Flow is the result of the inverse relationship between pressure and
resistance.  Thus, reducing pressure will reduce flow, reducing resistance
will increase flow *and* reduce overall pressure.

Try blowing through a pipe with your hand covering half the end.  Now do it
again without the blocking.  You can use same ammount of force to move air
through, but you will experience less pressure without the block, and higher
flow.

    KreAture


----- Original Message -----
From: "Josh Koffman" <listsjosh@3MTMP.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Sunday, February 02, 2003 1:01 AM
Subject: Re: [EE]: SMT soldering


> I had a thought about this. I'm no expert in fluid dynamics or anything,
> so this could just be totally wrong. I will hopefully testing my version
> of the hot air pencil tonight (if all goes well).
>
> Anyway, my thought is this. Perhaps the reason Lawrence isn't getting
> hot enough air because of the way he is modifying the airstream. I don't
> know how the pump with the built in control works. Perhaps it just
> squeezes the hose or something, thus narrowing the stream of air,
> increasing the pressure, and decreasing the volume of air. Just
> decreasing the voltage to the pump would seem to me to just decrease the
> volume of air without increasing the pressure.
>
> Ok, that was likely wrong...tear it apart :)
>
> Josh
> --
> A common mistake that people make when trying to design something
> completely foolproof is to underestimate the ingenuity of complete
> fools.
>         -Douglas Adams
>
> Matt Pobursky wrote:
> > I'm using a Million Air MA-200 pump for my hot air tool and don't have
> > any trouble getting mid-400:F air @~1cm from the tip, using the lowest
> > air flow on the pump (it has a built in control). It works great with
> > Kester 276 solder paste that Digikey sells. The air flow is quite gentle
> > and will reflow an 0805 chip resistor or cap in about 4-5 seconds
> > (without blowing it around).
> >
> > I purchased it for a whopping $6.99 at:
> >
> > http://www.petdiscounters.com/aquarium/air/pumps/ca_ma200.html
>
> --
> http://www.piclist.com hint: PICList Posts must start with ONE topic:
> [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads
>

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