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To: VintagVW_at_listproc.sjsu_dot_edu
From: mwest_at_cdsnet_dot_net (Mike West)
Subject: Re: RFC: Torque, and tools. and what not to do...
Cc: type2_at_type2_dot_com, Vintage Bus <vintagebus_at_type2_dot_com>

>when I started working on VW's, I was told by a very competent mechanic
>that whenever one uses an extension on a torque wrench, to set the wrench
>to 5 lbs higher than you would normally.  5 lbs for each extension.
>Later, I asked him about deepwell sockets.  He looked at me for a minute,
>then said he saw no reason to change for them.  the 5 pounds is not for
>the length, but for the flex that happens in each socket joint.
>I've been using this for a few years now with no noticed problem...anyone
>have any comments?
>David Raistrick  '69 Westy-Itchigo            keen_at_finally.atlasta_dot_net
>           '82 Westy-Baby Maxine (Mom's)
>           '66 SO-44 Westy (coming soon!)          in Augusta Ga
 - - - - - - - - - - - - - -

Raistrick put you guys up to this didn't he . . ?   :-)

First he goes by with the bait, then a couple of you throw rocks.

Then you get "physicsdude" AKA "thingguy" to light a smoke pot 
near my hole . .

OK . . . I'm awake and totally pissed off . . . !  :-)

That A/A+B = Torque is if you put a crows-foot on the end of the 
torque wrench . . . "old handle/new handle . . ?  a ratio 

Another example is the "slugging wrench" for the rear axle nuts.
It has a 1/2" drive socket in it that is 3-1/2" from the center
of the nut. . . . need to do that ratio thing that "thingguy"
brought up . . 

Assuming the 6" from "thingguys" example, a 200 ft-lb torque on 
a 6" extension would give you 285 ft-lbs . . .
It's a way to get more torque from your wrench than it's rated for.

Putting an extension or "cheater bar" on the handle end is not 
the same . . for that, you continue to read the gauge . . (bad)

David, however, was talking about an extension for the socket. .
That which gives you an offset position for the wrench from the
socket . .

For that we would have a torque loss equation . . .

You apply 50 ft-lbs of torque to a six inch extension to the 
socket . . the extension is steel and steel is still the most 
"elastic" material we have . . . .

Elasticity is defined as the amount of load that can be applied 
to a material under certain constraints and the material will
return to its original shape . . .

So that extension is a spring . . . in our case, it is a "torsion
spring" . . .  

When you apply your force, the "spring" starts to wind up . . 

When the spring rate reaches equalibrium with the force required 
to move the nut, then torque will be applied to the nut . .
As it gets harder to turn the nut the spring must first "wind up"
or deflect radially until a new equalibrium is reached. . .
The amount exerted to the nut will always be "less the amount used
to deflect the shaft around it's axis" . . .

The torsion spring rate is relative to material spring rate times
the cross-section of the shaft times the length of the shaft. .

You notice this when you are trying to loosen a nut with a long 
extension . .  you get a lot of angular movement before you get
the damn thing wound up enough to break that nut loose. . .
 Makes it almost impossible to use an extension on a impact-wrench.

I have this friend who is a power tool freak . .  he's pulling a 
tranny from a ford SUV  . . . he's clear behind the car, with about
a four foot extension made up of about five pieces and he'e got an
impact wrench on it to break a bolt loose up on the tranny. . . :-)
Might as well beat it with a flower . . .  :-)
 He doesn't take well to criticism so I left him to it . . :-)

So the spring is relative to the material of the extension and the 
diameter of the shaft and the length of the shaft times the force.

Going thru the numbers for a standard 1/2" shaft and 6" long,
5 lbs might be a good number for the 50 lbs in . . .

Only when you apply ten pounds or 150 lbs . .  the number needs
to change . . .

Without resorting to math, I'll tell you how to figure the spring
rate for your extension . .

For a 1/2" drive torque wrench, get a 1/2" bolt and nut . .
Get some lock washers and flat washers, 2 or 3 . . .
If you have a pipe spacer, throw that in too . .
Get a bolt about as long as you can set in the jaws of your vise.

No vise . . ? well you're SOL aren't you . . ?   :-)

The idea of the longer bolt is that it's a spring when it's pulled
too . .  the longer it is the more movement for a given force . .

Put the nut in the vise . .  thread all that garbage on the bolt,
put a flat washer between each lock washer and the faces of the 
nut and bolt-head . . .

Get a pair of calipers and your 12" extension bar . . 

Put the extension on the torque wrench and torque the bolt down 
to a good number for a 1/2 or 13mm bolt . . . 50-80 ft-lb . . 

Now take a measurement over the head to nut with the calipers.

Take the extension off and using the same number for tightening,
see if you move the nut . . . bets are you will . .

If you can't tell if it moves, mark it with an index mark,
nut to bolt . . .

Also take another measurement over-all. . .  it got shorter.

Now start adding a pound or five to the reading/extension
and testing with the real number w/o extension till it stops
moving . . the measurement stays the same . . 

You will have to do a series of tests relative to the torque
to work out a sliding scale you can use.
As in "add a pound for each 20 lbs of torque" . . .

Let's forget the whole thing and go get big heavy extension.

I have this maybe six inch extension for wheel nuts, etc. . .

It's 3/4 inch and looks like a nose-tackle . . :-)

Then I got a 3/4 X 1/2 short adapter to get me to my socket.

Has a spring rate of about 150 lbs on an 8 ft cheater bar. .

Oh, the number of socket connections is just slop to a torque wrench,
no big deal other than the thing wants to bend all which way . .
To an impact wrench it would be important if the spring rate didn't 
already defeat its purpose . . 

None of this could be categorized a "sin"  . .  
A sin is if you cause another un-necessary pain . .  causing yourself pain
is just stupid.   :-)

west   :-)