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GENERAL CHEESE MAKING BOARDS (Specific Cheese Making in Boards above) => EQUIPMENT - Forming Cheese => Topic started by: memkuk on October 03, 2009, 08:27:10 AM
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It's probably an overkill, but it works great: compressed air cylinder provides adjustable pressure. In order not to have to bring the compressor into the house, I converted an old fire extinguisher so it can be pressurized at the compressor and then connected to the cheese press.
Eric.
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Looks great Eric. What is the base made of? Looks like granite.
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Welcome to the forum Eric, great first post and great looking press, I assume you use the press area divided by the pressure gauge times the pneumatic cylinder area to get the applied pressure.
Base does look like granite, nice grooves for whey to run out through, if making cheddar you could have a lot of pressure/force, hope it doesn't crack that slab.
The old Dutch style hoops were all wooden, but I think closer slots, any concern of extruding sheets of curd out between the wooden slats?
Again great looking build!
EDIT: Just noticed your avatar image, assume that cheese was made in this press, form looks great, slots must be small enough to minimize extrusion. Sorry, didn't mean to be negative, just concerned.
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Very impressive! That would double as an apple press. Have you used it on cheese alot so far? I am curious about the cylinder size. What is the bore size and stoke length? John brought up a good point about the base possibly cracking under pressure but a simple solution would be a piece of metal tubing running from side to side underneath that both rods go through (you would have to add some short legs also i guess). I couldn't really see the base well but it looks like you might have counter sunk the bolt heads in the granite. is this right?
I used a piece of Corian counter top (sort of like granite)for my base too because you can router your trenches easily and it is easy to clean. Great idea.
This is the kind of post that I come here for! Seeing other people's ingenuity is a real blessing. Thanks again Eric for posting.
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Sailor, John, FarmerJd: txs for the nice reactions.
The base is indeed granite, made from a high grade leftover piece, using an angle grinder. The slab is 3 cm thick, unlikely to crack under pressure... I think (so far so good). The base rests on 4 little rubber feet, which allowed me to counter sink the bolt heads just a little bit into the granite, so as to safeguard its structural integrity.
The hoop is 20 cm high and has an outside diameter of 20 cm (18 cm inside diameter). The air cylinder has a stroke of 25 cm and a maximum rating of 1 MPa (Megapascal), which is 145 PSI. So far I tested the press up to 60 PSI, but normal usage has been 20 PSI and 40 PSI.
John, to be honest, I don't have a clue how to make the correct calculations for applying the correct pressure. So far I kind of guessed. What is the pneumatic cylinder area in the formula you list in your post? Can you deduce it from the measurements I listed above? Would really appreciate if you could solve this enigma for me.
Sorry for using metric measurements instead of imperial ones: I'm European (Belgian), lost in Asia (Thailand).
The cheese in my profile picture was indeed made using this press and the curds extrusion is minimal, but does give the wheel a typical character.
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Eric, from your linked website you don't look so lost, actually look like you are very happy there in Thailand, I especially liked the pictures I presume of you in 70's ;D.
The calculation is basically a ratio. Pressure is weight divided by area, normally measured in Pascals, kPa (kiloPascals or 1000's of Pascals), or MPa (MegaPascals or million Pascals) or in old imperial system mostly only used in US, psi, pounds per square inch. It is pressure that most people use to measure how much load they are putting on their cheese when pressing:
Step #1 - Basic Formula
Pressure On Cheese = [Pressure Pneumatic] x [Area Pneumatic Cylinder] / [Area Cheese]
- Area Pneumatic is area inside your air cylinder.
Step #2 - Convert Area to Formula
Pressure On Cheese = [Pressure Pneumatic] x [π x radius of Pneumatic Cylinder squared] / [π x radius of Cheese squared].
- π is pronounced pi and it's symbol looks more like a double capital t, ie TT.
Step #3 - Simplify Formula
The π's cancel out so we are left with:
Pressure On Cheese = [Pressure Pneumatic] x [radius of Pneumatic Cylinder squared] / [radius of Cheese squared].
- This formula works whether you are using Pa, kPa, MPa, psi or tons, but you have to use the same radius units, don't mix inches and cm.
