A Water-Collecting CraftPeter Dollimore
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Aim: To design and construct a craft to collect water samples from lakes or slow-flowing rivers for pollution testing. The collecting apparatus must be able to collect from different depths. Properties:
First Design
The collector collects the sample by being lowered on a string down to the desired depth. (Its string will be cut to the correct length.) It is then left to fill with the water from that depth (about 1 minute) then pulled back up again by a low-gear motor. After I had thought about the design for a while I saw two problems:
I have decided to stick with the idea of a catamaran for the reasons already mentioned but will redesign the collector and propulsion mechanisms. As the propulsion is also the steering mechanism in Design 1 I will also have to design this. I have decided to treat three problems, the collecting apparatus, steering and propulsion separately. Here is the catamaran base I have made on which these mechanisms will fit.
The Collecting Apparatus for Aim: To design and construct a device for collecting water samples at
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BUILDING A WINDMILLMukti Kumar Mitchell |
I first went to discuss the design of a windmill with Mike Agg, a former Rolls Royce engineer, who is very interested in windmills. He showed me various statistics such as:
Mike also gave me a book on windmills called Small Scale Wind Power. Ifound this very comprehensible and interesting, and from it got many ideas and information about wind, efficiency, location, towers, and much more. I decided to make a slow-speed windmill for the following reasons:
SIMPLY: High-speed windmills are far higher technology and are far more difficult to make. As my first windmill a slow‑speed one is a much more sensible idea because it does not matter if there are any imperfections in its construction. fig 1 deflection of wind. Windmills work by deflecting the wind. The best way to do this is to take the wind onto the blade at the leading edge at an angle almost perpendicular to the windmill, the angle it is already travelling at. The blade is curved so that as the wind moves across the blade it is slowly angled round to the angle at which it comes off the blade at the trailing edge. (See figure 1) A slow-speed windmill produces greater power, properly termed in this case torque, but less speed. So the blades need to be at not too great an angle to the wind. This also has the advantage that the windmill will start running at lower wind speeds. DESIGNING THE WINDMILL First I had to design the windmill. After finding out some things about slow and high-speed windmills, I decided to take Mike's advice and build a slow-speed windmill. It would have:
This was all that I thought about for now. The design of a vertical pivot enabling the windmill to turn to face the wind would come later. Mike suggested that I make a wooden mould over which I could hammer each blade so that they would all have the same curve. He brought two sheets of galvanized tin, each 6’ by 10². Seeing the quantity. I decided to alter the design and make 11 blades 2' long instead of 36² In order to avoid causing too many eddies and disturbances, the angle at which the air is deflected off the back of the blades should be the same all the way up the blade.
These diagrams show how I used the diagrams in fig. 3 to determine the angles and curves of the blade at different points on its height.
Fig. 3 Blades drawn onto the triangles
Building the Windmill
Fig 5. The mould, plan, section tip/hub side view The next step was to make the hub. I cut 4² off the end of a massive stake, diameter 6², and shaved it to make it fairly round. The reason the hub is so large is that the diameter needs to be big enough to attach the inner edges of all the blades to it.
Fig. 8. Attachment of hub to wheel.section.rear view
THE FIRST TEST I was amazed to see how well the windmill worked. As soon as I had finished tightening the nut that held it on and let go the blades began to spin. I had to stand back because I could see that if I touched it, it could easily chop off my fingers. *RPM test: 67 revolutions in 20 seconds = 201 RPM Tip speed
Allowing for inaccuracies and varying windspeed over the 20 second test, I can say that the tipspeed in this test reached around 50 kilometres per hour.
FURTHER MODIFICATIONS After the first test I took down the windmill. I decided to strengthen it by attaching the blades to the spokes of the bicycle wheel with wire. I drilled two tiny holes in each blade, about where they touched the rim of the bicycle wheel. I then put wire through the holes and twisted it round a spoke. The original aim of this project was to generate electricity so the next step I took was to attach a bicycle dynamo. Test No. 2 I set up the windmill in the dark, with the dynamo and light attached. As soon as I switched the dynamo into contact with the windmill I noticed that it had a serious effect on the windmill's performance. I had to give the windmill a push to start it, but after that it ran fast enough to power the light easily. Further modifications At this point I decided to try to make a vertical pivot which would enable the windmill to turn to face the wind.
