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Doc
Keeper of the Scrolls
2010 Posts
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 Posted -
28/05/2004
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16:27
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LANCASHIRE TEXTILE PROJECT
TAPE 78/AI/07 (Side two)
THIS TAPE HAS BEEN RECORDED ON APRIL 27TH 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..
Picture number 18. Negative number 776921
There’s very little left to describe in this picture. Hung on the wall on the right of the governor is the parallelogram gear which hung on the post we have seen on the bed and was connected to the crosshead. It was used when you were indicating the engine to convert the 4ft stroke of the engine into approximately 12” of movement on the string which drove the indicator’s chart drum. There were two sets of gear, one for each side of the engine and when not needed they were kept hung on the wall. The top of the column on the bed can be seen just to the left of the governor column.
Picture number 19. Negative number 778807.
This picture simply gives an impression of the governor in motion. It clearly shows the groove in the bottom end of the bob weight which carried a bronze ring to which the governor bars were pinned. As the weight moved, so did the bars.
Picture number 20. Negative number 776139.
This is an indulgent picture, I was fascinated by the fact that though the governor was running it cast a stationary impression on the wall. Once again you can see the parallelogram gear on the wall and two pictures of a lady. These pictures were all over the engine house. They were the covers of the Shiloh calendars from previous years.
Picture number 21. Negative number 767602.
This is a picture of the high pressure cylinder lubricator. There is a story about this lubricator. The lubricator was made by J&W Kirkham Limited, Lark Street, Bolton. Their works was next to Musgrave’s steam engine works and they were the first firm to make a successful high pressure lubricator for steam engines and the Kirkham lubricator came to be the accepted standard against which others were judged. When I took the engine over I stripped this lubricator down and cleaned it out and judged that its performance could be improved by fitting new stainless steel ball seals and volute springs in the two pumps which are driven by the shaft passing into the base. This shaft by the way is driven by a linkage connected to the eccentric rods in such a way that the stroke can be varied.
I rang the company up and spoke to John Kirkham the owner. I complained about the performance of the lubricator and the non-availability of spares and he was quite taken aback because they stopped manufacturing this particular model in 1925/26! I think he must have taken to me because he sent me enough spares to keep the lubricator going for the next 25 years at no charge.
The lubricator is specialised because it is pumping cylinder oil into the HP cylinder against boiler pressure. In other words the pumps and delivery glasses are working at over 140psi. The large glass tube in the centre is the reservoir and is made like this so that the oil level is always visible. The smaller glass tubes on each side are sight glasses through which the oil is delivered from the pumps. If you look closely you will see that there is a drop of oil in the middle of the left hand glass. The sight glass is full of distilled water and has a copper wire fixed in the centre. As oil is pumped in at the base of the tube it forms a droplet and when it has reached a sufficient size it breaks away and floats up through the water to the end of the delivery pipe at the top of the glass. In this way the flow of oil can be monitored very easily.
The next thing to recognise is where the oil is going to. When I took the engine over the two feeds went to a hole drilled in the steam chest above the middle of each steam valve. The theory was that it dripped on the valve and was distributed in the cylinder by the steam passing through the valve. As early as 1920 it was widely recognised that this was inefficient. I have a copy of a report made on the lubrication of the Bancroft engine in 1924 by the Vacuum Oil Company where they recommended this method. The best way to lubricate a steam engine was to introduce the oil into the steam main above the stop valve via a spoon shaped orifice with a slit in it. The effect of this was that the oil is atomised by the steam passing into the cylinder and lubricates every internal part of the engine including the LP cylinder. I altered the oil feed by fitting an atomiser and cut down the amount of oil used by half and the engine ran a lot better. I did things like draw one of the low pressure valves out of its housing to examine it and the theory worked, the surfaces were lightly oiled. It had taken 49 years for the Vacuum Oil Company’s advice to be put into effect.