- Notice that height of cheese hoop or length of Pneumatic cylinder does not enter into the above equation.
Example Calculations
For your example above we are missing the internal radius of the Pneumatic piston, for example calculations, lets assume it is 3 cm internal diameter, thus 1.5 cm internal radius. Therefore:
- Your low Pressure On Cheese was = 20 psi x 1.5 cm x 1.5 cm / 10 cm x 10 cm = 0.45 psi.
- Your high Pressure On Cheese was = 40 psi x 1.5 cm x 1.5 cm / 10 cm x 10 cm = 0.90 psi.
Or if like metric:
- Your low Pressure On Cheese was = [20 psi x 6.895 kpa/psi] x [1.5 cm x 1.5 cm] / [10 cm x 10 cm] = 3.10 kPa.
- Your high Pressure On Cheese was = [40 psi x 6.895 kpa/psi] x [1.5 cm x 1.5 cm] / [10 cm x 10 cm] = 6.20 kPa.
Lastly, instead of finding out the internal radius of your pneumatic cylinder and using the above formula, you could just stick bathroom scales between the granite slab and the follower, apply air pressure and see what reading you get ;D.
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Very nice build Eric! Looks a lot like the apple press Mom had when I was a kid but smaller. I love it!
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I spent 15 minutes working on this reply and then saw John's great response. I didn't cancel the pi's out like John did, but I figured this using the inside diameter of the hoop (18cm) instead of outside (20cm). I also assumed a piston diameter of 2.54 cm instead of 3. (Great minds think almost alike John). With that said here is the post:
I actually I think you have to have the bore or cylinder diameter to figure your pressure or at least that is how i do it. It looked like about a 1 inch cylinder so if that's right the area would be:
.5 in = radius of cylinder
Area = 3.14(pi) x .5 in (radius) x .5 in (radius) = .785 square inches
Next you multiply this area by the pressure you put on it : 60 psi x .785 sq in = 47.1 pounds
Then you have to divide this weight (47.1 lbs) by the area of your hoop:
Diameter of hoop = 18 cm or 7.1 inches which means radius is 3.54 inches
Area of hoop = 3.14 (pi) x 3.54 (radius) x 3.54 (radius) = 39.3 square inches
Pressure on cheese = 47.1 / 39.3 = 1.19 psi on the cheese.
If you go back and replace 60 psi with 145 psi ( the max pressure) you get 2.9 psi on the cheese.
Several disclaimers: I do not know the actual piston bore size so that would change everything.
Second, I taught math and physics for 13 years and I hope i didn't insult anyone's intelligence with all the details. I also could be very wrong and don't mind getting called out on it. I am sure others on here are better qualified to explain it. Third, I think the way you made the hoop with the open slots on the sides makes it much different than a simple solid hoop. This makes it much easier for the whey to leave; even more so than with the weeping holes and since the slots go all the way to the bottom you can still slide the cheese out even if it protrudes some. I may try to make one of those myself.
One other thing is that if you used a hoop that was only 12 cm in diameter instead of 18 cm, the max psi would jump to almost 10 psi on the cheese. Just another thought.
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John & FarmerJD - Txs so much for your extensive explanations. I'll have a look at it again tomorrow morning (it's almost midnight over here...). From a quick reading I gather that I put way too little pressure on my cheese. What I did until now was: when the recipe calls for 40 PSI pressure, I just converted it to MPa (MegaPascal), which is the scale on my pressure gauge, so I ended up putting a pressure of only 0.28 MPa. If I understand it right, I have to make a different calculation for each kind of hoop I use (since I also have a plastic tube type hoop of lesser diameter). BTW, the inside diameter of the pneumatic cylinder is 20 mm (2 cm). I'll make the calculations tomorrow after my first coffee.
John - pictures are from the 70-s and some from the 80-s. I aged like a Blue cheese, while my wife aged like a smooth Gouda. ;)
FarmerJD - indeed, the cheese slides out nicely, even with the curds protruding a tiny bit. It actually looks nice.
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Farmer, indeed great minds think alike ;D, we have same formula/method, different answer as we guessed at different bore of pneumatic cylinder.
