Lee -

Again, you're correct, but the question was not where the torque was applied, but what mechanical advantage could be figured at various lever lengths. I see no way to figure that without some formula similar to the "Ratio of Circumferences". The question (at least in my mind) is what circumference to use for the absent formula circumference element. We know the lever circumference. I think it's the mean thread diameter, but not really sure.

Frank

the "missing" sir cumference is more likely the distance from center of wrench contact on the flats to same point on opposite flat. That's the effective circumference over which you apply the torque with the wrench alone (and thus the wrench reading). You have to pull the wrench harder to torque a large fastener to 50ftlbs than you do a smaller nut, because your mechanical advantage is less. Now how did I screw up the logic on that one....

Dunno, Eddy.... that's what I originally said was the smaller circumference, but everyone seemed to think it wasn't so. This is a darned interesting question - at least to me. The next time I run into a physics professor I know what we'll discuss and maybe I can get the answer. There's gotta be a way to determine mechanical advantage on a flex handle or lever with a socket on it.

Frank

Question: What number of ft./lbs. Indicated on my torque wrench will give me the Actual ft./lbs. of torque I want on my bolt when I use an Extension ? There's gotta be a formula.
Answer: There is, I=A/(1+E) . I = Number of ft./lbs. indicated on your torque wrench's scale. A = Number of ft./lbs. of torque you want on the bolt. E = Length of extension,center to center,in feet (example: 4 inches = .333 feet or 4/12 = .333 feet). The kind of extension we're talking about makes your torque wrench a longer assembly, not an L-shaped assembly that you would get with a common ratchet extension. The extension should form a straight line with the torque wrench.A small deviation from straight should be okay,but take note,ALL deviations from straight will result in a bolt that is not quite as tight as the formula suggests.We're talking small amounts that need not be accounted for. Ideally,on a beam torque wrench,you would like the handle pivot,the drive end of the torque wrench and the center of the bolt to form a straight line when you reach desired torque.

Example:I want to torque a nut on the Starship Enterprise's,Transporter's Pattern Recovery Tank to 100 ft./lbs. but it's tight in there.I'll get a 9 inch extension (are you listening Deanna Troi)for the torque wrench so I can slip it into that oh so tight slot.Now the question is what indicated reading on the torque wrench will I need to reach the climax of 100 ft./lbs on the nut.Well the formula again is I=A/(1+E)or I=100/(1+.75)where 100 is the number of ft./lbs. I want on the nut and .75 is the length of the extension(in feet).Now it's I=100/1.75 or I=57.14 ft./lbs. Soooo,if I have my extension on straight and it's reasonably stiff(flexes but returns to original shape after use)and my three reference points(handle pivot,square drive and nut)are close to in line when I'm pulling hard enough to show 57.14 ft./lbs on the scale on my torque wrench then I know my nut is properly torqued,Deanna's should be and I need a cigarette.

Now for some editorial comment,the length of the torque wrench,the size of the bolt,the diameter of the thread,the number of flats,the size of the socket and my oldest child's birthday all have one thing in common.None of them have anything to do with calculating the correction factor when using an extension on a torque wrench.I googled "torque wrench formula" and visited six websites that wanted to factor in the length of the torque wrench in their extension correction formulae.I had no idea the web is this fouled up!Cheers IsayItUcanBelieveIt

Yeah, I posted the formula for determining torque settings using extensions, but that was never the question.

The question is how to determine torque on a long handle WITHOUT using a torque wrench. The only way I know to do it would be through figuring mechanical advantage relative to a known distance of handle. If you can't get the torque wrench socket on the nut to derive a known value from which to compare, then you must do the calculation by pure mechanical advantage, first tested with the bolt and nut off the vehicle in a place where you can get a torque wrench on it. Then you can determine handle length relative to applied torque. By using the Ratio of Circumferences you can then determine mechanical advantage on a longer handle and adjust applied force as necessary. However, if you cannot do the initial baseline calculation with the fasteners off of the vehicle, then you don't have enough information to derive an answer. There must be a baseline determination method when mechanical advantage is first figured.... i.e. - the difference in turning the nut with your fingers as opposed to putting a socket on the nut and turning the socket - obviously a difference in mechanical advantage. So what circle circumference is used as baseline? I suspect it's the mean diameter of the threads, but I don't know and one day intend to find out the answer.

Frank

Where? I've found zero ACCURATE extension correction formulae on this site,that is until I just posted it.I checked the links and they were/are erroneous.


