Torque wrench extensions

[Heatnbeat]

Does anybody have a formula to calculate the reduced settings for using extensions with a clicker wrench? All of the ones I've found reference the length from the center of the drive to the center of the handle. Two problems there; for one the length varies depending on the setting although leverage doesn't . Secondly although that center of handle works on beam type, on clickers it makes no damn difference. I put my hand as close as I could to the flex joint and then used a 3 ft cheater bar and it made no difference to the torque. So it seems to me that I need a formula that reduces the torque setting by a percentage based on the length of the extension.
I'm good with questions, but not so good with math. :-)

[Rockout Rocker Products]

There are various calculators online. The easiest way... always keep the extension 90 degrees to the torque wrench beam.... no correction factor needed. 

[Heatnbeat]

Yeah I know the extension at 90degrees doesn't require any calculations but this is more of an intellectual quest.

There are calculators on line but I really do think they are wrong for a clicker style. It's damn hard for me to believe they are all wrong and this dumb old welder is right but I need to understand it before I can concede.

If the length of the handle made any difference then my 3 ft cheater bar would change the torque, but it doesn't.

[FSG]

If the length of the handle made any difference then my 3 ft cheater bar would change the torque, but it doesn't.

It has to, post a pic of your torque wrench with the cheater bar fitted

http://www.harleytechtalk.com/htt/index.php?topic=1215.msg

[Karl H.]

...If the length of the handle made any difference then my 3 ft cheater bar would change the torque, but it doesn't...

As long as you do not use any torque adaptor the lengt of the handle makes no difference. But as soon as you use a torque adaptor the situation changes! Might this be the point where you're hanging?

Karl

[Heatnbeat]

 Just to be clear ALL of this applies only to clicker type wrenches. Bending beam are a different animal.

OK, so here's what I did so far. I mounted an old clicker wrench in a fixture ( made by Chas Parker Meridian CT LOL)
and set it for 190 in/lbs. I took a second wrench and upped the setting until they both clicked at almost the same time ( as close as I could get) then I took the wand from my shop vac which is a good 3'+ and slid it over the handle, Exactly the same as before, so the length of the handle on a clicker makes no difference.

As near as I could figure out my 3" extension reduces my setting by 20%on my 1/4 drive wrench but the calculators say it would change if I used it on my 3/8 wrench which is longer. I don't believe it.

Oh one other thing. Since the center of the grip area moves when you adjust it. If those calculators are right you have to re calculate your torque for the extension every time you adjust the wrench.  Does this make sense??

[Rockout Rocker Products]

The reason the length of the beam doesn't matter on the click type is all you're really doing by turning the handle is adjusting spring pressure on the mechanism. If it was 3" long I'm guessing it would still read the same.

[attach=0]

[Heatnbeat]

YES Rockout, you are correct. That's why the calculators on the internet and even the ones supplied by the wrench are wrong.

Maybe I'm missing something but I don't think so..

[Coyote]

Added length before the measurement head does not matter (at 90 deg). If off 90 degs, it follows the calculators.

[Heatnbeat]

Well I just did some more experimenting.


  According to the online calculator (https://www.belknaptools.com/support-library/extensions-calculator/)
To get 120 in/lb with my 8" long 1/4 drive torque wrench and a 3 inch extension I need to set the wrench at 87.3 but if I run the calculation with my 13" long 3/8 wrench I need to set the wrench at 97.5. But my 1/4 and my 3/8 with the 3" extension and set at the same setting give the exact same torque.

And Coyote, with all due respect that isn't true either. I didn't believe it so I made an 18" extension. I put my old wrench in the Chas Parker fixture and set both wrenches to 120 in/lb. With the 18" extension at 90deg I could not set the old wrench low enough to make it click.

If you guys don't believe me try it. Make a long extension and try to torque something with it. I admit an 18" extension is a bit absurd. But if it really did not matter then 18" wouldn't matter either.

Now if you guys will excuse me I have an engine install to finish up.

( why the heck does everything take so danged long. LOL)

[chaos901]

An extension (cheater pipe) on the handle of the torque wrench does not make any difference to the torque applied.  Just makes it easier to apply.  As previously stated, an extension from the drive (at other than 90 degrees) does make a difference.

[Coyote]

An extension (cheater pipe) on the handle of the torque wrench does not make any difference to the torque applied.  Just makes it easier to apply.  As previously stated, an extension from the drive (at other than 90 degrees) does make a difference.

