"...they have a soul and smoke impossibly well..."

[Kyle Weiss]

That's why I wanted Greg's most recent pipewrit to make its way over here. It says everything I already sort-of knew by observation (if not a little experience of my own), but it's still one of those cars circling the block that some might refuse to acknowledge. Or was it a bus full of bozos? :scratch:

:lol:

Far from over, never worn out--thanks for the thoughts, gents.

8)

 

[tyler]

It's initially counterintuitive, but from a flow dynamics perspective, it makes perfect sense. There's a point where decreasing the "back-pressure" of the pipe can actually degrade flavour performance, for similar, though different mechanisms.

The only mechanism I can image for this is reduced airflow to limit combustion rate/temp. Is there something else you are thinking of?

 

[asmoke]

I don't think its really possible to have back pressure, you can restrict airflow, but without a closed system (ok my nerd is coming out here, yes I'm an engineer) I think true back pressure is impossible. I have been wondering lately about how open is too open... there is a limit, and having an airway too open does seem to affect flavor. Mmm.... Another discussion perhaps?

 

[wintermute]

Time to geek this up a notch. You can have head loss (think of it as loss of pressure - causing you to pull harder for an equivalent air flow) due to bends, kinks, rough surfaces in the air hole, diameter of air hole, the way the air hole opens up at the bit (fast or slow transition), etc. Speed through the chamber and air hole will effect the amount of turbulence and mixing of smoke and air.

So Mr. Pease is abolutely correct - you don't want a wide open bore with theoretically zero head loss. There's a sweet spot somewhere in all the speed, flowrate, pressure turbulence, friction factors that's going to give you an optimal mixture so that you get the right amount of smoke (turbulence and mixing - also providing the necessary amount of air for proper combustion), pressure (sudden drops will cause condensation), etc.

 

[Kyle Weiss]

My brain was busy concocting a response defending Greg's standpoint, and wintermute beat me to it. To kind of add a bit of clarification for the non-eggheads, think of a river versus a water main pipe. One is filled with ruts, bumps narrow points and wide spots--the river: there's a lot of churning and mixing going on. When that equates to smoke passing from a burning wad of tobacco to the mouth, all of that "rough stuff" just causes condensation, debris build-up and eventually makes it really hard to draw. The other is the water main, (supposedly) smooth and direct, free of much to hinder the process. The "pressure" is regulated by the gravitational push (or mechanical pull) of something device somewhere in the system. In our case, it's our mouths doing the work. Those smooth pipes, provided they have the right diameter (like water mains, can't be too big, nor too small) do the finest job.

The "backpressure" issue is interesting. The amount of tug any of us are putting on a pipe is likely not beyond the exit capacity of the stem drilling itself. There is, however, a restriction that creates a controlled rate of flow that is ideal for the minimization of any turbulent points inside, and helps dictate the burn rate of the tobacco. On a very rudimentary scale, it's related to air/fluid dynamics in that it's mass going from point A to point B inside a purposed, cylindrical space.

I personally think there's more to the smoothness of the draft hole with as few bumps, edges, turns and mistakes as possible (which I think was Sas' original point) than "pressure." The eddies from obstructions are likely to filter out the moisture and smoke particulates by having circles of smoke-filled air continuously hitting these edges. Kind of like how a fan blade gets filthy with hair, dust and dirt--which, incidentally, only attracts more at an alarming rate.

Now, for purposes of the "impossible pipe," there's probably some combinations that haven't been directly observed or considered that may make the pipe perform badly in the eyes of an engineer, but the smoke taste good to someone else.

8)

 

[tyler]

Time to geek this up a notch. You can have head loss (think of it as loss of pressure - causing you to pull harder for an equivalent air flow) due to bends, kinks, rough surfaces in the air hole, diameter of air hole, the way the air hole opens up at the bit (fast or slow transition), etc. Speed through the chamber and air hole will effect the amount of turbulence and mixing of smoke and air.

So Mr. Pease is abolutely correct - you don't want a wide open bore with theoretically zero head loss. There's a sweet spot somewhere in all the speed, flowrate, pressure turbulence, friction factors that's going to give you an optimal mixture so that you get the right amount of smoke (turbulence and mixing - also providing the necessary amount of air for proper combustion), pressure (sudden drops will cause condensation), etc.

