about how it happened there is a very readable book. It is called “The Box. How the Shipping Container Made the World Smaller and the World Economy Bigger”. It is a marvellous story of how Containers did for shipping what computing did for engineering. Astonishingly there are no illustrations at all and only one simple graphic in the book and that is a line diagram on the title page.

One of the pleasures of the engineer’s tasks is the justified satisfaction in plucking out of her mind a design to do something and turning into a new object. True, the engineer is kin to the artist in that most artists also have a similar satisfaction in a task well done; that is of making something in their case mostly to give pleasure to the onlooker or to achieve a particular effect in their mind. It must be emphasised that there are occasions though when high artistry is vital. Even when it is not vital, it can still, combined with the right product or structure, add immeasurably to its quality. Few engineers can provide both qualities.

For the later, take the Olympic cauldron for London 2012 Games designed by Thomas Heatherwick. The concept needed an artistic intelligence of the highest order. It got it. Superb: there is no other word for it. First the artistic vision of many, separate petals: one for each of the countries taking part. Then the vision brought them together to become one cauldron. The engineering design then kicked in. It had to design the burners to produce the right flame picture; the fitting of the petals and the gas supply: the mechanism to raise them elegantly in synchrony into the air; to stand rigidly together in the stadium environment. A magnificent, dramatic blend of art and design.

Then there was the container that passed The Lad. Such ubiquity in modern life! Yet there is good engineering in this. You may argue that there is no artistry in the design of the shipping container. Even if you argue that fitness for purpose or form following function cannot be classed as such there is certainly intense creativity in its design. Then there are engineering drawings which have no artistic flourishes and are stripped down to the barest essentials to define any component or assembly of components. Nonetheless as an engineer The Lad finds in it, not surprisingly perhaps, a spare beauty. This is the General Assembly of a Shipping Container.

Standard Container example
An engineering assignment. "Design a Container"

 

One website sketched it as

  • 20′ ISO shipping container, new
  • All listed shipping container types have a double door on one end which can be opened completely.
  • Walls made of corrugated steel sheets, profiled steel frames, wooden floor on steel cross members
  • certified by Germanischer Lloyd
  • steel plates made of Corten steel (anti corrosive)
  • forged and galvanised door locking bars

There is a Technical Specification here

The heart of the design, however in the view of The Lad, lies with the corner fittings. They are not complex: they could even be called magnificently simple. They are the components that allow each container to be picked up and also to be firmly attached to the transporter or another container above or below itself. This is a drawing of one .

The heart and core of the Container's design

Not all clever pieces of engineering are complicated. Some are quite simple. You will see that there are a number of holes or piercings in the corner fitting which are not circular. Each corner fitting is multiply connected as the mathematicians would put it. That combined with their need for some reliable strength makes their manufacture worth considerable thought. How would you make them? Machine them from solid? Or forge them? Stamp them? Weld them?

There is a good video talking of corner fitting features here by Tandemloc.

There is a hair-raising video showing the problems that the engineer seeks to design against here. Such a problem though is one of the invariants in any engineering design. Engineers load up a piece of the real world and any failures will have real consequences. Some of those consequences will be serious. Uncontrolled release of forces in the real world can have explosive effects; leading them to exert large effects somewhere undesirable – usually nearby. Such a risk is the shadow under which the professional engineer labours: it is for what she or he is paid. Every person in the world every hour of the day has to trust that they are successful.

Note that container corner fittings are actually cast and the cast components are then welded into the Container structure. Consider why this is so.

By the way, apparently, the Gavin Turk, Rich Tea biscuits are now priced at £108 on the Turk website. He does have insight about this though by saying that people would wonder why they should pay. The Turk response though clears that up because that’s what “I liked about it.” No doubt.

Does Gavin Turk find fulfilment in his daily work? Is he delighted (or at least, at the end of the day, reasonably satisfied) with having achieved something? More likely, he is punching the air at having discovered how gullible some people are. He must be having a larff (all the way to the bank).

 

Engineering is one of the three drivers advancing the human race. This blog describes real professional engineering as it is in the real world. It is not well served by the current media. An engineer is posting: not a ‘scientist’. Its target is the career seeker and also the general public.

 

Super Puma Down III

Cracks and Cleanliness

The metallurgist calculated that the markings in the crack had been advancing for between 36 and 100 flying hours before failure. He found this from the marks [behaving almost like tree rings] on the fracture surface. If he could have looked at the fracture on the other piece of the gear [never found], he may have found that more than 100 flying hours could have elapsed.

So, it looks like it was a problem internal to the material of the planet gear that caused it to break up. Rather, that is, than damage introduced externally to the component or outside the mechanism.

What materials does an engineer work with? With what does he design structures? Nowadays, it is most frequently with metals. On some occasions though, he may need to specify a natural material like wood [such as a building structure of internals] or a non-metallic [like fabric for the O2 Arena roof or carbon fibre or plastics for racing car bodies]. For this post however, we will confine ourselves to considering metals.

What is it that is important about metals? Most often it is the raw strength of the material; how great the force is that is required permanently to deform it. Once permanent deformation starts to happen in a component from overload; then we do not know where it will stop. The engineer wants to avoid that. However, there are other strength aspects of metals that may, in certain tasks, trump raw strength such as fatigue strength, creep or toughness. Some metal alloys can be said to specialise in these different capabilities.