I agree but to do the calculation you do need to use the wrenches spec'd handle length.

So the Wrench TQ setting =  Desired TQ x  ( handle length/  (handle length + added length))

So if you have a 12" wrench and you add 2 inches and you desire 100ft-lbs you should set your wrench to

100 * 12 / (12+2)  = 85.7 ft-lbs    adding a cheater bar changes nothing on this.

[Rockout Rocker Products]

The click mechanism in a click type torque wrench doesn't know inch pounds from metric tons. It knows to click when the force overcomes the spring pressure applied to the mechanism. Apply that force from a foot away, two feet away, it knows no difference. It makes a difference on how it feels to you.

[Coyote]

True, that's what I said above...

[Panzer]

Now my head hurts.

[cheetah]

I think when speaking of "length," they are speaking about http://www.sears.com/stanley-proto-stanley-proto-j5100-3-8-inch-drive/p-SPM8849389223?plpSellerId=Edealszone LLC&prdN  not the length of the handle of the wrench.
When using an adapter as above, the overall length is extended, and one must use a calculator.
If using a pipe extension  without using an adapter on the wrench,  no calculations needed.
C

[Dan89flstc]

When you say extension, you are actually referring to what is known as a cheater bar (a length of pipe slipped over the wrench to make it easier to turn).

All you are doing is making it easier to turn the torque wrench, the wrench does not know if it is being turned by hand, or a 50 foot long pipe.

For a clicker type, it really doesn`t matter where the wrench is pushed from, the handle does not have a pivot point, it measures torque at the pivot point up near the head of the wrench.

The cheater bar does not change the effective length of the clicker type wrench.

On a deflecting beam torque wrench, the force must be applied at the pivot point in the handle.

The online torque formulas are correct, they have nothing to do with adding a cheater bar extension, they give the calculation for adding to the effective length of the wrench when using a torque adapter.

But...there is no reason to use a cheater bar on a torque wrench, the wrench is plenty long enough to pull the max torque the wrench can indicate.

[Heatnbeat]

No Dan, maybe I wasn't clear. No cheater bar on the wrench, I only used my shop vac wand to prove out an idea. Anybody that would use a cheaterbar on a torque wrench needs there tools taken away from them.

My extension is what you refer to as a torque adapter. And no the online formulas are as far as I can see not correct for clicker style wrenches, but correct for the bending beam type.

If you don';t believe they are incorrect try this experiment for yourself.
Use a torque adapter on your short handled 1/4" clicker and run the calculation. Then check force exerted. Use a 1/4x3/8 adapter and put the torque adapter on your longer handled 3/8 torque wrench, run the calculation and check exerted force. I get 2 different forces. if I set the 3/8 wrench to the same setting as the 1/4 I get the same exerted force.

[Karl H.]

...Use a torque adapter on your short handled 1/4" clicker and run the calculation. Then check force exerted. Use a 1/4x3/8 adapter and put the torque adapter on your longer handled 3/8 torque wrench, run the calculation and check exerted force. I get 2 different forces. if I set the 3/8 wrench to the same setting as the 1/4 I get the same exerted force.

I don't understand the logic yet. Could you sketch your setup please?!

Karl

[Dan89flstc]

You may not understand what is going on, but I have used these formulas in the aviation world for over 43 years as a jet engine mechanic, the formula is correct.

The formula is correct for any type hand torque wrench, be it deflecting beam, dial torque meter or micrometer type clicker.

[attach=0]

[Karl H.]

 

[Coyote]

Exactly the same as I posted above. 

[FSG]

Exactly the same as I posted above. 

and the same as http://www.harleytechtalk.com/htt/index.php?topic=1215.0 which has been around since 2008

[Coyote]

Exactly the same as I posted above. 

and the same as http://www.harleytechtalk.com/htt/index.php?topic=1215.0 which has been around since 2008

Good formulas stand the test of time.   

[Heatnbeat]

Dan,

I know, we've all been using them. I've used them for 50 years.

But answer me one question.

If as you state (and we agree!)


"For a clicker type, it really doesn`t matter where the wrench is pushed from, the handle does not have a pivot point, it measures torque at the pivot point up near the head of the wrench.

The cheater bar does not change the effective length of the clicker type wrench."


How can a formula that references the handle length work?
I do not think it does since handle length does not change the effective length of a clicker wrench.
It works for a breaker bar, or a bending beam torque wrench. But I can not see how it possibly can.

