NEW! Ultimate C/S Prop Wrench Anti Splat Aero

[Mike S]

Originally Posted by nauga

Correct - at the wrench head where the torque is sensed.

Is it sensed at the head, or actually sensed at the tilt block, and only applied at the head

[LAMPSguy]

I will not even touch the math/engineering side.

I see another equally troubling issue: It seems some people are unfamiliar with their torque wrenches. Essentially a torque wrench is a torque wrench, they just indicate differently. Here is a basic idea of the 3 main types we may have access to.

Micrometer setting (Click type)- uses various different types of clutch mechanism to determine when to "break" or click. Assumed to be fairly accurate since you are provided a positive indication when you reach your value. Some inherent issues though, this relies on a spring forcing some sort of mechanical device into some other sort (pawl, or ball in a socket, etc). Springs can become over or under sprung. Many manuals tell you to store it at 20% setting for max life. If you ever drop on there is a high probability that it's calibration may have changed. So, they are accurate and delicate. My personal opinion...I will never own one. I am a bit of a klutz, and drop them. Additionally, I want to know when I approach the value. Would you want a device where you set your target MAP and it beeps when you get there with no indication of rate of change or even if above or below the setting? Me either.

Beam type - Two parallel beams, one with a handle that you put force on. This also has the scale on it. One above it that has a little pointer. As you add force (increasing torque) the bottom beam "bends" the scale away from the stationary top beam. These are a little less accurate, you have to be able to see the scale, which introduces parallax error as well. But they are less prone to drop induced calibration issues. KISS type.

Dial indicator or Load cell - Basically a wrench with a complicated (or not) internal mechanism used to display the torque on an indicator. If a load cell, it is based on actual sensed load. Dial indicators are usually a beam that displaces from essentially a dial indicating micrometer. These can be very accurate, but can be very fragile and not always conducive to messy areas. These are my favorite when someone ELSE pays for and maintains the calibration (government).

Best case, Buy the best you can afford, keep them calibrated by using a reputable precision instrument shop. I prefer to only use the tool within 15-85% of the indicating range. Share with others, maybe you need 5 wrenches for the appropriate scales and guidelines above to cover aircraft, car, motorcycle, etc. Nice wrenches like that may cost several hundreds of $ each. I have a group of friends that bought the set that covered everything they needed, put them in a nice Pelican box, and they still share them (and they are still nicely useable) 20 years later.

[Veetail88]

I've been reading this thread and scratching my head for way too much time now and I think I know why I'm confused and maybe why others are.

I started out agreeing with Allan and thinking how can everyone else be so dense.

Then, confronted with math and ideas from a lot of smart folks, I starting thinking that I must be missing something fundamental, but couldn't put my finger on it.

I think the reason for "MY" confusion is the geometry of the problem. Maybe I'm wrong, just sayin.

I started thinking that if we're applying a true rotational force at point B in my diagram, that it flat wouldn't matter how we applied it. Wether it be by 12" torque wrench, 24" torque wrench or a finely calibrated highly trained monkey. It flat wouldn't matter, and any wrench indicating 80 ft lbs of rotational force at point B would be just like any other, providing the tool was accurate in measuring rotational force.

I still think that's true, but the fact is, that we are not applying a rotational force at B, but rather at A. In order for my early assumption to be correct, point B would have to be fixed. Problem is, if point B were fixed, we would not be able to put a rotational force at A, but we would be applying a linear force there. We're not.

So while my mind is still not 100% clear on the rest of the issue, I'm now satisfied that mental block that was going on in my head that was adamantly keeping me in Allan's camp has been removed.

I'm thinking that we are using a tool designed to measure a rotational force and instead trying to measure a bending force at a point in space somewhere away from the true axis and that's realling mucking up the works. I think in this case, how the tool actually works would certainly affect the outcome.

I'll stay tuned for more wisdom.



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[ccsmith51]

Jesse, the only place you are actually measuring rotational force (moment) is point B. That is what the torque wrench measures, moment at its head.

Since you cannot measure the moment at point A (unless point is A some kind of measuring instrument), you are using that measured moment at point B to calculate the moment at point A, .

What is being questioned is when working the equation backwards, will the measured moment always be 0.8 of the calculated moment for a 0.25' extension. One camp says yes, the other says no.

I, for one, am in the camp that says no, based on the FAA, torque wrench manufacturers, and others a lot smarter than I.

But, I continue to follow this thread because there are also a lot of people, most likely a lot smarter than I, that are in the opposite camp. So, I await additional proof in the way of mathematics and visuals that will finally prove which camp is correct, to the satisfaction of all.

[Mike S]

Jesse, thanks for posting the diagram, which I have shamelessly borrowed.

I have to take issue with what you have stated here, as it is both correct, and incorrect.

Point A is the new point where a rotational force called torque is manifested at, when the adapter/extension is added.

Point B is now part of a lever arm, but it is not a fixed one piece arm-----in a click type wrench, point B will rotate a small amount when it senses the correct (as set on the dial) torque. Until then, the diagram is correct.

For a beam type of wrench, point B is one end of a flexible link to C, and in fact will have a small rotational component in relation the C, but not to A.

This is what I was trying to describe back in post 67.

Overall, your diagram is quite helpful in visualizing the change from B being a rotational to a lineal force.

[Veetail88]

Thanks Mike. That's the way I'm thinking about it as well, just not able to fully put it into words.

This whole thing is kind of bugging me. I'm no genius in regard to some folks that can lock themselves in a dark closet and come out and fill a chalk board with a formula that they've been tracking in their mind, but I'm not a slouch either.

This mind mess is making me question my thinking capacity!

[CMW]

of showing the same thing (Sorry Larry). The system we're talking about is nothing more than a cantilevered beam. The moment (or torque in our case) along the beam is given by the linear equation M(x) = P * (L-x) where M is the moment, P is the force applied at the handle, L is the overall length of the beam, and x is a distance from the cantilever fixed end (the bolt in our case). So using that equation with a fixed length beam and a known load, plug in any (x) and you get the moment at that point in the beam. In our case (x) is 3 inches. The torque wrench simply measures what the moment is at that point. It doesn't matter what type of torque wrench you use. It is a device to measure the moment in the beam. Here's a moment diagram for three wrenches, a 12", 24" and 36". I hope this helps. My only question is what people would have done had Allan not given a multiplication factor. I hope refer to the many references given here.

[Mike S]

O.K., now for a different way to look at it.

If I use an electric motor, with an adjustable clutch set to slip at 100 lb/ft of torque on the output shaft, and then attach the 3" tool at the end of that shaft, how much torque will the end of the tool see????

This takes the length of the arm of the torque creating device out of the equation completely, other than Allan's tool there is effectively no arm to figure.

[LifeofReiley]

JMHO... this Gentleman, Allan has PAID for advertisement space on VAF. He has posted a Classified Ad, not a discussion thread. At what point do stop beating on Allan for his PAID advertising? If you like his products, buy them. If you have a question about them, call him. If I remember correctly folks getting BANNED for beating up PAID adverisers here on VAF...

[krw5927]

While I agree that it is a bit odd for a classified ad to have over 200 posts, the fact that this particular subject has generated so much discussion and controversy screams loudly and clearly that we NEED to talk about this.

Understanding how torque works is essential to safety. So if we don't discuss it here, we at least need to do it somewhere.

The rules of civility apply, as always, and a few posts have come close to crossing that line, in my opinion. By and large, however, I don't think this has turned into an Allan-bashing thread. My personal opinion, of course.

From the looks of it, there are just as many of us wrong as there are right.