A very frequent cause of engineering failures in aircraft is fatigue. That is a failure caused by the repeated application of a stress that is smaller than the ultimate stress that will break a component with a single application. Fatigue is, by definition progressive and usually releases small pieces of metal before final failure. A failure of this type is one of which helicopter designers are extremely wary. It is compressive failure in the bearing race under the balls or rollers, called spalling. It is mainly for such chips that the magnetic chip detectors are seeking.

It helps to understand how to choose a suitable material for a design if we allow ourselves a little over-simplification. For an engineering material, just as for a recipe for something to eat, there are certain defined ingredients and a definition of how they are prepared and treated [cooked?]. For the engineer and metallurgist their chosen material is defined by two aspects. There are the ingredients which are chemical elements [mostly metals but not always]. Then there is the preparation sometimes flattening, [not unlike rolling the pastry for food] or shaping or cutting, and, usually, some form of heating and cooling.

Every material that we use can be had in different grades starting from some form of the raw and passing on up to some form of the extremely pure or refined. From the former to the latter the cost invariably increases. This is not unusual. It is true for a range of fabrics passing from coarse, denim for a pair of jeans to fine silk for a shirt. So it is for metals used in engineering from pig iron to single crystal, nickel alloy for a turbine blade. Such a turbine blade can easily be rated, in terms of the skill with which it is made and its value, as the equivalent of a Fabergé Egg.

Although most workaday components are not made from pig iron; they are at least from mild steel which is. In somewhat simplified terms, iron that had been melted together [alloyed] with around 0.2 % carbon. Most metals however include several components; frequently ten or more. Each has to be carefully controlled; present in the right amount. In the old phrase, to be not too little and not too much. Such alloying components have an important effect on the properties of materials. As we said above, usually it is strength that the engineer looks for but she may be seeking other things such as corrosion resistance or even electrical properties.

These, then, are the materials. What about their preparation?

As we have seen, metal alloys are complex assemblies of crystals. The properties of even a given alloy composition may vary depending on exactly how, on a microscopic scale, the components are arranged. Heating in an oven and cooling carefully is a frequent method for arranging the components of an alloy to provide the grade of strength that the designer decides is necessary.

Another aspect of the preparation is to ensure sufficient cleanliness. The raw materials in the form of ores or scrap often contain traces of other elements or compounds of carbon as impurities. These, after melting, may gather at the crystal boundaries. They may also gather in slightly larger quantities where they force crystals a little apart and are called inclusions. Both will be a weakness or stress concentration. For most components this is only a theoretical weakness. The weakening will either be small or extra material may be designed in.

However, this is cannot be done for some other components that are under greater stresses or where the consequences of failure are too great. For these there is no space for extra material or stress concentrations cannot be allowed to encourage fatigue failure. Aircraft components frequently fall into this category and thus do Main Gear Box planet gears. Because of this, the engineer needs materials that have vanishingly small numbers of inclusions and oxides in the material that she specifies. Clearly, good housekeeping in the production process is essential. But there is one powerful process by which material can be cleaned up. This process is actually two and together they go by the dodgy acronym of VIM/VAR, which stands for Vacuum Induction Melting and Vacuum Arc Re-melting. Good technical data can be found at http://www.cartech.com/productliterature.aspx?id=1246.

Both processes ensure that whilst ever the steel is molten, it is under vacuum to ensure that gases in the atmosphere do not help form brittle compounds that would get mixed in. The feed stock for the VIM part is melted by electrical Induction from coils wrapped around a crucible. It. The end product of this VIM part is a precisely correct alloy composition and also ingots that are of the right size and shape for the next process. The VIM furnace looks like the following.

vim furnace from Timet.com
Vacuum Induction Melting furnace timet.com

 

However, another important feature of high integrity materials is the small size of the crystals. Normal heat treatment can, if it is extended over too long a time, make crystals grow. If we treat the alloy in such a way as to make the crystals small or ‘refined’, the denser network of grain boundaries makes it stronger. The VAR part does just this.

Here the electrodes that come from the VIM process are again melted in the vacuum, but this time by an electric arc. A diagram of such a furnace is shown below. That is, though, not the clever bit. The secret of making small crystals comes from the way that the newly molten pool of alloy is made to re-freeze or solidify. This can be summarised as “very carefully”. The electrode insertion in the crucible; the rate at which it is withdrawn; the electric current supplied; the rate of cooling water flow; and more; will all be controlled simultaneously. This control will ensure, firstly, that the crystals are carefully formed at the right temperature and, secondly with careful cooling, they will then be frozen at a suitable size without being allowed to grow too large.

schematic simple VAR furnace
Vacuum Arc Re-melting furnace

 

The end product is an extremely expensive material that has a micro-structure that is so fine, clean and refined that, compared to a batch of the same alloy before treatment, it is a Premier League football pitch compared to a farm meadow.

The material of the Super Puma planet gear as designed was marketed as a material that could be VAR treated or not. If it had been then there should have been no inclusions or oxides to cause a crack. Is this a case where, despite the best efforts, some unpleasant defect still slipped through? The forensic examination of the gear said that the material composition was correct but does not explicitly say that the treatment had been checked. Could it be that this one component had been made from the correct material but which had not had, as the manufacturer’s specification allows, the VAR treatment? http://www.tatasteeleurope.com/file_source/StaticFiles/Business%20Units/Engineering%20steels/16NCD13.PDF

There might be a case for reviewing the design of the planet gear. It is currently one piece doing two jobs; the inner part is a bearing race and the outer part is the gear. As we saw a crack passed from the bearing part and into the gear part and cracked the component asunder. There could be a case, it seems at first sight, to try and squeeze a separate gear shrunk onto a bearing race into the admittedly small space available. Thus the interface between the two would act as a crack stop avoiding this type of failure.

