Technical Actual meaning of inch pounds

I may be off the mark here but as I understand Squirrels original diagram... and please correct me if I am wrong... the top version, using the 12” (1ft) wrench will achieve 90 ft lbs on the bolt with a torque wrench setting of 67 ft lbs (due to the 16/12s of a foot overall length) however it will require 67 lbs of force on the torque wrench to achieve the desired torque wrench setting because the wrench is 1ft long.
Diagram 2, using a 24” (2ft) wrench will achieve 90 ft lbs on the bolt with a torque wrench setting of 78 ft lbs(due to the 28/12s of a foot overall length)..the 4” extension has less influence or impact. The big difference is that you can obtain the 78 ft lbs reading... and thus applying 90 ft lbs on the bolt... using only 39 lbs of force on the wrench. If you didn’t have the extension at all that 2’ wrench would require 45 lbs of force and a 90 ft lb setting to apply 90 ft lbs on the bolt.
To me, the trick is the realization that the calibrated setting on the wrench take into account overall wrench length. The force needed to achieve those setting will vary based on wrench length. The extension doesn’t have as much impact on the longer wrench.
**** that was wordy... sorry.

 

Oh, really! I’ve been having problems with a four inch tool for years! And now you throw in angles!
So at 90 degrees , no correction! At 180 degrees , you need correction? I’m in trouble! lol

No, really I can see that at 90 degrees you torque wrench is the same length as with out an adapter. I can see that! Maybe I’m catching on! Maybe! Lol




Bones

 

if you are using an extension on a crow's foot, make sure the extension ends are square and parallel to the hole in the crow's foot. i know snap on makes them that way. they had to make them for use ***embling pratt whitney engines when i worked there.

 

that is a good explanation, as far as I can tell. Thanks.

 

I finally got it figured out! I believe the four inch adapter should have a correction factor of 16.66%, period. To make me happy..... I’m only going to use my 20 inch torque wrench with it! Then my world will be round again!
By the way, I hadn’t thought of this torque wrench adaptor thing in years! Thanks ! Not! Lol








Bones

 

I'd like to give it a go!
I was a High School Auto Shop Teacher before and after a 22 year stint at Snap-on Tools, initially as an engineer. I've seen guys argue and come close to fisticuffs about this and other torque questions.

I've been thinking, "How would I explain this to a 17 year old student?" and "How come they're not getting it?"

I'll use the example @Boneyard51 posted to keep consistent.

First let's take the torque adapter out of the picture for a minute.
So we have a wrench with a 12" (or 1 ft.) effective length. If we hang a 90 lb. weight on it, we apply a torque to the fastener of 90 ft/lbs. If we use a 16" wrench we only have use a weight of 67.5 lbs to get 90 ft/lbs of torque on the fastener.
Here's the math: 12 is only 75% of 16. So, 90 *.75 = 67.5
Now, let's look at our 12" wrench with a 4" adapter. Still takes 67.5 lbs to torque the fastener to 90 ft/lbs.

If we get out our super long 24" (2 ft) wrench, we get 90 ft/lbs of torque with only a 45 lb weight. Everybody still there?

Now to unconfuse the confusing part:

In the examples above we didn't use a torque wrench because we calculated the necessary weight to achieve the desired torque. So let's figure out how the dumb ol' torque wrench messes with our minds.
With a 12" torque wrench and 4" adapter everything is pretty simple. You put a 67.5 lb weight an the end of the wrench, and it clicks and you have actually tightened the fastener to 90 ft/lbs. Cool!
The dumb wrench doesn't know it's got a 4" helper or that the fastener is torqued to 90.

Now, we go to Bones tool box and get the 24" Torque Wrench and add the 4" adapter. We now have a 28" wrench. In order to get the 90 ft/lbs torque at the fastener we need a weight of 38.5 lbs.
Math again: 12 is only 42.8% of 28. (12/28 = 42.8) More math .428 * 90 = 38.5

But wait!!!! The dumb torque wrench thinks its tightening to 77 ft/lbs 'cuz it's 2 feet long.
One last math (38.5 * 2 is 77).
So we hang a weight of 38.5 lbs on the end of our 24" Torque wrench plus 4" extension, it clicks and we have 90 ft/lbs of torque on fastener. Torque wrench is so proud to have given you 77 ft/lbs with only 38.5 lbs effort.

