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Doc
Keeper of the Scrolls
2010 Posts
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 Posted -
28/05/2004
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16:31
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LANCASHIRE TEXTILE PROJECT
TAPE 78/AI/05 (Side two)
THIS TAPE HAS BEEN RECORDED ON APRIL 26TH 1979 AT 13 AVON DRIVE BARNOLDSWICK. THE INFORMANT IS STANLEY GRAHAM WHO WAS THE ENGINEER AT BANCROFT MILL AND WHO HAS BEEN THE INTERVIEWER ON MOST OF THE TAPES..
Now then we start now with what could probably be described as the nitty-gritty, and that is the Bancroft Folio itself. A word or two about this folio before we start because I’m sure that the people who use this tape for archival reference in the years to come, as 1 hope it will he used, I think they'll be interested to know some of the reasons and some of the thinking behind the way that I did it.
The Bancroft Folio itself is a selection from a very large and extensive negative file which I have built up over the years while I have been working at Bancroft. I have already indicated the sort of influences that started me off into photography, and here I’d like to pay a tribute to some of the people who have given me unstintingly the best advice available. People like Daniel Meadows, Roger Perry and Barry Lane of the Arts Council. It's invidious to try and give a list like this because so many people have helped me and I'm forced to forget some of them. The thing is that I’ve received nothing but help and, obviously it sounds arrogant, but it’s obvious that there was some latent ability and the people that I've worked with have done their very best to bring it out.
Now we'll get the technicalities over straight away because I know that people are always interested to know just how things were done. All these pictures have been done in black and white. The reason for this is that we know that black and white film is good archival material. We know that negatives will last at least 100 years, we know that prints will last at least 100 years and probably a lot longer. I have attempted to process them all to the best of my ability. The prints are all done on what is, at the moment, a fairly new material which is resin-coated paper. I'm very conscious of the fact that somebody might be listening to these tapes in years and years to come when silver based film has been done away with and we are doing everything
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on video and a little computer prints out your picture for you straight away. [In 2003 we are there already of course. Much of my photography nowadays is digital but I still use Tri X and Roger Perry’s old Nikons for the archival stuff.] We have moved a long way from the days of the wet plate and the dark room but we are still working with almost the same materials. I use nothing but Kodak TriX 35mm film this in what we would call a fast film, A.S.A.400. An exposure in a fairly dimly lit engine house is 1/30 of a second at F4., F5 or F6. I try not to up-rate film, it is possible with TriX, you can up-rate it very simply by extending developing times, or using different developers. I try not to up -rate it, because picture quality does suffer, I tend to go in for long exposure and very, very seldom use a tripod. I depend mainly on what my friend Roger Perry describes an clean living and cast iron elbows. A lot of shots are shot at exposures of probably a quarter, half or even one second. It’s not as difficult as it sounds, if you get your shoulders into something solid and you use a good heavy camera. I started off using a cheap Russian camera, a Zenith. Very few of those shots survived because I wasn’t doing many at the time and I very soon moved on to a Leica CL which was not, the Leica camera is a camera of quality but the one I was using was one that they brought out about 1974, C.L. which was a cheap version of the
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Leica but which used the Leica lens which was the main advantage and you got brilliant quality, but I am afraid the camera body was not up to it. It wouldn't stand knocking about. I then decided that the next change I was going to make would be my last one, and I moved on to the classic 35mm system camera, the Nikon F, and I've used nothing but Nikon ever since and I don't intend ever to use anything but Nikon. It does everything I want it to, you can drop a camera 20 foot, go and pick it up and carry on shooting with it, they are just a beautiful tool.
All the developing, processing and printing has been done by myself. I have tried to fix and wash really adequately, never anything less than a 30 minute wash for film and even though 5 minutes is supposed to be enough for resin-coated paper, never anything less than 20 minutes wash for paper. I always over-fix. Time will tell whether I've managed. to crack it, some of these prints now are
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three and four years old and they look just as good as the day they were done. I have exposed some of them to daylight for long periods of time and the only thing I find with resin paper is that it does tend to go slightly yellow after a period of time but the quality doesn't seem to suffer.
