Author Topic: Torque needed to twist off a bottle cap  (Read 5862 times)

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Offline airman00Topic starter

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Torque needed to twist off a bottle cap
« on: August 31, 2007, 05:09:21 PM »
I need to know the amount of torque needed to twist off a bottle cap from a soda bottle. Can anyone guess an approximate torque? Or where I can find that out from?
Thank you,
Eric
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Offline ed1380

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Re: Torque needed to twist off a bottle cap
« Reply #1 on: August 31, 2007, 05:30:22 PM »
securly mount a 1ft long rod to teh cap. and lay the bottle down, with teh cap  hanging off of a table, and then start adding  weights at the end of the rod.
once it twists off, you know how many ft/lb you need
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Offline Gertlex

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Re: Torque needed to twist off a bottle cap
« Reply #2 on: September 01, 2007, 07:36:58 AM »
securly mount a 1ft long rod to teh cap. and lay the bottle down, with teh cap  hanging off of a table, and then start adding  weights at the end of the rod.
once it twists off, you know how many ft/lb you need

Account for the torque provided by the rod too, of course.

Unless you mount the center of the rod to the cap, then it cancels itself out.
I

Offline ed1380

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Re: Torque needed to twist off a bottle cap
« Reply #3 on: September 01, 2007, 03:46:30 PM »
securly mount a 1ft long rod to teh cap. and lay the bottle down, with teh cap  hanging off of a table, and then start adding  weights at the end of the rod.
once it twists off, you know how many ft/lb you need

Account for the torque provided by the rod too, of course.

Unless you mount the center of the rod to the cap, then it cancels itself out.
yeah didn't think of that.
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Offline Admin

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Re: Torque needed to twist off a bottle cap
« Reply #4 on: September 09, 2007, 02:42:49 PM »
Quote
Account for the torque provided by the rod too, of course.
FYI, its:

torque = .5 * (weight of rod) * (length of rod) + (weight of object) * (length of rod)

Offline SomeSaba

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Re: Torque needed to twist off a bottle cap
« Reply #5 on: September 23, 2007, 11:39:22 PM »
Quote
Account for the torque provided by the rod too, of course.
FYI, its:

torque = .5 * (weight of rod) * (length of rod) + (weight of object) * (length of rod)


I *always* been confused on that:

Torque= rF (disntace * force)


Weight is a force, but to calc weight dont u have to say W = mg (mass and grav. acc. 9.8m/s^2)!?!?

So if u mass it on a scale thats the mass right?? so u have to multiply it dont u?

Offline Ro-Bot-X

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Re: Torque needed to twist off a bottle cap
« Reply #6 on: September 23, 2007, 11:54:25 PM »
Wrong, you can scale only the weight, not the mass. Then you can calculate the mass using the formula you mentioned.
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Re: Torque needed to twist off a bottle cap
« Reply #7 on: September 24, 2007, 04:41:59 AM »
Weight is mass times gravity.

Weight is a force, while mass is not.

Offline dcole07

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Re: Torque needed to twist off a bottle cap
« Reply #8 on: September 24, 2007, 12:32:29 PM »
securly mount a 1ft long rod to teh cap. and lay the bottle down, with teh cap  hanging off of a table, and then start adding  weights at the end of the rod.
once it twists off, you know how many ft/lb you need

Account for the torque provided by the rod too, of course.

Unless you mount the center of the rod to the cap, then it cancels itself out.

Unless he uses one of those mass-less rods!  ;D

Offline MeKaDa

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Re: Torque needed to twist off a bottle cap
« Reply #9 on: September 25, 2007, 06:04:13 AM »
Couldnt he just use a torque wrench,just find a way to fit the cap in there.

Offline Tsukubadaisei

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Re: Torque needed to twist off a bottle cap
« Reply #10 on: September 26, 2007, 03:01:22 AM »
when calculating the torque the direction is also important.
T=rf is wrong

Correct
T=RxF (cross product)
  =R*F*sin(angle) (absolute value)
  =det [i     j     k ] 
          [Fx  Fy   Fz]
          [Rx  Ry  Ry]
where det is the determinant of the matrix.
« Last Edit: September 27, 2007, 06:39:26 AM by Tsukubadaisei »
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Offline ed1380

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Re: Torque needed to twist off a bottle cap
« Reply #11 on: September 26, 2007, 06:14:15 PM »
Couldnt he just use a torque wrench,just find a way to fit the cap in there.
AFAIK torgue wrenches are made for high amounts of toruqe
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Offline Robotboy86

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Re: Torque needed to twist off a bottle cap
« Reply #12 on: September 27, 2007, 03:06:56 PM »
..not to be mean or anything..

BUT:

Just use a big servo and call it a day.  Its going to be less then friction that human skin can withtake..  as such, its not going to be a lot.

my guess is under 40ft/lbs.


Probaly far under.

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Re: Torque needed to twist off a bottle cap
« Reply #13 on: September 27, 2007, 04:37:03 PM »
Quote
my guess is under 40ft/lbs.
I think you meant 40lb*ft ;D

btw, thats a lot!

Im guessing more like 5lbft . . .

Offline Robotboy86

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Re: Torque needed to twist off a bottle cap
« Reply #14 on: September 28, 2007, 11:21:09 AM »
ya I did mean that lol thanks Admin.

I agree its also FAR under 40, 40 would probaly shatter the glass while trying to twist..  lol

 


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