I would like to hear some ideas about pipe design, specifically with regard to the relation between wider airways and bowl size.
I mentioned in another thread that I have a really excellent Il Ceppo that is drilled just huge.... like, 3/16" for sure. And it has a very wide bowl - almost an inch. I feel that this pipe smokes differently from many others in my collection, and have emulated that setup, or at least the idea, in the pipes I have made.
What I notice is that my pipes are a bit harder to light right off the bat, because there is a lot of bowl and relatively less moving air (I can only suck so much!) than on a smaller pipe. But once lit, keeping this type of pipe going is very easy, and they smoke cool, which I put down to the airflow being plentiful but kind of "slow" moving.
What I mean is, with a wider channel (and bowl) sucking the same amount of air into my mouth, I am not pulling air through the pipe at the same velocity I would if it was drilled smaller. Another way to say this, perhaps, is that this drilling setup works well for my smoking technique.
So, are there magic formulas, rules of thumb, etc for finding the ideal bowl width (and height?) for a particular airway? Or rather, particular airway sizes for certain bowls....?
Your thoughts?
Air flow: bowl size, pipe length, and airway diameter?
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ToddJohnson
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If your pulling the same amount of air and the bowl size is the same, the air would be moving at the same speed through the tobacco on top of the bowl, right? It may be flowing faster or slower in the airway, but the speed of airflow at the point where the tobac is burning should be the same, right. If you're pulling 1 cubic foot of air per minute, the 1 cubic foot of air is entering the top of the bowl per minute, and 1 cubic foot of air is flowing through the draw hole per minute. Bowl size being the same that same cubic foot of air moves at the same speed IN THE BOWL. The rate at which it flows through the draw hole will vary with different draught hole diameters, as the rate at which it flows through the tobacco chamber would vary if you varied the tobacco chamber diameter. That's how I see it, could be wrong as I'm no physicist but did take a few classes in college.
What do you guys think?
What do you guys think?
I'm with Todd. I use 5/32 and mostly 3/4 to 13/16 bowls. 7/8 on larger pipes, but still 5/32 draft hole. Don't need no stinkin' 9/64.ToddJohnson wrote:My preference is for 5/32" draft hole and a 3/4" tapered chamber. If it's deeper than 1.75" I'll increase the diameter to 13/16" or 7/8". For nosewarmers I sometimes use 9/64 and a more cylindrical chamber no larger than 7/8".
Todd
A very few collectors prefer the larger, 11/64 to 3/16 draft hole, and they usually have their pipes adjusted to their specs after market.
I think it's best to go with what the majority of the market expects and prefers, which is usually no larger than 4 mm.
Of course, if you're making them for yourself, do what you prefer.
Rad
Rad
I stamp all my pipes "Rad Davis" so they sell pretty fast anyhow. 
ASB, you are right with your physics - no matter the shape, length, various tube sizes, etc, a pipe smoker is basically moving a set amount of air through a pipe with each puff. So the question becomes, with this amount of air going through, how is a pipe best set up for smoking.
I want lots of tobacco just barely burning and cool smoke delivered at the mouth. So...
Air in the pipe will be moving relatively slower in larger chambers, and relatively slower with wider airways. So I suspect that having a huge chamber and a really small airway would not work ideally - you would have a lot of hot air rushing very quickly to the mouth, which I assume is one point of a wider airway - the smoke would come back almost two times slower in an airway that is 11/64 vs 1/8.
Make a difference? Probably not.
One difference I can see for a larger airway is that a single drop of condensation is less likely to cause an issue than in a tighter tube, which it might block and cause to gurgle....
For all that, drilling well seems to be more important that the actual size used, with maybe some exceptions at the huge/tiny bowl ends of the spectrum...
I've been doing pipes with a 7/8" bowl and a 11/64 airway and really liking the results, in terms of smoking characteristics.
ASB, you are right with your physics - no matter the shape, length, various tube sizes, etc, a pipe smoker is basically moving a set amount of air through a pipe with each puff. So the question becomes, with this amount of air going through, how is a pipe best set up for smoking.
