RG 2007 September
| This page is part of The Cidermaking Year by Rose Grant
Tom Putts are falling
My friend Becky came round a few days ago with a bag of perfect Tom Putts. They were uniformly 3 inches in diameter, stripey and ribbed, just as if they had just jumped out of the picture in Liz's Pomona. "They are falling already, perhaps you would like to press them", she said. I had not wanted to start pressing quite so soon as I was still busy getting the equipment ready, however I realised I was in a situation of my own making.
Some years ago I gave Becky and Terry a Tom Putt to plant in their garden. It is now a sturdy young tree that produces a fine crop of beautiful apples every year. It has well outclassed those that I planted at the same time in my orchard, being in a more sheltered spot with its roots in the fertile loam of the valley floor. I had hoped that its apples might make a little cider for my friends, as well as apple pies! One day this may happen but Becky is far too busy at present with a responsible job in Poole, as well as the bringing up of their two lovely little girls. Terry's carpentry is continually in demand in the local area. You may remember I managed to coax him away from his customers for a few hours to rebuild our May Queen throne. I look forward to seeing his daughters taking their place on it in future years.
The sight of those apples on the table in the ciderhouse spurred me into action. I had been building and testing my pomace pump. The Mono pump that I bought second hand last month, needed to be fitted with a motor and the whole thing built up on a 5 ft long machine bed. To cut a long story short, I had found the ideal 1 hp motor plus gearbox on ebay and also a 3 phase inverter to power it from my single phase mains. I now built the whole thing up on a 5 ft piece of 9 x 3 building timber, filled the pump hopper with water and switched on. To my great delight it purred away beautifully and the water gulp gulped from the pump outlet. What I now needed to do was to test it for real, with some pomace. Tom Putts? Why, of course!
shaking the trees
Next morning I hitched Benji's lead to one handle of the wheelbarrow and we pushed on, up the path to the orchard, for his morning walk. On arrival it was no surprise to see lots of my own Tom Putts nestling in the grass. Only a gentle shake of each tree was enough to bring the others tumbling down to join them. There was also a good sprinkling of Redstreaks on the ground that I could add to my collection. Whilst Benji chased the rabbits, I filled the barrow with my first apples of the season. Later I picked the rest of Becky's apples, so I now had a worthwhile quantity to test the pomace pump.
I had made a small wooden hopper to extend the pump hopper so that the output of the Vigo mill could drop straight into the pump without splattering pomace all over the place. This was now bolted on to the flange of the pump hopper. I fitted a short piece of 2 inch hose to the pump outlet so that the pomace could be directed into a plastic box. The Mill was positioned over the hopper and now the anxious moment had arrived! Would it work?
sausage making machine
The milling began and the hopper was soon full of minced Tom Putt. I hardly dared to switch the pump on. When I did, it was amazing! The pomace was sucked away into the hopper and soon a sausage of pomace exuded from the end of the hose, into the box. I was ecstatic. Indeed this was a veritable pomace sausage machine! The pulsing of the pump ( due to the sequential formation of the cavities ) was causing the pomace to be ejected in regular short lengths that very soon built up a little heap in the box. Greatly encouraged by this I poured more apples into the mill. Now I discovered why Alex had mentioned the need for being able to control the speed of the pump. If the speed is set to match the mill output the pomace just unfolds like a thick ribbon from the mill, whereupon it is continuously gulped up by the pump. I'm so glad I went to the trouble of getting a 3 phase motor and an inverter, rather than mess about with single phase and gearing. It is so easy to set the speed by controlling the frequency of the inverter output.
