The spinning tube system relies on the tube forming part of a
centrifugal pump. The rapidly rotating water is thrown to the outside of
the tube by centrifugal force. You have a low pressure area in the
middle sucking the water in and a high pressure area at the outside
pushing the water out.
If you place a spinning tube in water it will form a pump BUT the water
will take the route of least resistance - straight back out the end of
the tube! What you need to do is stop the water from flowing back out
the tube. If you block the end of the tube apart from a hole in the
centre the water will be sucked up the hole then forced to the outside
of the tube. Now the only place for it to go is upwards. To work for
spray etching you will probably need a fairly large diameter tube
(50mm?) and a reasonable speed.
Les
cruizzer77 wrote:
> Thanks for your replies!
>
> I tried the one with the propeller, mounted a small cpu fan
> propeller on the bottom of the tube and the upper part of a half-
> liter fanta bottle over it to form a kind of funnel. The rotating
> direction was correct but there happened _nothing_ when I sped it up
> to 5000 turns (I used water to test it). By the way I simply used a
> drill with a flexible to drive it. The problem is that I'm using a
> KRH M20 electrician's installation tube with an outside diameter of
> 20mm which is too small to fit any propeller inside. But the idea
> with the 3 holes sounds interesting, I imagine that the holes are
> drilled with an angle. What diameter does the tube approximately
> have?
>
> Regards
> Martin
>
>
>
> --- In Homebrew_PCBs@yahoogroups.com, Markus Zingg <m.zingg@n...>
> wrote:
>
>>>Hi,
>>>
>>>I'm currently building my own spray etcher of the rotating
>>>perforated tube type. The most difficult problem is to get the
>
> fluid
>
>>>up that tube. Does anyone know what kind of mechanism commercial
>>>spray etchers like the ones from Bungard use?
>>>
>>>Regards
>>>Martin
>>
>>The one I have is having a small plate that basically would "close"
>>the tube but this plate is having three holes in it. Can't tell
>
> from
>
>>memory wehter these are just holes or if they are drilled with an
>>angle to form some sort of propeller as Stefan sugested.
>>
>>IMHO it's not too important as long as some fluid can get in. The
>>plate moreover seems to serve as a way to even limitt the amount of
>>fluid that otherwise would go up the tube. The problem here is that
>>yuo need a surprisingly powerfull motor to drive the tube and I can
>>imagine that having no plate there would simply make the tube
>
> rotate
>
>>less quickly leading to a less intense spray effect. These are just
>>speculations on my end. I never did eny experimenting yet.
>>
>>Markus
>
>
>
>
>
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