Eric, many professional recipes call for pressures which are I believe their pneumatic pressure and assume a certain size mold. They are not the applied pressure on the cheese. For example your 20 cm diameter cheese has a top surface area of:
3.14 x [10 cm / 2.54 cm/in] x [10 cm / 2.54 cm/in] = 48.67 in2
Therefore if you wanted to apply the 40 psi you mentioned to that whole cheese surface area would require 40 x 48.67 = 1947 pounds, the equivalent of a small car! That would easily break your granite base >:(.
I don't know what cheese type you are making but I'm sure members here will have lots of opinions on it ;D if you want to start a new thread on that subject.
Great press, beats the socks off my simple stepladder press (http://cheeseforum.org/forum/index.php/topic,1874.0.html) ::)!
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Silly me! Tropical morning freshness cools my brain and makes me realize that I misled both John and FarmerJD. :-[
I totally misread the Gouda recipe in the book "Cheesemaking made easy". The recipe calls for 20 and 40 pounds pressure, not PSI... How embarrassing!
But I'm still not out of the woods: the Gouda recipe on this site (CheeseForum.org) calls for "5 pounds per 1 US gallon / 1 kg per 1 liter of milk" for the first pressing and "12 pounds per 1 US gallon / 1.5 kg per 1 liter of milk" for the second pressing. What does this translate to when making batches of 10 liters of milk with the press I have? In other words: what should my pressure gauge read, knowing it goes from 0 to 1 MPa?
BTW, John's and FarmerJD's formulas will still come in handy for some other non-cheese related projects, so txs for the lesson.
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After the second cup of coffee I tried to resolve the enigma myself. I came to the following conclusion, primarily using FarmerJD's reasoning as outlined in his post:
Pneumatic cylinder bore = 2 cm, which equals 0.78 inch, hence the radius is 0.78 / 2 = 0.39 inch.
Pneumatic cylinder area = 0.39 x 0.39 x 3.14 = 0.47 square inch.
When I applied 0.28 MPa (= 40 PSI) pressure on the cheese, it was the equivalent of putting a weight of (40 PSI x 0.47 squ in =) 18.8 pounds on it.
It looks to me now that this is how far I have to take it, no further calculations needed.
It also means that the pressure I used was too low: if the recipe asks for 20 pounds pressure, I should have used 0.3 MPa (43.5 PSI), since 43.5 x 0.47 = 20.4 pounds.
If the recipe then asks to increase the pressure to 40 pounds, my pressure gauge should read 0.6 MPa (87 PSI) which will give me a pressure of (87 PSI x 0.47 sq in =) 40.8 pounds.
BTW, I use a converter program to calculate MPa to PSI and vice versa.
FarmerJD - did I do my homework correctly? Please let me know if all this makes sense: I used to be good in languages, but math was not my strongest subject. :'(
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Your math is right and if that is what the recipe means, you are on the right track. However, I am not sure your understanding of the recipe is right. Did the recipe specify a cylinder size? If not then you can't be sure of the needed pressure. Pressure is measured in psi not lbs. This has always irked me about recipes. I for one do try to go by the numbers given in the commercial recipes. In my cheddar recipe for instance i press at 2, 6, and 20 psi. As John mentioned this means huge numbers on the larger hoops. I am currently looking at a way to do this more effectively. I looked at making a press just like yours but with a 4" piston diameter. These are hard to find and expensive if bought new. I just recently came up with a new idea that I am going to try using a suspension air bag.
The bottom line is that I don't think you can put too much pressure with your press on a 18cm hoop. I would start with a fourth of the max pressure for 15 min and then work up to as much as I could.
John, I read your comment on the commercial recipes. I have read somewhere that there is a tool for measuring pressure within the cheese as it is being pressed. Have you heard of this and if this is the case it seems to support the idea that the pressure number is not just for the machine but is the actual cheese pressure. I really want to answer this question. Especially before I go to the trouble of building a new press for my 12 inch stainless steel hoop! ;D
Eric I hope i helped. If that didn't make sense let me know.
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You sure helped. A fourth of the max pressure, then up to max: I think that's what I will do in the future. Good to know that I don't have to worry about the maximum pressure with my setup: until now I was afraid that I would press the cheese too much.
A big txs to Farmer and John.