I went on to make cider from the pomace using the small press and produced 15 gallons. This will be used as a starter for the main fermentation in the next week or so. The pomace pump is now coupled by 10 metres of hose to the hopper above St. Em in readiness for the serious business soon to come. I've made a T shaped pusher tool that fits into the pump hopper without being able to touch the auger. This will be used to assist the operation if there is a build up of pomace in the hopper.
labour saving ideas
At the end of the pressing season last year I knew that I had to reduce the labour if I was going to do it all again. 70 hl is a heck of a lot of work for one person and Arthur Ritis was not at all happy about it. I wanted to complete the external elevator system that I'd been building. This needed a lot more building labour to construct the washing tank and water channel to transport the apples. It was impossible to find the time to do this due to Frances' illness this summer, so I've had to look at other labour saving ideas. The pomace pump will save a lot of the work in cheese building. I've also installed an electric hoist to lift the washed apples up to the hopper of the mill ( another back aching job ). The acquisition of a tipping trailer means that I should be able to drop the apples straight into the wash tank. This will save me from all the shovelling I had to do last year.
I will let you know how it all works out. Rose.
The elevator is a wooden box with rubber belt type from a grain drying barn. Last summer I converted it for use with apples by removing the rusty old scoops and fitting wooden paddles. I copied the idea from Julian at Burrow Hill. As you will have gathered, completing the project is beyond me at the moment. Heavy groundwork at the foot of the elevator and building work on the barn roof to get the apples from the top of it into the loft, has defeated me this year.
Stainless Steel Welder
Instead I've concentrated on various labour saving devices that can be applied to the process, whilst keeping everything at ground level. Yesterday I mentioned the pomace pump, but I've also looked at some sort of auger to lift the apples out of the wash tank. Like you say, stainless augers seem to be impossible to obtain second hand. A few rusty old 6 inch grain augers are the closest I've come to it. I asked Steve, my favourite stainless welder, to look at making me a 6 ft length of 10 inch diameter auger, to which I then hoped to add a motor/gearbox. When he costed the exercise he found that the stainless pipe alone would set me back £500. End of auger story for this year!
A week of two after this little episode I was visited by those nice people from Middle Farm in Sussex who wanted some boxes of my cider for sale in their wondrous cider shop. We chatted about cider making generally and I mentioned that I wanted an auger like the ones that feed the washing tank to the mill at the input side of a belt press. They told me that they had bought a belt press the previous year with the very same system and that they were most disappointed with it. Apparently there is a marked tendency for the apples "to fall back down the auger". I did not really understand the problem. Do especially rolly polly apples see it as a sort of helter skelter and prefer to roll back down rather than being borne aloft? Or is it perhaps that with soft apples, mushy apple drops back into the water, after escaping through the clearance between the auger and pipe in which it rotates? The auger had always seemed such a wonderful idea for getting the apples out of the water. Sadly I'm now somewhat disillusioned.
You mentioned the plastic pipe type of conveyor. I've looked at these too. They are wonderfully flexible and can be curved to suit most situations. Their diameter is too small for apples and I don't think the wiggly stainless flattened spring inside the pipe would work with pomace. The juice would almost certainly fall back down. I had a quote for a new one complete with its own stainless hopper. It was over £4000. Hmm!
It's back to the good old grass rake for this part of the job. However I have been able to make one improvement in this area. Last year I was filling B&Q plastic storage boxes with the washed apples. This year I've made a big apple box 2 x 3 x 2 ft deep. Its base is made from one of those big brown baker's trays which are essentially a heavy duty plastic mesh. The sides are made from scrap 3/4 ply. It is designed to fit on the top of my wheelbarrow. The idea is that I will wheel the apples into the barn ( the mill and pomace pump are in the Sputnik room ) and then the box is hoisted by an electric winch until its base is level with the hopper of the mill. Hopefully any remaining water on the apples has by this time drained through the base of the box into the wheel barrow. The barrow can then be pulled away when the box has been lifted clear. There is a small door at the bottom of one side of the box. This opens to form a chute that is placed over the rim of the mill hopper. It is still very much of a "hands on" job again at this stage, but at least the backache caused by all the lifting should be a thing of the past.
If the mono pump proves to be a big success I could progress to having the washing and milling together at the apple receiving end of the barn and pump the pomace over a greater distance to the press. A simple conventional belt elevator about 6 ft long to get the apples from the wash to the mill would then be the only thing needed to complete the automation. The old grain elevator outside would then be even more of a museum piece than it is now!
