| Topic: |
Science > Physics |
| User: |
"Henry" |
| Date: |
24 Sep 2004 11:33:32 AM |
| Object: |
request for mathematical formula |
Greetings. I'd like to know the theorem or formula or equation or
whatever it is (you see that I am not a scientist; my high school
physics class was 35 years ago) which explains why it is easier to
loosen a tight bolt with a socket on a heavier (i.e., more massive--I
remember that part!) ratchet than with a lighter box-end wrench of the
same length.
Thanks in advance.
cheers,
Henry
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| User: "Paul Draper" |
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| Title: Re: request for mathematical formula |
27 Sep 2004 10:28:29 AM |
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(Henry) wrote in message news:<1gkmu2d.1v3r0au198ymwwN%>...
Greetings. I'd like to know the theorem or formula or equation or
whatever it is (you see that I am not a scientist; my high school
physics class was 35 years ago) which explains why it is easier to
loosen a tight bolt with a socket on a heavier (i.e., more massive--I
remember that part!) ratchet than with a lighter box-end wrench of the
same length.
Thanks in advance.
cheers,
Henry
The torque is F * r * sin(theta), where F is the force applied to the
end of the wrench, r is the length of the arm of the wrench, and theta
is the angle between the force applied and the arm of the wrench.
Since r is the same, the claim is that sin(theta) is closer to 1 for
the ratchet wrench. The argument for that comes from the fact that the
faces of the box-end wrench are canted at an angle from the arm of the
wrench. This is a largely bogus argument however, since the details of
which faces of the bolt are pushed on are irrelevant to the formula
above. However, it IS true that there is a slight offset in a box-end
wrench: the line between the center of the bolt and where your hand
is, is NOT along the arm of the wrench exactly. This is still a bogus
argument however, compensated by pulling not perpendicular to the arm
of the wrench but perpendicular to the line between the center of the
bolt and where your hand is. I suspect that what you were TAUGHT in
school is one or the other of these bogus arguments.
The truth has more to do with what another poster suggested. Twisting
a bolt on only two faces of the head induces distortions and friction
that aren't as big if you apply the force to all six bolt faces
equally. The math behind THAT however, is complicated.
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| User: "Mike" |
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| Title: Re: request for mathematical formula |
25 Sep 2004 06:01:03 AM |
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(Henry) wrote in message news:<1gkmu2d.1v3r0au198ymwwN%>...
Greetings. I'd like to know the theorem or formula or equation or
whatever it is (you see that I am not a scientist; my high school
physics class was 35 years ago) which explains why it is easier to
loosen a tight bolt with a socket on a heavier (i.e., more massive--I
remember that part!) ratchet than with a lighter box-end wrench of the
same length.
Thanks in advance.
cheers,
Henry
Torque = Forxe x Distance (x stands for the cross product, r is the
distance from the point of application of force to the axis of
rotation)
Thus, the more massive rachet generates applies a higher torque. Of
course, when it gets too massive, moment of inertia comes into play
and the action is dynamic, which means you have to provide more
energy.
Mike
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| User: "Uncle Al" |
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| Title: Re: request for mathematical formula |
24 Sep 2004 03:41:42 PM |
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Henry wrote:
Greetings. I'd like to know the theorem or formula or equation or
whatever it is (you see that I am not a scientist; my high school
physics class was 35 years ago) which explains why it is easier to
loosen a tight bolt with a socket on a heavier (i.e., more massive--I
remember that part!) ratchet than with a lighter box-end wrench of the
same length.
Stiffness depends on aspect ratio (length to thickness). The exact
relationship depends on the shape of the member and how the stress is
applied if the cross-section is not radially symmetric (e.g., not a
cylinder). Moment of inertia analysis of an I-beam is particularly
instructive, and carries over into the wisdom of a hollow thick-walled
or a rigid foam-filled cylinder vs. a solid cylinder, stiffness vs.
weight.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
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| User: "Henry" |
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| Title: Re: request for mathematical formula |
24 Sep 2004 04:06:07 PM |
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Uncle Al <UncleAl0@hate.spam.net> wrote:
Henry wrote:
Greetings. I'd like to know the theorem or formula or equation or
whatever it is (you see that I am not a scientist; my high school
physics class was 35 years ago) which explains why it is easier to
loosen a tight bolt with a socket on a heavier (i.e., more massive--I
remember that part!) ratchet than with a lighter box-end wrench of the
same length.