I want lots of tobacco just barely burning and cool smoke delivered at the mouth. So...
Air in the pipe will be moving relatively slower in larger chambers, and relatively slower with wider airways. So I suspect that having a huge chamber and a really small airway would not work ideally - you would have a lot of hot air rushing very quickly to the mouth, which I assume is one point of a wider airway - the smoke would come back almost two times slower in an airway that is 11/64 vs 1/8.
Make a difference? Probably not.
One difference I can see for a larger airway is that a single drop of condensation is less likely to cause an issue than in a tighter tube, which it might block and cause to gurgle....
For all that, drilling well seems to be more important that the actual size used, with maybe some exceptions at the huge/tiny bowl ends of the spectrum...
I've been doing pipes with a 7/8" bowl and a 11/64 airway and really liking the results, in terms of smoking characteristics.
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GbpBulgaria
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Hi
i have "sensitive" approach.
I am always using 4.2 mm drill bit for final drilling of smoke channel.
The chamber is another story. I am using about 19 mm diameter spoon bit and for the deepness, well, I am using my smallest finger second ring. I put in the chamber and if it is up to the second ring it is just right, if it is over the chamber is deeper than expected so I have to re-design the pipe or it will be bigger than expected, if the deepness is bellow this ring – this will be small pipe (small chamber capacity).
4.00 – 4.2 mm draft hole – nice smoke
Tapered chamber – if not it will not burning well, I think.
I have made “pipe tuning” of all my pipes, purchased and made by me – from the lip to the draft hole. All I have drilled with 4.2 drill bit smoke fine. All drilled with 4.0 drill bit are not so good.
On the picture bellow
1. This is a Peterson “tuning” – one of my rotation favorites.
The draft hole was about 4.0 or less, now it smokes like hell, from start to the end. The smoke channel in the mouthpiece was corrected too and the mouthpiece was shorten and made thinner.
2. This pipe is very comfortable but it has problem in mortise size OR the mortise is not well drilled, anyhow same dimensions - good smoke.
3. This is the best smoker I have made until now, please ignore this pipe is has mistakes (mine). The problem here is in the depth of the mortise hole. BUT maybe this is the reason for its smoking capabilities. It is perfect smoker. It has actually a smoke capsule in the mortise, involuntary made, which is actually under the chamber. It cannot pass the test for smoking channel.
4. The pipe bellow is satisfactory smoker.
The chamber is smaller (the pipe is smaller too) and it is tapered much. Same drilling of the draft hole, smooth smoker and very thin mouthpiece (bellow 3,6 mm). Why it doesn’t smokes so well as pipe number 3? Any suggestions? It was big disappointment – I have made it for myself.
My conclusion is, far away of the precise measurements, if you start with one draft hole diameter you can make different chamber, but you have to taper it more or less depending of it deepness. If you start with one chamber diameter and deepness, which you cannot change, you cannot change the draft hole too. Am i right?
Best
George 
i have "sensitive" approach.
I am always using 4.2 mm drill bit for final drilling of smoke channel.
The chamber is another story. I am using about 19 mm diameter spoon bit and for the deepness, well, I am using my smallest finger second ring. I put in the chamber and if it is up to the second ring it is just right, if it is over the chamber is deeper than expected so I have to re-design the pipe or it will be bigger than expected, if the deepness is bellow this ring – this will be small pipe (small chamber capacity).
4.00 – 4.2 mm draft hole – nice smoke
Tapered chamber – if not it will not burning well, I think.
I have made “pipe tuning” of all my pipes, purchased and made by me – from the lip to the draft hole. All I have drilled with 4.2 drill bit smoke fine. All drilled with 4.0 drill bit are not so good.
On the picture bellow
1. This is a Peterson “tuning” – one of my rotation favorites.
The draft hole was about 4.0 or less, now it smokes like hell, from start to the end. The smoke channel in the mouthpiece was corrected too and the mouthpiece was shorten and made thinner.
