My Dutch cheese press...hooyah!

[Sailor Con Queso]

Farmer,

I am setting up a commercial kitchen for cheesemaking and other pursuits. I could go with an air pressure system (ala Carter) but I want it to look a bit primative and old fashioned, not industrial. This is a permanent setup, so one of my thoughts is to use a third single wheel pully attached to the ceiling, so there would be plenty of room for drop.

Don't have a working drawing, however the final working line would go from the lower block to the ceiling pulley. I know that this would lose 1 leg of the mechanical advantage but I could use a triple block instead of a double. This setup would give 8 feet of drop.

[Alex]

Sailor, IMHO, removing the pulleys system is always an option to decrease weight/pressure.

[FarmerJd]

Sailor, the only catch would be that the press might have to be attached to the floor if you are using an anchor outside the system. Not a problem but needs to be considered. In fact, you could actually put an anchor on the ground in front of the press for your last pulley and then go to the ceiling. That way you don't lose the MA you mentioned. I think I would use chain for my final leg so that you could always move up to another link and reattach to keep tension. I am sure Wayne has some chain you could borrow.


Alex, when you make your wooden pulleys, you may have to turn some for Sailor and I. Just to keep that old fashioned look. 

[Boofer]

Boofer, replace the lever arm with a 2"x1" RHS.

I don't understand why I should replace the lever arm.


Sailor - The lever arm and ramrod weighs in at 11 lbs.

Can you see anything in my calcs that would account for an actual of 157 lbs and my calculated 107 lbs?

(5 * (4*4. ) + 11 = 107 lbs  [lbs * (pulley advantage * lever advantage) + lever&ramrod weight]
3.14 * ((7.375/2)*(7.375/2)) = 42.7 sq in  [pi * mould radius squared]
107/42.7 = 2.5 psi  [lbs/sq in= psi]

If I am to believe my math, I have 2.5 psi to press my Gouda with.

-Boofer-

[Alex]

Boofer, You wrote that the arm is bending, or may be I missunderstood you.

Farmer

Alex, when you make your wooden pulleys, you may have to turn some for Sailor and I. Just to keep that old fashioned look.

With pleasure, that's the point, old fashioned look. Tell Sailor, when he will sail to the Italian west coast, to "jump" to Haifa to collect the pulleys.

[Boofer]

As far as the total mechanical advantage, the best I can figure is 24. That is 5 (pulley advantage) times 4.8 (lever advantage) = 24.

I'm a little confused (again)...you mentioned earlier that even with my quad pulley setup I was really only seeing 3 pulleys because one was only changing direction. Somehow you've given my system a pulley advantage of 5 instead of 4. That would bring it closer to explaining the disparity between calculated weight and actual weight, but how did you come by that? Please don't take this wrong. I appreciate your input.

Also, there is a slight bend to the RHS but not IMHO excessive, especially for the stresses I expect to see. If I were to really get crazy down the road and try to actually put 75 lbs on the lever (shudder!!), I would definitely need to make some heavy-duty changes to the press.

-Boofer-

[FarmerJd]

The short answer is I was wrong. You can skip the next paragraph unless you are just curious about the original setup.


 To figure the MA of a pulley system, you actually figure by the number of ropes/legs but some of them can be simply for changing direction so you have to evaluate it. I made a mistake the first time, because I am conditioned to look at pulley systems with the fixed point at the top and the resistance pulling down but movable. Our presses are different with the resistance pushing up and movable but the fixed point is below. I wrongly counted the first and last legs as simply redirection (really stupid; must have been late). To be honest, i looked at it again after I posted the first time and started to post again but then you moved the pulley so I just punted thinking it was a moot point. The way to figure the original setup really involves knowing the angle of the ropes because only a portion of those 3 middle legs are pulling straight down on the end of the arm. So you have to figure the first leg, middle 3 legs, and last leg separately. I didn't do that the first time. I still get numbers slightly larger than your original values (assuming a 45 degree angle) which leads me to believe you have a lot of friction in your system.