The time that the crack took to propagate to failure whilst only one chip was detected reminds us that although in-service inspection methods must be robust, they must also be sufficiently sensitive. They must detect the deterioration of a critical component before the ability of the component to carry its design load is compromised. In this sad case, those methods did not. A major plank of a safety case is that any damaged material is released from the outside of the components. In this accident, almost certainly, the fatigue failure began and progressed until the last minutes or seconds entirely within the planet gear. Thus it was contained under its surface and away from the oil flow.

All in-service inspection methods must be such that they can always be relied upon to provide advance notice of problems. The other way lies instant catastrophe.

The engineer designers always have to be eternally vigilant about the giant forces that they harness. Those forces allow us to speed about our business. But if they escape their bounds then they revert, in an instant, to savage cruelty and destruction. So it was at six minutes to one o’clock on April 1st 2009 when the drive exploded and the uncontrolled power flung the men on G-REDL from the heights to the depths in less than a minute.

References

Much of the interpretation and all of the engineering background in these three posts are the responsibility of Isambard’s Lad. Most of the facts and all but three of the images come from the Report on the accident to Aerospatiale (Eurocopter) AS332 L2 Super Puma published by the Air Accident Investigation Branch, Department of Transport, UK. http://www.aaib.gov.uk/sites/aaib/publications/formal_reports/2_2011_g_redl.cfm

Engineers’ responsibility

Engineering is one of the three drivers in the advancement of the human race. This blog aims to give to career seekers and also to the general public a taste of how this might be so. They are not well served by the current media. It is an engineer posting: not a ‘scientist’. It describes real professional engineering as it is in the real world usually in the present and occasionally as it was in the recent past.

For comment on this post use the ‘Leave a comment’ link below. For general comment on the blog, contact us at isambardslad@isambardkingdom.com .

Super Puma Down – II

CSI Metallurgy

 

So! There were chip detectors fitted and working on that day, 1st April 2009, in the gearboxes of the Super Puma G-REDL. How was it then that they had given virtually no warning that the main gearbox was a time bomb that was about to explode at any minute?

Mike M, in the business, told the Lad that a helicopter was mostly a flying collection of gearboxes. The passenger cabin is not much more than an appendage bolted to the engines and the mechanisms.

Gearbox and speeds
This shows the gears to the Main Rotor

 

For most engineering, structural failures, the earliest symptom is a crack. It, mostly, begins to open at the surface of a component. It extends, speedily or slowly, into the interior of the piece, some pieces [chips] breaking away as it does so. Final failure occurs when the crack makes the component unable to carry out its function. has not got enough sound material in its cross-section that is not cracked to cohere under tensile stresses. There is another type of failure that is particularly relevant to a helicopter. Underneath a rapidly rotating ball or roller in a bearing track [race], pieces of the track can begin to crumble away. This does not often proceed to fracture of a race as it is due to compressive stresses. These tend to keep the part pushed together rather than as tensile stresses tend to pull the component apart

The AAIB report tells us, in summary.

One chip had been found on one of the detectors some days before. The mechanics consulted the manual as to what should be done. They thought that it was just a piece of scale. They spoke to the manufacturer’s engineers by phone and email. At each end of this communication channel there misunderstandings as to what had been found, what had been done, had not been done and what should be done. The upshot was, terribly, nothing further was done because no significance was attributed to the ‘piece of scale’ In fact it was bearing steel – of dreadful import. 

In the middle of the last flight, one of the eight planet gears abruptly shattered into massive fragments.

One fragment was over-run by the next planet gear. If it had been the size of a matchstick, a piece of metal would, at the speed of this gearbox, have been crushed, passed through and flung out. There would have been some damage to the gear teeth but no more. This fragment however was of an awful, irresistible size. In the subsequent examination of the wreckage it was never found but everything else was. The size of the gap of its absence tells us in itself a grim story. It would have been a hellish boulder the size of a man’s fist: quite uncrushable. It burst through the strong metal shell of the gearbox outer case, splitting it like an over-ripe tomato with a shattering explosion.

The crew saw the emergency, on-screen warning of the catastrophic fall in oil pressure to almost zero. Two seconds later the craft ceased to respond to any flight controls. The grip of the gearbox on the main rotor was broken. The helicopter rolled and yawed and pitched as though it were a paper windmill in the hand of a child. Twenty seconds later the rotor lifted – free – away from the fuselage; it tilted and then hacked and severed the helicopter tail and its control rotor. The rotor then spiralled away into the air; freed from the burden of the fuselage. What was now left, the cabin and engines together, streamlined like an egg: plunged uncontrollably towards the sea far below, carrying the desolate passengers and crew.

As there had been only one chip found in the oil system, how did the failure start and progress without many more? Call in the metallurgists.

The metallurgists are the brothers in arms of the engineers. Tony T told The Lad that he had the best job in the world, as a failure metallurgist in an engineering organisation with an international reach. He travelled widely to study forensically a variety of failures. Luckily, none of his problems involved loss of life but even if they had, perhaps he would have helped with an understanding as a kind of memorial. If the study of metals appeals to you, go for metallurgy.

Metals are complex structures when you look at them with a microscope. Most people imagine, if asked, that even at that level metal is smooth like a bar of chocolate is smooth. Far from it. Solid metals are crystalline. In a crystal, the overwhelming numbers of atoms are lined up neatly in rows, sheets or repeating patterns. Tiny examples of crystals of this sort are sugar and salt. However a piece of metal is not one single crystal. It is almost always made up of millions of tiny crystals jammed together and each adhering to its neighbours.