2. This pipe is very comfortable but it has problem in mortise size OR the mortise is not well drilled, anyhow same dimensions - good smoke.
3. This is the best smoker I have made until now, please ignore this pipe is has mistakes (mine). The problem here is in the depth of the mortise hole. BUT maybe this is the reason for its smoking capabilities. It is perfect smoker. It has actually a smoke capsule in the mortise, involuntary made, which is actually under the chamber. It cannot pass the test for smoking channel.
4. The pipe bellow is satisfactory smoker.
The chamber is smaller (the pipe is smaller too) and it is tapered much. Same drilling of the draft hole, smooth smoker and very thin mouthpiece (bellow 3,6 mm). Why it doesn’t smokes so well as pipe number 3? Any suggestions? It was big disappointment – I have made it for myself.
My conclusion is, far away of the precise measurements, if you start with one draft hole diameter you can make different chamber, but you have to taper it more or less depending of it deepness. If you start with one chamber diameter and deepness, which you cannot change, you cannot change the draft hole too. Am i right?
Best
George
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ToddJohnson
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NateTheBookie
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In response to the Physics-based arguments here, I have to disagree with the model being used. When you're smoking the pipe, the tobacco itself is obstructing much of the Chamber bore, so your effective diameter is much less than the bore diameter.
Thus, an Ideal pipe would be one that has either A) no change effective airway area between the bowl and stem, or B) a gradual, smoothly sloping change from Atmospheric pressure (at the bowl mouth) to partial vacuum (the smoker's mouth). I think that A would be a virtual impossibility, since the degree of bowl obstruction varies greatly with the density of the pack (and thus varies based on the packer's skill and style).
So I believe B would be a better/more fault-tolerant approach and is a good argument for a tapered chamber and a smaller airway.
I also fear that your recommendation for a cylindrical bore and large draw hole could, in fact lead to a pipe with a bad "pressure shock" at the transition between bowl and airway, and in some cases, could even lead to a pipe with a larger effective area in the stem, thus leading to lower stem velocities and the need for a greater vacuum (stronger draw) on the part of the smoker to keep the pipe properly lit...
At least, that's what I'm thinking based on my knee-jerk understanding of Bernoulli's principles and Motorcycle exhaust systems...
Thus, an Ideal pipe would be one that has either A) no change effective airway area between the bowl and stem, or B) a gradual, smoothly sloping change from Atmospheric pressure (at the bowl mouth) to partial vacuum (the smoker's mouth). I think that A would be a virtual impossibility, since the degree of bowl obstruction varies greatly with the density of the pack (and thus varies based on the packer's skill and style).
So I believe B would be a better/more fault-tolerant approach and is a good argument for a tapered chamber and a smaller airway.
I also fear that your recommendation for a cylindrical bore and large draw hole could, in fact lead to a pipe with a bad "pressure shock" at the transition between bowl and airway, and in some cases, could even lead to a pipe with a larger effective area in the stem, thus leading to lower stem velocities and the need for a greater vacuum (stronger draw) on the part of the smoker to keep the pipe properly lit...
At least, that's what I'm thinking based on my knee-jerk understanding of Bernoulli's principles and Motorcycle exhaust systems...
To Todd: No, I am not suggesting that there will be no difference between pipes drilled with such different airways. However, I suspect that a smoker who prefers pipes with smaller airways (like, Stanwell, for example?) probably smokes with a technique (is "used to") that suits such a pipe, and likewise for larger airways and the people who prefer them.
Another way to put it: They will smoke differently, but one is not right or wrong.
So I think the conclusion I am coming to is that there is a spectrum of acceptable drilling conditions, and individual preference is at the end of the day going to determine what someone's favorite pipe is drilled like. (And if I start making group one pipes, I will back off on the airway size.)
To Natethebookie: you may be exactly right, but it could be seen as a positive - if your conclusion is correct, it is harder to oversmoke a larger drilled pipe - the bowl stays cool and the smoke stays cool even if you puff like a madman (puffing harder just to keep it lit, as you say). It's stupid proof!