I'm not trying to be stubborn (my ex said I didn't have to try to be stubborn, it came naturally) and I really don't want to tie up the forum so if anyone would like to continue this via messages I'm all "ears".


Update:

I've been looking and I may have a better way to explain my issue.

Lets say you have 2 torque wrenches, 1- 12 in long and 1- 24in long. Torque 2 bolts to 50lb/ft and they will be equally tight. Correct? Now put your 2"  torque adapter on both wrenches, tighten both bolts to the original setting. They will both still be equally tight. Correct? But the calculators tell you to use different settings.

[Karl H.]

Torque is force times leverage. That's simple physics! The clicker mechanism indicates that at the pivot point of the clicker mechanism a preset torque (T1) is achieved. The torque at the clicker pivot is force exerted (F) times leverage between grip position and clicker pivot (L). The torque at the screw (end of the extension) (T2) is force times leverage too, but leverage is extended (L+A). Therefore the torque at the end of the extension is always higher than the torque at the clicker pivot. The relationship between the torque at the clicker pivot and the torque at the end of the extension is expressed by the well known formula which can easily be deduced from the basic leverage rules.

Karl


[attach=0]

T1 = F x L
T2 = F x (L+A)
=>
T1/L = T2/(L+A)
=> T1 = T2 x L / (L+A)

[Heatnbeat]

Karl, if what you say is correct then lengthening the lever arm with a cheater would increase the torque. But it doesn't.
Basic leverage rules do not apply to clicker wrenches.
Look at the design of this wrench, it's simple to under stand and it makes it obvious that handle length plays no part in the applied force.

http://www.appliedtorque.co.uk/p/handtorquewrenches/torquewrenches11/slippingwrenches/default.htm

It took a whole lot of looking but I finally found a formula that I believe works because it does not reference the length of the wrench.

I can't type it out here because I'm not good enough on a keyboard to know hoe but here it is:

Indicated torque ( wrench reading)= required torque / (1+ extension length).
Divide the extension length by 12 to find what fraction of a ft. the extension is (e.g. 3"= .250 ft)

Here's a link to a whole discussion of this problem. If you don't want to read it all
look at Oct/3/2008  - Mar/21/2011 - Dec/30/2011

[1FSTRK]

That formula does the same thing.
You are right about the applied force but you need to understand that in all the previous formulas L is a constant in the formula for the wrench being used and has the same formula value as 1 in your formula.

[Heatnbeat]

1FSTRK

My math skills are weak so I'd like to believe that.

But since I may be screwing up the formula I use this calculator from Belknap.

https://www.belknaptools.com/support-library/extensions-calculator/

Using my formula I get an actual torque of 100 with an indicated of 80 with a 3 in adapter
With the calculator I get
100 actual with indicated 72 for an 8 in wrench
100 actual with indicated 80 for a 12 in wrench
100 actual with indicated 89 for a 24 in wrench

What am I doing wrong? If the formula is normalized ( correct term?)  for wrench length why the difference?

[1FSTRK]

I stand corrected, happens when I post quickly based on others math.
This will require some additional investigation on my part to find the source of the discrepancy.

It appears at first glance that the original formulas will be accurate to calculate handle force changes but as you say not corrected wrench settings or readings because the wrench readings are taking place at the wrench head and not on the handle where the force is applied.

[Karl H.]

Karl, if what you say is correct then lengthening the lever arm with a cheater would increase the torque. But it doesn't.
Basic leverage rules do not apply to clicker wrenches.
Look at the design of this wrench, it's simple to under stand and it makes it obvious that handle length plays no part in the applied force...

You are right and wrong! Lengthening the lever arm will not increase or change the "click" torque T1 (which is preset and unchanged) but will decrease the "click" force F and slightly decrease T2 as well. T2 remains greater than T1. All that is correctly expressed by the equation.

Karl

[1FSTRK]

Look at the clicker wrench design in reply #6. I think the problem is with a clicker wrench L is the distance from the center of item #18 in the diagram to the center of item #12 and T1 is the center of item #12. The measured force is being applied at item #18, the length of the handle from #18 back has no effect on the force at #18 because of the spring/clicker will be overcome at the set point.

[Dan89flstc]

Lets say you have 2 torque wrenches, 1- 12 in long and 1- 24in long. Torque 2 bolts to 50lb/ft and they will be equally tight. Correct?