A very important factor in cylinder lubrication is the formulation and quality of the cylinder oil. The first thing to be taken into account is the conditions inside the cylinder. There is a great deal of difference between a cylinder running on dry steam with high superheat as many later engines did and an engine like Bancroft running on what is known as ‘saturated steam’, in other words steam at boiler temperature which is carrying water with it. In the former case a very thick, high temperature oil is needed with characteristics which can resist the tendency to carbonise in the cylinder. For saturated steam you need an oil which can resist emulsification by the water in the steam. This isn’t rocket science and my way was to approach a firm called Walkers Century Oils at Newcastle under Lyme who I knew supplied all the cylinder oil to the National Coal Board for use in their steam winding engines. It was a fairly safe bet that they had investigated the properties of the oil supplied to them and ensured that it was correct. This was the case, I changed over to Walker’s oils and we saw an immediate drop in oil consumption and an improvement in the running of the engine.
As part of the process of deciding on which oil to use Walkers took a sample of the oil that we were using when I took over and reported that it wasn’t cylinder oil at all. I had seen the name ‘Core Oil’ on the barrels and had assumed that this was the name of the manufacturer. I was wrong, this was exactly what it was. It was an oil used in foundries to bind the cores used when casting metal into shapes with cavities in them. It was nothing to do with lubricating steam engines. The only properties that it had going for it were that it was cheap, black and thick. The walker’s oil was thin and transparent. If you look at the drop travelling up the sight glass you can see that the light is shining through it. [In 1986 when I was running the Ellenroad engine I was in the fortunate position where I could call on the resources of the Total Oil Company to recommend the best oils to use on the Ellenroad Engine. By that date it was very difficult to find a supplier with technical experience of steam cylinder oil because the market had vanished. Total had not got an oil that would do the job. Walkers were still in business and Total approached them and got them to recommend a formulation. What we got eventually was an oil almost identical to the oil we had been using at Bancroft but with the addition of a modern ingredient that ensured that the residual oil left on the cylinder walls became a waxy coating when it cooled down, thus giving us increased protection during the long periods when the engine was stopped. As a matter of interest their recommendation for the thin oil used for lubricating the bearings on the engine was exactly what we had used at Bancroft. A straight SAE40 mineral oil.]
I will come back to an illustration of the quality of the cylinder oil when we describe one of the later pictures.
On picture 21 you can see one of the nuts on the holding down bolts at the front end of the cylinder casting. These were the only ones which were bolted dead tight. Even so, when the engine was heavily loaded if you looked very carefully at the joint between the cylinder casting and the base plate you could see a very light movement as the engine was running.
The oil can resting on the casting to the right of the lubricator is an old one made of tinned steel plate. It holds cylinder oil and is kept on the casting so that it is hot. The handle could be grasped with the bare hand but the body of the can was hot enough to burn you.
If you look at the base of the lubricator on the right hand side you will see two threaded screws with lock nut securing them. The nearest screw is for adjusting the stroke of the internal pump and thence the amount of oil delivered at each stroke. The far screw is a stop screw. If it is screwed home on the seating at stops all oil delivery to the glass. This was used if a glass burst while the engine was running. There was a valve on the delivery pipe as well so that the glass could be isolated from the system while a new one was fitted. I have had sight glasses burst and have isolated the feed but never changed a glass while we were running. Because I had fitted new valves and springs in the pumps and because both pumps were delivering to the atomiser in the steam pipe all I had to do was increase the feed on the remaining pump.
Picture number 22. Negative number 776213.
This is a closer view of the high pressure valve gear, showing clearly the Dobson Block, the valve rods and the back steam valve with the bell crank. Notice the small lubricators - this engine was running when I took this picture, that’s why it's slightly blurred. You can see the action of the catches from this photograph, the far one is open, it has let go of the valve rod and the spring loaded rod to the dashpot has slammed the valve shut. The near valve is closed and the catch on the Dobson Block has grabbed the valve rod and is opening it by pulling the back valve rod forward. This turns the bell crank, which rotates the valve spindle. This opens the valve and at the same time lifts up the dash-pot rod against the compression of the spring ready for snapping it shut when the catch on the Dobson Block leaves go of the end of the valve rod. This is a very simple motion and very efficient. It has its faults but it has tremendous advantages. There are no small springs, cams or catches to go wrong, everything very solidly built, and engineered to last a life time as was everything else on this engine. 1 should point out that when this engine was made redundant it was nowhere near worn out. The high pressure cylinder was bored or rather rebored and new valves fitted in about 1958. Brown and Pickles did the job and when Newton heard I was taking the cover off to fit a new packing he came up and measured it and the wear was negligible on it in 1976.