Well I think that's enough about technicalities. What I am going to do is start at the beginning of the Bancroft Folio and I shall use the numbers which we have used throughout when building the folio up. Each number is followed by the negative number as well. The negative number refers to my negative file, and a word on how that number is built up. I’m looking at photograph number 1 which is a picture of Bancroft shed, the first two digits 77 refer to the year when it was shot, the last two digits refer to the frame number on the actual film, in this case 35, it was evidently the last or next to the last frame on that length of film, because they are all in 35-36 frame lengths. I should add that I roll some of my film out of bulk so you will understand that the numbers
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don't always start at No 1 and move through in a film. It's possible to have a film that starts at 35 and goes up to 42 and then back to nought again. So this shot isn't necessarily 35, it could be the first frame on the film. The middle numbers in between the two outside pairs refer to the consecutive number during that year of the film that I shot. This evidently was 41st film I shot in 1977. This is just a way of giving a ready reference for me to get back into my neg file to the location of a particular negative, which you'll understand is critical when you are dealing with the numbers that I’m dealing with.
So now, without any further ado I'm going to move in and start to describe these pictures just as you see them. The idea is that you sit down with this tape and with this book of pictures and listen to me telling you all 1 know about what is on the picture. [I’m digitising this transcript in 2003 and I’m not regarding it as a sacred archive. If there is anything I want to add to the 1979 description with the benefit of my greater experience now I shall do it in square brackets at the end of the original description ]
Folio number 1. Neg no 774035.
So we’ll start with number 1 which is an overall view from the north, well north-east of Bancroft Shed in winter. It's taken off a little lane which leads across, you can see it going down to the right in the corner of the picture, a little foot path that goes across, between the Greyhound Hotel and Gillians, which is the name of the area where the shed stands. This is known as Forty Steps and is a very ancient footpath indeed. I should think the right of way will go back, well as long as the town, if not further.
The shed itself, as you see it there, the nearest building to you is the engine house. To the right of that can be seen the chimney, to the left of it a large blocky going away down towards the end, a two storey construction. That is the warehouse below with the preparation and winding and tapes department on top. That structure extends back for about 50ft and then drops again to single storey behind, which is the weaving shed. This stretches back into the hillside behind. The large building, well large, the fair size building sticking out at the end of the warehouse at the far end, is the office block which contains the main offices, the board-room and storage-room and the directors toilet. The small block sticking out in the middle of the warehouse is a distinctive feature of mills built at this time. It’s the outside toilets which are approached through doors inside the warehouse wall, or in some cases, the shed wall. The idea was, you pop the toilets in a little building on the outside which made them colder for one thing which discourage people from spending too much time in there. That isn't meant facetiously, that was actually one of the things that they were thinking about. It meant that any smells from inadequate drainage didn't penetrate into the building
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which was considered to be more hygienic and it also meant that they weren’t taking up space inside the buildings. And I have often wondered whether it meant that they were a relief on the rates as well. I don't know whether they were rated at the same figure as the inside toilets. Please, don't think that I am being facetious when 1 say about them being cold to discourage people from going in, very adequate ventilation was provided, ostensibly on the grounds of hygiene but certainly so that in winter they were not congenial places to go and have a smoke, or sit round in. The two windows that you can see are boarded up at the bottom, the top halves are cast iron grilles which let the air through. One of the interesting things about Bancroft, I mean obviously this picture has been taken in the depths of winter when there was a very keen frost and there is still some snow on the ground. The shed is surrounded by fields, trees and in summer some sheep in the fields. The buildings across the road from Bancroft are a small farm, it used to be a tripe works but is now a small farm. This is one of the dark satanic mills. They weren’t all dark and they weren't all satanic. For every mill that you can show me in a cobbled street in the middle of a city I’ll show you three or four that are like Bancroft. There is one more building there that I should mention, a square building which stands in front of the engine house, that in an air-raid shelter which was erected during the second world war to provide protection for the work people in the case of enemy action. This was never actually used as such because of course there never were any air-raids in Barnoldswick, and eventually this got to be used as a junk store for storing everything from barrels of old dirty oily and sweeps [floor sweepings] to things that people didn't want any more but didn't like to throw away because it looked as if they'd come in useful at sometime or other. There's all sorts of stuff in there, some marvellous stuff.