On Monday I collected my first load of apples. We carefully monitored the weight, as the new trailer was loaded. Having worked out that the tractor front loader bucket held 220 kg by filling it with boxes weighed on a spring balance, from then on it was just a matter of counting. At 1760 kg the apples were only an inch below the top of the trailer's mesh sides. I had calculated that with the new sides the trailer should hold 2 tonnes. However it looked as though an extra bucket would heap the apples above the top, so I decided not to risk it. I should have realised that they would shake down, because after the first mile or so there was about 3 inches of clear mesh showing. Two tonnes it will be, from now on!
Apples on the move
It was good to see all the apples in my rear view mirror gently swaying from side to side and I felt excited that the new season was about to begin. It's a much more pleasing view than the blank aluminium of the old cattle trailer and the new galvanised mesh looks really good, I mused. Suddenly an oncoming Landrover flashed its lights. Soon afterwards a car driver bipped his horn. Was there something wrong with the load? Then the penny dropped, the drivers must have been cider drinkers! There is only one reason that such a load of apples could be on the move.
I had to discipline myself not to start milling the moment I got home. I was dying to see if the mono pump would deliver pomace to the press, but decided I would make an early start the following day. Hygiene was not to be overlooked in the excitement. I forced myself to spend the rest of the day cleaning the ciderhouse and sterilising everything that would be in contact with juice. I scrubbed St Em's racks and put them and their cloths in the tank to sterilise overnight.
I was rather nervous about starting on Tuesday morning, being fearful that the Mono would clog up and be completely useless. How sad this would be, after all the work involved getting it fixed up with a 3 phase inverter, motor and gearbox. I thought of Alex's warning about cavitation and how a bore of at least 60 mm was desirable. My little Mono is only 30 mm and yet its specification allows for 5mm hard particles and 13 mm soft particles......Sounds rather like pomace, surely? I thought. I had also emailed Julian who thought that I may need to feed back some juice into the hopper, to help keep it running.
( The Mono pump in action. Note tube to provide juice feedback )
I mentally prepared myself for disappointment and the hopeful modifications that would then follow. I had taken a 2 inch pipe from the pump up the stairs and draped it down through the hopper above the press.( I'd decided not to try filling the press hopper at this stage of the trial). Looking down through the hopper I could see the pipe dangling over the cloth of the first layer of the cheese. The whole prospect of it actually working began to seem rather unlikely.
pomace sausage plopping
The tipping trailer and washing tank combination worked well. It was not long before I had the first box of apples hoisted up so that its little exit door was level with the hopper of the mill. Action commenced, apples rattled into the mill and the pomace oozed into the Mono's hopper. I switched on the pump and watched carefully. I was spellbound, as once more I saw the pomace being slowly gobbled. Then, to my delight I could see it climbing up inside the plastic pipe towards the ceiling! In the press room pomace sausage was soon plopping out of the ribbed pipe in a rather disgusting, but highly delightful, manner as it started to fill the first layer of the cheese!
I called Frances to come and see my descending colon. ( We can joke about this sort of thing now that she's fully well again, thanks be to God).
So it went on all day, reliably filling layer after layer. I increased the speed of the Mono from 70 to 140 rpm. This was the speed that was found to be the fastest I could match, in feeding apples to the mill. Stopping the pump in between the layers, to attend to the racks and cloths, I did notice a hesitancy for the Mono input flow to restart, when milling began again. I deduced that this was the cavitation problem that Alex had mentioned. The interruption of the process had created an air pocket in the pomace stream. Here the problem was solved by using the home made T shaped pusher tool.
sheer magic prevails
Once the pomace is fully pressed down into the hopper and in full engagement with the auger, then nothing else needs to be done. Everything is fine. It is not necessary to add any extra juice. I soon found that the secret is to keep the Mono hopper filled at all times. The mill needs to be always tending to overfill the hopper. In this situation sheer magic prevails. A thick tongue of pomace emerging from the mill is continually swallowed as it enters the pump. Next door in the press room a heap of pomace quickly builds up on the next cloth within the cheese former. Wonderful!
