[NAFEX] Apple pressing

Claude Jolicoeur cjoli at gmc.ulaval.ca
Sun Dec 7 16:47:49 EST 2008


Quite a few questions around - I will try to answer all here - Hope I don't
forget any...

>From David:
>(Claude, does the French Canadian word <<cidre>> refer to sweet as well as
hard cider?  
>This whole concept is an American creation, dating from Prohibition, and
certainly in France, 
><<le cidre>> refers unequivocally to the alcoholic beverage.)

Everything that is not fermented should be called "juice" in my opinion.
"Cidre" would never be used around here for anything else than what
americans call hard cider.

>From Jim:
>What kind of fabric do you use to hold your mashed apples?  I've used
muzzlin (sp), a slightly heavy cotton cloth but it sometimes blows out at
the gaps between the vertical basket slats and there is no way it would
remain intact if I used it for a cheese press.
>
I bought some nylon fabric, of the type used for semi-transparent drapes on
windows. It might also be used for wedding dresses... I tried to choose the
sturdiest one. My wife did a bit of sowing to give the shape. I have just
added a new picture in the album showing the cloth (it will be the last
picture of the album). Same link as before:
http://picasaweb.google.com/cjoliprsf/ApplePress

>From Mark:
>In short, a typical acme 1 1/4" screw will only deliver about 4 ton of
force, and that's with a thrust bearing, if 100 ft/lbs. of torque is
applied to the screw.
>
I will now put my mechanical engineer's hat... The general relation for
torque vs axial force in a screw is:
Torque = 0.2 x Axial Force x Screw Diameter
This is a simplified, but fairly accurate, formula for standard friction
coefficients between screw and nut. If the diameter is in inches, you get a
torque in inch-pounds. You need to divide by 12 to get foot-pounds.
Interestingly, from this formula, you would think that by taking a smaller
screw, you would need less torque. However, there is a minimum screw
diameter required in function of the axial force to keep the stress at a
reasonable level. Further, the longer the screw, the more chance it may
become unstable (this is called buckling) and the diameter has to be beefed
up. I have a project to write an article some day on elementary press
mechanics, but it seems I never get the time for this...

Claude




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