Re: Water cutting

Hi Arne,

What you are describing is very much like a Q-switched laser. There is an optical switch in the laser system and the energy is
allowed to build up and then suddenly dumped as a one shot pulse. This usually happens at a high rate, for example, 1 kHz. It
gives much higher peak power then in CW mode. The high peak power allows melting and vaporizing the could not be done with the
power available in CW mode.

Your are proposing to use a pulsed water jet. I do not think the one way valve is needed. I think we can expand on the pulse
jet idea and possibly create something, even if not useful, it would be interesting.

Think about plumbing and what happens if a valve is closed quickly: There will be a momentary high pressure peak, a "water
hammer".

The design needs to have "long" a straight tube with a dump nozzle at the end and our small cutting nozzle, which is always
open, mounted near the dump nozzle. If the the dump nozzle suddenly is closed, there will be a pressure buildup from the
kinetic energy in the fast moving water. That will be our pressure pulse. Once pressure falls, the dump valve is opened and
the cycle is repeated.

To reduce the load on the water pump, there should be an accumulator (air thank) at the beginning of the pipe to momentary
absorb the energy and water while the pressure nozzle is closed.

One major design problem will be the dump valve.

After all this writing, I do not know if it will work. These are my thoughts as I am typing and I have not evaluated the pulse
hammer water jet further than this.

Bertho Boman
=========================================

> From: "Arne Chr. Jorgensen" <instel@...>
>
> Wow !
>
> All I read was the initial comment that Henry Bawcum made, that he
> had decided to go with a water jet. I didn't expect to see this
> subject explode !
>
> I would like to comment on my own previous words + a little more.
>
> I was not thinking of just something small. I have seen something,
> but with a much larger diameter. I was just thinking of something
> small, DIY kind of stuff. I don't think you have to worry too much
> about the water. You can keep the cutter some place outside of your
> table, - just extend it with something .
>
> As for the amplifier I made a drawing of, - I do know that this
> principle have been used on systems with higher pressures than
> 50.000psi, because they had problems to make any plunger or piston
> hold that pressure. In the system I indicated, - the water itself
> is used as a kind of "piston".
>
> The very first valve, is nothing more than a non-return valve. I
> can find something more on the other valve, - but it is the water
> that normally close this. But, you could use a rotating spindle with
> a hole in it. This could be driven with a small motor. What I am
> talking about, is nothing more than a head you would put on the end
> of the pressure washer. Because of the non-return valve, the high
> pressure will not be seen by the pressure washer, and the hose and
> other stuff would remain the same. Someone mentioned an orifice of
> ruby, sapphire, or something. Yes, - for a industrial type, running
> 24h a day, - you may need something like that, but not for a home
> shop.
>
> If I take some data from a pressure washer: 1500 psi, 8 litres/min.
>
> ( I am guessing here, but say the orifice is 0.1"=2.54mm) This
> should give a velocity approx. to 26 m/s
>
> You know the mass of water, and if you abrupt the water with this
> velocity, - and you calculate the length of the bore, then it should
> be possible to find out what kind of pressure you would be able to
> get, together with the size of the new nozzle.
>
> ( this should be something similar to an electric current in a coil.
> If you abrupt it, the voltage just sky rocket )
>
> I was thinking of something stupid simple. If you are afraid of
> water, then maybe use oil. I once worked with a fellow that
> witnessed I guy losing three fingers. This was on a hydraulic system
> with 1300Bar pressure. There was a leak the size of a needle, and
> they could not see it. He told me the fingers just fell off.
>
> As far as I can tell, several of you are familiar with water
> cutters. Am very wrong about this idea ?
>
> //ARNE