The argument about the tobacco in the chamber is interesting - we certainly are not smoking empty cylinders. That said, a wide bowl has more square inches available for burning tobacco, so I think the idea of "smoke volume" being proportional to bowl diameter is not way off.
To George: I have been basically unable to pinpoint why my best smokers are my best smokers. Some are drilled small, some big, some have conical (tapered) bowls, some do not. And I have "bad" pipes that are basically functionally identical to "good" pipes, and just don't smoke as well no matter what. Your idea seems to be that after a certain size, a bowl should probably be tapered for best performance, and that makes some sense to me.
To all: Thank you for your insights. I am fascinated by the mixture of physics and art in pipes.
Another way to put it: They will smoke differently, but one is not right or wrong.
So I think the conclusion I am coming to is that there is a spectrum of acceptable drilling conditions, and individual preference is at the end of the day going to determine what someone's favorite pipe is drilled like. (And if I start making group one pipes, I will back off on the airway size.)
To Natethebookie: you may be exactly right, but it could be seen as a positive - if your conclusion is correct, it is harder to oversmoke a larger drilled pipe - the bowl stays cool and the smoke stays cool even if you puff like a madman (puffing harder just to keep it lit, as you say). It's stupid proof!
The argument about the tobacco in the chamber is interesting - we certainly are not smoking empty cylinders. That said, a wide bowl has more square inches available for burning tobacco, so I think the idea of "smoke volume" being proportional to bowl diameter is not way off.
To George: I have been basically unable to pinpoint why my best smokers are my best smokers. Some are drilled small, some big, some have conical (tapered) bowls, some do not. And I have "bad" pipes that are basically functionally identical to "good" pipes, and just don't smoke as well no matter what. Your idea seems to be that after a certain size, a bowl should probably be tapered for best performance, and that makes some sense to me.
To all: Thank you for your insights. I am fascinated by the mixture of physics and art in pipes.
Last edited by Sasquatch on Thu Apr 02, 2009 6:58 pm, edited 1 time in total.
I learned to use 5/32" from Todd years ago. I haven't deviated. Why mess with a good thing.
Generally I'll pair this with a 3/4 or 13/16" chamber. If it gets deeper I'll usually widen this to 7/8". I almost always use a straight walled chamber with a rounded bottom, although some pipes call for a tapered shape.
I also have a few customers who prefer 11/64" airways and I have no problem increasing my standard sizes for them.
Best,
Jeff
Generally I'll pair this with a 3/4 or 13/16" chamber. If it gets deeper I'll usually widen this to 7/8". I almost always use a straight walled chamber with a rounded bottom, although some pipes call for a tapered shape.
I also have a few customers who prefer 11/64" airways and I have no problem increasing my standard sizes for them.
Best,
Jeff
Everything I know about making pipes (which isn't much) has been learned here and in my shop over the last few months. I use a 5/32" airway and tobacco chambers of 3/4", 13/16" or 7/8", because those seem to be the currently accepted norms for American pipe makers and that’s good enough for me. At this stage, I need to work on artistic and aesthetic issues, not engineering principals.
A picture worth a thousand words. This link has an interactive demonstration of Bernoulli's Principal of fluid dynamics - which applies to sucking air through a pipe. You can adjust the diameter of the inlet (think of it as the top of the tobacco chamber) and the outlet ( the bit end) and a few other points in between to see how both pressure and speed are affected as the diameter is changed. Click the Q++ button at the bottom of the page to increase the flow rate and play with it a while.
A picture worth a thousand words. This link has an interactive demonstration of Bernoulli's Principal of fluid dynamics - which applies to sucking air through a pipe. You can adjust the diameter of the inlet (think of it as the top of the tobacco chamber) and the outlet ( the bit end) and a few other points in between to see how both pressure and speed are affected as the diameter is changed. Click the Q++ button at the bottom of the page to increase the flow rate and play with it a while.
"Cut your own wood and you warm yourself twice." - Henry Ford
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NateTheBookie
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