Engineering

[glpease]

Funnybusiness aside, an aftermarket port-and-polishing concept of an engine ain't all that far-fetched. Strangely, though, it's kind of backwards, since all we're interested in is the exhaust providing us with the flavor/nicotine horsepower, and reducing the moisture while increasing good flavor.

...some people prefer in-line fours, others like a V-12. :twisted:

I've built enough motors for the analogy to stick. I could still rebuild and tune SU carbs in my sleep. I've tuned more British iron than I can remember, and there are many similarities between a motor that breathes properly and a pipe that does. AND, minimal back-pressure is not optimal back-pressure in both cases. A properly tuned exhaust requires the RIGHT back-pressure to ensure complete scavenging of the combustion chambers during the overlap of exhaust/intake phases.

Pipes have proved themselves to be similar in that regard. This whole "wide open" thing can be like putting a 3" exhaust system on a Vespa. There's a point where performance begins to suffer. The flow dynamics are different, but the concept is similar. Bigger is better until it isn't, and there's no turning back. It's all about velocity, laminar and turbulent flow, pressure, cooling. Not rocket science, except that it is. (The nozzles of rocket motors are constrained by similar physics. I've played there a bit, too. Nothing like a few 4th order differential equations to make the morning coffee taste better.)

More metaphors?

 

[SpeedyPete]

Near Johannesburg is a town called Brakpan. Apparently people who live there, are "otherwise" They are called the 1 2 3 guys.

1 litre brandy )
2 litres coke ) = Brakpan champion on a Saturday afternoon.
3 litre Cortina )

A 3 litre V6 Cortina, fitted with a pancake aircleaner and a "see through" exhaust, delivers the most beautiful music at 6000rpm.

I'm sorry, I've lost it a bit. I've "engineered" a couple of Fords in my day. Most famous was my 1963 997cc Ford Anglia 105E. Dropped suspension, double barrel carb, double valvesprings, banana branch exhaust system with only one Monza "see through" muffler right at the back. This wonderful little car could reach a true 100mph and 0-60 in a shade over 10 seconds. This was outstanding performance from a 997cc motor in those days.

I'm smoking BR Admirals Flake in a Brebbia at the moment. See, I did not loose track completely.

Please forgive an old man his nostalgia, my brothers

 

[glpease]

Near Johannesburg is a town called Brakpan. Apparently people who live there, are "otherwise" They are called the 1 2 3 guys.

1 litre brandy )
2 litres coke ) = Brakpan champion on a Saturday afternoon.
3 litre Cortina )

A 3 litre V6 Cortina, fitted with a pancake aircleaner and a "see through" exhaust, delivers the most beautiful music at 6000rpm.

I'm sorry, I've lost it a bit. I've "engineered" a couple of Fords in my day. Most famous was my 1963 997cc Ford Anglia 105E. Dropped suspension, double barrel carb, double valvesprings, banana branch exhaust system with only one Monza "see through" muffler right at the back. This wonderful little car could reach a true 100mph and 0-60 in a shade over 10 seconds. This was outstanding performance from a 997cc motor in those days.

I'm smoking BR Admirals Flake in a Brebbia at the moment. See, I did not loose track completely.

Please forgive an old man his nostalgia, my brothers

This sort of nostalgia I can really get into! Love those old Anglias. Always wanted one of the Lotus Cortinas, but could never find the blessed convergence of available cash and an available car. I still have a thing for 60s cars.

One of my first micro-rockets was a '68 FIAT 850 spyder, 903cc bored somewhat bigger, kitted out with ridiculous compression, polished and ported, chambers cc'd, Abarth cam, pistons, exhaust, lightened flywheel, conrods, the works, and balanced to an extreme level by a guy whose day job it was to balance turbines of big jet engines. When I went to pick up the bottom end from him, he gave it a spin on the v-blocks. We went inside, had a cup of tea, did our business, and when we came back out to the shop, it was still lazily spinning. That motor would effortlessly turn to over 14k. It didn't last long, but it was sure fun while it did. Loved that car. One of the few tiny cars that could accommodate my 6'4" frame, and let me stretch my legs out. (Motors in the back have some advantages.)

Ah, the memories.

 

[Kyle Weiss]

More metaphors?

Need you ask? You know where you are, right? :cheers: :lol:

I've always looked at pipes as combustion engines for the soul.

:mrgreen:

8)

 

[Wet Dottle]

There are two basically accepted notions for engineering a pipe. One is the idea that the airway should be smooth and uniform, with basically no changes of volume (cross-sectional area if you prefer). The idea is that you reduce/minimize condensation by not offering any turbulence inducing zones, no restrictions. Get the smoke in one smooth tube from bowl to button.

Sasquatch, if you compute the Reynolds number inside the airway of a pipe, you'll see that it is very low. I find a Reynolds number of 50 if you puff relatively vigorously, but 15 is, perhaps, a more reasonable value. Pipe turbulence occurs when the Reynolds number reaches a value of 2,000 or higher, therefore the flow in smoking pipe airways is definitely laminar (i.e., non-turbulent). Also, pipe roughness has no impact in heat transfer in laminar pipe flow. This means that two equal pipes, one smooth and the other rough, will transfer heat at the same rate (assuming same temperatures and flow rates), therefore condensation will occur equally in both.

This works. And pipes with ragged tenons or obstructive designs generally will gurgle and fuss.

I am not doubting this at all, but most of the time my pipe gurgles I can fix it with a light tamp. In other words, it gurgles in the bowl and not because there is condensation in the stem. I can understand that poor drilling may increase flow resistance in the pipe (you have to suck harder to get the same flow rate), but I don’t understand how it influences what is going on in the bowl…

You can up the anti on this idea a bit, and add a nice touch: as a gas moves faster, it exerts less pressure on the side walls of a tube containing it (this is why planes can fly). So you might build a pipe that has an airway that gets smaller and smaller with the idea being that as the smoke cools on its way out of the pipe (and is therefore more likely to condense) it should be moved faster and faster. So a tapering airway seems to work too.

I don’t understand what you mean by this statement. As air moves around a body, or inside a pipe, there are two forces: drag and lift. Lift keeps the planes in the air and drag is flow resistance. Excluding sharp bends, there’s no lift due to flow inside a pipe, only drag. How does this impact smoking quality?

Regardless everything that has been said, I still don’t understand what makes a pipe smoke well. Neil’s blog does explain a lot and I also read the original paper he quotes, but I was left with more questions than answers. For example, I was left with the impression that most condensation actually occurs in the bowl, not in the airway. To determine how significant condensation is in the airway, one would have to compute the drop in temperature through it, but there isn’t enough data. Back of the envelope calculations indicate that a drop of 10 degrees C or more is possible, but I have no way to say if this is even close to the right answer. Nonetheless, if I buy an expensive pipe I expect perfect drilling and fitting regardless of how it impacts smoking quality of a pipe.