To go with the pivot mechanism I naturally had to make come kind of protruding fin which would turn the windmill to face the wind.
Fig 12. The finlveinlpivot assembly.
Test no. 3 I set up the windmill. with the new pivot and vein on a not-so-windy day. I immediately observed that because of the weight of the windmill there was a lot of friction in the pivot mechanism. Taking this into account the vein was not really big enough for the wind to turn the whole windmill unless, perhaps, in a very strong wind. Further modifications I decided to make a new larger vein. I cut the vein from a sheet of 3-ply wood. It is a sort of triangular shape 78cm high by 81cm long and with a totalarea of 4018cm square. (much larger than the last vein who's area was 726cm square.) I attached this to the pivot with a piece of copper pipe about 80cm long.
Test no. 4 Further modifications The general use of slow speed windmills around the country is for water pumping. Since I was not very impressed about my windmill powering a tiny little bulb, I decided to try and adapt it to pump water. This I could see would not be easy. The problem would be that however I took the power off the windmill this mechanism would have to be able to turn round and round. Therefore however I took the power off the windmill it would have to be right in the centre of the turning pivot. The obvious way to take power through the centre of the windmill would be to have two gears at right angles above the centre of the pivot driving a shaft which went down through the centre of the pivot, as in fig 14.
The problem with this would be the non‑availability of the necessary gears, and the setting up of the shafts with bearings to make them turn smoothly and without too much friction. I had been meditating on this awkward problem for some days when I suddenly noticed car speedometercablesfor sale in a garage. This immediately gave me an idea. I could use a car speedo cable, because it would bend and still turn and could take the place of the two gears and shafts in 'the obvious solution'. The only thing which needed changing in the present design of the windmill was that, instead of a solid metal bolt as the pivot, I would need to use a piece of metal pipe. This had to be thin enough to fit inside the metal bracket, fat enough to put a car speedo cable through the centre of and thick/strong enough to be able to take the strain of the windmill in the wind. By amazing chance, whenIwent to apologise to my next door neighbour about waking his family up at midnight with our motorbikes, he had just such a pieceof pipe and gave it to me! I purchased a speedo cable in Bideford. First I took down the windmill and reassembled it with the piece of pipe as pivot. I also added a piece of metal to hold the wheel I planned to use to drive the cable. I also needed to add another piece of flattened copper pipe to hold the wheel right against the bicycle wheel. I cut a curved piece of copper pipe in which to case the cable where it was bent. When I had put the cable through the pipes I attached a small wheel to the end of the cable.
Fig 15.The wheel, rear view, to show how I attached it.
Test no. 5 I assembled the whole thing on a reasonably windy day. The drive mechanism caused much friction in the windmill and gave a high resistance, but once started the windmill worked quite well and went quite fast even with the drive on. I am quite happy about it because with the drive on the windmill can still turn right around and around and the drive is not affected. I left the windmill for a few days with the drive on and during these days it did not rattle itself to pieces and nor did the drive get broken. Future modifications Well, what's the use of a drive that doesn't drive anything? The next step is obviously to attach a pump to the drive. I just have to wait until I can find a pump. If I were to come across a washing machine pump I could quite easily attach it. Otherwise, if I got hold of a hand water pump I would need some other apparatus for working it. I have thought about the set up of both these different kinds of pump.
CONCLUSIONS I can say that I greatly enjoyed this project and learnt about wholefields of knowledge which Iknew not about before I started. Most of the science I have learned about during this project is Physics, which is my favourite science. I learnt a lot about the theoretical side of windmills, wind, air, and use of the wind from Mike Agg. I alsolearnt a lot from the book Small Scale Windpower. On the practical level, I can say that I designed, built, and modified this windmill with my very own hands. Not a single other person helped, and I feel that this is THE GREATEST PRACTICAL ACHIEVEMENT I HAVE EVER MADE. With pleasure! This project was published by the Northern Examination Board as an example of work deserving 100% marks.
