Just out of curiosity, what's the formula for figuring the actual torque setting when using an extension? I have seen some formulas plastered on the web, but they aren't what I would consider factual although they are useable to a certain extent.

I recently had to torque drive shaft bolts and had to use the extension to reach in. While the job is finished, I thought it might be fun to see who really knows their physics.

Also if 1 pound is applied to a three foot lever is it the same as if 3 pounds were applied to a 1 foot lever?

I can't wait to see these!! The one I needed once was to torque a nut that could ONLY be accessed with a crowfoot. The "offset" was about 1" from the center of the nut to the center of the ratchet drive. Then... does the angle of the crowfoot on the ratchet make any difference? The Snap-on, Cornwell, and Mac guys all had no clue, and no magic tool to help. I guess it's still running, but I sold that business <img src="/forums/images/graemlins/lol.gif" alt="" />

Also from the reservoir of useless knowledge:



I can't paste the drawing and scale, so you'll have to access the site:

http://www.mdmetric.com/tech/data1torque.html

http://www.specialpatrolgroup.co.uk/spooky/torque/torque.html

Just tighten the danged thing! <img src="/forums/images/graemlins/lol.gif" alt="" />

Frank <img src="/forums/images/graemlins/cheers.gif" alt="" />

Now for the useful repository - how to use a crowfoot extension with a torque wrench:



http://www.jag-lovers.org/books/xj-s/04-Engine2.html

Frank

Torque primer..... to understand this is to totally know torque:

http://hyperphysics.phy-astr.gsu.edu/hbase/torcon.html

Do I get some kinda prize or sumptin'? Gee, I hope it's a set of sliderz..... <img src="/forums/images/graemlins/lol.gif" alt="" />

Frank

Missed your last question...... I think the answer is .... "yes" - BUT........

If the lever is a torque wrench which turns a nut and bolt, then more than likely the mechanical advantage formula used should be the "Ratio of Circles" - that is, the circumference of the force applied to the torque wrench handle as a multiplier of the nut circumference:

http://www.laurencenet.net/mechadvantage.pdf

Of course we could always argue the variance between where the force is applied on a 6-point vs. a 12-point socket... <img src="/forums/images/graemlins/lol.gif" alt="" />

Really, it's sliderz, ain't it? Please?

Frank

I see you've been to the jag lover site.

The bolts is tight.

I just can't see why the formula's I found on the net perpetuate using the length of the torque wrench in the formula when it has no real bearing on the applied torque except to make it easer to apply the torque.

In other words, once I calculate for the extension, it shouldn't matter how long my torque wrench is. Or for that matter if I haven't got a torque wrench how do I figure the force needed to be applied to the end of the extension to acheive the correct setting?


So maybe I'll use a beam torque wrench or maybe a dial torque wrench or maybe a wieght on the end of a 3 ft bar. But in order to determine how much weight to put at the end of the bar I need to know how much torque correction for the extension, anybody have that formula?

I think you just answered your own question...

If you're talking about extending the handle, then, since either the beam or the clicker wrench is measuring twist at the head, the formula is : a=b.

If you're talking about using extensions on the DRIVEN end, i.e. between the socket and the wrench, there's a similar formula : I=O!

Or there's another question here that I'm tmissing... <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

Ahhhh, so what you're trying to figure out is how much pressure and at what distance from the fastener to apply it.

First, you're correct that an extended length of handle lever on a torque wrench only increases mechanical advantage on the fastener and makes the force easier to apply - and as long as in attaching it you don't interfere with the designed ability for the beam to deflect on a beam-type wrench, your torque value for a given reading is not affected.

I would not suggest that you attempt to tighten a rotating fastener to a specified torque value by the determination of mechanical advantage and applied force. It can be done, but the force MUST be applied exactly perpindicular to the lever arm and you MUST know the exact mechanical advantage and frictional values.

If you want to try it and can afford a mistake, I THINK (not absolutely certain) that mechanical advantage can be found by the "Ratio of Circumferences" formula. One way to test the formula for accuracy would be to set a control experiment using a fastener that's easily accessed and a standard torque wrench. The radius of the nut probably should be figured to be half-way between the points and the flats (not absolutely certain about that either), and the radius of the applied force should be the point at which the middle of your hand (or whatever applies the force) holds the wrench handle. From each radius determine the circumference (radius x 2 x 3.14 - or diameter x 3.14) and divide the smaller into the larger. The result should be the mechanical advantage. Divide the required torque value on the fastener by the calculated mechanical advantage and apply the determined amount of force to the handle of a torque wrench pre-set at the required value. If the torque wrench agrees with the experiment, then the formula should translate in fairly trustworth fashion to another application.

If the correct torque value is absolutely critical and you can't get a torque wrench into place and you are working with a bolt and nut, the easiest thing is to remove them from the assembly, set them up in a fixture or somewhere where you can find the correct torque with the torque wrench. Then apply the tool you will need to use when the fastener is in place and see what the required force "feels" like - or if you must, make an attempt to measure the force - just make certain it's applied perpindicular to the handle.

If you try the circumference formula, I'd like to know how accurate it is....... and where on the fastener you have to measure to make the formula work in practice as opposed to theory.

Good luck,
Frank

Frank

I see the problem you're having (I think). Note that the beam wrench is calculating deflection of the beam over the distance from the socket end to the gauge. The deflection measured over ONLY that distance generates the indicated torque value as read on the gauge. Increasing the handle length does not change the relationship of the measuring length to applied torque as read on the gauge so long as nothing between the gauge and the socket end of the beam is altered.

Frank