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Picture number 2. negative number 763834.
This is a view of the engine taken from the, actually I was sat on the gantry which carries the overhead crane over the top of the engine and if you notice the engine's going at the time. I admit that I was rather foolish climbing up and taking this picture while the engine was running but I wanted a picture of the ropes while they were moving and the engine while it was running. I am a great believer in taking pictures of the engine while it's actually operating. There are far too many pictures of engines about that were taken when they were stopped, people seem to like to be able to freeze the motion, I like to see things blurring. Now, this is a very interesting picture giving you a very good idea of what the inside of a Lancashire engine house looks like. Now you’ll notice that I have said two things, that’s a Lancashire engine house even though it's in Yorkshire, it is a Lancashire set up. And I didn’t say a typical Lancashire engine house. Engine houses are usually thought of as being places like chapels, with plenty of light and where the engine was set in the middle of the floor, something like a God, and everything was looked after beautifully. This just isn’t the case. Most small engines were set in
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very cramped surroundings, often badly lit, sometimes no windows at all. Bancroft is very lucky, or rather I was very lucky. The engine house is a magnificent building with plenty of light coming in and there is plenty of room to work round the engine. It was a really well laid out and really thoughtful job. You can see from this picture that there is plenty of room to move round the engine, plenty of room to get to everything, any maintenance jobs you want to do, anything like that. Now, this is as good a picture as any to give a really detailed explanation of the things on the engine so I shall start off in the top left hand corner and describe everything in fairly close detail.
Starting at the top left hand corner and looking at the engine, or rather looking at the top left hand corner of the picture we see the steam pipe coming in to the engine. It's coming in to the high pressure cylinder which is the smaller cylinder of the two and is on the left hand side. That was a 6” steel steam pipe, but funnily enough the bend and the valve housing are in cast iron, and I have been told many a time that actually that was against the law. The factory inspectors would have been most annoyed if they had found out that that bend was made of cast iron because it was carrying steam at 160 lb to the square inch and subject to vibration. However we never had any trouble with it, and there it stands. It’s lagged with what was always called ‘pig muck’, the reason for being called that was that originally it was pig muck that was used for lagging pipes but is of course powdered asbestos and asbestos fibre put on while it's wet and allowed to dry and then a finishing coat of finer paste was put over the top and coated with paint. In recent years it's been found out that such lagging is very bad for people in that the dust can cause asbestosis, cancer and God knows what. My own understanding of it is that the sort of asbestos that
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was used at Bancroft was not the really dangerous sort, it was the blue asbestos that was really bad. Interesting thing to know up there is that the flange on the horizontal piece of pipe, just before it goes into the bend seems to have something wrapped round the flange. It's very difficult to see but if you look very carefully, you'll see that it looks as though something is wrapped round it. This is in actual fact correct, the flange had a turn of asbestos rope wrapped round it. That was in case there was ever a very slight leaky in which case the water soaked into the asbestos and evaporated instead of dripping on to the floor. Leaks in pipes like this weren't uncommon, we were very lucky at Bancroft, we had none even though it was a very long steam range. The steam then goes down into the stop valve of the engine. I shan't go into too much detail about the actual fitments on the engine, because this picture is fairly complicated in taking in a lot and there isn't really enough detail to explain everything properly. Then it goes into the stop valve, which is directly on top of the high pressure cylinder. The cylinders of course weren't square as they appear in these pictures, they were round and in fact they were different shapes, there was a steam chest on top of that cylinder. What you are actually looking at is the blued steel casing or cleading with nickel plated strips and bands holding it in place which covered the pig muck which also covered the cylinders to give better insulation for the engine, and better thermal efficiency. Out of the front of the high pressure cylinder we have