Why is this? When the metal is molten, every atom is rushing madly about in all directions. As it cools, pairs of atoms begin to adhere to each other in millions of places, called nuclei. Then other atoms arrive and stick to the first two but only in a neat, repeating array. Imagine 4 footballs: three touching each other to form a triangular pattern and the fourth sitting on top and in the middle of the triangle below.. Such an arrangement could extend as far as you like if you have enough footballs. As the atomic pattern grows, forming a crystal, it continues until it hits another nearby. This is happening in all the nuclei but in a direction depending on the orientation of the first pair of atoms. Each crystal array is at a different angle to that of its neighbour. Thus as the metal cools, each of the millions of atoms in a single crystal is rushing to slip into its place in the pattern. Until, thud, – thud, – thud – and every crystal is jammed up against its neighbours and the whole mass jerks into a solid, rigid mass of thousands and millions of crystals.

In recent, two or three decades some special components such as aero-engine gas turbine blades have each been made of a single crystal. But this can be done only with enormous difficulty, technical cleverness and great expense that are not justified for any other components.

In addition to the conventional processes that are equivalent to standard police work or ‘boots on the ground’ Lots of cutting, polishing and etching with acid to show the structure under the microscope.

Then they zoomed in on the critical areas. The materials engineer has an army or techniques and instruments to study his materials??? Because of the critical importance of the investigation of this accident, she brought to bear some of the Special Forces of the army. There was conventional optical microscopy but also 3D surface optical mapping, 3D X-ray tomography, high resolution Field Emission Scanning Electron Microscopy, and (FESEM) Transmission Electron Microscopy, TEM.

The pictures below show the view, like a geologist overflying a mountain range, of the fracture surface that they had to study to tease out answers.

 

Raw fracture
This is the metallurgist's first sight through a microscope at low magnification
Fracture with areas defined
After a lot of close examination, the metallurgist decides that these areas of the fracture had different causes

 

One of the significant, engineering features of the planet gears is that the bearing track or race and the gear teeth are all in one piece. As we have said before, most of the stresses caused by the bearing rollers are mainly compressive and tending to close any cracks; but here’s the rub, with the integral gear teeth much of the stress field produced is tensile and crack opening. The result with the two fields is that in this double function component, once a crack has crept beyond the race stresses, it enters the gear, tensile stress region opening and, perhaps accelerating. It can eventually pass through the whole gear pinion and break it into pieces.

The morphology [the shape] of the fatigue crack in the second stage planet gear, 13. suggested that it had initiated from a point at or close to the surface of a highly loaded section of the bearing outer race,

The following pictures show a 3D view of their conclusions.

3D image for crack origin
The metallurgist, after much work, was able to calculate the origin of the crack.

 

Ultimately, this suggests to The Lad that the failure and any chips began, if not entirely internally, then at least, within the compressed area of the gear pinion material body. The result? Nothing – no crack – broke the surface to provide chips until the fracture was almost complete and only minutes away from catastrophe.

What can we do about this problem, this type of behaviour? Let’s look at this in the next post.

Engineers’ responsibility

Engineering is one of the three drivers in the advancement of the human race. This blog aims to give to career seekers and also to the general public a taste of how this might be so. They are not well served by the current media. It is an engineer posting: not a ‘scientist’. It describes real professional engineering as it is in the real world usually in the present and occasionally as it was in the recent past.

Super Puma Down – I

Without Warning?

It was April 1st 2009 and the Eurocopter Super Puma L2 helicopter was expecting to land at Aberdeen at 1314 hrs. This was still 20 minutes away but, at the 2000 feet cruising altitude, the coast landfall 10 miles away was just in sight.

Super Puma
The crashed helicopter was one like this

It was about half way through its busy schedule to and from the rigs that day, flying at nearly full speed with a full complement of 2 pilots and 14 passengers. The co-pilot radioed base that all was normal. Only twelve seconds later came two MAYDAY calls

Below, was a modern, powerful, rig supply ship, the ‘Normand Aurora’, on a so-far uneventful trip. Someone on watch on the bridge changed all that. It was good visibility and there was a shocked shout of alarm. Two miles away, the helicopter was hurtling into the sea with separated rotor following it. Then came the bangs, the black smoke and the explosion. The ship swung towards the smoke.

Normand Aurora
Normand Aurora was the nearest ship to the crash site and rushed to the rescue.

 

Launching their fast,-rescue inflatable. It hit the water with a loud slap and accelerated away. Leaving the mother ship quickly far behind as its helmsman gripped the steering wheel with white knuckles and stiff-armed the throttle fully forward. He and his crew were desperate with hope that there would be something that they would be able to do: that there would be someone that they could help among the unfortunates in the helicopter cabin that had plummeted into the sea at high speed. But fearful at the same time. After the headlong two miles, its crew found a large circle of churning water. Within there were life rafts and debris. They also saw eight people; none were alive.

Epicyclic Gears

Planet gears recovered
Recovered from the sea bottom. Note the missing pinion at four o'clock.

 

Above are planet gears from the downed helicopter showing corrosion from their immersion in the sea. They are without an outer casing destroyed in the accident. There should be eight gears but it can be seen that one is missing. The destruction of the one, missing planet gear was the cause of the tragedy. Above shows only a part of the gear boxes and trains in the Super Puma [and other similar helicopters].