Stiffness depends on aspect ratio (length to thickness). The exact
relationship depends on the shape of the member and how the stress is
applied if the cross-section is not radially symmetric (e.g., not a
cylinder). Moment of inertia analysis of an I-beam is particularly
instructive, and carries over into the wisdom of a hollow thick-walled
or a rigid foam-filled cylinder vs. a solid cylinder, stiffness vs.
weight.
Thanks very much for that rambling waffle, Unfortunately, it contains
neither theorem nor formula nor equation.
Wanker.
cheers,
Henry
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| User: "bleetbaer" |
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| Title: Re: request for mathematical formula |
24 Sep 2004 04:51:36 PM |
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"Henry" <henry999@eircom.net> wrote in message
news:1gkn6vb.pj2ow91ajj3s3N%henry999@eircom.net...
Uncle Al <UncleAl0@hate.spam.net> wrote:
Henry wrote:
Greetings. I'd like to know the theorem or formula or equation or
whatever it is (you see that I am not a scientist; my high school
physics class was 35 years ago) which explains why it is easier to
loosen a tight bolt with a socket on a heavier (i.e., more massive--I
remember that part!) ratchet than with a lighter box-end wrench of the
same length.
Stiffness depends on aspect ratio (length to thickness). The exact
relationship depends on the shape of the member and how the stress is
applied if the cross-section is not radially symmetric (e.g., not a
cylinder). Moment of inertia analysis of an I-beam is particularly
instructive, and carries over into the wisdom of a hollow thick-walled
or a rigid foam-filled cylinder vs. a solid cylinder, stiffness vs.
weight.
Thanks very much for that rambling waffle, Unfortunately, it contains
neither theorem nor formula nor equation.
I would use a closed box end.
Doesn't slip off, as with an open box end
more contact and feel, just one piece of metal,
not two or three separate parts as with a socket wrench.
"easier" is a judgement call of the operator, the situation, not a simple
equation.
I would also give the bolt 1/8 turn to tighten first, then swing back to
untighten.
Which equation incorporates that?
(a shot of WD-40 before that too, reduces k)
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| User: "Uncle Al" |
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| Title: Re: request for mathematical formula |
24 Sep 2004 05:14:21 PM |
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Henry wrote:
Uncle Al <UncleAl0@hate.spam.net> wrote:
Henry wrote:
Greetings. I'd like to know the theorem or formula or equation or
whatever it is (you see that I am not a scientist; my high school
physics class was 35 years ago) which explains why it is easier to
loosen a tight bolt with a socket on a heavier (i.e., more massive--I
remember that part!) ratchet than with a lighter box-end wrench of the
same length.
Stiffness depends on aspect ratio (length to thickness). The exact
relationship depends on the shape of the member and how the stress is
applied if the cross-section is not radially symmetric (e.g., not a
cylinder). Moment of inertia analysis of an I-beam is particularly
instructive, and carries over into the wisdom of a hollow thick-walled
or a rigid foam-filled cylinder vs. a solid cylinder, stiffness vs.
weight.
Thanks very much for that rambling waffle, Unfortunately, it contains
neither theorem nor formula nor equation.
Fine. Look up the formulae for round vs. square cross-section
orthodonture wires.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
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| User: "pete" |
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| Title: Re: request for mathematical formula |
26 Sep 2004 08:45:56 PM |
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Henry wrote:
Greetings. I'd like to know the theorem or formula or equation or
whatever it is (you see that I am not a scientist; my high school
physics class was 35 years ago) which explains why it is easier to
loosen a tight bolt with a socket on a heavier (i.e., more massive--I
remember that part!) ratchet than with a lighter box-end wrench of the
same length.