There are some major benefits. The obvious saving of labour is accompanied by an increased processing speed. I found that I could complete a pressing of St. Em in one day. Last year I had to settle for a 2 day turn around due to the time and effort needed. It is now almost like having another person working alongside, making up the press while I do the milling. The Industrial Revolution has arrived in Winterborne Houghton!
An unexpected benefit is yield. Last year St. Em leached out 100 litres of juice before pressing began. When the pomace has been pre-squeezed by the Mono I now get 200 litres before pressing begins. Instead of a total yield after pressing of 300-350 litres, there is now 400-450. I'm going to try for 500 tomorrow, by building a full 13 layer cheese.
Such fun! I must be careful not to accumulate 7000 litres too soon!
13 layer cheese
Well I did it, 13 layers!
St Em was stuffed full with as much pomace as can possibly be placed within her jaws. As predicted, 500 litres of juice was obtained. The interesting thing was that 300 litres went straight through the cheese and into the tank before St Em was switched on.
The Mono pump appears to doing a pre-pressing juice extraction job. When the action of the pump is considered, this is hardly surprising. The pomace is firstly compressed by the auger which forces it into the receiving end of the progressing cavity pump. I had a good look at the pump when I had it all apart for cleaning and found it hard to believe that anything could pass through it at all. The rotor fitted very tightly in the stator tube. A small eccentrically rotating clearance area between rotor and stator of about 1cm diameter was the only way in for product entering the pump. It's no wonder the pomace is pulverised and the juice released even before it is forced through the 3 cm diameter output pipe.
The strange thing is that the pomace does not appear to be any different on its arrival at the press. It still has the same porridge like look and texture. I can only assume that with most of its juice pre-released the solid matter part of it occupies less volume. More apples therefore have to be milled to make the cheese. I estimate that I processed at least 3/4 ton to fill St Em instead of the usual 1/2 ton. I can't calculate the actual yield per ton until I've emptied the trailer, but it is looking good.
At the end of play today I had filled my first 1000 litre tank. I celebrated the first tank of the new vintage by drinking one of the last pints of the a old. It has been a solid 10 hours of work and I'm exhausted.
Must fall into bed now, Rose.
How do people sterilise their equipment?
I wondered about this problem and still do.
A while back I decided that the answer was to make a tank using one half of an IBC. This is large enough to immerse my 33 inch racks, in between pressings. Nothing scientific, i just throw in half a handful of metabisulphite to make a weak solution. I do the same thing with the press cloths using a sawn off blue poly barrel as the container. It is an insurance that works well for me. I know some people use bleach but I hate the smell of it, even more than the 'up your nose' sulphite. Bleach also needs a lot more rinsing off to be sure it has all gone, whereas a little residual sulphite can only be beneficial.
The blackberry indicator
The recent discussion about the ripening of apples has been interesting and informative. Every year I take a bite of each variety that I pick and kid myself that I can foretell the quality of the end product. Actually I think it is impossible. It is easy enough to get some idea of the amount of tannin and acid but sweetness is difficult to gauge as it is masked by them both. The potential quality of the flavour that will be imparted to the cider is even more difficult to determine.
The old countrywoman in me can't help but look for signs when confronted by the eternal mysteries. Since Benji our black labrador arrived six years ago, I've been taking him on our morning walk up the Whiteway. This is a path that climbs up the downs surrounding the village, so called because the underlying chalk turns it white in dry weather. Where the steepness starts to become more level nearer the top, the path breaks out of a beech copse and there exposed to the total sunlight received throughout the year is a long clump of brambles. I pick a handful of these as I get my breath back and then savour them whilst enjoying a birds eye view of the village. Benji is also adept at blackberrying, a typical labrador!
