Newtown U3A

Discoveries & Inventions                             Group

• Wind turbines
• The Sterling engine
• Solar panels
• The Marshal group
• Articulated locomotives
• Tracing inheritance through genes and mitochondrial DNA
• Homes with passive heating 
• Iron, steel and stainless steel - history and  technology
• Achievements of IK Brunel
• Oceans & Climate

Colin Small started our new year with a slight departure from technology.  He talked about carnivorous plants.  There are more than 600 species, including several in Britain, and the carnivorous habit appears to have arisen independently in various groups of plants.  Capture mechanisms vary, including the rapid trapping mechanism of the Venus Fly Trap, sticky leaves of the butter wort, and the slippery slope down to digestive enzyme soups in pitcher plants.  Insects are the main prey but tropical pitcher plants can grow to the size of a rugby ball and eat mice and other small mammals.
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The December meeting was on the subject of corrosion in the home.  Examples from water systems and other applications were presented to illustrate general, pitting, microbiological, erosion and galvanic corrosion.  Dezincification and stress corrosion cracking were also described.  A case study of corrosion of an outboard motor in South Africa was presented and explained.  Examples of positive corrosion actions included batteries, patina on copper roofs and cathodic protection.
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The meeting on 10th November was a presentation by Ralph on Marshalls of Gainsborough.  This company, started in 1848 making portable and semi-portable steam tractors, traction engines, road rollers, etc.  From 1870 they provided machinery used in the tea plantations of the Indian sub continent.  1n 1887 they produced the 'Rapid Roller' selling 250 a year for at least 20 years.  During the 1st World War they meade gun emplacements, munitions and an early form of tank.  In the 2nd World War they continued to produce and service agricultural equipment together with shells, naval guns and the top secret midget submarine.  In 1945 they began producing Field Marshall tractors and this continued until about 1960.  Ralph also showed a DVD entitled 150 years of Marshalls and the Gainsborough Works' and the group viewed a model of a Marshall traction engine provided by Colin.
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On 3rd October the group met to hear John talk about power generation in conventional power stations. Of particular interest was the recent improvements in control and instrumentation technology that has made power stations safer to operate and more efficient.  The latest generation can produce at about 60% efficiency instead of the older 30 to 40 % .  John described the process , highlighting the technology and problems of the boiler drum, and the improvement of electrical and conductivity probes over the old fashioned visual systems.  Similarly,  electronic governors have replaced mechanical ones.

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On the 8th September the Tech (sic) group met to receive and discuss a talk by Neil Upton on the subject of Perception.

The point was that our brains receive signals from all our senses. These have to be interpreted based on previous knowledge, and then a perception is made.   We do not just "see" or "feel" things.   We make a perception depending on the signals received and the prior knowledge gained from previous perceptions.  Different people can make different perceptions of the same circumstances.   The talk was illustrated by a series of optical illusions on the magic lantern.   Beauty is in the eye of the beholder said Miss Piggy to the frog. 

Neil – described a possible 4^th dimension and the ‘Flatlanders’ who have only 2 dimensions.  Talked about the end of space and expanding universe.  Maths and philosophy envisage multiple dimensions and possibly multiple universes.  This led to discussion on other imponderables including string theory, the star ship Enterprise and time travel.
Colin – discussed some of the inventions that he was involved with.  An inventor thought you could move an object by manipulating weights inside the object.  Colin built a prototype that apparently worked.  Laithwaite and NASA were interested but couldn’t explain the effect so didn’t take it any further.
Ralph – Described the miracle plant moringa oleifera, which has 4 times the calcium and high levels of vitamin C.  The fruit purifies water.  Nottingham Contempary Gallery has several growing in controlled environment using special soil.
John  - has been following the Japanese nuclear incident and wondered whether this should end the nuclear industry.  He felt that what we should do is look again at the design and consider whether some UK ones should be shut down early rather than have lives extended. 
Paula – talked about the idea of keeping all our mobile phones, electric cars, etc plugged in all the time.  When not being used they could feed power back into the grid. 
Alan – is having pv panels fixed to their roof.  12 panels, 250 watt each on a South facing roof, 3kw total. Output will decrease with time to 90% after 10 years and to 80% after 25 years.  On the present feed in tariff and assumed usage this will take 10 years to pay back the investment. Average carbon benefit is 1.3ton/y saved.
Pat – raised the question about individual wind turbines and could they be fitted on domestic roofs.  The general consensus was that this was not feasible and separate masts would be required.
Mike – Showed images of bamboo bikes, originally intended for low cost local consumption in Ghana.  Now becoming an export item with frames costing around $600 and high end racing bikes being sold for up to £3000.  Bicycle wheel rims and motor cycle helmets have also been made from bamboo.
Nick – Was unfortunately absent but wanted to discuss his topic which was:  " I have had numerous e mails on Tesla's secret free energy generation by capturing radiation and producing enough energy to run your home, the patent of which has been suppressed by the energy lobby for 100+ years.  Is this truth or spoof?"   This topic will now have to wait until the next meeting.