I think part of the confusion comes from mixing ft/lbs with inches in the beginning. If we said we wanted the torque to be 1080 in/lbs instead of 90 ft/lbs it might help.

I agree with Squirrel, when you are talking about technical stuff, you need to relate to your audience. If they say, "Foot Pounds" why do you need to make a big deal of it. I used to explain this to my students this way. "Engineers say, 'Pounds feet' and everybody else says, 'Foot Pounds'. So, when you're around engineers say 'Pounds Feet'. They'll think you are smarter than you are. Your education should be like your underwear, you should have it with you, but you don't have to show it to everybody."

That being said, Newton Meters (Nm) is a pain in the ***. When doing calculations using vectors, finite element ****ysis, and **** like that, it certainly has its place. But when torquing nuts and bolts or talking engine torque output it complicates rather than simplifies. If you don't think that's true, just try to explain the effect of torque adapters without having to first explain what a Newton is.

 

Cheez Bones,
It took me a long time to 'splain that.

 

Ok, Gearhead, that’s exactly how I understand it! Seems pretty simple in my books. But here’s the kicker! The longer your torque wrench is, the HIGHER you have to set your wrench! That’s what I don’t get! According to Gatz’s chart on a previous post. But it’s on a sliding scale in ratio with the length of wrench and length of adaptor. I did huge amount of figures on his torque calculator! It’s crazy! Then you throw in angles! At 180. ( straight) you have to decrease the setting on your wrench, then as you change angles the amount of change decreases to 90 degrees! At 90 degrees you have 0 correction factor! Then after 90 degrees you have to add to your setting!
I think here lies the clues to my answer and understanding of this phenomenon! If an explanation ever going to wedge itself into my brain! Lol








Bones

 

'Cuzn the Torque wrench is dumb. The engineer that designed it was smart. The setting of the wrench takes into account the the actual length of the wrench. The engineer lied to it.

 

A mechanic pics up the proper tool and does the job. Rube Goldberg is liable to use a bowling ball a string and a drunkin mouse and never ever get the job done correctly. learn to be a mechanic and leave U tube to Rube.

 

if you really want to have fun, do the math with a torque wrench that is 12" long, and a 12" extension that points back to the handle of the torque wrench. you end up dividing by zero, and the equations go nuts, you have to set it to infinite torque, and you still won't get your 90 ft lbs

 

I still have a hard time believing that! It makes no difference as to the length of a torque wrench when I’m torquing a head bolt to 90 lbs! The shorter the wrench, the harder I have to pull, the longer wrench I don’t have to pull as hard, but either way I still get ninety ft/ lbs of torque on the bolt! The length of the wrench is no factor here! But you add an extension and that 90 ft/lbs of torque need correction factor based on length of the torque wrench! That’s where I have the problem. The torque wrench is an instrument that measures torque, it’s length shouldn’t come into play! A 4 in adapter should have a set correction factor! In my mind!
I can actually “ see” the angle correction because the wrench is actually getting closer to the bolt, in a way!






Bones

 

Squirrel, that’s exactly why I had trouble trying to figure this out. It seemed right at some distances , but didn’t compute at other length . But today I did figure something out using Gatz’s computer! It shows that that torque needed was on a sliding scale! That actually answered some problems I had figuring this thing out.
I can’t remember exactly, but the difference in torque of a 18 vs a 24 inch wrench were substantial, say about 10 ft/lbs. But to get the next ten ft/ lbs you needed about six or more feet. You could actually get long enough that your correction factor would be zero, at about 725 inch long torque wrench! LoL I have a big torque wrench...... but not that big!








Bones

 

NO!!