We have to descend into the mysteries of the governor again at this point. Notice the levers mounted on each end of the Dobson Block. Recognise two things about them. First, they are connected to the governor by the rods fitted to the top bar of the frame which holds the pair of levers rigid. Notice the hook on the base of each lever which contacts the catch plate mounted on the same pivot when the block has reached a certain position.
It’s important to realise that the rods from the governor do not move apart from the very small adjustments to the position of the end of the rod where it connects to the frame transmitted from the governor. In effect, this position of the top of the frame is a fixed point which can be adjusted by the governor. As the Dobson Block is driven backwards and forwards by the top eccentric rod the effect is to cause the levers attached to the governor rods to oscillate on their pivots. During this oscillation they alternately lift and drop the catch plates thus making or breaking the connection with the steam valves. The actual point in the block’s travel where they release the steam rod is adjusted by the governor moving the tops of the levers closer together or further apart. If they are moved towards each other the catch is released later in the piston travel. If they move the levers apart, the hooks lift the catch plate earlier. The linkage is so designed that if the governor rod drops the lever tops are moved so far apart that the catches are permanently held up thus stopping the ingress of steam to the cylinder. This simple mechanism can control the shutting position of the valve, the cut-off point, at any value from zero, always closed, to 90%, steam admission for 90% of the stroke.
One word about the catches themselves. The catch plate had a small dovetailed slot cut in each side into which a very precisely cut piece of leather could be inserted. This cushioned the contact of the catch plate with the block when it was dropped. These had to be very carefully fitted because they actually altered the grip the hardened steel wedge on the bottom of the catch plate had on the mating surface on the steam rod. The wedges themselves were made of high carbon steel treated after manufacture to make them ‘pot hard’, in other words, as hard as glass. This meant they were very brittle but this was no matter as they were solidly fixed to the catch plate by three countersunk headed bolts solidly nutted to the plate. Newton once told me that when making these wedges it was important to machine them so that any machining marks were in line with the motion of the catch. If this wasn’t done he said that the catches would give trouble in service. The wedges were machined in annealed condition and then heat treated to harden them after manufacture.
The wedges need to be hard because if you think about it, once they have been lifted to release them, the block drops them back down as it moves back in the opposite direction and in order to reach a position where it can operate again it has to ride backwards over its mating wedge and drop down again behind it. This constant contact and sliding motion over the mating wedge would wear the edge of the catch if it wasn’t dead hard. As far as I know, the wedges on the Bancroft engine are the original fittings.
Picture number 23. Negative number 776217.
This is a general view of the inside face of the HP cylinder. The engine is running and the Dobson Block has almost reached the extremity of its forward travel. It will then reverse and open the front steam valve a fraction of a second before the piston reaches the end of its stroke. This admission slightly before the crank has reached dead centre is known as ‘lead’, the valve is ‘leading’ the piston. The affect of this is to ensure that when the piston reaches the end of its stroke steam is already entering the cylinder and cushions the end of the stroke. If you look very carefully at the front end of the back steam rod you can see the back edge of the hardened steel wedge which the catch plate will engage with as the Dobson Block reverses its stroke. Notice that all the rods have adjustment both for length and for adjusting the bronze bearings on the pivots.
This is a good view of the dashpots. Notice that the open end is covered by a heavy leather washer on the dashpot rod. This muffled the hollow noise that the piston made when it slammed down into the dashpot.
This view also shows the tin kettle specially shaped to sit inside the insulation to warm the cylinder oil up. You can see the handle just in front of the steam pipe framing the Shiloh lady’s face. Notice the handle of the drain cock in the tray. It is lying across the pipe, and not in line, this tells the engineer immediately that it is closed.
Picture number 24. Negative number 776204.