I've got to know these brambles as well as if they were cultivated in my orchard. There are 3 varieties. Early, ripening in July/August. Main crop, in August/September and a less prolific later variety that has berries with a pale blue bloom. I think of these brambles as an indicator of solar absorption and rainfall for our locality. I start tasting about the end of July and usually the early variety is very juicy though not highly flavoured. The berries have more sharpness than the main variety and not very sweet. Last year was an exception. They were pleasantly sweet due to the exceptional summer. This year however they were mouth curlingly sharp. This does not bode well for the apples, I thought.
Then came the main crop basking in the early autumn sunshine, or should I say the late summer with which we are now blessed. These blackberries are the tastiest and juiciest that I can remember. Delicious!. They've been a very tasty reward for climbing the hill during the last 3 weeks!
I am therefore inclined to agree with Con. I think the mid and late season bittersweets will be superb. After all, the early sharps always give around 1045-50, don't they? I've got 1000 litres of it, just like last year, but I'm optimistic about the overall blend.
trailer load competed
Today I completed the first trailer load and was able to calculate the yield of the new set up. 1160 litres was made from 1760 kg of apples. This is 65.9% or 145 galls per tonne. Last year I was getting 136 galls per ton. Of course it may be that the apples are juicier this year so I can't really attribute the increase to the Mono pump. Nevertheless it is a step in the right direction.
Actually the apples I did today were mostly Cider Lady's Finger and seemed less juicy than the early varieties I've done already. They weren't very finger like this year. Due to the heavy crop, they were hard little oval shaped green bullets. I found it necessary to take Julian's advice and feed back some juice into the pump hopper. It was easy to arrange this by connecting a small plastic pipe to take some of the newly pressed juice from the small Sputnik tank close by. It made a world of difference and I found that I needed to slow the pump down because I could not mill fast enough to keep up with it.
The big difference with using the Mono pump is in the amount of juice that simply flows through the press before pressing begins. This means that fewer pressings are needed to produce a given quantity of juice. Last year it took 4 pressings per 2 ton trailer load. This year it's been 2 1/2. Admittedly the load was 240kg short of 2 tonnes so the true figure is probably nearer to 3 pressings per trailer load.
Pumps instead of a press?
I can't help wondering whether a series of mono pumps could be as good as a belt press! Say a 60mm, followed by a 40 mm, followed by a 20 mm, followed by a filter to let all the accumulated juice run out from the remains of the pomace. I'm throwing this in to tickle your engineering mind Dick! I know that you are interested in these pumps. I suppose something like the law of diminishing returns would spoil this idea. I have this daft vision of a continuous process that isn't one of those hugely expensive belt machines, but then what would be the POA for three of Alex's Schneider pumps?
Upsetting the apple cart
I've done a daft thing already. The new apple box that I made to fit the wheelbarrow is an accident waiting to happen. I wanted it to hold enough apples to make 3 layers on St. Em, to cut down the journeys between the washing tank and the mill. I found that 200 kg perched on the barrow was impossible to push and had to make do with having the plywood box only half full. Even so the high C of G meant that the whole thing is very unstable. The accident in waiting, inevitably occurred. As I rounded the corner into the ciderhouse the barrow lurched sideways. Next thing I knew was that I was sitting in a heap of apples with the barrow and box on top of me!
It was rather a shame because I was almost there and about to hitch the box to the electric hoist beside the mill. This part of the idea works very well and saves lots of apple lifting so I must persevere. I've bought one of those small, 4 wheel garden trolleys. It is basically a steel mesh box 4 x 2 ft with 1 ft sides, and here it is filled with redstreaks ready for milling:
I am fitting hooks to it so that the whole thing can be hoisted up to be level with the mill hopper. Wheelbarrow to be relegated to garden use.
Yesterday I took the trailer to west Dorset to collect a load of apples from Oliver's orchard. When I arrived Oliver and family were busy refilling the large roadside hopper for the next day's collection by the lorry that takes them to the cider mill at Shepton Mallet. They had shaken a good many apples down but Oliver still had a lot of collecting up to do with his tractor cum harvester. It was good of him to break off from this for a while to fill my trailer.
