Chamber shapes on full bent pipes

[Sasquatch]

Okay, in the spirit of overthinking things, I would like to pose a question about whether there is a greater danger of burning some briar if you make a full bent pipe with a conical bowl. I've been up all night making this highly technical diagram.



So the question surrounds the little "peninsula" of wood left just above the draft hole on a more conical chamber. Seems to me that this is a bit of a hot spot for some guys anyhow, so I worry about leaving it thin. A chamber with a much more blunt bottom seems to offer a more durable section right there, because the angles of intersection of the airway and the chamber wall are more perpendicular.

Any thoughts? I like to drill pipes as close to the bottom as I can, and usually get a presentation on a full bent where the hole is in the bottom "corner", and I've been using a pretty round chamber bit to do so.

[kbadkar]

If you like your conic bents, I would suggest that you adjust your airhole drill angle so the you just miss or barely puncture the chamber with the airhole drillbit at the desired point of intersection. Then complete a circular hole (as opposed to oval) from inside the chamber into the air path (a tiny rotary burr works well with steady hands and good light). It will mitigate some of the thinness, especially if you "miss" the chamber and can drill/shape a little tunnel from the chamber to the draught (rifler files are good to clean things up).

I do this on all my bents now, regardless of chamber bit. In the beginning, I made a couple with air slots rather than holes and ate too much hot ash... that's what happens if you leave an airhole slit and try to smoke your bowl down to mythical fine gray ash.

[ckr]

I have done both on full bents exactly like you have shown. I have not had a problem with any burn out of the peninsula. It is pretty caked up down there but I can see where the very sliver over the hole has opened. On the couple I have with a rounded bore they have also opened up at the top of the drilling, more so that the conicals. None of them seem to have been impaired as far as performance and actually the rounded bores have more of the peninsula missing, likely because I prefer rounded chambers and smoke them much more than conical's. I have always felt that conical's do not cake properly at the bottom and wet dottle is likely to occur more often, even with blends that smoke to ash in pipes with a rounded chamber.

I don't consider myself either a light or heavy puffer, somewhere in the middle ..... I think.

[DMI]

I've done four like this, I was concerned about gurgle but have had no problem above my normal. A lot of late 19th century French pipes have similar drilling, the most common variants being the connecting tube coming out of the chamber at 45 or 90o and the extension under the chamber becoming a well. It's basically a variant on Cavalier drilling, or maybe the other way around, how old is the Cavalier design?



David

[CedarSlayer]

Interesting question, and one I have been asking myself. I have been making and varying pipe hole positions, often on purpose.

Just by looking at cross sections, it seems a perfectly match the entry hole to the bottom of the pipe, when the angle between chamber and air passage is sharply less than 90 degrees, the arch of the chamber bottom needs to taper a bit or be flat like a poker.

I am not ruling out pokers here, they seem to smoke quite well apart from being more effective dottle makers.

I favor an ellipse more than a cone, but my justifications for that preference are fairly thin. Many of the chamber shaping tools I see on line seem to have less gracefully curved profiles, so it could be that my preference is actually a poor one.

By simple Larger holes mean lower velocity of air for the volume drawn. Lower velocity means gentler and more even. Larger holes increase the odds of the occasional strand of tobacco being sucked into the users mouth. From my online investigations of air passage sizes, the ideal seems to approach 3/16" but not include 3/16"

As far as the quality of smoke goes, it is probably desirable to have an even path that may reduce in size but should never increase.

I would love for pipemakers with actual experience and knowledge to enthusiastically rip into my conjectures and observations.

I have a lot of questions, and until I can afford to cat scan a few of lars' pipes, I suspect that a lot of them will remain unanswered.

Bob

[DMI]

Bob

What you are talking about is the 'Airflow' school of pipemaking, the basic idea is that the airway is the same diameter from the chamber to just before the bit, perfection would be a slot of exactly the same area as the airway.

Different pipemakers favour different size airways which range from 3mm up to 5mm (sorry I don't do small imperial), some use different sizes depending on the chambers others don't.

For non filter pipes I use a 3.5mm bit, to cope with the restriction caused by a filter I use a 4mm.

Somewhere on here is a thread which includes a working airflow diagram where you can play with input/output diameter as well as the bore size, if you can find it's fun to play with.

David.

[CedarSlayer]

Thanks, David!
The 5mm is larger (by a smidge) than the 3/16" that I had put down as a limit.

Thanks for the heads up, I am always looking for the right search words to filter through and find stuff.

Nick had an interesting entry, with a pile of formulas in 2004, viewtopic.php?f=15&t=615&p=5328&hilit=airflow#p5328

Bob

[Sasquatch]

Cedar, for what it's worth, in my fooling around, er, in my detailed experiments, I've come to a number of conclusions about airways. 1st, it's right that the air moves slower in a big airway and I think it's valuable. You are actually LESS likely to suck in a chunk of tobacco because you are not moving a rush of air in a small space. And I think the smoke is a bit cooler. I've had excellent results starting at 11/64 at the chamber and tapering down into the stem, flaring out flat at the button. I get a lot of "holy cow this pipe smokes dry" sort of comments.

