Subject:
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Re: On LEGO Compressors & Pump Testing
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Newsgroups:
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lugnet.robotics, lugnet.technic
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Date:
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Fri, 22 Nov 2002 04:55:02 GMT
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Viewed:
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864 times
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Thomas Avery wrote:
>
> In lugnet.robotics, Gaurav Thakur writes:
> > This is probably my favorite Lego-related website out there. :) Great
> > article there too; I need to try that pressure test sometime.
> >
> > So are the handpumps or the minipumps generally better for compressors? I am
> > currently building a model which uses a couple of the small pumps, but that
> > was mainly due to space restrictions; it might be worth trying to replace
> > those with handpumps and see how the model operates.
>
> I think Soh's previous tests showed that motorizing the large hand "pumps"
> (compressors) provided no extra benefit over the small pumps. This new test
> by Charles Steadman (excellent work, BTW) shows that motorizing two large
> hand pumps can be more beneficial than motorizing the little ones.
I understand why compressors using large pumps are still around - many
people simply don't have the little ones. Whereas they are likely to own
the large pump which comes along with the Technic pneumatics sets
(except 8868 which includes a small pump motorized compressor). So a
page has been done up for them at:
http://www.ozbricks.net/cssoh1/compress/compbig.htm
But the small pumps are now more easily available in the 5218 Pneumatics
pack and also in the 3800 Ultimate Builder's Set (where it's in blue).
These sets include designs for using the small pump as an air
compressor.
I was delighted to receive Charles' dual large pump design as it
appeared to beat the minipump compressor. I agree that pressure
measurements alone are insufficient, compressor tests should also be
done under load. I always follow up pressure measurements with a dynamic
test in which the compressor is connected to drive my 2-cylinder engine
(which btw is based on the pneumatic control loop that I learnt from
Eric Brok). This is a more stringent test than the simple control loop
of three cylinders in Charles' test setup.
I built and tested Charles' design and was rather disappointed that it
didn't performed as well as it should. With both motors running, the
dual large pump compressor was barely able to move my 2-cylinder engine
with intermittent stops to regain pressure.
On the other hand, with Ralph Hempel's improved double acting pump, the
engine could be
kept continuosly moving albeit slowly.
Since Ralph's pump uses only a single motor, so to provide a fair
comparison, I repeated the test running Charles' compressor with only
one motor. It stalled immediately it was connected to my 2-cylinder
engine.
I think the reason is that the large pump is too stiff (even without the
spring) to be used in a motorised compressor. LEGO designed it to be
operated manually, in which situation it works very well indeed.
Previous experience had shown that the LEGO 9V geared motor needs
further 5:1 gear reduction to be able to move the springless large pump.
So I think Ralph Hempel's improved compressor still stands as the most
efficient motorised air compressor, in terms of performance and economy
of parts. But of course, for most pneumatic applications, nothing beats
the large hand pump operated manually like crazy!
--
C S Soh
CSSoh's Lego Pneumatics
http://www.ozbricks.net/cssoh1
... where air is power!
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Message has 3 Replies:
 | | Re: On LEGO Compressors & Pump Testing
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| (...) couple of years ago and used to think that the large one was the only option. (the 8868 Airtech Claw Rig was not properly advertised in the US and I didn't hear about it until 2000) However, there is a pack of two available on the Dacta (...) (22 years ago, 22-Nov-02, to lugnet.robotics, lugnet.technic)
| | | Re: On LEGO Compressors & Pump Testing
|
| Hi guys, You all missed this page about a year ago, I presume. My double stroke compressor, with build-in 9V power-supply and automatic on-off switch. When used in combination with an airtank, it stops pumping when your desired max. pressure is (...) (22 years ago, 22-Nov-02, to lugnet.robotics, lugnet.technic)
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Message is in Reply To:
| | Re: On LEGO Compressors & Pump Testing
|
| (...) I think Soh's previous tests showed that motorizing the large hand "pumps" (compressors) provided no extra benefit over the small pumps. This new test by Charles Steadman (excellent work, BTW) shows that motorizing two large hand pumps can be (...) (22 years ago, 18-Nov-02, to lugnet.robotics, lugnet.technic)
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