Had there been no advance warning of the impending catastrophe at all?

The drive shaft from each of the two engines in the helicopter runs at 23 000rpm [that is, the internals of each engine is rotating 380 times in one second or around 5 times as fast as a family car engine!]. The main rotor blades rotate at 265rpm. This means that the helicopter design engineer had to design a gear box to give a reduction of nearly a factor of 100. It has to fit in as small space and have as low a weight as possible.

When the designer needs to slow down the rate of rotation of a shaft by a large amount like this, she usually goes for an epicyclic gear design. These are commonly known as a sun and planet gear sets. This is what is found in a Super Puma between the fast spinning engines the relatively slowly rotating main rotor.

This epicyclic design was shown in the textbooks of The Lad like this, and similar diagrams are still shown today.

Textbook diagram
The textbook version is rather lightweight compared to the real thing.

 

In real life where very large power has to be transmitted in as small a space as possible, there are more planet gears than in the textbook diagram. They fill the circumference and each is wide and massive. Such planets of half of the Super Puma epicyclic gear train are shown in the salvage photograph above.

To see how designers calculate the variables in a real design of epicyclic gears see – http://www.roymech.co.uk/Useful_Tables/Drive/Epi_cyclic_gears.html

Magnetic Chip Detectors

Even though the designers seek to make engines and gearboxes as reliable and free from the risk of components failing as possible there is still a need to keep a check on machinery health. For a Power Station generator or a car engine there is no great, inherent problem to be anticipated if it rapidly comes to a halt after 30 sec of noisy running. It is quite a different problem if the engine is powering an aircraft flying several miles high over the ocean. Here a significant risk of such a sudden stop is not acceptable. They must head off such failures before they happen. They must search for signs of any problems well in advance.

The magnetic chip detector is one of the neat ideas that help maintenance teams do this. It is a simple concept. Many of the most highly stressed components are made of steel which is magnetic. One of the commonest symptoms of failure, when such a component wears or suffers fatigue cracking, is that chips of metal are generated and released from the parent component. The oil, as it is circulated throughout the engine, washes such chips away and usually takes it to the lowest part of the engine. En route, if it washes over a single small magnet, it will be captured by the magnet. The maintenance team simply unscrew the magnets at regular intervals and an early alarm can be raised if any chips are found sticking to the magnet.

Such detectors are positioned at various places within the engine oil flow where any chips may be washed over them. An alternative design is to provide twin magnets close together. Coupled to this type of device is a power supply and electronic detector to signal to the helicopter pilots, even in flight, when a chip bridges the two magnets. Such a design is shown below.

Chip detector
This is the operating principle of the more capable design that can provide a signal in flight

 

There are many such detectors designed into the Super Puma. Several are in the vicinity of the main gear box. The design of such detectors is another one of the many examples of the nexus where the design principle of “simple and reliable” approaches close to the principle of “too crude for the risk burden”. The designer has to consider which is the truth in every such case. Did the detectors work this time or not? If not, why not? See the next post.

Memento Mori

Engineering turns the forces to the benefit of mankind and the results have immense consequences. These consequences are, on the whole, beneficial but sadly, as with any efforts of the human race, for some individuals can be malign.

Bloody skirmishes to understand each way that a structure can fail and to avoid them all are a repetitive feature in engineering history. For ordinary structures most of the skirmishes have been avoided and, nowadays, fewer new ones appear. But fresh demons occasionally burst forth to confound us in new campaigns to complete new tasks or use new materials. When they do, they extract their price in blood or treasure.

Professional engineers have to be continually alert. The engineer knows that the nature of her or his work usually brings great benefit. But it can, also on occasion, bring tragedy.

So it was with G-REDL on 1st April 2009.

RIP deceased

Engineers’ responsibility

Engineering is one of the three drivers in the advancement of the human race. This blog aims to give to career seekers and also to the general public a taste of how this might be so. They are not well served by the current media. It is an engineer posting: not a ‘scientist’. It describes real professional engineering as it is in the real world usually in the present and occasionally as it was in the recent past.

Some machines swim

One, unseen, already-submerged diver was filming near to a hole in the thick ice sheet above: as the elegant cylinder dropped vertically at high speed through the still, -1°C, water below. Immediately, as though alive, the vehicle swung gracefully into level flight towing a tail of yellow cable behind it. Ministering to and checking on the machine on this, one of its early test swims, was a black-clad, scuba diver.

The Lad was transfixed by the magic sight in the vast under seascape of a thousand shades of blue and green. The voyager looked as though it had been born there instead of being designed by human beings. Tell-tale features, though, were the lights: a white searchlight beam for a camera and a pair of scarlet, laser beams lancing through the gin-clear water from each side of the nose of the vehicle. Another was the complex internal structure clearly visible with, not the fluent curves of a living body, but the lineaments of straight lines and exact circles of a densely packed machine. It was about 2m long and 20 cm in diameter.

It was the 30 November 2011 and “The Frozen Planet” Part 6, ‘The Last Frontier’ on BBC Television that was the unexpected carrier of the strikingly beautiful images of this example of the art of the engineer.

Then the vehicle darted straight ahead at least twice its previous speed into a corridor among the irregular blocks of the ice pack above. It gave an impression of a shark but without any sweep of a muscular tail but with a rapidly accelerated spin of a propeller.

The Lad was captivated and vowed to find out more of this masterpiece. A search only just begun and the results will be reported here. This machine seemed to The Lad to encapsulate what engineers do.

