How can I build a better pulsed pressure generator?

[gregz]

I did exactly one project with this Wagner, a lattice fence. It clogged
up about every 20-30 minutes. The Wagner may be good for thin paint but
IMHO not for robust outdoor Latex paint.



Well, that's just the point. I do not wish to compromise the
specification of the product just to make a tool work.




The Sherwin-Williams can be thinned but they recommended not to do that.
Plus it might compromise the warranty. In the end doing the whole house
with roller and (small) brush was less onerous a job than I thought.
Considering that the pros want $6-7k for this job we came out ahead
financially as well because that would have been after-tax money.

We wanted the best paint there is and this one seemed to come really
close to that requirement. Of course, we waited for the 40% off sale

I used the Wagner once to paint cinderblock. I had to thin too much, poor
coverage, and the drips !! I also used Wagner ?, roller pump. That worked
well, but a pain to clean.

Greg

 

[John K]

Then I'd also need earmuffs for all the others in the house, tell
people not to call between 8:00am and 6:00pm, put a note on the
doorbell to forget about ringing it, and get custom-made earmuffs for
two labarador retrievers

Sound is attenuated by distance and closed doors. You are sitting right
next to the source. If it is loud enough to be annoying, it could be
damagng your hearing. I never worried about loud sounds before, and now I
have lost all frequencies above 8KHz.

The 26 dB earmuffs do not completely shut out all sound. They merely
attenuate it. Hearing is logarithmic. You can still hear things like the
phone and doorbell, but the sharp impact noise will not be as severe.

I still do many things that generate a loud noise, often enough to be
painful. After a few minutes, I ask myself why am I doing this. I put on
the earmuffs and lo, the noise is much more reasonable. For only $11.77,
you should give them a try. You can always take them back and get a
refund!

By the same token, you should be wearing eye protection around machinery.
If a part fails, a chip could destroy sight in one eye. I am also a bit
lax in this area. I tell myself my glasses will stop any stray missiles.

But I am only fooling myself. I have a pair of high impact safety glasses
that will fit over my regular glasses. They are not expensive. I really
need to get into the habit of having them handy so I can put them on
whenever I am working on anything that could break. You can only lose
your sight once.

The labarador's hearing can also be damaged by impact noise. They should
not be exposed to it regardless if you are wearing protection or not.

Put them in the back yard and tell them to chase any chickens that try to
get in.

Anyhow, it's also that the current scheme does not produce a very
repeatable pressure pulse. Often I need umpteen attempts to get it
close to what it was yesterday.

JK

 

[Jasen Betts]

The Wagner "Power Painter" sprayers have an "airless" design. The
reciprocating driving piston is directly immersed in liquid paint, and
forces the paint out through an atomizing valve via direct pressure.
The chamber is refilled from the paint cup (or an external paint can)
via suction - the paint cup is pressurized by the gun.

There might be a very small amount of air occasionally suctioned
upwards into the driving chamber along with the liquid paint
(e.g. small bubbles from the paint cup), but this isn't either
necessary or desirable... it's just a side effect.

The result is a spray of atomized paint from the nozzle. This spray
will of course "entrain" some exterior air after the paint leaves the
nozzle... but it's the paint moving the air, not the other way
around. The spray of atomized paint is quite powerful... Wagner warns
that the sprayers are quite capable of injecting paint through the
skin if you get your hands near the nozzle, and that this can have
dire consequences for your health!

High-pressure-air paint sprayers move a lot more air, and the newer
"high-volume low-pressure" sprayers move even more. Both of these
depend on the pressurized airflow to atomize the paint and/or carry
the atomized paint to the work surface.

HVLP is "newer technology?" I've got a 40+ year old electrolux sprayer
accessory in the shed.

 

[Anthony Stewart]

Joerg,
I am not following exactly what viscosity fluid you want to pump but your specs of pressure are too low and there is no flow rate.

Again an expresso pump works from a half wave rectified line voltage operating a spring loaded solenoid with an iron core piston and nylon valve. It pumps cold water up to 150 psi and up to 2 cups/ minute. This may not be suitable for high viscosity fluids or your desired flow rate but is tiny (thumb size).

Can you revise your specs for pressure vs flow rate and viscosity of fluid?Without these, it is guesswork.

Tony