Nehou and Tremletts
They were working hard to clear the early varieties. Browns had all been done but there were plenty of Tremletts and Nehous left. Unfortunately the Nehou trees which had started falling some weeks ago now had too many bad apples on the ground for a usable crop to be Harvested. Oliver could not risk sending them to Shepton Mallet. Apparently if they are not satisfied with the quality on arrival, then the whole load is dumped and the grower has to pay all the costs involved! Fortunately there was a good crop of Tremletts which is an apple that keeps well, so hardly any of these were bad. Last year I was still collecting good Tremletts off the ground in early November
Nehou Apples pic by Andrew Lea
I was happy to take a 1/4 ton of the Nehous. I've been wanting to try my hand with them since tasting Ni's wonderful Nehou and Perthyre cider back in May. They will take a bit of sorting at the washing stage but it will be interesting to do a quantity on the small press. I can't resist experimenting with a variety that I've not come across before. The rest of the load was made up of the excellent Tremlett's Bitter, my favourite early.
Where to buy cider apples
Several people have emailed me to ask for a source of cider apples. The orchard I buy from in Somerset is over committed this year but Oliver Strong is happy to sell some from his orchard at Waytown near Bridport. Buyers must have a trailer and be prepared to take a minimum quantity of 1/2 ton. ( one harvester hopper load which is dropped into the trailer ). If you are interested, Oliver can be contacted on 01935 891600 or mobile 07818 274004. The going rate agreed by the big boys for this year is £92 / tonne.
Those little red pointy Tremletts have been rattling into the mill today. They have also provided an opportunity to try out the new blue Chinese garden cart. It is a great little thing for pulling apples along and each load is enough to make two layers of the cheese. Once in the Sputnik room, the cart is attached fore and aft to the two red Chinese electric hoists. It is then raised so as to be level with the top of my old friend the shiny Vigo Tyrolean mill. Much manual lifting has been saved!
More on process improvements
My new cart only cost £80 which was worth it for the 4 wheels and their integral ball races alone. True it is flimsy, but I will leave the sides locked together. That way it should carry enough apples for 2 layers on St . Em..... in safety. I'm not messing with removable boxes this time, I going to hoist the whole trailer up. One of its mesh ends has a convenient opening in the middle, so I should be able to drag the apples out and into the mill without too much trouble.
I have also invested in another cheapo Chinese electric hoist. With two lifting points I can progressively tip the little trailer in mid air and further assist with getting the apples into the mill. I know that young and fit cider makers will laugh at my machinations, but at my age I have to be continually finding ways to outwit Arthur. He is not troubling me at present, not even after my wheelbarrow fiasco, so I must be winning!
I think there is much to be gained by exploring ways of de-juicing pomace before its final pressing. It is not easy though, on a DIY scale. I think Gary just designed the DIY belt press! I would love to have a go at it but it is beyond my skills with all the gearing etc that would be needed. On the other hand I could imagine taking three mono pumps and setting their speeds so that the throughput rate is constant ( to avoid back pressure on each preceding pump). Only the first pump would need to have a hopper with feed auger, but they would all still be hard to come by. They are not easy to find second hand in this country. I speak from many weeks of searching and I was very lucky to find one in stainless with a hopper.
Thinking of rollers brings to mind those old cumbersome, wooden, sometimes cast iron scratters, usually tractor driven, that we have all seen at one time or another. I'm thinking of the ones that have a pair of heavy stone rollers following the initial scratter mechanism. A fair bit of pomace de-juicing must have been part of the process with those. Those old boys knew a thing or two! Perhaps they realised that fewer pressings would be needed by employing such a machine. It is really what is happening with the mono pump.
I have the feeling, as of times before in engineering, that I've gone round in a circle. It has been exciting nevertheless.
efficiency of milling
It is the efficiency of milling that could be improved. The mono 'enhancement' has made me realise that modern centrifugal mills aren't quite as wonderful as I thought they were. As you will have seen in my further paragraph I'm beginning to think that the old scratters with integral stone rollers were (are ) more efficient at releasing the juice. Like the mono they also crush the particles. The modern mill could do with an extra stage.
