# Backwards extension torque wrench formula + cheat sheet review

1. Mar 6, 2016

### leaning

• Poster has been reminded to post schoolwork in the Homework Help forums
Hello! I took a quality certification test yesterday and there was a question on there about torque wrench formulas. I didn't have anything about that in my notes, so I took some time this morning to create a cheat sheet based on what I could find on the web.

1) In some of the forums, they talked about how a crowsfoot adapter/extension when rotated backwards creates a reduction. I can't find a formula for that. Can someone look at my sheet, and let me know what I need to add to show that?

2) I still have some white space on the sheet, so if anyone sees anything I can add, if I'm missing anything, or something's wrong, I'd appreciate the feedback before I add this to my notes.

Regards,
Leaning

Last edited: Mar 6, 2016
2. Mar 6, 2016

### haruspex

Not an area I knew anything about, but from a little reading it looks to me as though this is already covered by what you have; it corresponds to θ values > 90 degrees. If used completely backwards, 180 degrees.

3. Mar 6, 2016

### leaning

haruspex,

Yep, I think you're right. COS(0) = 1 (which is straight ahead and everything is in a straight line). When it rotates clockwise or counterclockwise from -90 to 90, the COS is positive so that "COS(theta) + AL" would be more positive (additive). But when the crowsfoot starts heading backwords (>90 and <-90), then the COS is negative, and "COS (theta) + AL" is less positive (reduction). So, yeah, the formula already works for that. Sweet.

I'm still hoping for someone to rip it apart, though. It bugs me to think I've got something down, then somebody pops up and sees stuff I am missing.

Thanks for the assist!

Regards, Leaning

4. Mar 6, 2016

### leaning

Here's the latest version, if anyone is interested. (The deadline for editing my first post passed.) Regards, Leaning

5. Mar 7, 2016

### Tom.G

Their seems to be a problem in the last formula: "1 with 2 and 4".

'HEL' only has an effect when 'Force' is involved and 'Force' does not appear in that formula.

6. Mar 8, 2016

### leaning

Tom G,
Thanks! You are definitely right, but I can't find this example anywhere on the web, so I want to make sure I get the math right. I'm trying to figure it out. Here's the latest. (It's Excel vice PPT.)
Regards,
Leaning

7. Mar 9, 2016

### Tom.G

Your four equations are calculating different things.

The first two show ST based on applied force to the handle or handle extension.
(I don't see where this is particularly useful. Although it may have been included for completness. If needed, you can approximate it mentally.)

The second two equations (attempt) to show ST based on the desired torque of the fastener, FT. In these cases HEL is irrelevant so Eq. 4 would be the same as Eq. 3.

If you want to calculate Force for conditions 3 & 4, use the ST you get from them and then us Eq.1 or Eq. 2 as appropriate.