### Author Topic: Pressing - So Confused  (Read 792 times)

#### DragonAndy

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##### Pressing - So Confused
« on: April 07, 2013, 05:47:14 AM »
I've been pouring over post about how to calculate pressure when using a dutch press and I have to say I'm still very confused. I'm no engineer so some of the terminology is baffling me.

I just got this press as a birthday present, but I don't know how to calculate the pressure being applied. my books all state just straight pounds weight to apply, not psi.

I have attached a picture of my press, if someone could tell me how to calculate and also when using terms like 'pivot point' 'fulcrum' that's sort of thing tell me exactly which part of my press this relates to. in other words I don't know if the pivot point is the bit on the middle or the bit where the lever arm attaches to to the rest of the press.

« Last Edit: April 07, 2013, 05:54:41 AM by DragonAndy »

#### H-K-J

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##### Re: Pressing - So Confused
« Reply #1 on: April 07, 2013, 10:41:44 AM »
I don't know if this attachment will work
If it does it is a calculator and explains what to do to get psi
I'm not sure who on the forum came up with this I just know I sure as heck didn't
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#### smolt1

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##### Re: Pressing - So Confused
« Reply #2 on: April 07, 2013, 10:53:03 AM »
Looking at the picture of your press, on the left where the lever arm attaches to the the vertical part of the press is the "FULCRUM". In the middle where it presses down on the cheese in the mold is the "PRESSING POINT". On the right is where you hang the lever arm weight. The mechanical advantage ( MA ) of your press is calculated by measuring the distance from the fulcrum to where you hang the lever arm weight DIVIDED by the distance from the fulcrum to the pressing point. By looking at your picture it looks like your press has a MA of about 3. So if you hang 10 kg on the lever you will get 30 kg pressing on the cheese.

In many cheese making recipes that give WEIGHT it is assumed that you are doing a small ( 1 gallon ) batch and the mold is 4 or 4 1/2 inch diameter. If you do a larger batch with a larger mold you will need more weight to get the same results.

To understand weight and pressure try http://sturdypress.com/?page_id=201
« Last Edit: April 07, 2013, 11:37:43 AM by smolt1 »

#### Mike Richards

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##### Re: Pressing - So Confused
« Reply #3 on: April 07, 2013, 11:03:53 AM »
The first thing you need to find is the force (think of this as the weight) that the plunger (the piece of wood that presses down on the cheese) is putting on the cheese.  To do this, do the following:

Measure the distance from the far left pin (it's a bolt, probably--the metal thing on the left that lets the horizontal piece rotate, but not move up or down) to the pin through the plunger (this is the one that is held on with a wing nut--remember the plunger is the wooden piece that pushes down on the cheese).  Then measure the distance from the far left pin to the rope on the wooden are.  You might get numbers like 10 cm for the first measurement and 30 for the second.  Now, divide the second measurement (the bigger one, 30 in my example) by the first measurement (the smaller one, 10 in my example).  You'll get a number between 2 and 4 (in my example, I got 3).  This is your mechanical advantage.  It is the ratio of how much output you get divided by how much input you put in.  Take that number, the mechanical advantage and multiply the weight you hang on the rope by it.  This is how much "force" you're putting on the cheese.  So, in my example, if I hung a 10 kg weight on the string, I'd get the equivalent of 30 kg on the cheese.  You know, I'll add a picture here in a minute...

Next, I need to see how much pressure I'm putting on the cheese.  This can get a little more complicated because we were just pretending that mass, kg, was weight (which it's not).  If you'd like that explained, too, I can do that for you, but why don't you start with this and let us know how it goes.
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#### DragonAndy

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##### Re: Pressing - So Confused
« Reply #4 on: April 07, 2013, 03:37:09 PM »
That's brilliant guys. That clears things up perfectly.

Thanks very much for your help.