When I do that, I usually use a long extenstion on the socket.
The reason is so that I can grab the extension with my left hand
and hold it straight, while I push the wrench handle
with my right hand. It helps a lot.
--
pete
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| User: "John Polasek" |
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| Title: Re: request for mathematical formula |
27 Sep 2004 09:11:37 AM |
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On Mon, 27 Sep 2004 01:45:56 GMT, pete <pfiland@mindspring.com> wrote:
Henry wrote:
Greetings. I'd like to know the theorem or formula or equation or
whatever it is (you see that I am not a scientist; my high school
physics class was 35 years ago) which explains why it is easier to
loosen a tight bolt with a socket on a heavier (i.e., more massive--I
remember that part!) ratchet than with a lighter box-end wrench of the
same length.
When I do that, I usually use a long extenstion on the socket.
The reason is so that I can grab the extension with my left hand
and hold it straight, while I push the wrench handle
with my right hand. It helps a lot.
Yes Pete but that is not the only reason. Take case of 50 lbs on 1
foot for 50 pound feet plus a side force of 50 lbs. that increases
friction.
Now put a 4 foot pipe on it and you have 50 ft lbs = 12.5lb x 4 plus a
side force of only 12.5 pounds.
It you used a 1 foot T-handle you would have a
side force of +50 - 50 = 0 pounds.
Mr. Dual Space
If you have something to say, write an equation.
If you have nothing to say, write an essay.
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| User: "John Polasek" |
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| Title: Re: request for mathematical formula |
24 Sep 2004 06:54:53 PM |
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On Fri, 24 Sep 2004 19:33:32 +0300, (Henry) wrote:
Greetings. I'd like to know the theorem or formula or equation or
whatever it is (you see that I am not a scientist; my high school
physics class was 35 years ago) which explains why it is easier to
easier? you've proved that it is easier? or it's known in your
industry that it's easier? or does the homework say it's easier?
It definitely isn't easier. I say this because the box-end wrench is
lower down on the bolt, nearer the neutral point, thus reducing the
parasitic side friction a bit. The easiest is to use a T-handle and
then the principal side friction is reduced to zero. You'll find this
will give you miraculous improvement.
A proper formula would use cross products you would not bother with.
loosen a tight bolt with a socket on a heavier (i.e., more massive--I
remember that part!) ratchet than with a lighter box-end wrench of the
same length.
Thanks in advance.
cheers,
Henry
Mr. Dual Space
If you have something to say, write an equation.
If you have nothing to say, write an essay.
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| User: "tj Frazir" |
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| Title: Re: request for mathematical formula |
24 Sep 2004 10:05:40 PM |
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The mass of the socket wrench is a pound or 2 in your direction if the
bolt is horisonal.
Fucking retated machanic..
Science Fair Projects - Torque
Address:http://www.all-science-fair-projects.com/science_fair_projects_encyclopedia/Torque
Changed:5:07 PM on Monday, September 20, 2004
a junior math question gets a JR answer.
FOOT pound including the tool.
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| User: "John Polasek" |
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| Title: Re: request for mathematical formula |
25 Sep 2004 09:24:51 AM |
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On Fri, 24 Sep 2004 19:33:32 +0300, (Henry) wrote:
Greetings. I'd like to know the theorem or formula or equation or
whatever it is (you see that I am not a scientist; my high school
physics class was 35 years ago) which explains why it is easier to
loosen a tight bolt with a socket on a heavier (i.e., more massive--I
remember that part!) ratchet than with a lighter box-end wrench of the
same length.
Thanks in advance.
cheers,
Henry
You said bolt but maybe you meant nut. A thin nut would be distorted
into an ellipse by the open end wrench which only contacts in two
points, thus aggravating the friction.
Hopefully the socket wrench with 6 or 12 sides would leave it circular
and minimize friction.
Obviously, mass has nothing to do with it.
For a T wrench you get T = FR and with a straight wrench
you get FR + F sidewise
Mr. Dual Space
If you have something to say, write an equation.
If you have nothing to say, write an essay.
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