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Drop-and-Stop Test

For Really Testing Tensile Strengths of Materials
 (-2) [vote for, against]

(This may not be the best HB Category for this Idea --perhaps "Science: Engineering" ?)

In a different place here on the HalfBakery (linked), there has been a duscussion about how scientists and engineers have not needed to pay much attention to a particular oddball notion. The notion is that there might be a Force that is proportional to the rate-of-change of Acceleration (or "jerk") --but the actual equation describing that notion requires an extra factor, called "propagation time" or "Critical Action Time".

F=(M)(a) + (M)(j)(t) --in that last expression, jerk multiplied by time equals acceleration, which means, overall, the last part of this equation has the same "dimensional units" as the other parts (Very Important in equations!).

Most of the time, either the propagation time or the jerk are too small for that last part of the equation to matter. Some people think it never matters, and so the last part of the equation never needs to be invoked. This Idea is about testing that math PRECISELY.

So, start by imagining an old-fashioned guillotine. It has two tall supports allowing a sharp blade to slide between the supports. The blade is lifted and latched into place; the victim is placed beneath the blade, and then the latch is released....

The blade of a guillotine is not square or rectangular; it is a "quadrilateral" with all sides having different lengths. While the top of the blade is perpendicular to the vertical supports, and the sides of the blade are parallel to the vertical supports, the bottom (sharp edge) of the blade has a significant angle to it, which allows it to cut more efficiently.

In this variant of a guillotine, we replace the blade with a simple rectangular or square shape, and it is not sharp, at all!. Also, it could be beneficial to separate the two vertical supports more than normal (a bigger "blade" would be needed, of course). On the surface of this blade we will mount our test-material, such that most of it can dangle beneath the blade (more on this below).

The next difference is that instead of one latch near the top of the vertical supports, we want a lot of latches, spaced at intervals (might as well have some on each support, alternating). This lets us raise the blade to different heights, for purposes of increasing the versatility of the Drop-and-Stop Test.

Penultimately, near the ground, but at a reasonable distance above it (say two meters), we fill the "slides" of the vertical supports with stop-material --stuff that we know can withstand a lot of pounding. In a guillotine the normal stop is called a "chopping block", but here we want the blade to stop moving while the space beneath it is mostly clear. The sudden stop, of course, will necessarily be associated with jerk. It should be obvious that the amount of jerk will depend on how high the "blade" was raised, before being latched and released.

Finally, it may be necessary to dig a deep pit underneath the "blade". This will allow long lengths of test-material to dangle beneath the blade, without contacting the ground during the tests. (We might also want to put the whole thing in a vacuum chamber, to remove air resistance as a factor in computing jerk.)

We will now assume that our material to be tested is available in the form of spools of wire. We obtain several spools, all the same (same weight and same wire-length and same wire-diameter). We want each spool to be a little bit special, such that some amount of wire can be unwound, while the rest can be "locked" in place on the spool.

From each spool, we now unwind 1 meter of wire. This length of wire we attach to our Drop-and-Stop Test "blade". If the blade is big enough, we can attach multiple spools at the same time, and none will bump into any of the others while they dangle beneath the blade.

Now recall that we want this Test to control TWO things, the amount of jerk and the amount of propagation time. With all the spools attached to the "blade", we now unwind them to different lengths (say, 1-meter intervals). So, the shortest is very near the underside of the blade; the next dangles a meter below that; the next dangles two meters below the first one, and so on.

The total MASS that is dangling, from each attachment to each locked spool, is still the same. And every wire attached to the "blade" will receive the same amount of jerk when the blade Stops Dropping. Only the propagation times will differ, as each different length of dangling wire conducts jerk toward its attached spool.

And the result? If the detractors of the equation presented earlier are to believed, then whenever the amount of jerk is sufficient to break one of the dangling wires, all of them will break. But if the equation is relevant, then the longest-dangling wire will always break first, the second-longest will break second, and so on. Another way to say it is that if the amount of (jerk x time) is insufficient to break some of the shorter-length wires, it could still suffice to break all the longer-length wires (because for them the "time" factor is larger).