Engineering is one of the three drivers in the advancement of the human race. This blog aims to give to career seekers and also to the general public a taste of how this might be so. They are not well served by the current media. It is an engineer posting: not a ‘scientist’. It describes real professional engineering as it is in the real world usually in the present and occasionally as it was in the recent past.

UK enters Swedish Turf

The Queen Elizabeth Prize for Engineering” certainly has a ring to it.

The Lad is glad to see the announcement of a big new prize devoted to Engineering excellence. Its aspiration to be equivalent to a Nobel Prize by being open to engineers across the globe shows admirable boldness and determination. http://www.raeng.org.uk/prizes/qeprize/default.htm http://www.bbc.co.uk/news/science-environment-15778326

Was it a problem The Lad wonders, that this global reach made it more or less difficult to raise the money from the financial backers in the engineering industry . Depends if they have a global presence themselves, he supposes. The website says they are BAE Systems, BG Group, BP, GlaxoSmithKline, Jaguar Land Rover, National Grid, Shell, Siemens, Sony, Tata Consultancy Services and Tata Steel Europe. That’s seven UK or UK based companies and four non-UK based companies.

A group of the great and the good have so far have been appointed to be Trustees to manage the endowment fund and thus deliver the Prize. The Lad is reluctant to venture into the political [with a small ‘p’] snake pit but he thought it worth having a quick look from an idiosyncratic standpoint at their engineering antecedents.  They are

Lord Browne of Madingley [Chairman of the Trustees] who seems to have started as a Physics graduate and a BP apprentice forty-four years ago. The plan seems to be that he is there to provide serious gravitas via the enormous chemical and petroleum engineering clout of his BP past.

His fellow trustees are

Sir John Parker, who studied Naval Architecture and Mechanical Engineering at the College of Technology and Queen’s University, Belfast and began as a member of a shipbuilding design team forty-seven years ago. He is chosen as, presumably, the nearest they knew in the London network to an engineering creative;

Sir Paul Nurse is a geneticist [geneticist!?] and cell biologist and won a Nobel Prize in Physiology or Medicine in 2004 and can only have been chosen to offer, one imagines, judgement on the benchmark to the Nobel standard, and

Mala Gaonkar is a Harvard economics graduate and 1996 MBA presumably will monitor the care of the endowment funds in the maw of the City.

The Government Chief Scientist, Professor Sir John Beddington is a biologist and has accepted an invitation to be an adviser. His is the task of advising the Trustees on how, when required, to screw a response out of the government departments. Sorry! Guess it would be better to say ‘how to press the hot buttons‘.

Anji Hunter, who was an history graduate 23 years ago and sometime advisor and Director of Government Relations to Tony Blair, has been appointed Director of the Prize. Because ‘administrator’ is no sort of term for an engineering outfit, can The Lad suggest that she takes to herself the title of ‘Clerk of the Works’. Now this has a good engineering flavour and a long pedigree. Nay! An ancient pedigree it has; far older than that of ‘Prime Minister’ for example. As a job, it dates back to the reign of Edward the First when such a Clerk was the vital organiser of the building of those mammoth civil engineering feats: the Castles in North Wales around 1285.

A fine group. All the men have lately spent many more long years at the stellar managerial, coal face than at the engineering design scheme. They will appoint a judging panel next year who will include additional members presumably. It will be interesting to see who they turn out to be.

He notes that all, or at least the head office, has not ventured to far from the warmth of Westminster. Carlton House Terrace,SW1, darling!

Well, even if the current staff, sorry – Trustees, do not clearly have ‘engineer‘ running right through them like seaside rock, The Lad wants to give them the benefit of any doubt and wishes them success in making the Prize a glittering success and all engineers proud of them. He will be watching them.

How will the MacRobert Award fare now?

Ignorance, quarrels and the feedback loop

Or people shouting at each other

Some commentators are a constant irritation. The grand panorama of modern media allows any ideology by any believer to be broadcast. This is a complex world and some have little underpinning of demonstrable truth and others have an unwavering fixation upon only one of several alternative world views.

There are those who advocate a particular belief system. Some such are militant proselytisers for religious beliefs. Others are those, finding the world behaving incorrectly, setting out to drive everyone down the ‘correct’, usually narrow, path

Then there are those who are driven less by unwavering urgency and more by a plan to make a comfortable living from the commentating process. They have a facility with words; access to the prints; and no restraint from knowledge of their ignorance. They do like the sound of their own voice and their words in print are, for them, like a nice, warm bath.

These latter, articulate writers are insidious in their effects when they comment on engineering topics. None are engineers and many are politicians. Too often it is here that the irritation develops due to a faulty premise.

Faulty premise.             If some project is not yet completed then it is obvious that it cannot be done or will be too difficult.

This premise is applied widely but has appeared in connection with safe burial of nuclear waste and, more recently, Carbon Capture and Sequestration.

Forsaking the phrase “Let us be clear that….” destroyed by politician when matters are obscure or untrue, let us go for a bald statement instead.

Correct premise.           Engineers create something when it is needed and has some apparent economic basis. If a project does not violate one of the laws of physics or thermodynamics, it can probably be done.

If you ask them in advance, engineers will take the line boldly, and not unreasonably in the evidence of the historical record, that if a project does not violate one of the laws of physics or thermodynamics, it can probably be done.

What is it that inflames this irritation by lathered ideologues or flushed commentators? There is heat when each holds forth in isolation. But it is the process of interaction with each other that increases the din greatly due to the engineering effects of positive feedback and synergy.