STIRLING CYCLE ENGINES.                                                Colin Small

 The idea of using the expansion of air on heating to convert heat into usable power goes back a very long time. The earliest written record is of Hero of Alexandria making small figures move, and remotely opening the temple door, dating from the first century A.D. However, his writings refer to considerably earlier designs.

Much later, in Elizabethan times, hot air rising in the chimney was utilised to drive a fan, which worked a spit for cooking (smoke jack).

A number of systems have been used which drew in a new charge of cold air, expanded it to drive a piston and expel it to the atmosphere, but this is inefficient and noisy.

 Real progress came in the early 19^th century.  A minister of the Church of Scotland named Robert Stirling obtained a patent in 1816 for a closed cycle engine, but the main feature of the patent was the regenerator.

Stirling was honoured by the church for his religious scholarship, but with his brother, an engineer continued to develop his engines, some of which were large, 20 hp or more and some were conversions of existing steam engines.

Robert Stirling’s sons were engineers working on railways in several countries. One of them, Patrick was a well known locomotive designer, responsible for some of the most famous of all time the Great Northern Railway, 8ft singles one of which survives in the National Railway Museum.

 Stirling Engines were considerably more efficient than the contemporary steam engines, but as the best material available for the hot parts was wrought, or cast iron, which had no cooling water on the other side as in a boiler, the cylinders did not last long, and some engines were converted back to steam.

 How does a Stirling engine work?

In its simplest form there are two cylinders, side by side. One cylinder is sealed apart from a passage to the other and has a fire under one end and water or air cooling at the other. Inside is a loose but sealed container (the displacer) which is worked up and down by one of the two cranks. As it does not fit like a piston, there is little resistance.

 When the displacer is at the cold end, the air is at the hot end, and so it expands, increasing its volume and pressure. When the displacer is at the hot end, the air is displaced to the cold end, contracting and reducing the pressure and volume.

 There are no valves, and the second, or power piston, which is fitted like the piston of an internal combustion or steam engine is moved by the changes in volume of the air.  There are two cranks, set at 90 degrees to each other so that when the power piston is rising and turning the crank-shaft, the displacer crank is already moving the air to the cold end for the return stroke. Thus, although not self starting, the engine will continue to run whilst there is sufficient difference in temperature between the two ends.

 OK that’s the theme.  Now  the variations;
There are obviously other systems providing for two pistons to be 90 degrees out of phase and other layouts to provide the same relationship of the cycle.

The Robinson engine works with one crank and two cylinders at right angles.

  Heinrici  and others used one cylinder, with the piston rod for the displacer passing through the centre of the power cylinder and operated from a crank by levers.

 Later Heinrici  used a three throw crank, enabling the engine to operate at higher speed having eliminated the use of levers which tend to distort.

 The versatile Dutch firm of Phillips, well known for electrical equipment entered the scene.   Phillips engines, which were made to drive a generator for field equipment, were built until about 1960, when transistors replaced valves in radios and small batteries could provide all the power necessary for radios in the field. The Phillips engine utilised a rhombic drive to operate the displacer. This is an ingenious piece of geometry, nicely in balance reducing vibration at speed, and silent operation.

 Stirling’s other innovation was the regenerator, which could take a number of forms, but basically passed the air through a matrix of thin plates or gauze between the hot and cold ends, taking up heat in one direction and releasing it on the return. This greatly increases the efficiency of heat transfer. Some engines do not use a displacer at all, but get the same effect with a moving regenerator.

 The Harwell Laboratory produced a frictionless motor utilising a vibrating diaphragm to drive a linear generator. It is used in lighthouses and buoys, being self starting, requiring no maintenance for its lifetime, only changing the gas cylinders after many months.

Harwell’s other contribution was a small valveless water pump operating by using the water surface as a piston by careful tuning.

 NASA have made use of Stirling engines for generation of electricity. Space can be very hot in the sun, and very cold in the shade. A gentleman named Dr. Senft designs the engines professionally, and makes and publishes plans for them as a hobby. (I have made three of them, and they run very well.)

 It is of course now possible to buy executive toy  Stirling engines, some of which will run on the warmth of  ones hand or a cup of coffee.

 About 30 years ago, a paper was read at the Institute of Mechanical Engineers on conversion of surplus steam locomotives to large Stirling machines. However,  they were not taken seriously and were laughed off the stage. This was unfortunate as it was probably a very useful and potentially successful idea.

 Stirling engines have been used successfully in vehicles. In the 1960s, Ford installed a 130 hp engine in a ‘Torino’ car.  It was silent, multi fuel and had better fuel economy than comparable internal combustion engines. A little later General Motors were operating a DAF bus with a similar machine, made in 1971. It used high pressure helium as a working fluid and produced 100 hp at 3000 rpm. The power weight ratio was good, the engine only weighed 171 lbs. Both these engines were very successful, but both firms dropped the project, it is believed due to pressure from the oil companies who objected to the lower fuel consumption.   I don’t believe we have heard the last of this application to transport..