Say you want 1000 ft./lbs. torque on that fire hydrant cap so your neighbor's house burns completely to the ground,regardless of the firemen showing up.Hypothetically. <img src="/forums/images/graemlins/smile.gif" alt="" /> We take a wrench, slide a long pipe over the end of it. Cut the pipe off 10 feet from the center of the nut. Take bathroom scale out to end of pipe.Put scale on end of pipe(With scale stroke creating a tangent to 10 foot wrench's swept arc,you know what I mean)push on scale till it reads 100 lbs.You will have to follow the end of the pipe for several feet with that bathroom scale,but rest assured you just applied 1000 ft./lbs. of torque to that cap.If this answer doesn't suit you I suggest you ask another question because your question above has been answered in total.

Scotty

So, you're saying that the two links I posted are erroneous? Bear in mind that the initial question didn't state whether the extension was on the handle end or an adapter forward of the break-over point on the torque wrench. Here's the original question:



so I posted these formulae that deal with FORWARD extensions:

http://www.mdmetric.com/tech/data1torque.html
http://www.specialpatrolgroup.co.uk/spooky/torque/torque.html

Again from memory, I think the discussion was subsequently clarified to specifically ask about the handle end. Meanwhile the Ratio of Circumferences generated some measure of curiousity to me as it is used to figure mechanical advantage.

After reading your post I'm guilty of not going back to actually check if the formulae I posted ALSO included extensions on the handle end, so excuuuse me. From memory I thought the material covered both.

As for your formula, thanks for providing it and the explanation. That's appears to be the correct method of determining torque settings in the situation described. However, it still doesn't answer the question I posed as to the baseline point of mechanical advantage.... that method becomes moot given the formula you put forth, but it's still an interesting question and one I'd like to find the answer to before I die.

IOW, reducing the handle length in your formula by half yields 500 ft/lbs.... by 3/4 yields 250 ft/lbs, and so forth until you finally reach the threads. You can use the Ratio of Circumferences to also find mechanical advantage by the relationship between them, but at some point the initial calculation has to be made. My question is where is the baseline circumference for that calculation set? It can't be the bolt center, because being -0-, all subsequent results would yield -0-.... not an argument of how to determine torque... I think that was abandoned long ago in this thread..... but now you've answered it...

Thanks very much....

Frank

Yes,they are wrong,do you aknowledge that? Secondly,there is no way to add an extension to the handle end of a beam type torque wrench and then have the scale have any meaning at all.A non-beam type torque wrench will allow use of a extension on the handle end (a pipe).It will read correctly,no formula needed.


I guess he finally found one guy ,eh?



And they are wrong!

What formula for handle end extensions?ALL my remarks have referred to Front end extensions.

You're welcome

Sorry I can't jump on that one, but if tou find an answer I think I could follow the explanation.So I look forward to that.


Reaching the threads is not the final stop.In the above example the threads on that cap are 4" in diameter,yet with a 0.12" handle my 100 lbs exerts 1 ft./lb. of torque to the hydrant cap. I suspect this base circumference you seek is irrelevant on such simple matters as torqueing one bolt into a stationary hole with different length levers.Just a thought,probably wrong.

Nice sparring with you,Frank. <img src="/forums/images/graemlins/cheers.gif" alt="" /> Scotty

No, I don't acknowlege that, but I'll let the publishers of the data know - perhaps they've got a big job waiting for you. Meanwhile, perhaps you could explain to us why the drawings are wrong. The drawings were not for beam-type torque wrenches - they are for the break-over click-type torque wrenches. I do agree that a handle extension on a break-over torque wrench makes no difference except in the amount of effort (mechanical advantage) required to establish torque at the fastner.



Yes, you seem to be a real maven.



You do seem to enjoy jumping.... but then the "sparring" comment was a clue.

Say, Scotty - your knowlege is appreciated here, but I doubt the "sparring" is as much. This board has a lot of congenial folks who are trying to learn as much as they can about their vehicles. I'm sure they would benefit from your remarks if they're offerred in a constructive way - so why not lose the attitude and join the fun, eh? Maybe we can repay the favor of your knowledge and give you some charm school lessons in return?

Who knows - maybe even you will learn something? <img src="/forums/images/graemlins/cheers.gif" alt="" />

Frank

Hey "Scotty"

You have three posts to your name and I don't believe what you say. My advice would be to get a new login name, post your locale, your truck info, and stop acting like some pseudo-troll. Don't try and be a hero.

Sorry to retorque the topic. Please continue.