Feedback is a widespread and important operation in control engineering. Feedback is the process of measuring changes in a process as it proceeds. There is negative and positive feedback. Negative is changing a process to reduce the measured change. Positive feedback is changing the process to increase the size of the measured change. A problematic feature of positive feedback is that it is frequently unstable sending a process rocketing to some far off regime. Thus it is with the irritating commentators.

There is also synergy which is defined as increased effects produced by combined action. Working together, even if it is in opposition, means that both sides of an argument work each other up to a frenzy.

There is a interesting example roaring away in the field of climate change where all these features can be seen. There are a multitude of websites. Just visit one of each and you will be rapidly flung into many others There is Greenpeace of course at http://www.greenpeace.org/international/en/campaigns/climate-change/science/ for those who discuss how worrying are the changes and what should be done to reduce them. Then there is another, The Global Warming Policy Foundation http://www.thegwpf.org/ , that believes that climate change is not what it appears and that many plans to modify the changes are misbegotten.

Speaking above of Carbon Capture and Sequestration, this is a topic of the next post.

Engineering is one of the three drivers in the advancement of the human race. This blog aims to give to career seekers and also to the general public a taste of how this might be so. They are not well served by the current media. It is an engineer posting: not a ‘scientist’. It describes real professional engineering as it is in the real world usually in the present and occasionally as it was in the recent past.

An Engineer’s must-have

It was years ago when The Lad first reached for the spanner for the usual 3/8 UN nut. It wasn’t there.

“What scruff  [actually, a less repeatable name] has nicked the spanner?”

One of his compatriots had either left it lying around near where he used it last or nicked it for his tool box. In a busy workshop, it cannot be surprising if any tool goes walkabout. It happens even in the best, practical, production engineering school. But then everybody needed to use them so it was worth putting one that you have used back where it came from and everybody else could find it when they needed it. At least that’s what the instructors said – piously.

It was round about that time that The Lad first saw an advert for  tool sets. The big ones with dozens of spanners within a steel tool box that attracted his covetous, young eye. The biggest and most complete ones even had castors as they were too heavy to carry. Have a look at one – product TKU 1014 at http://mdmetric.com/prod/kingdick/products/kd_toolkits.pdf   ,
212 pieces and 67 kg! The Lad supposes that you could call it the secret of the engineer’s inner Nerd. But then who does not have such a secret?

Why so many pieces? Well, if the golden path and self-styled foundation of the modern world – Information Technology – can suffer from legacy systems even in its youth; then so can Engineering, that has been around many times longer. As well, the spanner has several forms for different jobs such as open jaw; socket; ring spanner etc.

The spanner is  important to a mechanic. The screw thread has an ancient lineage and so has the regular shape of a nut or bolt head, most often a hexagon, that is required to manipulate it. Both are still ubiquitous in all engineering structures. The ancient lineage means that in its early days many different standard sizes of nut, bolt or screw were used. A major  problem was that interchangeability of fasteners between manufacturers and machines was impossible.The thing about screw threads is that they are likely to be in use in some machines for decades or even longer. If you want to maintain one of those machines, you need a matching spanner.

It’s not just the diameter of the bolt that allows it to fit in a screw hole. Put simply it’s both the shape, usually a triangle, and also the depth of the spiral groove. The screw or bolt will not even begin to do its job if the bolt diameters match but both these features do not.

After an initial push in the early 19th Century when an accepted range screw thread designs that pairing a nominal screw or bolt diameter with a standard angle and depth of grooves was early seen to be useful subject for agreement between even competitive entrepreneurial engineering firms.   A series developed by the great pioneer, Whitworth, and named after him became widely accepted. Around the same time also very widely used was the BA [British Association] series. This latter series had the advantage that the series went to much smaller diameters of screw which made it suitable for small instrument applications. The United States had its own, non-interchangeable series’s known as the US Standard developed by the engineer, Sellars. For pictures of any of these threads without The Lad infringing any copyright consult any engineering handbook.

It was only after the Second World War in the early 1940’s that further significant strides were made to reduce the still remaining variety of ‘standard’ designs. It was the unprecedented explosion of engineering production during  and supporting the recovery after the war that led to the realisation of the  serious inefficiencies and wasted costs were caused by the lack of an even more widely standardised, and interchangeable system of threads. At this the national engineering bodies of the USA and Canada and the UK  came together to design a more rational series which they called the Unified series. Even this series was still restricted to the Imperial units of measurement. The final stage, to date, was to derive the ISO Metric series based upon the metric unit of length; that is the millimetre in the case of the thread. The Lad says the final stage but that will  be completed only when everyone across the world uses the metric screw series. That’s certainly not easy and indeed he can’t say that it has yet happened. The USA still uses its standard AF [Across Flats] series widely.

The Lad has described a simple outline of the field. There’s a lot more to it of course: many professional engineering designers have to move, for good reasons, into much more detail such as fine and coarse thread series and limits and fits and indeed other more specialised thread forms such as ‘buttress’ and ‘knuckle’. Then of course there are the very different components called power screws……

As engineering is the most powerful and essential tool in the advance of human civilisation across the globe and the management of force is at its core; so the screw thread in its principal task of storing force grew to be and remains vital to most engineering structures and power plants. It is a most subtle adaptation of the wedge whose unknown inventor must be saluted as a genius on a par with Isaac Newton and above Leonardo da Vinci.

 

Engineering Snapshot Header

This post introduces a snapshot of what some engineers work on. You see the header? What is it? If  you cannot guess, see below.