Yes

Now put your 2"  torque adapter on both wrenches, tighten both bolts to the original setting. They will both still be equally tight. Correct? 

No, not correct...

If you torque both wrenches to a 50 pound setting, with a 2 inch torque adapter installed, the bolts will not be torqued to an equal value.

The 12 inch wrench set at 50 lbs, using a 2 inch adapter will torque the fastener to 58 lbs.
The adapter is adding 16.66% to the overall length, the wrench cant see this, that is why we need to calculate using the formula.

The 24 inch wrench set at 50 lbs, using a 2 inch adapter will torque the fastener to 54 lbs.
The adapter is adding 8.33% to the overall length.

The 12 inch wrench must be set to read 42 lb.
The 24 inch wrench must be set to read 46 lb.

[Rockout Rocker Products]

Lets say you have 2 torque wrenches, 1- 12 in long and 1- 24in long. Torque 2 bolts to 50lb/ft and they will be equally tight. Correct?

Yes

Now put your 2"  torque adapter on both wrenches, tighten both bolts to the original setting. They will both still be equally tight. Correct? 

No, not correct...

If you torque both wrenches to a 50 pound setting, with a 2 inch torque adapter installed, the bolts will not be torqued to an equal value.

The 12 inch wrench set at 50 lbs, using a 2 inch adapter will torque the fastener to 58 lbs.
The adapter is adding 16.66% to the overall length, the wrench cant see this, that is why we need to calculate using the formula.

The 24 inch wrench set at 50 lbs, using a 2 inch adapter will torque the fastener to 54 lbs.
The adapter is adding 8.33% to the overall length.

The 12 inch wrench must be set to read 42 lb.
The 24 inch wrench must be set to read 46 lb.

In the example, the torque will be different because the percentage of added length is different.

[Heatnbeat]

Sorry guys but I don't believe it.


But I'll let it rest until I have a chance to set up some sort of test rig. If only I hadn't retired I'd have the stuff to do it.

[Karl H.]

Good luck! I'm out...

Karl

[build it]

i have this formula somewhere, if anyone is interested I can try and dig it up. Assuming a 3 foot extension and perpendicularity, don't worry about it.

[convert1967]

When adding an extension it is easy to not be 100% perpendicular, and you will lose torque.

[hattitude]

Karl, if what you say is correct then lengthening the lever arm with a cheater would increase the torque. But it doesn't.
Basic leverage rules do not apply to clicker wrenches.
Look at the design of this wrench, it's simple to under stand and it makes it obvious that handle length plays no part in the applied force.

I'll give this a shot, but it's been years and I'm not the world's best teacher....

With a clicker torque wrench, used without an extension, the fulcrum is on the end of the lever (on the pivot point, the bolt). This is a class 2 lever.  A longer handle makes it easier to apply the same torque value at the end of the lever (pivot point) AND, if desired, it will also allow for more torque to be applied at the end of the fulcrum.

When you add an extension, whether it is 2", 3", or 10"  and you keep the torque wrench inline with the extension... you are moving the fulcrum from the end of the lever and putting it in the middle of the lever (in the case of a torque wrench, "inside" the pivot point). It is now a class 1 lever. To measure the torque at the fulcrum, which is now in the middle area of the lever, the length of the lever becomes pertinent. Since it is at the fulcrum (where the torque wrench mates with the extension) that the torque measurement is taken, adjustments must be made to get the desired torque value at the end (pivot point) of the lever.

It's been awhile since I've was taught the physics of levers, but in my head this clear as can be.... my explanation, however, maybe lacking, if so, I apologize....

[Heatnbeat]

hattitude, I really appreciate your explanation!!

I could use some more teaching; would you mind if I emailed you?

[hattitude]

hattitude, I really appreciate your explanation!!

I could use some more teaching; would you mind if I emailed you?

You PM me, but that's about all I remember on the lever stuff.....

Sadly, I took some great physics courses back in college in the late 70's. No calculators or computers... all old school math or a slide rule (which I never really got the hang of).... but then I went into a career where physics wasn't needed on a regular basis and I've gotten rusty (meaning all but forgot) most of what I learned.

I was researching torque wrenches about 5 years ago and did a bunch of internet reading. It led me to extensions and formulas, that stimulated a few old memories. It got me reading even more.... I hate when I have to relearn something I used to know...

I'm pretty sure I remembered it correctly and more glad I was able to explain it .....