 

The torque wrench is altered into a different tool when the adapter is added.
The wrench is no longer rotating around its drive.
It is now measuring beam deflection resistance at a specific point of the total beam.
Key term “total beam”

 

The torque wrench measures rotational torque from the centreline of the bolt [similar to a dyno measuring torque from the centreline of the crank]
The calibrated bending forces of the torque wrench is how it calculates the measurement [against an indicator that doesn't bend]

If for example we use 12 ft/lbs as an example, we would need 12 lbs force on a 1 ft lever to get 12 ft/lbs rotational torque at the centreline.
If the lever was changed to 12 ft you would only need 1 lb force to get the same 12 ft/lbs rotational torque at the centreline.

When you add an extension to the torque wrench, It does not have the same calibrated bending forces that the torque wrench has [it is rigid]
So the torque wrench only measures the torque readings from It's original centreline [the 1/2" or 3/8" drive] which is no longer relevant because bolt centreline is now further away.
Calculated adjustments need to be made because the centreline has been moved out further.

Or the calibrated bending forces of the torque wrench are now moved somewhere between the centreline and the force applied

 

I understand all of that and totally agree with your post 100%. What I can’t figure is where the length of the torque wrench comes in! In my way of thinking a two foot or three foot torque wrench set at 90 ft/ lbs both delivers 90 ft/lbs of torque to the female drive end of the adapter. To me , 90 ft/lbs of torque is 90 ft/ lbs of torque. That’s way you use a torque wrench, to deliver an exact amount of torque to whatever needs to be torqued!

I fully understand is has to be reduced due to the additional leverage.

I guess you I’ll never figure out how that four inch adapter knows how long the torque wrench is! And why 90 ft/lbs of torque on a two ft wrench is different than 90 ft/lbs of torque on a three ft wrench. Maybe it’s just me! Lol










Bones

 

It alters the angle of the dangle, Bones!

 

Well! Why didn’t you tell me that 20 post ago! Now I understand! Lol








Bones

 

Imagine tightening an axle nut [eg:banjo] on a car in neutral on flat ground with a torque wrench. The car will roll slightly.
If you move out to the lug nuts and torque them , less torque is needed to roll the vehicle. The force applied at the lug nut is further out from the axle nut . And the lug nut rotates around the axle centreline.

An extension on the end of a torque wrench is similar! the torque wrench head rotates around the bolt centreline

90 ft/lbs applied on a 24" wrench is from the centreline of the square drive. That is all the torque wrench knows how to measure.
Now if you extend the leverage 4" to a total length of 28" ,less torque is needed from the torque wrench to get the same 90 ft/lbs at the bolt.
To get 90 ft/lbs at the bolt, you need 77 ft/lbs at the torque wrench.

90 ft/lbs = 45 lbs force applied 24" away.
90 ft/lbs = 38.57 lbs force applied 28" away.

So 38.57 lbs force applied to 24" long torque wrench = a 77.14 Ft/lb reading [so math is needed as the torque wrench can only measure within it's own dimensions]

The math is simple easy.
Multiply Ft/lbs needed x 12 to get in/lbs. Then divide by inches of total leverage to get force.
once the force is known,
Multiply the force by leverage of the torque wrench ,then divide by 12 to get the ft/lb reading needed.

The quick math is 90 ÷ 28 [overall length], then x 24 [torque wrench only length]




This stuff is easy compared to motion ratios of suspension, or engine dyno ********ters

 

Don’t add any extra stuff! That’s good! Lol.
I just can’t get the need to know the length of the torque wrench. That’s the only thing that throws me! Everybody has been great trying to educate this old country boy! I get the fact that an adapter x number of inches long gives more leverage , so you get more torque with the exact same force on the handle of the torque wrench. I get that. I even get that when you turn the adapter to 90 degrees , it makes the length of the adapter 0, so you don’t need a correction factor. I get that.
What I don’t get is why there is not a constant correction factor just for the adapter!
I have , like mentioned, several length torque wrenches that over lap in capacity. My hard head thinks that the 90 ft/ lbs on my short wrench is the same as 90 ft/lbs on my longer wrench. If it’s not why even use a torque wrench! I was under the impression a torque wrench actually measure “ torque “ or twist resistance!
This has bothered me for years! I had problems with it 30 years ago, before the internet and just had to look at books! All this help is greatly appreciated.
I want to thank Gatz for providing that torque wrench computer! I bet I ran 100 different combos... quickly. I did learn.....some...... but apparently not enough! Lol








Bones

 

90 ft/ lbs on a short wrench is the same as 90 ft/lbs on a longer wrench .
The only difference is the effort required by the monkey swinging on the other end of it.

