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How wide are KM downstems?

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  #1  
Old December 2nd, 2008, 12:51 PM
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Default How wide are KM downstems?

I hear the downstems are a bit bigger, but how much bigger? Anyone have an exact or close estimate?
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  #2  
Old December 2nd, 2008, 01:01 PM
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Default Re: How wide are KM downstems?

I can fit my chinese downstem inside my KM's downstem :O
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  #3  
Old December 2nd, 2008, 01:20 PM
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Default Re: How wide are KM downstems?

i think the usual chinese is ~1cm and a km is ~1.5cm...
which doesn't seem like much but as far as total volume inside the downstem, it's like twice as large?? my math may be off, it's been awhile lol
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Old December 2nd, 2008, 01:32 PM
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Default Re: How wide are KM downstems?

Volume of cylinder is [(pi)r^2]*height just assume height is 1 for this example..... if radius is .5 then the volume is .25pi which is ~=.8, if radius is .75 then the volume is ~=1.75. So slightly more than double. If you are talking about 1 versus 1.5 in diameter.

Those numbers are rough mental math numbers tho, so accuracy may vary.
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  #5  
Old December 2nd, 2008, 03:18 PM
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Default Re: How wide are KM downstems?

Quote:
Originally Posted by bradedup View Post
Volume of cylinder is [(pi)r^2]*height just assume height is 1 for this example..... if radius is .5 then the volume is .25pi which is ~=.8, if radius is .75 then the volume is ~=1.75. So slightly more than double. If you are talking about 1 versus 1.5 in diameter.

Those numbers are rough mental math numbers tho, so accuracy may vary.

i have no idea whats going on lol

there pretty big
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  #6  
Old December 2nd, 2008, 03:38 PM
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Default Re: How wide are KM downstems?

Quote:
Originally Posted by bradedup View Post
Volume of cylinder is [(pi)r^2]*height just assume height is 1 for this example..... if radius is .5 then the volume is .25pi which is ~=.8, if radius is .75 then the volume is ~=1.75. So slightly more than double. If you are talking about 1 versus 1.5 in diameter.

Those numbers are rough mental math numbers tho, so accuracy may vary.
Use a 26" hookah just for the sake of being an average size.

A 26" Hookah is 66cm high using the standard conversion formula of (Inches)*2.54 = (cm)
So with a diameter of 1cm on a chinese hookah you get

[(Pi)(.5)^2]*66
-> [(3.14)(.25)]*66
-> [.785]*66
-> 51.81cm^3

Now take a 1.5cm KM Hookah

[(Pi)(.75)^2]*66
-> [(3.14)(.5625)]*66
-> [1.76625]*66
-> 116.5725cm^3


116.5725 / 51.81
-> 2.25

A KM has 2.25 times more volume capacity @ 1.5cm in diameter than a Chinese hookah at 1cm in diameter.

Now, if Hose ports and Hoses are equal to the diameter of the downstem (unlikely) you'll get optimal volume of smoke. More than likely the port is at least smaller than the downstem, even if the hose isnt. So at the very least, you'll never be drawing the thing to capacity.

So if the hose port is equal on both hookahs, and smaller than a chinese downstem, and smaller than a km downstem, neither will produce better smoke volume.
If KMs have larger hose ports, then they achieve greater volume and you inhale more smoke at an equal rate than you would with the chinese.

Last edited by HookahWaffle; December 2nd, 2008 at 03:43 PM.
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  #7  
Old December 2nd, 2008, 03:46 PM
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Default Re: How wide are KM downstems?

So you are limited by the volumetric efficiency of the smallest hole right?

And stem size isnt the same as how tall a hookah is right? But i guess it would be an "ok" assumption to make as long as you take both as the same. I think we should note though that if you have a short downstem that doesnt go that deep into the base, then you cant assume your "29inch" whatever is going to perform like a 29" KM or whatever that has a longer downstem.
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Old December 2nd, 2008, 03:48 PM
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Default Re: How wide are KM downstems?

Quote:
Originally Posted by nmcgrawj View Post
So you are limited by the volumetric efficiency of the smallest hole right?

And stem size isnt the same as how tall a hookah is right? But i guess it would be an "ok" assumption to make as long as you take both as the same. I think we should note though that if you have a short downstem that doesnt go that deep into the base, then you cant assume your "29inch" whatever is going to perform like a 29" KM or whatever that has a longer downstem.
Correct, actually I didnt bother to take into account the fact that the hookah is measured from top to bottom, not on stem size.

So yes, assuming both stems are the same length, the larger diameter stem produces more volume, but the limiting factor is the smallest junction in the circuit, the hose port.

Also, thats not taking into consideration the use of a diffuser, which would have to have enough holes to equal the volume capacity of the downstem itself, otherwise it will restrict flow as well.
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Old December 2nd, 2008, 03:51 PM
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Default Re: How wide are KM downstems?