To Be Determined By Actual Tests, of course!

 — Vernon, Mar 28 2011

Origin of Drop-and-Stop Test Non-working_20Reactionless_20Drive
As mentioned in the main text (search for "as it happens" in the annotations of the linked page). [Vernon, Mar 28 2011]

About the origin of the equation http://www.rexresearch.com/dean/stine.htm
It is a tale, reasonably well told. Some will call it a tall tale, some might be intrigued enough to conduct actual experiments. [Vernon, Mar 28 2011]

Model Guillotine pictures http://en.wikipedia...uillotinemodels.jpg
All sides of the blade can easily be different lengths. [Vernon, Mar 28 2011]

If you're not logged in, you can see what this page looks like, but you will not be able to add anything.

Annotation:

 I'll predict that the shortest length of wire will break first.

The wire has certain elasticity, and the "jerk" propagates through it with the speed of sound. The larger length is able to stretch elastically and thus the tensile force on the longer length of the wire would be less for the same amount of jerk applied.
 — neelandan, Mar 28 2011

If this effect is real, it's very very small, so any observations of wires breaking will almost certainly be due to normal physics acting on microscopic imperfections in the wire rather than what you propose. Also you've ignored the elasticity of the wire. When the strain is at a maximum (when the mechanism comes to a sudden halt) the strain will be spread over different length wires and so you'd expect the shorter wires (which have less capacity to deform elastically) to break first. [edit: Damn you, [neelandan]!)
 — hippo, Mar 28 2011

 [neelandan], nice try, but you are neglecting the fact that the jerk propagates at the same rate through all the wires, since all are the same substance.

 The main text here says that the shortest spool is "very near" the "blade" --let's call it two centimeters of dangle. The next spool is thus 1m+2cm, of course, and the last spool might be 10m+2cm.

 Anyway, for every one of them, the same total mass is dangling beneath its first two cm of wire! Which means that if the jerk suffices to break the shortest dangle, it should also break all the others, as well. None of them will have had TIME for the jerk to propagate to the regions where such stretching as you have described could happen!

[hippo], not to ignore you, but we were writing at the same time.
 — Vernon, Mar 28 2011

You have not defined 'jerk'.
 — pocmloc, Mar 28 2011

 Wouldn't the longest wire break last, since there's more material to bend before reaching critical point, and thus, more 'give' to reduce the rate of change of accelaration. And if so, how does this help?

 Don't we need to find some material where propagation of change of velocity is as near to instantaneous as we can find, in order to test this "jerk = something special" hypothesis, otherwise, we're just doing materials science.

 Not that I'm a materials scientist, but I'd have thought that some dense, incompressible material would be good for this, like mercury for example, where an individual particle can only go as fast as the particles in front and behind it will allow. I've heard water pipes 'banging' due to compression hammers, no doubt a suitably set up set of mercury plumbing would perform even more noisily.

Setting one up in orbit, where there is no friction to worry about, might allow for any jerk-specific differences to be carefully measured and studied.
 — zen_tom, Mar 28 2011

I don't think a guillotine would work if all the sides had different lengths as stated.
 — Wayne Scotting, Mar 28 2011

 Okay, I'm willing to debate, but this is just plain wrong. The mass of the wire below the spool produces tension on the wire above it as it stops. There is no difference between a line with two meters spooled out and a line with one meter spooled out and a weight equal to one meter of wire attached at the end. Since the longer wires have greater hanging weight, they will break much sooner. Remember, the real equation is F=Ma. More mass equals greater force, equals earlier breakage.

Unless you're saying that what will happen is that the spool attachment point to the blade will break first, in which case I agree that they would all break at the same time (approximately, allowing for differences in structure and weight do to less than perfectly identical materials). I don't see how that bears any relation to propagation time, however.
 — MechE, Mar 28 2011

 [pocmloc], see the second paragraph of the main text.

