torque (new thought inside)

[auditude at cox.net]

I think we have the answer around here.  Here is where I'm at in this torque thing.  I learned 
something here so it was worth it to me.  Believe it or not, I think there's some interesting 
new stuff in this email.

The way I was reading SJ's posts, it was as if torque wrenches measured the torque at the 
handle instead of the lug (bolt).  In more than on post it read like (and maybe was intended 
to be) torque wrenches of different lengths set for the same target torque resulted in different 
torque being applied (without an extension) to the bolt.  This is where my intuition got me 
going, I disagreed with that and still do.  

I just checked out the link below, for the first time this thread, and I see that when trying to 
do what we are trying to do, calculate backwards to determine the equivalent bolt torque 
without the extentsion, the length of the torque wrench affects the amount of the "difference" 
between the actual torque and the measured torque.  When an extension is used, we have 
to use the formula to know what's going on.

So really, we do need to know how long the torque wrench was that was used to create the 
Bentley specification.  We definitely need it to figure out the setting for a torque wrench used 
directly on the crank bolt, and I'm thinking it matters even with the extension in place.  So 
one person can use the extension

I think I see what SJ is trying to say.  I won't say that it read that way tho'. =)

The math tells us that the torque wrench length affects bolt torque when using the 
extension.  We don't know how long the "Bentley torque wrench" was for sure, but we can 
get close using common sense.  Which led us to the calculations below.

SJ syljay at optonline.net wrote:
<snip>
> **** The only specified torque value is the 258 ft lbs using tool 2079.
<snip>
> If you follow the proper procedure and use the proper tools, you still dont
> know what you are doing. Thats what this discussion is finding out.
<snip>
> Tool 2079 is exactly 12.0 between centers.
<snip>
> **** 32" wrench will result in 355 ft lbs on the bolt. A 42" wrench will
> result in 343 ft lbs on the bolt.

This is that part that bugs me.  If we are talking about the bolt, then doesn't:
a 32" wrench set at 355 ft lbs result in 355 ft lbs at the bolt,
a 32" wrench set at 343 ft lbs result in 343 ft lbs at the bolt, 
a 42" wrench set at 355 ft lbs result in 355 ft lbs at the bolt, and 
a 42" wrench set at 343 ft lbs result in 343 ft lbs at the bolt?

This is the stuff that makes it seem like SJ is saying that torque wrenches measure 
something at the handle instead of the lug.  But that's one issue, separate from the others 
numbered below.

Beyond the terminological issue, when I do the math I get different answers.  Using the 
formula from the link at the bottom of this email, the 2079, and those two wrenches, I get 
and 355 ft lbs for the 32" and 332 ft lbs for the 42" wrench.

My math is as follows:

setting/(wrench/(wrench+2079)=bolt torque

32"=2.6'
42"=3.5'

258/2.6/(2.67+1)=355 (ish)
258/3.5/(3.5+1)=332 (ish)

This is where my mind is at on this:

1.  As tight as you can get it is probably fine.
2.  We don't even know how much torque gets to the bolt following the Bentley procedure, 
because it doesn't tell us how long a torque wrench to use (they used). (my new thought!)
3.  We can make a satisfactory guess by assuming Bentley torque wrenches are about the 
same size as the torque wrenches the rest of us use.  The range of possible bolt torques is 
small enough that any standard torque wrench should be fine.

Cheers,

Ken

<snip>
> >for those having a difficult time comprehending torque multipliers and
> such, just check out:
> >
> > http://www.specialpatrolgroup.co.uk/spooky/torque/torque.html