 

With all this discussion on "inch / pounds" and "foot / pounds" there is also "inch / ounces" as well
I used to measure rotational values of roller bearing using a torque watch.
https://deter****line.com/products/...-mid-range-reaction-torque-watch-gauge-detail

 

Hey Sarge, that “ pun y”! Lol I get leverage. The longer the cheater bar the less force it takes to produce the same torque! Or with the same force you get more torque. I get that!
I guess I’m not making myself clear, but I do not know of another way to put it.
The torque exerted against the female end of the adapter is, say 90 ft/lbs. That's all that adaptor can sense! Why do you have to set two different length torque wrenches at different settings to obtain the proper desired torque. The adapter is the same length, the torque is the same at the female end of the adapter... why does the length of the wrench come in to be a factor! In my mind 90 ft/lbs of torque in the female end of the adapter should react exactly the same way, no matter where it comes from, 2 ft wrench, 3 ft wrench or 45 lbs of rocks hung from a two ft cheater bar. To me torque is torque. That’s my problem! I have trouble distinguishing between 90 ft/ lbs on a two ft wrench and 90 ft/lbs on a 3 ft wrench, to me they should be the same!








Bones

 

Darin , I’m not arguing that I’m right! I know I’m wrong! Too many learned people said it’s the other way! You have to measure the length of your wrench. I just want someone to explain to me why 90 lbs ft/lbs of torque on a 2 ft wrench is different than 90 ft/ lbs on a three ft wrench, only when you use a short adapter! That’s my question. 90 ft/lbs on a head bolt is the same with a two ft wrench as a three ft wrench! Right?
I just can’t get it through my thick skull! Lol






Bones

 

1) The click-type torque wrenches sense torque close to the axial center-line of the fastener being torqued, so it doesn't matter where you apply the force to the wrench. (The beam-type torque wrenches measure how much the beam deflects, so you have to apply the force to the handle of the wrench.)

2) If you do something such that the center of the wrench's socket is no longer close to the center-line of the fastener, like adding an adapter or extension, the torque wrench senses the torque where the wrench attaches to the adapter or extension because it doesn't know any better. That's different from the torque that the adapter or extension applies to the fastener.

3) If you insist on using something that increases the length of the torque wrench, then you must decrease the force you put on the torque wrench by the ratio (length of torque wrench) / (length of torque wrench + length of extension). Note that the torque wrench and adapter or extension have to be close to being a straight line.

4) So if you wanted 80 ft-lbs on a bolt and your extension is the same length as the wrench, you'd set your clicker to 40 ft-lbs. If your extension is half as long as the wrench, you set your clicker to 53 ft-lbs.

 

I'm sure glad I learned how to use a torque wrench and rebuild banjo rears before I read this thread.

 

Darin, sorry to hijack your thread! Sometimes things just happen and grow a life of their own!
But to your original post, putting the torque wrench out eight inches from the center bolt is most definitely going to give you more pre load than if you put it on the nut itself, if the torque wrench is not adjusted to the eight inches.
I think we all agree on that. Now did it give too much preload as to cause bearing failure? That I do not know. Too much pre load on the pinion will mostly only effect the pinion bearings and it will not have that much effect on the wear pattern. It will have a little effect, but very little. Pinion spacing is usually accomplished by moving shims.






Bones

 

Darin, It takes me about 12 hours to set up a banjo rear. I'm old, tired and worn out. After checking or replacing bearings I set the carrier preload without the pinion installed. One of my Fordbarn buddies showed me how to make some cool tools to do this procedure. I then set the pinion preload in the vise out of the carrier. I heat the carrier to 200 degrees and drop the pinion ***embly into the carrier. Then ***emble bells and move gaskets around til I get the proper backlash. I use a cheap inch pound torque wrench. I see if I can find some pics of the last one I did.

 

But what happens if you choke up on the torque wrench?