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THE ELDERFLOWERSimon Rodway |
PROLOGUE: THE DEATH OF A HERO I sit huddled over the flat‑topped boulder that serves me as a writing desk. It makes a poor desk, when I could curl up in a warm corner by old Ielfstan's hearth with a black‑oak. bowl of honey‑mead at my elbow and Garm(2), the deaf old boar‑hound sleeping at my feet. But I felt that in some way I had to be near Gunnar Osricsson, my lord, in this moment, More than a year I have been in writing this saga; sorting through the tangled strands of his incredible story and weaving them together, embroidering them with the jewels of a skald's art. As I write, my pen skittering across the uneven surface, I remember that wet autumn evening so long ago; the blue spear‑heads inviting the ravens to feast; my lord, veteran of many frays, spitted on an Irish lance, his orichalc brand from lost Atlantis bespattered in gore. Afterward I found him, face down in the delicate heather‑blooms, with a little breath in his body still. 'Write my story for me," he said. "that in later ages men may still remember my name. Do this thing for me, lend a Honeytongue, my shield‑companion, when we have parted for ever." A while later the Angels came for his soul. I layed him in the earth, with his head towards the rising sun. These long months since, I have travailed that his memory is not lost. Now I have finished l feel an emptiness. Where is a man who has no lord?(3) For this past year the tale I was writing kept me from facing the emptiness. Now it, too, is gone. I weep a little: for Gunnow, for myself; for all the people whom strife and the clangour of saexes has bereaved of children, lovers, fathers, lords. In a while, I will return to old Ielfstan and his avaricious penny‑pinching, to fat Helga and her whiplash tongue, to the maimed, wheedling beggars, the bragging warsmiths(4), the widows with emptiness behind their eyes, to the petty, war‑torn world of men; I who have looked on the glory of Atlantis and the greatness of Yggdrasil, the Quickwood(5). What will they care for the memories of one more lost hero? Never-the-less, I present the fruits of my labour for what they are worth(6).
CHAPTER ONE: THE WANDERER I am Gunnar Osricsson, youngest son of Osric the Angleman and of Gunnhild the daughter of Hawk Redbeard son of Egil the Strong and of Gudrun daughter of Ketil Fox son of Kol and of Halbera the White daughter of Ragnar the Black son of Gutthorn the Raven(1). Osric the Angleman was a seafarer who rode the whale‑path to Denmark where he met my mother. He is the son of Eanwulf son of Osmod son of Eawa son of Pybba son of Creoda son of Cynewald son of Cnebba son of Icel son of Eomaer son of Angeltheow son of Offa son of Waermund son of Woden (or Odin as we say in Denmark) son of Freotholaf son of Freothowulf son of Fin son of Godwulf sone of Geat son of Taetwa son of Beaw son of Sceldwea son of Heremod son of Itermon son of Hratha of Hwala son of Bedwig son of Sceaf who was the son of Noah and was born in the Ark. Noah was the son of Lamech son of Methuselah son, of Enoch son of Jared son of Mahalaleel son of Cainan son of Enos son of Seth son of Adam who was the first man on Earth and was created by God our Father, Amen(2). Being a youngest son and having no inheritance, l left my father's hearth and took a knucklebone from the basket of Herulf Kolsson and went a‑Viking with the crew of the Red Hawk. It was my first experience of seafaring or warring and the faces and characters of my sword‑brethren still stand out in my mind; Herulf himself, gruff and fiery‑tempered, with skin like tanned leather, Kolsson himself with white scars from a life‑time of guiding beaked war‑prows through rain and shine, calm and storm(3); Ulf Crow, with grey hairs in the tangled black mane that had earned him his name; Gorm Lombard(4) with the strength of a Troll; hump‑backed Thrand the Red(5); Thormod who scolded like an old woman; Kolsegg the Skald whose fine lays kept us going when ill‑fortune had almost broken our will; Ulf Hedin(6), a baresark of great strength and ferocity who was timid and shy when the fit was not upon him ‑ before battle he would tremble like a leaf in snow-water so that he could not hold a tind(7), but when the blue blades began to keen he would run naked upon the foe and rend them with his barehands(8); Grim Fairfax(9) with his barley‑pale hair and his girlish good-looks; Lodin Longshanks, a tall, dour warrard(10) with a useless withered arm; Eirik a cantankerous old seafarer whose near sightless eyes were milky‑white; these are but a few of the men that sang and rowed and fought and died beside me. For long weeks we ploughed