The Mighty Oak

[hoopy mike]

Ok - I'll stop posting on this topic and go and do some more reading. Interested bystanders with open minds might like to compare and contrast the term: rheology, Young's Modulus and friction coefficient. Others can do as they please.

[JTC111]

I thought Guinness translated to lubricity.

Only around 4 a.m.

[Jerry Freeman]

OK, I've missed my postal deadline, not because of this thread but due to other circumstances beyond my control, so I'll chime in again.

If something soft (which is what we were talking about) is fitted onto something else, it will have some flex before it breaks loose. If something hard is connected to something, it will break loose sooner, all else being equal, because it doesn't have the flexibility to absorb as much of the force, so more of the force goes to release the connection.

Think of it like this. There are tiny indentations on the surface of the metal tube, a bit like a screw thread, only much smaller (surface roughness). The plastic head is put on hot and takes up the profile of the metal tube. You have two choices - you can either pull the stiff plastic off cold and try and snap off the microscopic bits of plastic (freezing will help) or you can let the plastic soften slightly so it can deform to slip over the grooves (heating will help).

We're dealing with polished metal here. What you've described above would hardly come into play even if it were possible under the existing conditions for the plastic to deform and permanently key into surface irregularities. In practice, there's a difference between nickel and brass in how easily the whistlehead slips off, but it's not a big difference, and it may have more to do with the fact that a layer of lacquer enlarges the brass tubes beyond the diameter of the nickel tubes, which have for all practical purposes, no coating (the nickel plating is microscopic compared to the thickness of the lacquer). Even if there could be some keying in of the whistlehead on the polished metal surface, the expansion of the whistlehead would exceed the depth of the tube's surface irregularities and release the tube from the socket regardless of any keying in effect.

You keep citing various engineering terms to support your hunches, but the one that would be most relevant here would be to identify how much pressure would be necessary to deform hot but not melted ABS plastic to create the permanent little bumps keying into the deformities in the polished metal.

I can guarantee you'll find the pressure of the hot whistlehead shrinking when the whistle is assembled will not exceed whatever threshold would be necessary to permanently deform the plastic.

I'm having trouble comprehending why you can't let this go. I'm certain of the facts here. It appears that this has something to do with proving you know more than the next person and less to do with figuring out how something works.

Best wishes,
Jerry

[hoopy mike]

I'm having trouble comprehending why you can't let this go. I'm certain of the facts here. It appears that this has something to do with proving you know more than the next person and less to do with figuring out how something works.

Ditto from me. Well, ditto apart from being certain and unwilling to listen or learn from the experience and knowledge of others.

[MTGuru]

Mike can you please let this go? I have work to do.

I think you gave up that way out on December 30, 2002. It's too late now, Jerry. You're doomed.

This is why people who work every day with their hands and their senses get impatient with engineers. Some things are obvious enough and simple enough, they can be worked out without this kind of over-analysis.

But, you know ... It was exactly your excellent appeal to the science - the empirical coefficients - that convinced me to re-examine my view, not your anecdotal experience. So you can't so easily dismiss the same science by arguing against it now.

Whatever is going on, there is one right answer (or set of answers), because we're talking about a deterministic physical phenomenon. And I'd rather know the truth, even if it contradicts my intuition or yours, or whatever practical heuristic models we've constructed in our heads. And even if there's little effect on what we do in practice. The wonder of science is that the "obvious enough and simple enough" is often wrong. So I wouldn't be so quick to shut down Hoopy's contributions if he's willing to share his expertise with us. He doesn't need to prove he knows more than the average next person. Because in this particular area, he probably does. For example, I don't think my degree in English literature covered Young's modulus.

[ For those who don't know, Hoopy is a tenured professor of materials science engineering, so I take his speculations as informed. ]

[Whistling Pops]

[ For those who don't know, Hoopy is a tenured professor of materials science engineering, so I take his speculations as informed. ]

When I was attending college 40+ years ago I knew a tenured professor who mowed his yard each week with an imaginary lawnmower.

[Jerry Freeman]

But, you know ... It was exactly your excellent appeal to the science - the empirical coefficients - that convinced me to re-examine my view, not your anecdotal experience. So you can't so easily dismiss the same science by arguing against it now.
[ For those who don't know, Hoopy is a tenured professor of materials science engineering, so I take his speculations as informed. ]

I'm not dismissing or arguing against science at all.

Please provide the science that quantifies how much pressure it will take for the whistlehead to deform and permanently key into the irregularities on a polished surface. I have good reason to predict it will be far above the conditions in play when assembling a whistlehead on a tube.

The problem is, what I do is scientific in the sense that I observe something happening, I devise a hypothesis, I test that hypothesis, adjust the hypothesis according to the results of the previous test, devise new tests, continue to make observations, etc. Please don't discount my drawing conclusions from observing a phenomenon thousands of time in materials I work with every day as rejecting science.

I'm not certain whether Mike's academic credentials help or hurt him in this discussion. He's made at least two seat of the pants assertions that were easy to check and clearly not correct (racing tire operating temperatures vs. whistlehead removal temperatures, and tire rubber melting temperature vs. ABS plastic melting temperature). I would have to ask you to extend your concerns about arguing against science to include Mike's approach to this discussion as well. The problem here is, I see Mike starting with seat of the pants assumptions about what's happening here, and then NOT actually looking up the engineering to confirm whether his hypothesis holds water, but rather, using scientific terminology to try to impress the people he's arguing with. He's making me look up the science for him, which is the thing I don't appreciate about the approach he's taking here.