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the piston rod coming to the cross head which is blurred in that picture. And then on to the connecting rod which goes forward to the crank pin and crank. These are on the end of the fly shaft which runs through the fly wheel carrying the fly wheel itself, which of course is delivering the power developed by the engine to the mill by way of the cotton ropes. You can see these in the grooves on the driving wheel. These ropes, although they look black are in fact cotton ropes. They are black because they are kept covered in a compound of graphite and tallow which puts a skin on the outside of them, preserves them, helps them to slip round the grooves and stops them from fraying as they bend round the wheel. These ropes last a tremendous length of time. They are 1 ¾ inch ropes and some of them will be 30 or 40 years old. The ideal speed for rope drives is 4000 ft per min and at that speed a rope will transmit 50hp. Most driving ropes were this diameter and so it’s very easy to calculate the horse power of an engine, on a rope drive engine, by taking the number of grooves, subtracting an odd one, subtracting probably one groove because they always put an extra one on, and then dividing the resultant number of grooves by two which gives you the number of horse power in hundreds. A quick calculation there'll show you that there's 13 grooves in that flywheel, knock one off that's 12, divided by 2 that's 600hp and that was what this engine was put in to develop. The criterion taken was, approximately, in a place like Bancroft where there were tapes and winding machinery running, was approximately half a horse power per loom. Bancroft was a 1200 loom shop, well 1152 so that gave you 600hp. Of course the other machinery was to drive, but all of the looms weren't running at the same time, there were always a few stopped with empty shuttles or waiting for warps. And a steam engine is always capable of delivering 25% to 50 % overload with no difficulty whatsoever. So an engine this size was quite capable of delivering all the power needed to run say 1200 looms and all the associated machinery. On the right-hand side of the picture, the low pressure side,
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is the low pressure cylinder, piston rod, cross head and con rod. This drives on to the crank just the same as on the HP side. Notice the cast iron beds, very strong heavy beds bolted down right through the foundations of the engine house to make everything absolutely solid. When I say absolutely solid, don't get the impression that all those nuts were tight, they weren’t. There were only four nuts on that engine, holding down nuts, that were dead tight. They were the two on each side that you can see immediately in front of the cylinder where the engine bed divides into a double wall. If you look at the front cover of each cylinder, and look to the left and right of that, on the high pressure side you can't see it because of the governor but on the low pressure side it's particularly clear. You'll see two round castings coming up through the bed right to the top and two nuts. Those two were dead tight, all the others were left with a certain amount of movement in them. The reason for this was that a large piece of cast iron such as an engine bed needs room to breathe and move as the temperature goes up and falls, otherwise it'll crack itself. Roberts’ beds were particularly prone to crack just behind the large bearing which carries the fly shaft. When I say behind, I mean just on the cylinder side of that large bearing. Those bearings were called pillow hearings and carried all the weight
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of the flywheel and fly shaft and took the weight of the drive. In the case of the Bancroft engine the makers made a slight mistake when they made it and the low pressure cap was never machined out properly. Those nuts which hold that cap on at that side were never more than finger tight because if you tightened them down with a spanner that bearing immediately got hot. The reason for it was that there wasn't enough clearance between the cap and the shaft and if you tightened them down the cap used to rub on the shaft and increase the pressure in the bearing which lead to the bearing getting red hot in about 10 minutes. So we used to leave those alone, those bearings were moving quietly all the time. If you look at the driving ropes, follow them from the large wheel to where they come under the camera itself. On the left hand side, where the engine beds and the railings which are on the edge of the bridge over the rope race you'll see the top of another cylinder. If you look very carefully in the shadow behind the pillow bearing, in front of the pillow bearing on the high pressure side you’ll see the shadow of the top of another cylinder. That’s the small barring engine which was used to turn the engine over for purposes of maintenance, if you were timing the engine, or you wanted to grease the ropes, anything like that. It's another small steam