Farmer - Looking forward to hearing/seeing more of the new press you are planning to build.
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Eric,
That is a truly beatiful press. Well done.
John and Farmer, Very nice and well thought out responses. I'm completly diggging the math. It drives me absolutly crazy to see cheese recipes that do not specify a hoop diameter yet calling for 20 lbs of weight.
Eric,
What are the specs on that cylinder?
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Eric
So you are making Gouda based on the webpage recipe here (http://cheeseforum.org/Recipes/Gouda/Recipe_Gouda.htm) that I posted based on the comparison of four Gouda recipes here (http://cheeseforum.org/forum/index.php/topic,1811.0.html).
As Farmer says, any recipe that gives pressure needs to also give the hoop size, otherwise it can be very inaccurate as one cheese maker can be using a 12" diameter hoop and another 6". The recipe above uses weight per amount of milk which is better than nothing. Even that is a rough guide different sized hoops, 2% vs full fat milk, raw vs past & homogenized etc. Gouda is a washed curd type cheese and is only lightly pressed, vs Cheddar's which are milled and highly presses, so do not got to max. In the end I think it all comes down to experience.
Farmer, I hadn't heard of that sort of gauge, would be good idea. Also, if you are building a new monster press, have a look at the antique cast iron double compounding vertical presses in this thread (http://cheeseforum.org/forum/index.php/topic,1198.0.html). The way I see it, 50 pound weight on ~10:1 first lever gives 500 pounds which then compounds on second ~5:1 lever = 2500 pounds weight on cheese.
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Eric,
i keep forgetting that you are making gouda. I am sure John is absolutely right about not maxing out the pressure. I am only a cheddar man and really not very good at that. I'll just stick to the math! :)
john, first thanks for the correction. Second, wow what a link! I am a kid in a candy store! Forget the cylinder! I have laid in my bed at night trying to think of a way to compact the lever so my pressing unit is a little more contained. Long pressing arm = large piece of furniture= unhappy wife! I feel pretty dumb now. I am definitely going to build one of these. There is actually one more multiplier in some of these that you didn't mention. I attached a pic of one. Notice the weight is attached to a chain that goes through a pulley with a fixed end. That doubles the end result. I can just see that guy jump out of bed when he thought of that one! ;D
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Farmer, right, I didn't think of that single pulley, yep again doubles it!
Those two metal rods, one on each side must take quite a tensile load! The picture like the one your posted is I think more British style with very high triple (not double, thx for correction) compounding for more cheddar type cheeses, it looks like it's out of Industrial revolution era but still works fine ;D.
The pictures of antique Dutch style presses are smaller and single, sometimes double compounding for more lightly pressed Continental Washed Curd type cheeses.
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I would love to find one of those.
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Me also, I check eBay once a month hoping one will show up, bit of sandblasting and paint . . .
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How about a cheap bearing press? I've played with this idea for awhile.
http://search.harborfreight.com/cpisearch/web/search.do?keyword=bearing+press (http://search.harborfreight.com/cpisearch/web/search.do?keyword=bearing+press)
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I have one of these, and I've thought of this as well, i just don't think this will work.
I mean, you could absolutely smash the largest wheels with these.
But placing a constant, known, measured pressure on a wheel would be tough to do with a hydraulic jack.
I could put a load on a wheel, but I would have difficulty knowing exactly how much pressure is being applied unless i put some kind of gauge between the wheel of cheese and the press.
Then, as whey escapes from the wheel, and the cheese wheel shrinks, the pressure on the wheel would lessen and the jack would have to be slowly increased to match the size shrinkage of the wheel.
I have opted not to use mine because of these complexities.
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Erics press kinda looks like a cooler version of my new basket grape press.
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Then, as whey escapes from the wheel, and the cheese wheel shrinks, the pressure on the wheel would lessen and the jack would have to be slowly increased to match the size shrinkage of the wheel.
This is why I like the suspension air bags. see link
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=260484566273&viewitem=&sspagename=STRK:MEWAX:IT (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=260484566273&viewitem=&sspagename=STRK:MEWAX:IT)
With this you could put a simple regulator on the bag adjusted to the desired air pressure and it would automatically kick on to keep the pressure where you want it. These things also produce massive amounts of pressure. With a 8 inch diameter, and 40 psi you would generate 2000 lbs. I was going to do this until I saw those antique press pics. I talked to a welder today. I have got to have one of those.