This is an overall view of the HP cylinder including the tail slide which, because of the long exposure has completely disappeared. This is a good place to discuss the question of tail rods. A lot of visitors used to ask why the engine had a tail rod on the HP side. They could see the reason for it on the LP as it was needed to drive the bell crank and thus power the air pump in the cellar. The HP tail rod looked redundant to them. In point of fact it probably was, plenty of cylinders of this size function quite reasonably without a tail rod. However, if you think about it. What we actually have here is a heavy steel rod probably 12 feet long with a heavy cast iron piston fitted on it. If there was no tail rod the piston would tend to lie in the bottom of the cylinder due to its weight not being supported. In practice this wasn’t necessarily the case while the engine was running. The inside of the cylinder is coated with a mixture of oil and condensate and the piston tends to float over this coating. However, it is undoubtedly a better quality of construction to support the back end of the rod and Roberts obviously made this decision when they designed the engine. Personally I like the idea, it is a more satisfying engineering solution. However, I have to admit that if there is no tail rod there is no need for a gland and no leakage because the cover is solid.
Think about the case if you had this piston rod set up on ‘V’ blocks outside the engine. You would have a heavy steel rod approximately twelve feet long with a heavy cast iron piston hung on it. The rod, despite its heavy construction, would sag slightly. Newton Pickles told me that when they were building these engines they would put the rod and piston on a lathe and jack it up in the middle to give it a slight curve or ‘set’ which compensated for the sag caused by the weight of the piston.
There is a story about the Bancroft engine in this respect. Newton’s father, Johnny Pickles, once told him that when Bancroft engine was first installed the low pressure was giving a lot of trouble. He said that Roberts’ men stripped it down one weekend and rotated the piston and rod through 180 degrees. Johnny reckoned they had put a set in the rod but had assembled it the wrong way up. After that there was no trouble.
There is one more thing to consider about the fitting of a tail rod. Think back to our discussions about pistons and steam pressure. We have agreed that the force exerted on the piston is the product of steam pressure in pounds per square inch multiplied by the area of the piston. Take the example of a piston 16” in diameter. This gives a surface area of 201 square inches. Given a steam pressure of 140psi this gives a force on the piston of 28,140lbs. However, the area of the piston rendered unusable by the 3” diameter piston rod is 7 square inches, a loss of force of 980lbs. A loss of 3.5% of the effort. Consider a cylinder with no tail rod, the back end of the cylinder is producing 3.5% more effort than the front end and in order to get a smooth running engine this has to be allowed for in the valve setting. This is a relatively small amount but needs to be taken into consideration if you are aiming for perfection. However, a word of caution, there is a further complication to this matter which is to do with unequal events in the cylinder caused by the angularity of the connecting rod and the characteristics of driving on a crank. I don’t intend to go into this here, it is too complicated but if you are really interested, get a good book on steam engine principles and go further into it. And they say steam engines are simple machines….
At one time it was suspected there was a crack in the tail-rod of the Bancroft engine and while the new one was being made, the tail-rod was taken off, the gland blanked off with a piece of steel plate, and the engine was run without a tail-rod with no apparent ill effects.
At the back of the high pressure cylinder you'll see the other drain cock, coming out of the bottom of the cylinder, the back high pressure drain cock. There again, that's shut, the handle's in the cross position, if it was pushed down that was open. When you were starting the engine you always started with these drain cocks open in case there was a slug of water there. As the engine speeded up and the cylinder's got to working temperature and there was no chance of a slug being blown up the pipe the valves were shut so that you got full pressure otherwise you were wasting steam of course, it blew out down those pipes. You'll see that the drains from the steam bonnets to carry away condensation and oil into a pipe at the bottom of the cylinder and come down and then go down into the cellar. The bucket which stands at the back of the cylinder was the oily waste bucket. When you had dirtied a piece of waste and covered it with oil, you just threw it in there and when that bucket got full the firebeater used to take it down into the boiler house and throw it in with all the other dirty waste and it was used either for lighting the boiler fires or simply burnt at weekends in the firebox to give us a bit of steam and get rid of it.
Picture number 25. Negative number 777229.