The calculation for any simple pulley system really comes down to simply this: All the ropes in a pulley system have the same tension. If they are all pulling in the same direction you simply count the legs. Of course, there are complex systems that are figured differently but your current setup is not one. It has 5 legs and all are exerting a force downward therefore the MA = 5.

Can you see anything in my calcs that would account for an actual of 157 lbs and my calculated 107 lbs?
[/size]
(5 * (4*4. ) + 11 = 107 lbs  [lbs * (pulley advantage * lever advantage) + lever&ramrod weight]
3.14 * ((7.375/2)*(7.375/2)) = 42.7 sq in  [pi * mould radius squared]
107/42.7 = 2.5 psi  [lbs/sq in= psi]

If I am to believe my math, I have 2.5 psi to press my Gouda with.[/size]

I am not sure I understand the first line of this. How much weight is hanging on the end? If it is 10 lbs then I would calculate the predicted force on the scale this way:


5 (pulley MA) x 4.8 (lever MA) x 10 (weight attached) + 11 (lever and piston weight) = 251lbs


If you get a greater value than this, let me know. Sorry so long. Hard to know where to start and end. I hope it is helpful.

[BigCheese]

Forgive me, but am I the only one thinking "way too much math here"?

[FarmerJd]

Sorry. It's an obsession. Kind of like cheese.

[wharris]

You all have inspired me to start thinking about a new press.
My thoughts so far....

[Boofer]

Forgive me, but am I the only one thinking "way too much math here"?

Yeah, me!

No, actually I built the press and I'd like to just have some assurance that I'm pressing somewhat accurately. There's a decided difference between 50 lbs and 250 lbs. If I use a 5 lb weight to develop 107 lbs pressing on my cheese, I want to know what's being delivered. Short answer: it is a momentary obsession. Once it gets ironed out, then I can rest...no, that's not true...making baby swiss early in the A.M. (Using Sailor's guidance.)

Farmer - Excellent tutelage. I'm seeing this press in an entirely new light. Thank you for not letting me work this out in a vacuum. 

Wayne - Cool graphics.  Does it come with any dialogue to describe what we're seeing?

-Boofer-

[Nonius]

Hi Wayne

Force multiplier of a double lever system is high, but your design will give little travel on the plunger. What I see from your graphics your long lever can rotate only about 40 degrees till it hits the upper cross beam, resulting in ~10 degrees on the lower lever. Since the pressure point is very close to the hinge point the plunger will travel only 3% of what your pulley at end of long lever will travel.

This is why I asked before how much travel you need for pressing cheese or how much does the cheese compress. This is especially relevant overnight/ during workhours as knowbody is there to readjust, and your press is delivering all that force to its own frame, instead of on the cheese :-)

Amnon

[FarmerJd]

Amnon, I realized when I was tinkering with that idea that this was the reason that the old double levered presses had a threaded rod in the middle; so that they could constantly keep the pressure on the cheese in the small window of travel. So the question is can it work effectively with a taller frame. You set up your levers in the diagram just like I tried but in my case it bottomed out and I abandoned it because I couldn't justify making it any bigger. I need to go back and study the pics we have of old double levered presses. Good discussion.

[Nonius]

Hi Farmer

Just curious, as I still have to start my first pressed cheese...

I read Gouda and the like are first pressed with a lighter weight for 2x or 3x 1 hour, only later pressings are with more weight.

Would it work to use the long lever in the beginning with lower multiplier and enough travel for initial compression of curds. Only at last pressing using the double lever assuming cheese will not compress too much?

Would you have numbers on compression per stage/ pressure applied for e.g. your cheddars?

Amnon

[DeejayDebi]

I know I have mensioned this before and didn't get much of a positive reaction - but now you all seem to be thinking in the same direction so ...

I have been playing with the idea of building an almost all wood version of this beasty since late last fall - just can't work in the basement in the winter - to cold for the old bones no heat down there. I have most of the parts I need, still looking for weight ideas and I am going to use an veneer press screw for the pressure piston.