Wayne, I love the grape press!
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Wayne Harris - The pneumatic cylinder is a CM2B20-150 from SMC (smcusa.com), which I ordered from their Thailand branch.
It's a double acting, single rod cylinder with a 20 mm bore and 150 mm stroke (I incorrectly mentioned in an earlier post that its stroke was 250 mm). ::)
Its maximum pressure is 1 MPa, which equals 145 PSI. All specs can be found following this link: http://content.smcetech.com/pdf/cm2.pdf (http://content.smcetech.com/pdf/cm2.pdf)
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In the end I think it all comes down to experience.
John, roger that. It's what we call in Flemish: "Fingerspitzengefühl". (I know, it's a German word, but we never managed to properly translate it). :)
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Great press Eric:) and would you believe it we are practically Neighbours! Maybe I can commission you to make me one?
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So,
If that cylinder has a 20mm bore, and a 150PSI max internal pressure, I think that means that it presses down with about 73lbs of force.
(20mm is 0.79 inches) or (.48square inches.)
150PSI/.48SI=~73lbs
Now spread that down force over a standard 8in Wheel (~50square inches), that is max PSI of 1.4lbs on the cheese itself.
Sounds a bit light for hard cheeses..
Not trying to be critical, just thinking about one for myself.
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Nick - Hi neighbor, I'm sure we will get in touch soon. Great to have someone else nearby who is interested in cheese making.
Wayne - I'm a bit ignorant in this field. Only after John and Farmer came up with formulas to calculate required PSI of the pneumatic cylinder in relation to surface area, I realized things were more complicated than what I assumed. To me it was just a matter of equaling the pressure of the cylinder to putting weights on the wheel. After following the discussion I realize that things are more complicated. Maybe I should get a cylinder with a larger bore. Any suggestions from your side, taking into consideration that I'm trying to make Gouda with a hoop of 18 cm inside diameter?
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I did some playing with the numbers and just decided to write a small spreadsheet to calculate the max pressure of a given bore size of a piston against different mould sizes, given a constant max cylinder pressure.
I am not a Gouda expert, but It looks like John has used about 2.7PSI on his Gouda. (80lbs on 6” wheel) in the past.
So, given his PSI, and your desire for a slightly bigger wheel (18cm~7inches.), you will need a bit more downforce than his 80lbs.
If you look at the chart, at 150PSI, you can get those kinds of pressures with the 25mm bore.
Looks like the most PSI your rig can deliver to a 7in wheel given 150PSI and a 20mm bore is 1.9PSI
As you can see by the chart, a 25MM bore will be able to deliver 2.97PSI, more than enough for your sized wheel.
I have included the actual spreadsheed if anyone wants to tweak it, or check my math for errors. Trust me, I make em.
<Clarification>, the pinkish area in my graph is the PSI being applied to the cheese.
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Since the piston is not making actual contact with the cheese, I don't understand why the bore size comes into play. On a French press, the shape or size of the ramrod pushing down on the follower doesn't (to me at least) make any difference. It's the follower that's pushing on the cheese.
For simplicity, assume my mold has a surface area of 50 sq. inches. If I put a 50 pound weight on the top of the follower, the FOLLOWER, not the weight, would be transferring 1 psi (50 pounds / 50 sq. inch = psi) onto the surface of the cheese. The shape (or diameter) of the weight doesn't make any difference. The ramrod from the hydraulic unit is just a different source of "weight" i.e. pressure. Without the follower, the ramrod would easily go right thru the cheese, but the follower disperses that weight evenly over its surface area.
The end location mark on the lever of my French Press delivers a 5 to 1 mechanical advantage. If I hang 10 pounds of lead, sand, or whatever, I get 50 pounds at the ramrod. (I have used a very accurate commercial scale to take measurements). So, if I used a hydraulic ram to push down the same 10 pounds at the end of that lever, I would still get the same 5 to 1 advantage with 50 pounds pushing down on the cheese. The bore size doesn't have any effect. Neither does the lever. It's the surface area of the follower as determined by the diameter of the mold. The PSI for 5o pounds applied to the follower of a 4" mold is very different than the PSI on an 8" mold.