This is just an overall picture of the high pressure side and the flywheel. The engine is stopped, notice that the governor bars are on the stand and the spindle of the stop valve is as far in as it can go. You have clear view of the small ladder for oiling the governor and behind it the splash guard for the high pressure crank. Behind the governor is the distribution board for all the electricity in the mill and behind that the room where the alternator is. You can clearly see the pipe into which the bonnets drain into the cellar. Notice the drain cocks, it is immediately obvious they are open by the position of the handles. If you look at the gauges you can see the pig tail traps and the fact that the cock to the compound gauge is partly closed to stop vibration in the gauge. The cock on the steam gauge on the bottom right is choked down as well but that isn’t as obvious.
Picture number 26. Negative number 777236.
This is a picture of the back cover of the high pressure cylinder. The thistle oiler for the rod is clearly shown as is the large housing for the metallic packing. The most interesting thing about this picture is probably least obvious. Look at the pipe leading away from the drain valve at the bottom of the packing housing. Notice that it is covered in encrusted oil and carbon except for one part where the oil from the packing that escapes through the opening in the housing for the piston rod drips down on to the pipe and then into a small bowl underneath. I left this pipe like this to demonstrate what the effect of using good quality cylinder oil is. The whole of that pipe used to be covered with crust but as the new oil worked on it it gradually dissolved the old deposits away. I’m not suggesting that the internal surfaces in the engine were as heavily contaminated as this pipe but there is no doubt that some would be present. I think it’s fairly obvious why the engine ran better on the Walker’s oil. When the managing director asked me why our oil was more expensive I showed him this and told him to note the fact that we were using less. He went away and never queried it again.
The metallic packings were very good. There was never any leakage but occasionally you would see a thin drift of steam there especially if the light was behind it. This wasn’t leakage, it was simply a small amount of condensation carried out on the rod. As soon as it got to atmospheric pressure it flashed off into steam. This happened to a lot of the condensate in the engine that was exhausted into the receiver, it flashed into steam. Incidentally, one thing I could never understand was that the receiver pipe in the cellar wasn’t insulated. The engine would have been more efficient if it had been.
Pictures 27 and 28.
These illustrate the fact that there was a good view out of the engine house. The end window was made so that it could be removed in order to get the largest part of the engine out if need be. The condensation illustrates the fact that the atmosphere in the house was always moist. This was no problem as far as the engine was concerned because it was always warm.
Picture number 29. Negative number 770203.
This is a picture down the high pressure side of the engine at night. This is a very long exposure, you can see that the con rod and crosshead have dissolved into streaks of light. I have to admit that I love making images like this, the engine actually looks alive.
Notice the carpets on the floor. These helped deaden the echo in the house and modify the sound. They were also safer to walk on, less chance of slipping. Another advantage was that they tended to trap the dust that was always floating around. I always took the view that the more dust trapped in the carpet the less in the slides on the engine. One thing you may have noticed in the engine house is that I had no plants. The previous engineer used to grow tomatoes in there but I could never see the sense in it. What was the point in bringing grit into the house? I wanted to keep it out.
Picture number 31. Negative number 770241
This is a picture of the governor running on the edge of darkness illuminated by one point source of light. It used to fascinate me that this produced a halo.
One point of interest on this picture is that there is a small notice hung on the governor stand. Newton once told me that when they replaced the Whitehead governor in 1948 with the Lumb, the engineer was so pleased with it that he hung a notice on saying ‘The Boss’. When I had finished my improvements to the valve gear I was so pleased with the steadiness of the governor I put my own notice on; ‘I’m in charge’. It was too! It’s possible to get quite attached to an artefact that gives nothing but good service.
One final point. If you look in the bottom left hand corner you can see the top of the front HP relief valve and the cover on the back of the front steam valve seating. Look at the casting in front of the cover. This is a rough casting straight from the foundry but notice that it is lightly oiled, shiny and the edges are polished by 60 years of wiping down. This finish can’t be reproduced artificially, it’s like the patina on a piece of furniture that has been cared for over the years. This gives an indication of the level of care and attention that was given to these lovely machines over the years. You don’t see electric motors polished like this.
SCG/13 September 2003
4,911 words.
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Stanley Graham (Engineer & Researcher) Tape 11