engine. The feed pipe to that is the pipe which you can see coming in from half way down the left hand-side of the picture and dropping down and going into the space in between the two small cylinders. You can just see the Pickering governor which controlled the speed of that engine. Interestingly enough that was one of the original Pickering governors, an American governor. A lot of these are called Pickering governors but they are actually made in England under licence by a company called Evans. On the right of the ropes you can see a table covered with drums of oil, oil buckets and things like that. All things which are needed to run the engine. If you look on the engine bed on the right hand-side, just to the right of the splash shield which stops the oil flying off the crank and going all over the floor, you'll see there is what looks like a little teapot on the bed. That's just exactly what it is. If you look even more carefully at the high pressure side, you’ll see another. Those are part of a tea service presented to my mother and father in about 1950 and they were eventually relegated to use in the engine house as vessels for holding oil for filling the lubricators for the cranks. In the top right-hand corner of the picture can be seen the seat, the engineer’s seat, the desk with the pot on, the obligatory pot of tea and one or two photographs
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on the wall. That's the corner where the engineer spent most of his time sitting, watching and listening. That's what his job was to watch and listen to the engine. But you'd listen to it very carefully to be on the ball immediately anything started to go wrong.
Picture number 3. Neg number 772307.
Now, we go on to picture number 3 because we are going to see more pictures of the engine, a lot of this detail which we have not gone into on picture 2 will come in on the other pictures. Picture number 3 which is negative 772307. This is a picture of the back end of the low pressure cylinder. The first thing to notice is that it’s got a name, Mary Jane. Mary Jane was Mary Jane Nutter, the wife of James Nutter, who was the man who first conceived building this shed, Bancroft Shed. He actually died before it started to run. He died in 1918 I think, but it shows what they thought about the machinery in so far as they called it Mary Jane and James is the high pressure. The cylinder cover is obvious, the cover over the actual bore. That's the circular casting with all the nuts on it holding it down. In the middle of the cylinder cover is what looks like a large block, that is the slipper which runs in the low pressure tail slide and carries the linkage
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to the bell-crank, which goes down into the cellar and drives the air pump. Notice the acorn shaped lubricator, the thistle shaped lubricator, which in on the metallic packing housing at the back of the cylinder, that provides a constant slow drip of cylinder oil on to the rod to keep the rod lubricated and to make sure that it's got a good seal. The slide is heavily oiled, with thick oil as you can see. It carries quite a lot of weight that slide actually because of the fact that it's driving the bell-crank and the air pump underneath. Polished steel railings round it, solid steel railings polished with emery paper and constant rubbing. To the left of the cylinder you'll see a large, insulated pipe coming out of the floor and joining the cylinder. That is the supply of steam for the low pressure cylinder which comes from a receiver under the floor which is fed by the exhaust from the high pressure cylinder. On top of that pipe, on top of the bendy just as it goes into the cylinder you'll see a small round object sticking up off it. This is the pressure relief valve which is there in case there is ever a slug of water caught in the cylinder, or for any reason the pressure gets greater than the low pressure will bear. That valve at about 65 lbs to the square inch and if the pressure in that pipe exceeds that, it'll lift and let any excess pressure off. It's a very large orifice valve so that it can get rid of a large amount of pressure quickly. There are also two more of those valves, one on each end of the cylinder. You can just see the edge of one of them sticking out. If you look at the cylinder cover at 9 o'clock and just look round the corner of the cylinder, you'll see the edge and part of the cylindrical body of the relief valve on the back end of the low pressure cylinder. On the right hand-side of the cylinder you can see part of the valve gear. The Bancroft engine was built by Roberts of Nelson and is a cross compound. This means that it has a cylinder on each side of the flywheel, it's a compound because the high pressure cylinder feeds the low pressure cylinder. Corliss valve engine. Now, Corliss valves, actually that's nothing to do with the valves. Henry Corliss devised a means of closing circular valves quickly at any point during their travel so the term ‘Corliss’ properly refers to the mechanism for shutting the valves rather than the valves themselves. It's the method of shutting the valves. The valves are shut by large dashpots one of which can be seen on the right of the low pressure cylinder, at about 3 o'clock. Those dashpots contain a large spring which is put into compression when the valve in opened and obviously snaps it shut when the linkage leaves go. And at the bottom is a small open ended piston into which the end of the valve rod fits with a piston on the end. When the rod drops it forms a cushion of compressed air which can be adjusted by a small release valve on the bottom of the cylinder. This stops the spring slamming into the bottom of the dashpot each time. This means that you can run the engine fairly quietly, you can cushion the blow of the spring driving the valve rod back down to the bottom. At the bottom, at approximately 5 o'clock on the cylinder cover can be seen the bonnet of the low pressure exhaust valve, the back low pressure exhaust valve, and the ends of the two eccentric rods which are driving it. One rod drives the valve from the eccentrics on the flywheel shaft and the other drives the front low pressure exhaust valve. Just behind that can be seen two oil cans sat in a little pillow of cotton waste cotton waste, the cotton waste in these trays is to soak up any oil drips. Those oil cans contained thin oil for use on the governor or on any joints in the linkage if it's needed. A drop of thin oil on them as opposed to the thick cylinder oil. I think we’ve just about squeezed the juice out of that one, we’ll move on to the next picture.
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Picture number 4. Negative 767440.
This is a view of the engine on the low pressure side. You are standing next to the low pressure cylinder and looking down towards the pillow bearing. Notice how all the motion is blurred and the connecting rod has vanished completely. This is because of the length of the exposure. It's a very long exposure, probably half a second. This means that you have got a fairly good depth of field and also you have got a bit of movement into the engine, it's obvious that that engine's running. Notice the very heavy construction of the bed, follow the bed down with your eye, there’s a lump of cotton waste lay on it handy there to wipe up any spills and wipe the rails, anything like that. There’s a pair of gas pliers lay there to slacken off the adjustment on the drip feed lubricator which is attached to the railing above the cotton waste and which is feeding the crank pin bearing. And then of course the coffee pot full of oil for topping up the lubricator. The big splash guard stood up behind which catches any drops of oil that are thrown off the crank and drains it back down into the tray underneath from where it drains down into the cellar into a tank from which we take the oil and use it again. The construction of the pillow bearing is quite obvious, a massive cast iron block bolted down on to the bed and wedged at the same time. This carries the bearing housing containing the gun metal steps or bearings which in turn carry the shaft. On top of that is the bearing cap which, if everything was well would he bolted down tight but in this case those bolts are only finger tight and the lock nuts nutted up to them. The ornamental pagoda like structure almost on top is what we call the fish tank lubricator. The top half, the top window is the oil vessel and the bottom is to let light through so that you can see the oil running out of the lubricator cocks down into the bearing. There's a pipe running up from a pump down at the right hand side of the pillow block. This pump is driven by a rope drive off the flywheel shaft. That oil runs through the bearing, it goes into troughs on the pillow block, one of them can be seen at this side, and they run back through and down a
pipe into a tank on the floor behind the engine bed. And from there the oil is pushed back up into the top tank of the fish tank by a small pump driven by rope drive off the flyshaft. It's, in other words it's self lubricating once the engine gets going, it just keeps pumping the oil round and round. There’s a good view in this picture of the ropes sinking down in a curve as they come off the flywheel. If they were flogging about they would be blurred. This is a sure sign that the engine is in good condition and running smoothly. The curve also shows by the slack side being on top that the engine is ‘running over’. The flywheel, looking at it from this side, is turning in an anti-clockwise direction, so the tension is in the ropes below the floor level, and the top side is the slack side of the ropes. At the top end of the engine house can be seen the second motion pulley. This second motion pulley is on the end of the lineshaft which goes right the way up through the mill and drives everything in the shed. The left hand end of it can be seen sticking out