But there's no combustion going on in the areas of turbulence. The areas of "bends, kinks, rough surfaces" and etc. are merely smoke delivery spaces.

 

[Kyle Weiss]

Tyler, mechanically-speaking, are you talking about the combustion pressure from a cylinder or the exhaust post-valve system? In this case, I think people are referring to the routing dynamics through pipes. The best scenario I can think of where it really matters are small, two-stroke engines for say, a small dirt bike or a Vespa.

8)

 

[number_seven]

Pipes are female. :lol:

There's beautiful garbage, and there's plain-looking gold.

Choose wisely.

:face:

And when you get the beautiful one that's gold, hold on for dear life....

 

[tyler]

Tyler, mechanically-speaking, are you talking about the combustion pressure from a cylinder or the exhaust post-valve system? In this case, I think people are referring to the routing dynamics through pipes. The best scenario I can think of where it really matters are small, two-stroke engines for say, a small dirt bike or a Vespa.

8)

Are we talking about pipes or engines? Because I thought we were talking about pipes.

 

[Kyle Weiss]

Are we talking about pipes or engines? Because I thought we were talking about pipes.

Both. Read back, the analogies/metaphors went a little myopic, but the connections are there.

8)

 

[wintermute]

But there's no combustion going on in the areas of turbulence. The areas of "bends, kinks, rough surfaces" and etc. are merely smoke delivery spaces.

Sure there is - in the chamber. Even if the chamber is perfectly smooth, it doesn't mean that there will be laminar flow - and you wouldn't want it. Turbulence allows the smoke and air to mix. The addition of tobacco adds all sorts of convoluted pathways, eddies, short-circuits. So the physical shape of the tobacco mass itself will affect the smoke/air mixture and draw. The combustion will add convection currents into the mix as well. Are you inside or outside? Wind blowing along the top of the bowl will affect the pressure inside the pipe, as will humidity.

If you could build a perfectly engineered pipe, it would probably suck.

 

[glpease]

Time to geek this up a notch. You can have head loss (think of it as loss of pressure - causing you to pull harder for an equivalent air flow) due to bends, kinks, rough surfaces in the air hole, diameter of air hole, the way the air hole opens up at the bit (fast or slow transition), etc. Speed through the chamber and air hole will effect the amount of turbulence and mixing of smoke and air.

So Mr. Pease is abolutely correct - you don't want a wide open bore with theoretically zero head loss. There's a sweet spot somewhere in all the speed, flowrate, pressure turbulence, friction factors that's going to give you an optimal mixture so that you get the right amount of smoke (turbulence and mixing - also providing the necessary amount of air for proper combustion), pressure (sudden drops will cause condensation), etc.

Well said. All the little things, like the shape of the inlet funnel at the tenon end, and the exit funnel at the bit end, and the sudden cooling from expansion outlet, with its commensurate increase in the mixture's density will have an upstream effect on flow. Back pressure is not a very precise term, but serves since it's generally understood. Pipes are deceptively complex systems, and there's often too much reductionism (nothing wrong with reductionism as a first step, but actual understanding of complex systems is wildly incomplete when we stop there) applied in discussions about how they work, what makes one better than another. It's one of the reasons I eschew the term "engineering" when applied to pipe construction. Engineering is a discipline of applied science, not just building something to arbitrary specifications.

When the overall system is considered, the bowl chamber shape and size, the airway's characteristics, the smoker's cadence, the volume of smoke mixture drawn per puff, ambient air temperature and pressure, relative humidity, the packing density of the tobacco, the shape and surface area of the ember cone, the temperature gradient through the system, the change in viscosity of the fluid with respect to many of these variables, and on and on, it's beautifully complex, rapidly becomes a non-linear system of differential equations of several orders—just a bit more complex than a typical hydraulic system. Bernoulli would have had a blast with this stuff.

Fortunately, we don't have to think about this stuff to enjoy a good smoke, and, for most, thinking about it too much would likely become antithetical to that enjoyment, but it's fascinating how something so apparently simple—burning dried leaves in a wooden vessel and sucking the smoke through a straw—can in reality be sufficiently complex to foil attempts at pencil and back of the envelope analysis.

