Subject: Waterjet project

From: John Haddy <[email-masked]>
Date: Mon, 09 Dec 1996 13:37:22 +1100

Hi All,

I was toying with the idea of making a high pressure water jet,
as are sold for home maintenance (my father just bought one to
clean mildew off the outdoor slate terrace).

My question is: does anybody have a feel for the pressure
required? Obviously, too much will abrade the surface, whereas
too little will fail to do the job. I assume the mode of
operation is through cavitation?

Also, what are the NG's recomendations for the style of driver - 
e.g. multi stage centrifugal pump, or double acting piston, etc.
What size motor will be required?

Thanks in advance for any assistance,

JohnH

-- 
      |  _  |_   _   |_|  _   _|  _|              Electronics Department
    |_| (_) | | | |  | | (_| (_| (_| \/           Macquarie University
    ---------------------------------/-           Sydney, AUSTRALIA 2109

    Email: [email-masked], Ph: +61 2 850 9090, Fax: +61 2 850 9128

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From: [email-masked] (Jens)
Date: Sun, 08 Dec 1996 07:41:40 -0800

John Haddy <[email-masked]> wrote:

This whole thing is silly - buy a commercial pump and be done with it!

>required? 

Depends on what you want to do, how fast you want to do it, what kind
of water flow you have available.

1500 PSI is about the minimum useful pressure, 2500 PSI would be real
nice. The pressure will do you very little good if you havent got a
decent flow rate .... 3 gal/min is minimum and the more the better.

>Obviously, too much will abrade the surface, whereas
>too little will fail to do the job.

No, not really ... you could run it at 100000 PSI if you would like
to, just don't put the nozzle too close to the job surface :)

> I assume the mode of

Unknown  ....

>e.g. multi stage centrifugal pump, or double acting piston, etc.

Most commercial units are piston pumps

>What size motor will be required?

depends on pressure and flow rate selected. A 1500 PSI @ 3 gpm will
require about 3 hp.

>Thanks in advance for any assistance,

You are welcome but I still think you would be nutty trying to build
one of these when commercial units are available so cheaply.
Save some time and efford and build something that can't be bought for
a few dollars or can't be bought at all.

Jens

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From: [email-masked] (Jens)
Date: Mon, 09 Dec 1996 05:04:20 -0800

"Ray F. Abadie" <[email-masked]> wrote:

>Jens,
>
>RE>> This whole thing is silly - buy a commercial pump and be done with it!
>
>Commercial waterjet cutters start at about $100,000 do you know of any
>cheaper? Heck even the pump unit is over $20K and I know of only 1
>manufacturer.
>
>> > I assume the mode of operation is through cavitation?
>RE> Unknown  ....
>
>Most have abrasives in the stream which requires a very, very hard nozzle
>
>> ...I still think you would be nutty trying to build one of these when
>commercial units are available so cheaply.
>
>Where can I get a cheap one?
>
>Ray

If you had read the original post you would have known that we are
talking about a pressure washer to remove mildew from concrete and
stuff of that nature !

Jens

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From: [email-masked] (Fitch R. Williams)
Date: Tue, 10 Dec 1996 05:18:25 GMT

Jens,

Can't we tell him about forges first?  And have a long
involved discussion about whether or not to use inflatable
wheels on the cart? And whether or not the Northern X2
nozzel actually does that?   And start a lottery on how many
will be in the next Harbor Freight Catalog under $625.00.
We could invent pressure sprayer rated motors.

And as a bonus get a well deserved lecture from Jim who is
back (whew) and starts long threads.  

Please?

Don't be such a kill joy.

Fitch
These things have "ceramic" pistons - now there an
"opportunity".   I'd almost pay a dollar for a catalog that
didn't have two or three of them in it - almost.  Always at
least one with a "CAT" pump too (image of Big Yellow Machine
- real *men* have CAT pumps - grunt grunt).

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From: "Ray F. Abadie" <[email-masked]>
Date: 9 Dec 1996 22:25:37 GMT

Jens,

RE> Unknown  ....

Ray

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From: [email-masked]
Date: 9 Dec 1996 21:16:07 GMT

>a few dollars or can't be bought at all.

Agreed!

Peter