Incidentally at demonstrations, a lecturer from General Motors is reputed to have  regularly run a small Stirling with an electric motor until the hot end was hot enough to light his cigar, whereupon he switched off  and used the residual heat to run it as a generator to light a bulb.  Running in the opposite direction produced condensation (reputedly, but doubtfully, liquid air) on the cylinder and again power to generate electricity until equilibrium was regained.

 So, if one drives a Stirling engine with a motor it can be a very efficient heat pump. Physics labs use them for all very low temperature work, and it appears that they are becoming used for large refrigerated stores, and there is at least a possibility that they will become the domestic refrigerators of the future. The only problem seems to be sealing, also a problem with many model engines.

 Due to their silence of operation they were popular with the makers of Victorian mechanical musical instruments. I once managed to talk the curator of the collection in Birmingham science museum into showing me  the works of their extensive collection.

 Air is not the ideal medium for Stirling engines. Hydrogen or helium are more mobile, and better conductors and so work better. Unfortunately they cost more and are not so readily available. The system also works better if the gas is pressurised. Ideally the whole engine needs pressurisation, in order to increase the capacity of a given volume to absorb heat. A closed crank case is necessary and a pressurising pump, so it is usually dispensed with.

 Old Heinrici engines often had a non return valve fitted so that one side of the engine was pressurised, but I find that it gives very irregular running except under load.

 My own involvement with hot air  engines originated in childhood, when a lad in the village where we lived, had one of the toy hot air engines then available. I was fascinated, but of course, had no idea how it worked. Thirty years later, when I was working in Nigeria, a KYKO  fan was sold with the effects of an old officer who had died. I was outbid by a local man who appeared to have money to burn.     30/-… it seems ridiculous now!.

In the early 1970s, I found a plan for one built by Edgar Westbury   in the 1930s, to the rough design of an earlier (1890) prototype for operating a small compressor for a domestic petrol-air lighting plant. I built one from junk and was hooked. I have since built 8 and restored 6 old ones. These, I demonstrated at exhibitions and traction engine rallies, eventually tiring of having to give numerous lectures on how they worked. I also normally found myself closely surrounded by numerous noisy oil engines

 An acquaintance of mine, living near Clun, came to me with a proposal to provide a radio operating from a Stirling engine made from a bean tin with a beer can displacer. I declined to take the job on, but someone else made him one using a small motor as a generator and a small radio which worked very well.  His idea is to provide the plans so that African villagers could make their own !  I was however proved wrong that the project was impossible, although the Third World proposal is not likely to take off. ( I should be very surprised if the fan I failed to buy lasted more than a month in “bush conditions”)

Hot air fans are still made commercially in India, where they have a reputation for being efficient at distributing cool paraffin fumes!  

The inventions and Discoveries Group held their july meeting on the 8^th July and the subject was

                                         False teeth  By  Pat Small

Pat gave an interesting, informative and amusing presentation on the history of false teeth from the Egyptians, through the Etruscans who perfected a form of bridging with gold wire, some fascinating hinged and spring assisted dentures which must have been exceedingly uncomfortable to wear, vulcanite rubber introduced in the 19^th century, to the acrylic resins and plastics of today. The teeth have been represented by wood, ivory,  bone, recycled teeth and porcelain. The practice of dentistry is relatively recent. Extractions were undertaken by all and sundry and without anaesthetics, they used to have a second person to hold down the victim.

In the 18^th and 19^th centuries false teeth were used to improve your appearance and improve your speech but were generally removed for eating. The most famous set of dentures, using Hippotomus tooth, were those used by George Washington, which are in Washington museum. He must have a serious reason to wear something so atrociously uncomfortable

 Thank you, Pat.

A meeting was held on 6^th May at Mike and Paula’s house

We had a lively meeting with 2 potential new members. With apologies from Colin Small, we were seven. We commenced by introducing ourselves to each other.

The main part of the proceedings was a presentation by Mike Davies on “gas and oil production”.

From geological anticlines and faults and historical beginnings, through drill rigs and production platforms on land and in deep sea water, to tar sands with its vast costs in money, energy for production and pollution, the vast subject was covered with lucidity and thoroughness compressed into 40 mins or so. On the way we were informed of the problems encountered, especially the recent BP blow out and looked to the future with its new techniques and the limits in the known crude reserves. Plenty of discussion and questions followed, especially on ‘Peak oil’ and our need to reduce consumption.

 Thanks to Mike for that.

We had a discussion on a Gaia project and it was agreed to think about it for the next meeting.

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The meeting before this one was on 4th February at Mike and Paula’s house.  

Nick gave an excellent summary of the life, times and achievements of Isombard Kingdom (IK) Brunel.   Structures designed and built by him were described and discussed together with his interesting history.