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beyond the end of the second motion pulley. Also on that end can be seen another smaller version of the fish tank lubricator like the one on the flyshaft bearing, the oil pumping round the top bearing. There were four of those pumps, one on each pillow bearing on the flywheel and one on each pillow bearing on the second motion pulley. In some ways rather a strange layout at Bancroft because the second notion pulley to many people seems to be a lot higher than it ought to be. The reason for it is that for some reason they built the engine bed 18” below the height that the millwright had evidently wanted it in the first place. The reason I can say this with some certainty is because of the mason’s on the wall in the engine house and they point to an 18” discrepancy in level. Newton and I have talked about this often and decided that it must have been something to do with the relative levels of the water in the lodge or dam, and the position of the air pump under the engine. This is the only thing that we can think. Of course it did mean they could build the engine house 18” lower and save them some brickwork on top of the cellar wall but this might just be the only reason they did it, to keep the engine beds a bit lower. The pillar which stands up on the low pressure bed directly in front of the camera and directly in the middle of the picture is one that was used for putting the parallelogram motion on which transmitted the drive from the crosshead slipper to the indicator when you are indicating. Now if you follow that rod downy and look very carefully at the blurred impression of the slipper when it's at the end of its slide you'll see the circular head on the end of it, and in the middle a small dark patch which is actually the hole in which the parallelogram motion was threaded. I think we'll find that there is one picture in here that shows the parallelogram motion actually on the engine. The only other thing I can think of to take particularly note of on there is in the bottom right-hand corner of the picture. If you look across the end of the slipper bed, the slide, front slide, you'll see
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two large brackets at the other side that obviously have big pins running through them, and some sort of cross levers running on them, some sort of bell cranks and levers. These are for carrying the motion of the eccentric rods which are driven from eccentric sheaves on the flyshaft between the pillow bearing and the flywheel at each side of the engine. These rods come back and transmit notion through these rocking cranks to other rods which run down the side of the cylinders and actuate the valves. That’s where the valve timing comes from.
Picture number 5. Neg number 777234
We'll go on to picture number 5. Which is a very plain and simple
Picture. Negative 777234. This is quite simply the low pressure crank and banjo oiler. The low pressure crank is the large block of metal you can see, it’s shrunk solid on to the flyshaft which goes through the middle of the flywheel. When I say
‘shrunk on’, the way to fix the crank is to bore the hole for the flyshaft end undersize. The old fitters usually allowed one thou of nip for every inch diameter of the shaft and then added a bit more on judged from experience. A ten inch shaft would probably be given up to 15 thousandths of an inch. The procedure for fixing the crank on was to hang it off the crane in position where it could slide on the shaft as soon as it was free. The crank would be covered with asbestos blankets over the top to conserve heat and large paraffin blowlamps placed below directing very strong heating flames on the crank. These days we would use large oxy propane pot burners. The heat was applied until the crank became white hot, at this stage the hole would have expanded enough to allow the crank to slide on the shaft. It’s important that the crank be fixed on the shaft in exactly the right place in relation to the HP crank on the opposite side. In the case of this engine, and this was the usual practice, the LP crank is set 90 degrees in front of the HP crank. In order to ensure that this angle is correct a keyway is cut on the shaft and a keyway in the crank. A key like this is usually used to prevent any movement in relation to the shaft but in this case was simply a location aid as the grip of the crank on the shaft is such that there is no way it can ever move once shrunk on. As soon as the crank gives evidence of trying to slide on the shaft the burners are shut off, the locating key put in place and the crank is pushed on using say a large piece of timber. It is held in place as cooling commences, this happens quite quickly as the cool shaft draws heat out of the crank. If all the preparation work has been done correctly the crank is then immovably fixed on the shaft and all that remains to be done is clean up the crank and re-assemble the engine. The crank pin is fixed into the crank in exactly the same way but without the locating key as position doesn’t matter.