It is the first of a new series of headers aiming to provide a collection of key hole views of her or his engineering world.

Every item that you see in this picture and its position has been defined precisely in many drawings. The definition of each component will be of its material; its dimensions and tolerances; the way that it is manufactured; and how it is protected against its environment. The positions to enable all to fit together will be relative to one or more datums nearby in the picture field or, more likely far away.

There are bolts and valves and electrical connectors and cables and hoses. See the forged support piece: once upon a time long ago it would have been a solid, machined bar or casting. Now it is more carefully stress analysed resulting in a lighter, more efficient design of component. At the right there is a pressed sheet structure that has been coated with sealant and then that itself has been painted over.

Some engineers wrestle with this type of machine. Other engineers create in a different environment. See pictures in the future headers.

Oh yes! What is it? It is part of a car engine compartment. Yes, but what car?

Can You Stand the Engineering Heat?

Large scale engineering projects often have to be designed to withstand thunderous events: sometimes in reality and sometimed figuratively. The engineers of such projects need the technical knowledge, the professionalism and, yes, the courage to master the challenges. The Lad is talking here to those who may be thinking about an engineering career. For some of those it is just these challenging aspects that will appeal to them and perhaps give meaning to their careers. Do you look to having the opportunity to address and master major challenges? Do you?

More details are slowly emerging of a tragedy that is an example of a, thankfully rare, concomitant of such challenges: a real thunderous event. It is that of the Airbus A330-203 flight AF 447 which, on 1st June 2009 in the dead of night during storms over the Atlantic Ocean, vanished with every one of the 228 souls aboard. The aircraft was an example of the most modern and enormously powerful technology in flight.

There is still much to discover about, and to learn from, the cause of the accident. here we can only allude to a small aspect. There have been some suspicions voiced that the cause of the destruction was an operating failure of a small device for measuring the aircraft speed. This device is called a pitot tube.

This is a device that could hardly be simpler. The idea that its malfunction could be such a catastrophe requires a particularly wide-ranging imagination. Either that or an innate engineering wariness; a wariness founded on the possibility that ANYTHING could lead to problems. The operating principles of the pitot tube can be shown by the simple diagram below.

Pitot Tube Operating Principle

” Pitot Tube Operating Principle [Apologies for the very bad image quality. I must get a decent CAD application.].

This simple device is vital to the control of the even the modern aircraft. Indeed it has been so since the days of the earliest airliners. It and the details of its detailed design are part of the hundred thousand design decisions that are made as every large scale project, in this case the airliner, takes shape.

The pitot really is so simple. How does it work? There are two tubes that face forward into the air flow and are supported by part of the aircraft structure, probably the fuselage or the wing. One of them, called B in the diagram has an opening facing directly into the airflow. The air in that tube is driven in by the impact of the plane’s forward speed. Thus the pressure in the  tube is raised and measured by the pressure gauge at its inner end. This you might think is a good measure of the total speed but it is not. Part of that pressure is that of the static atmospheric pressure. This is the pressure which at sea level is measured by a barometer. The static atmospheric pressure varies greatly for an aircraft as it climbs and descends in its flight. This is part of that pressure which is measured by tube B but which is nothing to do with the plane’s speed. So Tube A is tasked with measurement of the static air pressure throughout the flight and whatever the air speed. This it does because it has no opening pointing forward but only one at the side of the tube. The side opening does not see the impact pressure due to the speed but only the static air pressure that acts in all directions. This pressure is measured in Tube A by its own separate gauge and is subtracted form the pressure measured by Tube B. So there we have it: the resultant modified pressure is due solely to the speed. Simples.

But watch that neither tube or opening is affected by storms or icing during the flight. Closure or even change in area of any of the openings by ice build up will entirely destroy the accuracy of the airspeed measurement. This, in turn can then baffle the computer controls of the aircraft. The design engineers would not have wanted this to happen but, nonetheless, this is what is suspected to have happened.

The engineers, metallurgists, chemists, physicists and all the other professions do not work as lonely individuals in the bringing of such a project to fruition. They all work together, struggle and debate on solving known and predicted problems as men and women in teams from one company and with others from other companies over periods of months and sometimes years. Despite this each one person is a professional, responsible for the accuracy of her or his own work. It is here that any decision may prove to be pivotal in subsequent events. The decision may be small,: indeed so small as to go unremarked and not reviewed by the others in the team or by its leaders. It can be successful or it can be fatal. Each engineer must consider frequently as he or she works, if he or she can stand up in a court and answer for this decision as being a reasonable and proper thing to do.

This is where the heat is in the kitchen. Can you stand it?

The end of this flight came when all forward speed had drained away and so, inescapably, the sealed, metal vessel weighing around one hundred and fifty tons and full of over two hundred sentient human beings careened vertically downwards at about ninety miles per hour. After three and a half minutes, its whole structure and its entombed passengers were destroyed as it hit the sea, belly first. Poignantly, the stalled plane had slowly rotated at intervals as it fell till, at the end, it was facing almost back the way it had come.

The French Aviation Regulatory Authority is Bureau d’Enquetes et dAnalyses pour la securite de l’aviation civile, known more simply as BEA. Its latest technical report can be found in English at
http://www.bea.aero/en/enquetes/flight.af.447/info27may2011.en.php

The numbing details above of the horrifying plunge from the stratosphere to the chill depths of the Atlantic Ocean come from that report.

See my posting of “The eternal question: can you answer for it?” on December 9 2010.