This is all terribly interesting but it is keeping me from my tax return. I promised myself that to get the perishing thing done before getting the next load of apples! The strong wind today must have brought the Redstreaks down. They were hanging on a thread yesterday and I picked up enough of their windfalls to make a layer on the press. The Tom Putts have now all been done.
Health of St Em, the big press
Here I have a confession to make. I know St. Em is capable of better things but I'm very worried about her health. Old though she is, 4000 psi is still attainable but now I stop at 2500. The trouble is her old big end is knocking more and more when the pressure builds up and it seems to be getting worse. I dare not push her too far or I could have a major repair job to sort out at just the wrong time of year. Next year I will get the bearings replaced, rebushed or whatever.
It is hard to switch off early because the juice is still running out of the cheese, even though at nothing like the rate it does to begin with. I know I'm losing the last few litres, but better to be safe than sorry.
Her Vital Statistics
The ram is 5.5 in dia, 23.75 sq in. The actual size of the cheese is 32 x 32, or 1024 sq in. I make the pressure distribution on the cheese to be 57.9 psi at 2500 and 92.7 psi, if I go to 4000.
labour and time.
This was the aspect of using the mono pump that I found so exciting and had everybody hitting the delete yesterday (Sorry folks!). The confusion was then triggered by me, throwing in an efficiency calculation, when a known quantity of apples, the first trailer load, had been completed. It is necessary to separate the two aspects. Firstly the labour saving.
Instead of making 4 cheeses for a given volume of apples, I am now making 3.
Instead of getting 350 litres each time I press, I now get at least 450 litres.
Instead of pressing 20 times to get 7000 litres, I will now only have to press 15 times!
There is more apple handling and milling work for each pressing because each pressing uses nearly 3/4 ton instead of 1/2 ton of apples. In spite of this, cycle time is much reduced because the pump makes loading the press so much easier. Importantly, the number of times that worst part of the job; downloading the press, clearing up and cleaning, is reduced by 25% !
In short, I think the mono pump was a clever invention and remember being fascinated when it was discussed here a few years ago. I will enjoy following Andrew's links to learn more about it. From my present point of view, it is 'the best thing since sliced bread'.
juice per ton
The other aspect of efficiency is the actual juice extracted per ton of apples. Certainly the cheese layers are denser and this could hinder juice liberation during pressing. However St Em still produces 200 litres from the press cycle, the same as last year. The extra juice obtained from each cycle being entirely due to the pre pressing run off. I am aware that the efficiency of the pressing part of the cycle could be better.
As the useful discussion showed, the pressure needs to be increased. To get 70 psi on the cheese, for a target yield of 70%, I need to get St Em's pressure up to a bit over 3000 psi. She can do it, but I am having to treat her gently at present (Arthritis in her joints. She's getting a hip replacement next summer! )
inside the pump
I think that squeezing the pomace through the continually varying cavities of the pump is pulverising the apple particles produced by the mill. In so doing this further breaks down the cell walls releasing more juice. The juice then runs free from the pomace when it arrives at the press leaving a depleted and more flaccid pomace in the cheese. The layers of the cheese can accommodate a greater density of this depleted 'floppy' pomace which is why it takes more apples to build a given volume.
That is my reading of what is going on and why I considered the mono to have a first stage pressing ability.
blood out of stone
70 psi is the peak pressure needed. The peak is not achieved until the cheese is fully compressed. At this point the cheese has changed from being parcels of something akin to sloppy porridge to a stack of dry biscuits. The maximum pressure is then needed to wring the last few litres out of these biscuit like layers. They do not appear to have any juice left in them, but it is there nevertheless.. It always seems to me like wringing blood out of a stone. However it is those last few litres that make the difference between a yield of 65 % and one of say 70 %.
I always monitor the hydraulic pressure during each cycle and find that most of the juice has been released by the time this reaches 1000 psi. This equates to a pressure of only about 25 psi on the cheese itself. The initial elasticity of the stack is fairly easy to overcome. It is the final compression that is crucial.