 

[glpease]

If you could build a perfectly engineered pipe, it would probably suck.

Quote of the day!

 

[Kyle Weiss]

If you could build a perfectly engineered pipe, it would probably suck.

I don't think a "perfectly-engineered pipe" would even use briar, if internal delivery became the focus, there's much "better" materials to make a pipe from, just from a design standpoint.

http://www.thepipe.info/history/index.html

Finally, we're getting to the meat of the matter. Oddly, to throw more metaphors here, the plight of character "Data" from Star Trek TNG comes to mind...perfect in practically every way--but wants more than anything to have the flaws, nuances and soul of a real person.

8)

 

[wintermute]

the plight of character "Data" from Star Trek TNG comes to mind

Geek level is climbing near red line.

 

[Kyle Weiss]

the plight of character "Data" from Star Trek TNG comes to mind

Geek level is climbing near red line.

:twisted: Great segue from vehicles to true nerdiness, by the way... 8)

 

[Zeno Marx]

By 4.7mm, it became a beautifully designed incinerator of pipe tobacco that delivered little flavour, but huge volumes of effortless smoke. It was efficient, and useless.

This describes my estate Boswell to a T. But I cannot seem to get rid of it because of how great it feels in the hand. I smoke it very rarely...well, because, it's practically a flavorless smoke. I haven't measured the draft hole, but it feels like I'm smoking through something as large as a McDonald's straw. Last week, I read a poster on another board say something to the order of "there's no draft hole too big", and after getting over my immediate association with this Boswell, I thought, "This person obviously chases a different type satisfaction than I do." Not that their chase is lesser...but it certainly is wrong for me.

 

[Kyle Weiss]

Fortunately, we don't have to think about this stuff to enjoy a good smoke, and, for most, thinking about it too much would likely become antithetical to that enjoyment, but it's fascinating how something so apparently simple—burning dried leaves in a wooden vessel and sucking the smoke through a straw—can in reality be sufficiently complex to foil attempts at pencil and back of the envelope analysis.

It's this juxtaposition that makes pipes fun! In lieu of that, though, I try and put something else in front of me rather than simply trying to ponder the pipe itself, because that's one deep rabbit hole to fall down. No wonder a good book compliments a good pipe so well.

8)

 

[monbla256]

And I thought the idea was to buy a pipe you liked, put some tobacco in it you liked and smoke it. Has worked for me all these years but I'm not as much of a real conesuer as most obviously are here Guess I've missed out on all the "good" stuff all these years

 

[glpease]

By 4.7mm, it became a beautifully designed incinerator of pipe tobacco that delivered little flavour, but huge volumes of effortless smoke. It was efficient, and useless.

This describes my estate Boswell to a T. But I cannot seem to get rid of it because of how great it feels in the hand. I smoke it very rarely...well, because, it's practically a flavorless smoke. I haven't measured the draft hole, but it feels like I'm smoking through something as large as a McDonald's straw. Last week, I read a poster on another board say something to the order of "there's no draft hole too big", and after getting over my immediate association with this Boswell, I thought, "This person obviously chases a different type satisfaction than I do." Not that their chase is lesser...but it certainly is wrong for me.

Something you might consider trying is installing an "inner tube" of sorts. Many hobby and hardware stores sell aluminium and stainless steel tubing in small gauges with thin enough walls to do the job. Just cut the appropriate length of the right diameter tubing to fit snugly into the draught hole, and long enough to kiss the stem's airway where it tapers down. I've done this to a couple of pipes with surprising results. Despite the introduction of metal into the airway, they were transformed in a positive way. It's an interesting experiment, if nothing else, and reversible if you don't like the result. And, since they come in sizes that can fit within each other, you could play with different internal diameters and see the effect this has on the taste and smoking characteristics.

It seems the pipe community at large has become overly obsessed with the smoking dynamics of their pipes, and have not paid as much attention to how they taste, which for me has always been the most important dimension of the experience.

That said, I do have a very large old Comoy that delivers an amazing smoke, and will, if left alone, practically smoke itself. This is evidence that the airway diameter must take into consideration the size of the chamber and the overall length of the pipe. A small chambered, short pipe would produce a rather different experience with the same airway.