Funny torque tricks

[SJ]

> From: "Al Powell" <apowell at gocougs.wsu.edu>
> Subject: Funny torque tricks
> To: <quattro at audifans.com>
>
> SJ said:
>
> [As Ameer pointed out, everyone got it right about the tool, and the use
of
> different extensions, and the basic torque formula. The difficulty was
that
> we did not realize how important the torque wrench length was to the
> discussion.....]
>
> I guess I'm the holdout.  I've saved SJ's lengthy explanation for review
> since I'm running out the door for a biz trip...however, the statement
above
> and his whole argument just don't make any sense to me.
**** You're not the only one that that had a problem with my explanation. I
did also. But, after staring at it and rewriting it, and thinking about it .
.. I think its an accurate explanation.

>
> All my common sense and logic tells me that if you apply 100 lbs/ft to a
> point of turn (including the famous tool 2079), it doesn't make any
> difference whether the wrench used is 1 foot long or 100 ft. long. 100
> lbs/ft is the same amount of force regardless of the length of the tool
used
> to apply it....so it does not matter.
*****Right. The wrench length makes no difference at the original "point of
turn" which is the working end of the torque wrench. 100 ft lbs is 100 ft
lbs.
Hang a 50 lb weight at the end of a 2 foot breaker bar and you got 100 ft
lbs of torque at the "point of turn".
Now add a 1 foot extension to the point of turn. The new "point of turn" is
at 3 feet from the 50 lb hanging weight. What is the torque at the "new
point of turn"?  50 * 3 = 150 ft lbs and not 100 ft lbs.

Lets try a 100 lb weight a the end of a 1 foot breaker bar. Again we have
100 ft lbs of torque.
Add the 1 foot extension, and the new "point of turn" is 2 feet from the
hanging weight. The torque at the new "point of turn" is now 100 * 2 = 200
ft lbs and not 150 ft lbs, or 100 ft lbs.

The length of the torque wrench does make a difference at the new "point of
turn".

>
> If SJ's statement about length of the wrench were true, then Audi would
have
> specified NOT ONLY the tool 2079, but would ALSO have specified the
precise
> length of the torque wrench used to apply the torque.  They did not.
Hence,
> in Audi's eyes, the length of the torque wrench is immaterial. Audi is
anal
> enough that if it mattered, they would have specified the length of the
> wrench to be used.
**** I've been in Manufacturing Engineering long enough to know that things
are often overlooked in Design Engineering. What worked on the prototype in
the engineering lab does not work on the production unit. Somebody forgot
something and it wasnt the poor slobs on the production line. BTDT

>
> Therefore I (respectfully, to avoid hurting anyone's feelings) cannot
agree
> with SJ's conclusion.
****Nahhhhh . .Politically Incorrect folks dont get their feelings hurt.
Audi owners, especially owners of old audis are not PC. The PC folks usually
drive Beemers and Mercedes.
Challenging another's logic or conclusion is a part of a healthy debate. It
makes us think.

Here is your homework assignment Al. Somebody else is doing this exercise
also.

Here is an exercise that demonstrates what we are talking about.

A------------B-----------------------------C
A-B is 1 foot
B-C is 2 feet
A-C is a piece of wood with holes drilled at points A, B, C

Put a screw at point B and screw the wood to a barn door. Put a washer
between the wood and the door so we dont introduce any friction between the
2 surfaces. Tighten the screw so the wood will not rotate.

We want a torque at point B of 258 ft lbs. How much weight to hang at point
C?
Easy, T=FD . . 258/2 . . 128 lb weight hanging at point C

Now put in a scew at point A, make it real tight. Remove the screw at point
B. What is the torque at point A?
Easy, T=FD . . . 128 lbs X 3 feet = 384 ft lbs

See! The problem is simple. Simple when you know all the details.

Now try this out.
A-B is 1 foot
B-C is unkown . . but its most likely between 1 foot and 4 foot
Torque at point B is 258 ft lbs

What is the torque at point A? Point A of course is the bolt torque.
Multiple answers are not acceptable.

You have 8 hours to complete this homework assignment. Failure is not an
option.
Drinking beer while you work is optional.

SJ
85 Dodge PU, D-250, 318, auto
85 Audi 4k - - sold but still on the road
88 Audi 5kq
90 Audi 100q