Quote:
Originally Posted by nmcgrawj View Post
So you are limited by the volumetric efficiency of the smallest hole right?

And stem size isnt the same as how tall a hookah is right? But i guess it would be an "ok" assumption to make as long as you take both as the same. I think we should note though that if you have a short downstem that doesnt go that deep into the base, then you cant assume your "29inch" whatever is going to perform like a 29" KM or whatever that has a longer downstem.
You are not necessarily limited by the volumetric efficiency of the smallest hole; if this were true then upgrading a hose would not increase airflow, as in most cases the hose is still wider than the host port even in generic hookahs. The exact correlation cannot really be determined without aerophysics and some fluid mechanics principles applied to gases. Because the speed of the gas being pulled through the hose port will speed up at the choke.

Also the length of the stem is NOT equal to the height of the hookah.
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Old December 2nd, 2008, 03:53 PM
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Default Re: How wide are KM downstems?

Quote:
Originally Posted by bradedup View Post
You are not necessarily limited by the volumetric efficiency of the smallest hole; if this were true then upgrading a hose would not increase airflow, as in most cases the hose is still wider than the host port even in generic hookahs. The exact correlation cannot really be determined without aerophysics and some fluid mechanics principles applied to gases. Because the speed of the gas being pulled through the hose port will speed up at the choke.

Also the length of the stem is NOT equal to the height of the hookah.
Ding ding, winner. Was just talking this over with a friend on aim actually.

You'd have to measure the air volume at any given time across each choke point, bowl, stem, diffuser, hose port, hose, hose tip, and add them cumulatively, and the density of the smoke factors in as well.
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  #11  
Old December 2nd, 2008, 03:53 PM
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Default Re: How wide are KM downstems?

gotch
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  #12  
Old December 2nd, 2008, 04:52 PM
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Default Re: How wide are KM downstems?

Quote:
Originally Posted by HookahWaffle View Post
Ding ding, winner. Was just talking this over with a friend on aim actually.

You'd have to measure the air volume at any given time across each choke point, bowl, stem, diffuser, hose port, hose, hose tip, and add them cumulatively, and the density of the smoke factors in as well.
There are other factors that come into play other than average volume.

Just think for a second about if you had a 2 inch diameter hose that was a foot long...except the end had a cap on it with a hole poked in it with a diameter of 1 mm. The pull on this hose would be much harder than a hose with a 1 inch diameter and no cap even though the average volume of the larger hose would be greater.

There are a lot of factors at work here, gaseous molecule sizes, average kinetic energy of molecules, even taking into account things like airfoils (rounded port versus square port or slopingly smaller circumference or sudden decrease is circumference (like the cap with a hole)).

Basically there are a lot of variables that can't easily be accounted for.
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  #13  
Old December 2nd, 2008, 05:39 PM
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Default Re: How wide are KM downstems?

there are different kms, some have a bigger diameter than others. one of my old brass core kms is only slighter bigger than a nour, while the new stainless steel ones with the bulb i can fit the nour into
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  #14  
Old December 2nd, 2008, 08:33 PM
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Default Re: How wide are KM downstems?

Quote:
Originally Posted by HookahWaffle View Post
Use a 26" hookah just for the sake of being an average size.

A 26" Hookah is 66cm high using the standard conversion formula of (Inches)*2.54 = (cm)
So with a diameter of 1cm on a chinese hookah you get

[(Pi)(.5)^2]*66
-> [(3.14)(.25)]*66
-> [.785]*66
-> 51.81cm^3

Now take a 1.5cm KM Hookah

[(Pi)(.75)^2]*66
-> [(3.14)(.5625)]*66
-> [1.76625]*66
-> 116.5725cm^3


116.5725 / 51.81
-> 2.25

A KM has 2.25 times more volume capacity @ 1.5cm in diameter than a Chinese hookah at 1cm in diameter.

Now, if Hose ports and Hoses are equal to the diameter of the downstem (unlikely) you'll get optimal volume of smoke. More than likely the port is at least smaller than the downstem, even if the hose isnt. So at the very least, you'll never be drawing the thing to capacity.

So if the hose port is equal on both hookahs, and smaller than a chinese downstem, and smaller than a km downstem, neither will produce better smoke volume.
If KMs have larger hose ports, then they achieve greater volume and you inhale more smoke at an equal rate than you would with the chinese.

and i thought geometry wouldnt effect my life!
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  #15  
Old December 3rd, 2008, 09:24 AM
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Default Re: How wide are KM downstems?

No one is talking about Bournolli's Principle in here and yet we are talking about air flow scientifically. I would have though Bournolli's equation would have been at least quoted. You all should be ashamed. LOL.
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