the Whale‑Path, seeding the furrow behind us with empty wine‑skins, torn sail-cloth, gnawed bones and fish‑heads(11). And when my soft hands had blistered and hardened at the oars, we came near land amid a quarrelling squall of sea-mews(12). Many of us were all for going ashore at once, but Herulf said: We were greatly cheered by this speech and we sangas we pulled at the oars, eager to fill our chests with riches and our bellies with fresh meat. But it was not to be so. For there dwelt on this desolate island an evil weather‑worker and he made a terrible magic that aroused the North Wind which came howling across the sea, whipping the waves into green mountains that gaped wide to glut us(13). The rain came down in grey sheets like a fall of spears. The thunder seemed to shake the very world and the lightning split the sky‑roof. And through the roaring elements the hideous Draug in their sodden wrecks came sailing into the wind grinning their horrible grins, clutching barnacle crusted prows that impossibly stayed afloat, sternless, with staved‑in ribs. Ulf‑Hedin cried aloud: “Ragnarok! The Wrack of the Gods is upon us!" until Gorm Lombard tied his mouth with a cloak to stop his noise for the men were unnerved by his words. Then black rocks, like teeth, leapt from the water to chew our craft and spew it, shattered, upon the strand. The Draug cackled as we floundered in the brine. The Vikings called upon the Allfather to save them (we were pagans then, may the Lord forgive us) but to no avail. Ram, the Mother of Storms(14), snared them in her net and they were gone. Some few of us were cast upon the shore, battered and soaked through. Herulf was gone, standing grimly on the steer‑board till the end; Thurmod's scolding tongue was cold(15); Kolskegg sang no more. As we staggered up the beach through the growing darkness, too dazed to comprehend what had befallen, wild shapes leapt at us through the gloaming. They swung at us with swords blackened with soot to prevent moon‑gleam betraying their ambush. These were the Painted Folk; the weather‑worker's warriors; scrawny, half‑naked men, shrieking like hell‑devils, their bodies stained blue with woad. Few of us were armed but still we fought hard and died well. Thrand the Red and Eric Thorfmusson fell, pierced by Pictish war‑spears. Their life ebbed with the tide. I snatched an axe from a howling, painted wose and split his skull with it. Sinister Lodin was a hawk with a broken wing, his beak of flashing, Pictish steel. He died at the hub of a wheel of blue‑painted corpses, Ulf‑Hedin reaped a harvest of blue sheaves, but they surrounded him and brought him down like a bear. The day opened its yellow eyes upon a dolorous scene. Of the Painted Men, none still breathed. Their bodies lay tumbled upon the blood‑soaked sand, Viking bodies too. Of my shipmates three only still stood; Ulf Crow cradling a bleeding arm; Gorm Lombard cursing softly as he struggled to extract a lance‑head from his thigh, and wasp‑waisted Grim Fairfax. We had not time to send the dead off in the customary way of the time which was to burn their bodies, that the spirit would be released to return to the Allfather on the wings of the Valkyries; but we laid them together apart from the Pictish beasts and heaped rocks upon them to spare them from the ravens. Lord God, have mercy upon their souls. They died in ignorance, but they were good men in their own way, They knew of Your Son, who went into the earth-darkness for the good of Your people, and who rose from the cairn like the Lord Barleycorn. As we straightened our backs from this task we beheld a troop of Painted Men marching across the forsaken heath towards us. Arrows, whining like beaten curs, rained upon us, We fled across the broken ground, down swart‑toothed cliffs. A tiny coracle tossed on the heaving grey waters below us. We splashed through the chilling brine and clambered aboard the frail vessel. Grim Fairfax and I seized paddles and laboured to haul the unwieldy craft clear of the rocks, The Painted Folk appeared to sting us with their darts, but we were soon out of range of their short bows. I wondered that the weather‑worker did not crush us with another tempest. Perhaps he was not able to summon another so soon after the first. Perhaps he was content with the casualties he had already caused. His motives for the original assault were not clear. If it was loot he was after, he would be disappointed, for we had none. For whatever reason, we were spared his wrath and drifted aimlessly for many days. Poets regale the sea with honey‑sweet names: Whale‑Road; Swan‑Path; AEgir's Meadow. They speak of the prancing wave‑horses; of the Selkies, the