 [hippo], [zen tom], and others, the purpose of this Idea is to FIND OUT for real whether or not the equation is valid. So, if it is valid, the longest dangle will be most likely to break first, as mentioned. If it is not, then some other will break first. Simple! (The actual complexity involves selecting a jerk such that we can be confident the shortest wire WON'T break!)

 [MechE], it is exactly the point that there must be no difference in the dangling masses. It is ALSO exactly the point that different lengths must be involved, to allow different propagation times to exist. You do agree, don't you, that IF the expression (j x t) applies, then for a short length (t) will be small, but it could be much larger for a long length?

 So, if there is any Force at all associated with (M)(j)(t), and (M) and (j) are both the same in a given Test, then (t) must be the controlling factor for any associated Force.

This Idea is about testing the very essence of what Dr. Davis proposed, regarding why Stine's cables broke (per "origin of equation" link). The proposal is basically that the longer the cables, the greater the actual force they experienced, instead of what was calculated per Standard Newtonian Mechanics. The claim is either true, or not, And it can be tested!
 — Vernon, Mar 28 2011

 Vernon, is the dangling mass supposed to break at the cable or the spool support?

 If at the cable, it cannot be tested this way. The longer cable is supporting it's own mass, which is greater than the shorter cable. So if there is a F(weird)=Mjt, yes, t is longer, but so is M greater. And since M is greater and you acknowledge any such force must be much less than that accounted for by F=MA, it will not be detected by this experiment.

 If at the spool support, the design of that support will have to eliminate uneven torque due to the different spool position/contents, and all sorts of similar effects. Even then the difference in diamater and relative compressibility of the extra layers on the spool is probably going to be more of a variation than this is.

 Dangling one 3m cable, one 2m cable with a lump of material equal to 1m of weight, and a 1m cable with a lump equal to 2m weight comes closer to what you want. Even there simple differences in the homogenity of materials and mounting techniques are going to matter a lot more than what you claim exists, so you better plan to do many repitions with as close to a standardized approach as is possible. In fact, I'd skip the 3m, simply because the difference in having the weight mounted or not is going to swamp anything else.

 Do you understand statistics well enough to determine what is statistically rigorous?

I wouldn't waste my time on it.
 — MechE, Mar 28 2011

 [lurch], you haven't been paying close enough attention. I have not changed horses at all. If jerk can do the thing associated with the equation described here, then the OTHER equations of Dr. Davis imply that it can also cause some momentum to get radiated. But this thing here is more easily tested, so....

 [MechE], I don't know where along the unwound cable it is most likely to break. I also don't particularly care. I do agree that it is important for the cable-mountings, against the "blade", to be as nearly exactly alike as possible. Note I mentioned possibly using a vacuum chamber to eliminate the effects of air resistance upon the dangling spools.

 You may have misinterpreted something in the main text: I specified that all the cable spools needed to be the same, BEFORE any cable is unwound from them. So, at the "blade" mount-points, the total dangling mass will be the same for every cable, no matter how much of each has been unwound from a spool.

 If the longer cables break before the shorter ones, then despite the fact that the spool-masses dangling at the end of the longer cables are (due to unwound wire) a little less than the spool-masses dangling at the end of the shorter cables (that didn't break), the point of this experiment will have been made.

 In fact, the point should be considered to have been "hammered home", if a slightly lesser dangling mass (at spool-end of cable) can be more-associated with a broken long cable, just because a long propagation time was involved for jerk. I'm fairly confident that for most cables, (t) will go up much faster than the spool-mass goes down due to unwinding a few meters. And, yes, I presume that the experiment is replicable enough to gather all the statistical certainty you could want.

But of course the experiment has to actually be done, if one is to ever end the arguments.
 — Vernon, Mar 28 2011

Amen.
 — MaxwellBuchanan, Mar 28 2011

 interesting... the shorter cable should break simply because it's not as elastic as a longer cable, ie: the deceleration will be greater as the weight is propogated through a smaller length of material, thus a smaller length of time.

 However the longer the cable the greater the probability of a materials variance somewhere in its length.