I'll up the ante a bit and suggest that Mike take this entire thread to the head of his department and ask him or her to review his approach to this problem and this discussion.

I'll also suggest that you step back and take a look at the extent to which the engineering specifications of the materials and operations I'm talking about actually do fit my explanations of what I see happening. When all is said and done, that should lead you to take my comments a bit more seriously. I do know what I'm talking about, and I'm willing to predict that the engineering numbers will bear me out in almost every detail.

Best wishes,
Jerry

[MTGuru]

When I was attending college 40+ years ago I knew a tenured professor who mowed his yard each week with an imaginary lawnmower.

Well, Hoopy has been known to play the whistle standing on his head, and to dress up as a farm animal in class. They don't call him Hoopy for nothing.

[AbrasiveScotsman]

Materials Engineering is a funny business. They can engineer bridges to have very exact tolerances, with a precision unimaginable even just a few years ago.

But, sometimes what the engineers come out with regarding what materials will and will not do is just plain wrong.

I ride one of those funny lie-down bikes (recumbent). There is a recumbent manufacturer in the US that was approached by a materials engineer who claimed he had analysed their bikes' frame geometries and materials usage using some complicated simulation software, and had deduced that their was a critical weakness in their frame that would lead to failures. I'm guessing he was offering to fix this for them for $xxxx. They sent him packing. In 20 years of selling bikes, they had had precisely zero customers bring their bike in due to failures of the frame.

Course maybe he wasn't a very good materials engineer and was just trying it on. But I have no problem with a universe that does not always bear out what the numbers say.

[Jerry Freeman]

But I have no problem with a universe that does not always bear out what the numbers say.

I agree with you on that, but I also have to say, in this case I'm confident what I'm observing will be borne out by the engineering numbers.

Best wishes,
Jerry

[Denny]

I'll up the ante a bit

dang Jerry,
Ya asked Mike to quit posting views that ya don't agree with.
Mike agrees to wander off and be quiet.
You come back with a post that ends with

I'm having trouble comprehending why you can't let this go.

followed with a personal slur.

I'd think ya'd already upped the ante a few posts back.

[Jerry Freeman]

The problem is, Mike didn't leave it alone. He left with a parting shot that opened the whole can of worms again:

... Interested bystanders with open minds might like to compare and contrast the term: rheology, Young's Modulus and friction coefficient. Others can do as they please.

Here's what I would like to accomplish here:

1. Get to the bottom of what's actually happening, as verifiable by science.

Some things, we can rule in (coefficient of linear expansion sufficient to support the whistlehead loosening by expanding); some things, I expect we can rule out (permanently deforming the plastic to key into the polished metal tubing causing the whistlehead to lock to the tube so that little bits of plastic break off on removal).

2. Establish a sense of reality about what can be cited as a scientific or authoritative claim and what is a seat of the pants hypothesis and not to be taken as an authoritative fact until meaningful data are brought to bear.

If we're going to have a valid discussion about how something works, there needs to be some order to that discussion.

I've stated what I'm convinced is true based on considerable experience. When challenged, I've provided engineering numbers to support or refute the posited argument. I've stated what engineering number we will need, to determine the truth of the assertion that was most recently being debated (permanently deforming the plastic to key into surface deformities of the metal) and requested that the person most equipped to provide that number please check the data and publish the result.

These comprise a reasonable, objective approach. If I'm sure of my position, that doesn't mean I'm saying "You must believe me because I say so." Not at all. I do feel I'm being told to shut up and let Mike walk off saying "I know all about this, but you just aren't open minded enough to believe a true expert."

Please, let's do this by the numbers, and let's determine what's actually going on here.

Best wishes,
Jerry

[Whistling Pops]

When I was attending college 40+ years ago I knew a tenured professor who mowed his yard each week with an imaginary lawnmower.

Well, Hoopy has been known to play the whistle standing on his head, and to dress up as a farm animal in class. They don't call him Hoopy for nothing.

Oddly enough, the professor I referred to often taught class standing on his head.

[Whistling Pops]

The problem is, Mike didn't leave it alone. He left with a parting shot that opened the whole can of worms again:
Jerry

I agree with Jerry. Mike did NOT leave it alone. Launching a parting shot is not leaving it alone. I made a simple statement on a recent post and Mike started in on me. I left the discussion but he couldn't resist coming back at me.

[MTGuru]

Hey, c'mon guys. This "who said what to whom" business is for the birds. It's my thread topic, and the pissing contest (and cheerleading) isn't helping one bit.

Mike, don't go away. I want to hear more. No need to be shy about sharing your professional conjecture. I, for one, am listening.

Jerry, you already helped me change my mind about one aspect of the original question. A+. Now I'm open to learning more from you or anyone. No need to be defensive. I think I'm capable of sorting things out without being told how to do that ...

If it helps, address pros and cons about elasticity to me. I'm the one who needs to be convinced, and I ain't convinced yet one way or the other.