It is obvious that recipes need to talk about PSI and not just weight.
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Agree with you sailor on the french press. (damn I want one of those.)
But I think the piston bore size in this case does matter, because I first need to determine how much force, in lbs, is being applied to the follower, before I can determine the PSI being applied to the actual cheese.
The larger the bore, the more force.
The smaller the boor, the less force.
Why?
With a larger bore, that same 150PSI of pressure inside the cylinder has more square inches to push against. Thus the larger the bore, the more force than can be applied by the cylinder to the push rod, then to the follower, then to the cheese.
Ultimately the rod pushes with a force that is measurable in lbs. That force would be exactly 150lbs if the surface area of the bore was exactly 1 sq inch. (and 300lbs if 2in and so on...)
In Eric's case, the actual bore surface area is a bit less than 1/2 sq inch. That yielded about about 73lbs of force applied to his follower. Kinda like stacking 73lbs of rocks on the follower. Instead of rocks, he used a cylinder.
So the size of the bore determines the actual force applied.
Make sense?
So...
Step 1 was determining force applied by the cylinder in lbs. (function of cylinder PSI and bore size)
Step 2 was dividing that force across the surface area of the follower yeilding PSI in lbs/sqin
I think I'm right here. I hope. I trust the pros here will set me straight if not.
The reason I am going through these lengths is because this is the path I would like to go down at some point. I'm still trying to mature my own thoughts about these topics and will use these basic assumptions as i go forward.
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Once again I took too long to post! Wayne said the same thing but here goes anyway.
Sailor,
The reason you need to know the bore size is so that you can figure the force exerted by the cylinder to start with. Just like the weight on the follower is distributed so is the pressure inside the piston. To determine how much force is exerted by the piston when the pressure inside it is 40psi, the bore size has to be known. A piston with a 4 inch bore produces 32 times more force than a 1 inch bore under the same pressure. That 40 psi inside the piston is producing 40 pounds of force on each square inch of the piston bore. More bore = more force.
You are right about the size of a ramrod being unimportant on a french press. In your example you said, " So, if I used a hydraulic ram to push down the same 10 pounds at the end of that lever, I would still get the same 5 to 1 advantage with 50 pounds pushing down on the cheese." My point is that in order to know what pressure to put the piston under to get that 10 pounds, you have to know its bore size.
The PSI for 5o pounds applied to the follower of a 4" mold is very different than the PSI on an 8" mold.
Absolutely right. And for the same reason, the pressure applied to a 4" bore pneumatic cylinder produces a very different force than 1".
I especially agree with your last statement. Very frustrating at times. I wonder if the reason weight is given in recipes instead of psi is:
1. These recipes were created by home cheesemakers not industry and the recipes reflect that, or
2. A lot of people just don't understand the math but still make great cheese and pass on the process minus the science. Just a thought.
Hope I explained that ok.
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This holds true because it is not the pressure AT the follower end of the piston that is being measured (in this case in PSI) but the pressure that is PUSHING the piston rod out of the canister that is being measured in PSI. The pressure in the canister to force (and hold) the piston out uses energy so it is not a direct tranfer of force.
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To determine how much force is exerted by the piston when the pressure inside it is 40psi, the bore size has to be known. A piston with a 4 inch bore produces 32 times more force than a 1 inch bore under the same pressure. That 40 psi inside the piston is producing 40 pounds of force on each square inch of the piston bore. More bore = more force.
OK, Wow, I got it. Cool.. Between Wayne & FarnerJD it makes sense now. No question that with equal pressures a larger bore will exert more pressure (weight) than a smaller bore. I was looking at the metered PSI on the air feed line as being an absolute at the end of the piston - it's not. That PSI is spread over the area of the piston, just like a follower.
I have always thought that science has to be applied in a practical way to be meaningful to the masses. So, here is my practical solution. When I made my French Press I needed to know for certain the true weight applied to the follower. I did the math to figure out the mechanical advantage of my lever, but then used a commercial weight scale to calibrate 3 to 1, 4 to 1 and 5 to 1 set points. Why not just do the same with the hydraulic piston? Put a scale under it and turn up the air. Just check the scale to see how much weight is being applied at at various PSI readings? THAT is the weight being applied to the follower.