I'm also convinced that bigger airways can successfully condense a little moisture and not become occluded as a small airway immediately would. A drop of water in a 1/8" hole fills the hole. So there's a nice little fudge factor in the big airway as well.

I will fly in the face of convention here and say that yes turbulence in the airway should be avoided but it's really not that big a deal if you have a little dead space along the way. I've circulated a dozen or so full bent pipes constructed in what I will call non-typical fashion. They are built with regard to airflow, but with less regard to laminarity and no regard to passing a pipe cleaner. In terms of being built "right" they aren't. In terms of working like a damn, they do. I've had a lot of praise from guys who "gambled" on my design. I tell them that they won't pass a pipe cleaner and I guarantee they'll never need to. I'd have heard a lot of pissing and moaning if it didn't work. This leads me to believe that...

Good briar goes a LONG way. A crappy piece of briar won't save a well engineered pipe, but an extraordinary piece of briar will save a less than ideally built pipe in some instances (luckily I know the instances and could index them here but am out of space).

I realize that there are people here who are convinced that the best smokers have no space between mortise floor and tenon, or a hair-sized space etc. And as I see no reason NOT to build like that when possible, I do so. But I see no tremendous advantage in doing so, I haven't seen a doubling of moisture collection or anything like that, in pipes that do not. Now if you INTENTIONALLY condense moisture that's different - that's what the Peterson system pipes are all about, and that's another view entirely.

I think if a guy builds a pipe with a little care, and tries not to have any sharp edges inside the airway, and make a nice trip for the smoke.... it will be a nice pipe. The actual sizes of drilling etc are less important than just making a nice airway. So if you rig up with 11/64, great, if you rig up with 5/32, great, 9/64.. great.... whatever. But do a good job of it.

And if a customer says "Here's the setup I like" then I'd happily oblige him - hell, if he's gonna like the pipe because of it, then why not. I had one guy tell me a pipe smoked hot until he drilled the airway at 3/16 (or bigger maybe). Okay. Fill your boots, buddy!

[DMI]

I had to look up laminarity.

Sas while I agree with most of what you have said I think it should be in the context of well maintained pipes.

I have just reamed and S/A'd a dozen pipes (most designed for 9mm filters) and the amount of gunk that collects in the filter chamber is amazing, you get the same build up with non filter pipes if there is a space between the end of the tennon and mortice wall. Over time this gunk hardens and needs to be drilled out, it smells pretty foul too.

With the condensation thing I think this to can at least partly be blamed on poor maintenance, as tar etc is deposited in the airway it will seal the surface. If the tar is not regularly removed than any moisture which develops will condensate on the surface rather than be adsorbed.

David.

[Sasquatch]

I disassemble and clean after every smoke, so you may be right. Some of the repair guys I've talked to have told me some pretty gross stuff.

[kbadkar]

You make me feel dirty.

I clean my pipes (about 20 in rotation, mostly my handmades) every 6 months or more and only use a pipe cleaner to clear out airway blockages while the pipe is smoldering. Otherwise, I just blow through the stem before packing and I'm good to go. The pipes don't foul up, in my experience.

[CedarSlayer]

Good briar goes a LONG way. A crappy piece of briar won't save a well engineered pipe, but an extraordinary piece of briar will save a less than ideally built pipe in some instances (luckily I know the instances and could index them here but am out of space).

This leads me to a new question, how do I detect, obtain or otherwise make sure I am working with a good chunk of briar? I am still in the briar mangler catagory, much lower than apprentice really, so I probably unworthy of a top grade piece, but I would like to be able to determine the qualities that I need to be looking for. Apart from pretty grain, solid structure and minimal pitting, how do I determine that a particular chunk will be ideal?

When I started to get a bit more serious about the pipemaking, I decided that my first goal was to be able to reproduce identical internal structure. I am also practicing other skills as I finish the pipe, but my number one priority is making sure that I can produce the internal form that I plan from the outset. I have been using mesquite, since I have quite a bit, it is very pretty, and it makes a decent enough smoking pipe.

I have made several pipes out of mesquite now, and I must say that even with nearly identical internal architecture, different mesquite, smokes differently. The only thing that I can imagine would make such a difference is heat conduction. The air passages are burnished, so texture and grain should be of little importance. Odd how such small things can matter so much.

Bob

[Sasquatch]

I think your approach is smart Bob - it teaches you some important stuff, from how to build a decent pipe to the effect of the wood on the smoke.

In terms of briar, it's not hard to find good pipe building briar, stuff that smokes nice and isn't full of pits. I think budget is the limiting factor for most start-up sorta guys. It's a bit hard to cough up 30 bucks for a piece of briar when your expectation is to sell the pipe for 40 bucks after putting 15 hours into it.

I've built and smoked a pipe from every briar souce, and almost from every shipment, and certainly from every grade of briar that I've bought. Some of my thoughts (and others') are posted in this thread here: viewtopic.php?f=9&t=4883