You can see the crank pin coming through the centre of the connecting rod end. This pin has a shoulder on it which locates it longitudinally on the crank when it is pushed in the hole and a shoulder turned on the outboard end which stops the connecting rod end brasses floating sideways when the engine is running. The end of the connecting rod is designed so that the brasses can be fitted after the rod is hung in place. The arrangement of wedges and screwed bolt which fixes the brasses is also used for adjusting the nip of the brasses on the crank pin. A typical adjustment on this bearing would be one sixteenth of a turn on the adjusting bolt.
On the end of the crank pin is the brass spider which is a casting made to bolt on the crank pin and which has a threaded boss cast on it made to accept the end of the pipe leading to the ‘banjo’ on the centre line of the flyshaft. Because it is on the centre line the banjo has no apparent motion apart from rotation when the engine is running. As it is in effect stationary it is an easy matter to introduce oil into the banjo from where centrifugal force throws it out to the crank which is drilled to convey the oil into the bearing. When the oil has worked it’s way through the bearing it is thrown off and caught by the splash guard mounted on the end of the bed or the drip tray in the well beneath. A pipe leads from this tray into the cellar and this oil is collected in a tank and can either be filtered and re-used on the engine or more likely, and in Bancroft’s case always, can be used for low risk lubrication jobs. You’ll notice that a twisted rope of cotton waste is packed round the edge of the tray. This catches any waste oil before it can get under the beds and cause trouble and mess. This waste is occasionally replaced and the old oily waste burned in the boiler, usually for fire lighting three times a year. Note also the fact that the side of the flywheel is covered with boarding. The bare flywheel has large cast iron spokes and if this ‘wind boarding’ as it is called wasn’t fitted, the rotation of the flywheel would act as a huge fan, losing energy and causing serious air movement in the engine house.
Picture number 6. Neg number 776907.
This is a close-up view of the drip feed lubricator for the banjo oiler. This type of lubricator is widely used on the engine. It consists of a reservoir filled with oil which can drip through a small orifice in the bottom of the lubricator. The rate of feed through this orifice is controlled by a brass needle with a conical end which fits in the orifice and is controlled by the small lever and adjusting screw on the top of the lubricator. Raising and lowering this needle by the adjusting screw increases or decreases the amount of oil flowing from the reservoir by adjusting the size of the orifice. The needle is spring loaded and the lever on the top acts as a cam. If it is upright the needle is raised and oil flows. If it is over on one side the spring has forced the needle into the orifice and oil flow stops.
Immediately under the base of the lubricator is a small casting lined with a small glass tube and bored two ways to give four windows. Through this can be seen the bottom end of the orifice and the drops of oil falling off can be observed. Before the engine is started, the lubricator is opened and the rate of flow checked. At Bancroft I reckoned on one drop of oil every five revolutions of the engine and adjusted the orifice accordingly. Any impurity in the oil or change in temperature could affect the flow so this was checked every ten minutes while the engine was running. This was the most important single task that the engineer did during the day. Any interruption of flow could lead to a hot crank pin and the stopping of the engine.
The other thing of note on this picture is sight of the screw adjusters on the bearing cap which can be altered to put pressure on the individual brasses and wedges in the flyshaft bearing and thus adjust them. This was almost never done and in fact on this bearing couldn’t be done at all because the bearing cap holding down nuts are loose as this was the only way the engine would run.
SCG/06 September 2003
7,499 words.
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Stanley Graham (Engineer & Researcher) Tape 07