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Wayne, I sort of had an "epiphany" studying those double levered presses. It really is simple to add another lever to a press with one arm already. I am not sure if you have one of these but I think it was either you or sailor that did.
You simply attach another post ( call it Post B )on the side opposite of the original fulcrum post (post A). then attach a short connector from the first lever (about 1 inch away from Post A) to another lever (arm) above the first one that attaches to the new post B. In the middle of the new lever, bolt through the ramrod which extends through the first arm but doesn't attach.
ok- i just reread that and it makes no sense. I am attaching a pic of my current press with proposal added. i'm kind of giddy about it and the wife and kids just roll their eyes when I try to tell them. i hope someone on here appreciates it. :-\
MA = Y/X times W/Z x 2 (if I add the pulley too.) I know I can make it out of metal but if I can just add to my existing press ...walah! The idea of having a press with just a few small weights and no hoses or regulators or electricity that sits snug in a corner and can produce an MA of 70, a force of 2800 lbs with only a 40 lbs weight is really appealing. I just have to find out the shearing strength of my screws! Like John said, there's a lot of tensile strain.
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Wayne - Txs for the spreadsheet.
Farmer - I believe you are absolutely right with the statement you made:
1. These recipes were created by home cheesemakers not industry and the recipes reflect that, or
2. A lot of people just don't understand the math but still make great cheese and pass on the process minus the science. Just a thought.
The unscientific way I calibrated my press kind a reflects your statement: originally the press was hand-cranked (see attached pics). I used a stainless steel spring between the rod and the follower. The first pressing was done with the spring half compressed. For my second pressing, I cranked it up until the spring was fully compressed. The Gouda produced like this turned out fine. So when I later fitted the press with the pneumatic cylinder, I put the same spring underneath it and applied pressure until it was half compressed, then fully compressed. I simply read the meter readings on the pressure gauge on both occasions and that gave me my callibration: not a scientific way to do it, but effective nonetheless.
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Farmer - A block & tackle could be rigged from the press base to the lever end. 2 pulleys at the base and the lever end would be give a 5 to 1 M.A. So hang 40 pounds on the upper pulley rope. That would give 200 pounds pulling down on the press lever. Now if the lever arm itself has a 5 to 1 M.A. That would be 200 x 5 = 1000 pounds out of a 40 pound weight. Is that right??? College Physics was more than a few years ago. ;D
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OK. Here is a spreadsheet that I created showing press weights and the resulting PSI for various diameters of molds/followers. This was actually very enlightening. Makes me feel like I should be pressing a lot harder than I am. BUT.... my concern is that higher press weights would extract too much whey and result in cheeses that are really dry.
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Sailor, I actually thought about pulleys but i would still have the same problem of my press not handling the stress out on the arm.
I tried my upgrades tonite and I guess I should have thought it through a little more. Law of conservation of energy and Work = force X distance.
i forgot about distance shrinking at the same ratio that the force is increasing. That is why those double levered presses had the threaded bolt with a big steering wheel on it down the middle - so they could keep the force on the hoop because they only had about an inch of play in the ramrod. With a 70 to one MA your weight would move 70 inches down while your ram would only move 1 inch. Ouch. Oh well, back to drawing board.
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You might have guessed that I'm also a sailor. On a sailboat we use lots of cam cleats to lock loaded lines in place. I've thought about installing a triple pulley block & tackle system from the forward face of my press base to the end of the lever. I envision an inline spring scale to accurately measure line load. With a cam cleat you could apply whatever force that you want and then lock the line in place. With enough mechanical advantage, you could just pull down on the block line by hand until the scale shows the force that you want - WITHOUT using any mechanical weights. The obvious disadvantage is that the pressure would decrease as the cheese compresses.
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All, just wanted to say great discussion and especially like Farmer's drawing! Have fun y'all!
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This thread makes me want to build my own wood mold. It seems impossible to find any good, tall molds for cheese, or good, strong, wide molds. This way I could make my own to my own specifications.
