Formula For PSI

[coffee joe]

Boise,

I'm sure most of the folks on this forum have been exactly where you are today. The drawing in this thread is probably the cheapest way to resolve pressing in higher weights. This thread is about PSI. As the diameter of the mold grows the total weight must increase to maintain equal PSI. How much weight really needs to be applied per square inch of follower is one of the principle questions we all have.
There are a couple of us here that are wondering how high we can manage to go without busting something! You will find a few posts in other threads referring to broken sink tops, so far no bodily harm. As we move into attempting to put 1 full ton on a cheese, well...

[Boofer]

I believe the broken sink incident resulted from a stack of weights that toppled over. It wasn't from excessive pressure in a press.

The need for great pressure in a cheese press is limited to a very few cheese styles. The majority of cheeses will probably see less than 100 lbs.

-Boofer-

[coffee joe]

But we are having fun in the process!

[Sailor Con Queso]

The need for great pressure in a cheese press is limited to a very few cheese styles. The majority of cheeses will probably see less than 100 lbs.

Some cheeses like cheddar require more pressure anyway, but the real need for greater pressure is related to hoop size. For cheeses 7" or larger, you definitely need to go to 150 pounds or more. At 100, that's only about 1.5 psi (don't have my chart right now), so that is inadequate psi for most hard cheeses. MIGHT be passable for a light pressed Gouda, but very difficult to do a perfect cheddar at that weight.

[coffee joe]

More results for my 19.67 PSI( theoretical) experiment. 8" form with Cheddar

The Tube on the follower that allows for stacking, concentrated the pressure in the middle giving me a warped follower and a concave top on my cheese. For this pressure, the follower must be significantly more rigid. For next cheese a piece of 1" hardwood as a follower.

Otherwise, I am very pleased with the results. The cheese is noticeably drier and denser. I don't think more pressure, than applied, is needed by any means!
For the Record, I went 20 Min with 6Kg, turned over, went to 22 Kg for 1 hour then overnight with the 35Kg weights, all on the same setup, same MA.
 

[Sailor Con Queso]

Very cool Joe. 19.67 is getting up there, but you can see a difference in the results. I personally don't think you need to go over 10 psi if you are managing curds properly prior to pressing. A warming box around the hoop or a way to apply heat at 80-90F would make pressing a lot more effective. Your block/pulley setup to multiply the weight is simple but effective - I like it.

Definitely a case where the simplistic recipes (online or published) are jusy way off base. Hope the chart helped.

The fact that your follower warped is an indication that the molds might not be able to withstand commercial pressing. That's what LB was asking regarding plastic quality.

[9mmruger]

Coffee Joe, I see the cable and pulley on your press.  How much does that help vs no cable and pulley.  Cheese wheel looks great too!  I have read some of the posts regarding single and double pulley gizmos, but don't really understand the resultant effects.  Do you have an suggested reading?

[FarmerJd]

The pulley in his setup simply doubles the weight already produced by the press.

[coffee joe]

Sailor,
the mold held fine, the design of the follower, which allows for stacking, is not suitable for 20 PSI over the 8"mold area because it was actually closer to 100PSI concentrated on the 4 " diameter riser. Felt pretty "tenderfoot"when that dawned on me!
Need the 20 PSI to be evenly spread out, scratch one bent follower up to experience.

As to results, I like what I saw but won't be going for higher PSI as I just don't see the need. That may change
I have a feeling I'll end up getting talked into adding another pulley and going for 40PSI! The Peter Principle on Pressure.
Mr Kim,
Farmer JD said it all, one more pulley on the same cable would double it again - theoretically as there is loss to friction etc

[Boofer]

Coffee Joe, I see the cable and pulley on your press.  How much does that help vs no cable and pulley.  Cheese wheel looks great too!  I have read some of the posts regarding single and double pulley gizmos, but don't really understand the resultant effects.  Do you have an suggested reading?

I can hang 5lbs on my press and deliver 157lbs to the cheese. That's a 31x upgrade from just pressing with 5lbs. Granted, that's not necessary for a lot of cheeses, but when I need the extra OOMPH!...it's there. I used to stack up two 25lb barbell weights, two 10lb, and one 5lb to get 75lbs on my cheese. That was unwieldly and dangerous (It toppled off onto the floor one night and got my wife out of her chair!).

I attached my MS Excel spreadsheet on the first page of this thread. It shows the calculated pressure and what I really saw on my bathroom scale. I have calcs for two pulleys and for four pulleys. There are pics somewhere of my press. The expert engineering tutors here helped me tweak it in.

Using 75lbs I can theoretically deliver 42+psi at 1811lbs. Never tried it. I've got a strong feeling the mold would burst.

-Boofer-