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18th July 2016, 09:07 PM #1
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Bell Mouth inlets and outlets for optimum air transfer
For some time now you would have heard me droning on and on about Bell Mouth Hoods (BMH) as being the most efficient way to collect dust from machinery..
This idea is not new as it has been around in many fluid transfer situations.
Pictures of velocity stacks on carburettors as examples of BMHs have been posted but I stumbled upon this today and for those that haven't seen these I thought it might be interesting.
This grey box is what's left of an old Logitech PC amp/speaker system that belonged to my son.
The amp side of the unit died about a decade ago and has been up in the attic since then and during a cleanup last week when I was in the process of dumping it when I noticed it had a plastic BMH. The use of a BMH in speakers is to allow for the most efficient transfer of air from the speaker cabinet to the atmosphere. Failure to do this will dampen the speaker operation significantly
IMG_7118p.jpg
Logitech is hardly audiophile rated gear but I noticed the BMH was curved and was curious as to what was on the other side.
The speaker box was glued closed and I decided to cut it open on the TS!
I was lucky because unbeknownst to me there was a toroidal transformer that I managed to miss hitting by a couple of mm
There was also a rectifier bridge that the TS blade nicked the mounting bracket for but the bracket was Al so that was OK.
They appear to have gone to a lot of trouble with the 180) bend and because the curvature of the port appears to follow the optimum profile i.e. slightly more trumpet shaped than more simple 1/2r as the radius of curvature of the edge.
IMG_7119p.jpg
FWIW I might use the speaker box and BMH as a "sawdust fluffer upper"
i.e.
Face the speaker cabinet with the outer BMH facing upwards
Drop a small amount of sawdust down the BMH
Play some white noise on the speaker and
Poke the particle detector into the BHH and see what happens?
Cleaning the system out between testing is the thing that concerns me
Will probably have to seal that MDF with something as well.
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18th July 2016, 09:19 PM #2
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Onya Bob, you're a champ!
To my surprise I learnt just recently that Logitec is a Suisse company. Obviously made in China like all mass produced stuff, but at least it would be to Suisse specs.
Would it not be better to do this with some doof-doof?
I'm sure you can find someone to supply you with some. Doof-doof/white noise same same (as far as musical content that is).
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18th July 2016, 10:04 PM #3
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could lead to a whole new way of dust removal, doof-doof your way to a dust free shed.
Originally Posted by FenceFurniture
Would it not be better to do this with some doof-doof? I'm sure you can find someone to supply you with some. Doof-doof/white noise same same (as far as musical content that is).
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19th July 2016, 12:08 AM #4
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Now that just ain't gonna happen. But the converse (or maybe a corollary) could: if there was doof-doof in my shed, there'd certainly be no dust..... Originally Posted by BobL
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23rd July 2016, 11:33 PM #5
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That's a bit like RAP music, trouble is I think someone forgot the C that's supposed to be in front of it. Originally Posted by BobL
I'm surprised that no one has started commercially producing them yet, seeing as to how much of an improvement there is to a system.
KrynTo grow old is mandatory, growing up is optional.
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23rd July 2016, 11:47 PM #6
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I'm not that surprised. Originally Posted by KBs PensNmore
That's a bit like RAP music, trouble is I think someone forgot the C that's supposed to be in front of it.
I'm surprised that no one has started commercially producing them yet, seeing as to how much of an improvement there is to a system.
How many 4" and smaller dust ports do we see on machinery?
Before we see BMH's on machines I would hope we'd see a 6" dust ports with an easily removable 4" reducer as standard.
Otherwise we'll be cutting out 4" BMH to be able to fit 6" ducting.
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24th July 2016, 01:10 AM #7
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Didn't think of it like that. Bob, thanks for enlightening us with your wisdom in this field. Where would we be without your knowledge, in a very dusty place.
KrynTo grow old is mandatory, growing up is optional.
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