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It really isn't rocket science. I used some Spanish cedar for mine so that I didn't have to worry about it getting wet. The screws and bolts are the main cost factors. I used a piece of corian countertop that was leftover from a cabinet shop in the bottom that lifts out easily for cleaning. I have already drawn up plans with a welding buddy for my double levered metal press and I can't wait to use it. The only problem with building these things is that it is yet another piece of "furniture" to put somewhere along with the heating tank, assorted large pots, draining cooler, stirring device, cave, and assorted hoops and weights! I wish I had a spot like Wayne where I could attach a couple of 2x6's to the wall and have a long wall-mounted press that wasn't in the way. The problem with that is the potential for the curd to "float" the hoop and come underneath because there is no way of pinning the hoop down. I would love to see your plans if you decide to make one. Good luck.
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There is a simple, not too attractive, way to keep hoops from floating... hang weights from both sides.
2 10lb. weight lifter weights on hooks will do.
My camembert hoop floats, being very thin and light, but I just put a weight on it.
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That is a good idea but with 1500 lbs of pressure on my cheddar I am not sure that would be enough. It probably would be since there isn't very much upward force on the hoop.
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You need a simple cage to hold it down.
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Yea that would work. That is sort of what I did on my self-contained model (see pics) and I guess it could be designed to use with the wall press.
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Just a thought but has anyone tried a pony/pipe clamp? Maybe two with boards between them for a bigger or multiple mould(s)?
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You are saying to tighten multiple molds together and squeeze them together firmly? So they just need tightening every so often to maintain pressure and the run off goes?
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Could be multiples or a single mold.
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I really think that while you could apply lots of even pressure this way, it would be impossible to maintain a steady pressure.
This is why most presses for cheese makers of our caliber use gravity/air pressure/springs in some form or another.
All provide constant/predictable pressure.
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Very good point Wayne. A spring would have to be added somehow.
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I decided to install a bigger pneumatic cylinder on my press. Originally it was a 20 mm bore, 150 mm stroke cylinder. The new one is 40 mm bore and 200 mm stroke. Because of the higher pressure I also installed 2 flow control valves on both inlets of the cylinder. This way the cylinder moves slowly up and down, which should make it much safer.
Now I better revisit the earlier discussion that went on in this thread about pressure calculations, because the press is now operating quite differently than before.
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Wow,
I would love to know the details on this build.
Last I looked, Pneumatic cylinders were not crazy expensive. They were in the 50-130USD range.
Yours looks a bit more with t he double action and the mounting hardware.
From a math perspective, I will assume the same cylinder pressure.
I get the following: 40mm Bore is 1.947 Square inches.
@ 150PSI that will give you 292 lbs of down force.
292lbs of divided across the surface area of an 8in mould (50.26sqin) will give you 5.8PSI
You can see that my earlier post's graph backs this up.
I think that is closer to being on target for a hard cheese like cheddar.
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Eric, that is a really fine press now. Good luck with your cheeses!
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Very cool Eric. Makes my homemade French press look like a toy. :D
How many pressings can you get out of one charge to your fire extinguisher?
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Eric that's a real dandy!
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Debi and Farmer - Thanks for showing your appreciation.
Sailor - This cylinder "eats" more air indeed, but when the press is put under pressure, it keeps it when the hand valve is set to neutral. At that point I can disconnect my modified fire extinguisher and refill it with my compressor and reconnect it. So it's not giving me any problems. Worst case scenario would be to connect it straight to the compressor, but I don't seem to have to go to that length.
Wayne - All the measurements have been posted earlier in this thread. As to the cost of the pneumatic system, a breakdown follows below (all product codes are from the SMC company):
MDDB40-200 (air cylinder) 4,100.= THB ---- 122.35 USD
VH200-02 (hand valve) 1,450.= THB ---- 43.27 USD
AR20-02BG (air regulator) 750.20 THB ---- 22.39 USD
KQ2H06-02S (one-touch fitting) 5 x 31.= THB 155.= THB ---- 4.64 USD
AS12-1F-06S(speed controller) 2 x 150.= THB 300.= THB ---- 8.95 USD
Net total 201.60 USD
VAT (7%) 14.11 USD
Grand total 215.71 USD
Hope this provides you with the information you wanted.