seal‑folk who till the waves as we till the land; of the un‑tamed power of the ocean: of its haunting bitter‑sweet music. l, who have lain for seven nights upon its merciless bosom, speak of it in starker terms: Widow‑Maker. It taunted us, that long week, flaunting its unpalatable waters as we stared dry‑throated, empty‑bellied at the sun‑glitter, Then out of the brightness sailed a drake‑prowed longship dragging a salt furrow behind it. Wehailed it, beyond caring who these strangers might be. Lines were thrown and, weak with hunger, we hauled ourselves aboard. They were Saxons, blonde-haired giants from the Northern forests of Almain where the Trolls polish their dreadful eyes and peer through the gloom snuffling for human blood. Their speech was like enough to ours for us to understand them and them us. 1 also knew a little of the speech of the Angles, my father's folk, which was in essence the same tongue. The‑ man on the chest before me was a poet; Penda Honeytongue was his name. He told me many tales of his folk in the long weary days that followed: of Beowulf the bee’s wolf; of Scyld Scefing, the Targe of the People; of the great Mirk Wood that separated his land from the rich Southern lands where folk were brown of skin and white of tooth; of Wade the Halsing, a great weather‑worker, patron of the Saxon people. In return, although 1 am no skald, I told him the sagas I had heard as a bairn in my father's mead‑hall, squatting among dog‑gleaned bones, listening to the gleemen. Clumsy‑tongued, 1 spoke of the Peace of Frodi; of Sigurd the Volsung and his battle with the great Worm Fafnir; of the AEsir (the gods to whom I hearkened at that time) and of their strife with the Rime Giants. I came to recognise others of my new shipmates in those weeks: Simple-Offa with his broad, good‑natured face; fierce Cynergrim Head-hewer; Oswine, whose arm had been lopped off above the elbow in some long-ago skirmish; Brand Guthrumsson with his brawny blacksmith's arms. They boasted of theirprowess in battle and lamented the absence of their wivesand lovers much as the men of the Red Hawk had done. Seafarers are much the same whether they hearken from rime-bitter Denmark or forest‑bound Almain, I learnt that the Skua was bound South away from these Pict‑infested islets, to the rich farmlands of Albion. The crew of the Skua were‑ merely raiders, but many Saxons had taken their womenfolk and settled there. We sailed close to the coast, putting in at night where we could, occasionally stopping to sack cliff‑top villages. We amassed little wealth from these raids, for the folkwere poor crofters and fishermen. For the most part they fled when they espied the helmeted war‑smiths, but in one settlement a few sturdy herdsmen banded together to repel us. The headman carried a metal sword, but the rabble were armed only with picks and staves. We slew a couple and the others were routed. We took a handful of coins and some rough bronze and amber jewellery. The men grumbled. "We are tired of worthless baubles" growled Brand Guthrumsson waving a dented copper torque in Osgeat’s face. It was as he said. But some few days later, Cynegrim Headhewer sighted a longship ploughing serpent‑wise through the swell. As it approached, Olgeat cried out; He took up his broadaxe and made as if to leap overboard. I asked Penda about this. He replied that Gundulf had slain Osgeat's brother, Eoppa the White, for the slandering of Cynric, Gundulf's father, for which action Gundulf had been declared a nithing, Awanted man, he had turned Viiking. Now the Fates intheir perversity had crossed his strand with that of Osgeat, and Osgeatwas determined that one strand should here be severed. It appeared that the thing was in Gundulf’s mind also, forhe drew the Sea Mare alongside the Skua and greeted Osgeat from the deck. “Hail Osgeat Wiglaf's son!" he cried, He was a broad man with a tangled mane of red hair. They spoke together oftrivial things for a little. Then Gundulf said: "You have found your warg, His head is yours for the taking." His tone was light, as though he were speaking of the doings of a far‑away people who mattered little to him. "Then 1 will come and take it" cried Osgeat and he would have boarded Gundulf's ship in that instant, had not Penda restrained him, saying that it were better to do the thing his axe against Gundulf's than the Skua's crew against that of the Sea Mare. "We have no quarrel with Gundulf's men. Let there be a Holm‑Ganging instead." end of Chapter One
NOTES ON SOURCES for 'THE ELDERFLOWER' Prelude
Chapter One
This is a small selection of the 71 footnotes Simon gave to this story. He also has a bibliography of 42 books from 23 authors. |