Of course we're not considering two very important things relative to the discussion:
a) there's no such thing as an infinite deceleration (ie: "stop" is always a function of time), and
b) resonance of the cable.
 — FlyingToaster, Mar 28 2011

 Okay, I misinterpreted which end the spool was on.

 In which case [neelandan] is correct, the greater stretch of the longer cable will keep it together longer on average. The rate of propagation doesn't matter because the material doesn't fail instantaneously.

And I stand by my statement that materials variability is going to be a major factor.
 — MechE, Mar 29 2011

 [FlyingToaster], the jerk needs to be severe enough to be more-than-merely-ordinary. Other than that, we DON'T want it to be severe enough to break the shortest-length wire-with-dangling-spool. We want the propagation-time factor (if indeed it is a factor) to reveal itself with respect to the longer-length wires.

If propagation time isn't a factor, then none of the wires will break (barring faulty material). But again, the only way to find out for sure is to do the Test.
 — Vernon, Mar 29 2011

 //none of the wires will break//

 That's a stretch, Vernon. A standard test for steel reinforcing rods is to slowly pull it apart using a machine.

 All the rods break, every time.

You are spouting nonsense (as usual, and not surprising).
 — neelandan, Mar 29 2011

 [neelandan], as usual, you aren't paying attention (or you don't know that what you are talking about has nothing to do with what I'm talking about). I'm certainly NOT talking about slowly pulling on something!

 I quote you: " I'll predict that the shortest length of wire will break first."

 Now I'll quote me: "jerk needs to be severe enough to be more-than-merely-ordinary. Other than that, we DON'T want it to be severe enough to break the shortest-length wire-with-dangling-spool."

 Now, if BY INTENT in a Drop-and-Stop Test the shortest wire does not break when subjected to a certain magnitude of jerk, and all the longer wires are simultaneously experiencing the same jerk, AND you claim the shortest one will break first under SOME level of equally-applied jerk, then why should any of the longer wires break when the shortest one doesn't?

 I will note that not once have I suggested that the exact same dangling wires/spools be subjected to multiple jerks. I'm quite aware that an initial jerk might detrimentally affect the material in a way that could leave to to being more susceptible to breakage by a later jerk. While I HAVE stated that the experiment should be repeatable, the only way to do it right is to use all-new dangling wires/spools, with every Drop-and-Stop Test. ESPECIALLY if some of them break, of course!

 By Design, this Test is intended to allow a difference between Standard Newtonian Mechanics and Dr. Davis' work to be exposed, if such a difference actually exists. That means we need to at least give all the wires a chance of not breaking.

 So, I stand by what I wrote, in that per SNM, if the shortest wire doesn't break, then none of the longer wires should break, either. BUT, if Dr. Davis and Stine are right, then some of the longest wires should break.

 (CAVEAT: It is possible that high-strength cables and heavy spools and large Drops will be necessary, that ordinary wires don't allow enough Extreme-ness for Stine's breakage effect to be reliably detected. I have to be careful here in crediting folks --it is Davis' equation, but Stine's cable-breakage observation.)

 I suspect that RELIABLY discovering any long-cable-breakage will depend on first finding out what MINIMUM magnitude of Drop-and-Stop will sometimes cause the shortest wire to break --and then using only a slightly lesser Drop, for the main Tests with multiple spools and longer lengths of wire. **We ** need ** to ** be ** confident ** that ** the ** shortest ** wire ** won't ** break**. And we simply want to find out what will happen to the longer wires.

If the longer wires also don't break, then SNM would be vindicated. But if they sometimes break (especially the longest wire), while the shortest wire continues to never break, then a shortcoming of SNM may be getting revealed. A lot of tests, to obtain statistical significance, will be necessary, of course.
 — Vernon, Mar 29 2011

 //what will happen to the longer wires// At some point you'll hit a resonance length and they'll break into song.

Have you considered using magnetism to apply the force(s): like gravity you don't actually have to physically move an object to continuously apply it; unlike gravity it can be applied from multiple directions simultaneously.
 — FlyingToaster, Mar 29 2011

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