On Thu, 20 May 2021 07:22:42 -0400, "Jim Wilkins"
wrote:

"Ned Simmons" wrote in message
.. .

On Wed, 19 May 2021 12:43:21 -0400, "Jim Wilkins"
wrote:

Ned Simmons" wrote in message
. ..

On Wed, 19 May 2021 07:18:38 +0100, Richard Smith
wrote:



The set pressure of opening means you reach an aim maximum tension in
the sample.
That that valve stays fully open until the hydraulic pressure drops to
(very near) zero completely unloads the sample to no load.
The valve closes and the cycle repeats, etc.

Does such a valve exist?

Look at "sequence valves."

For example:
http://valveproducts.net/pressure-se...sequence-valve


Rich Smith

--
Ned Simmons
---------------------------

You need some bistable hydraulic, mechanical or electrical memory device
that remembers if the pressure should be increasing or decreasing after the
limit sensors stop signaling the limit condition, and operates the valves
accordingly, and that sequence valve could be the trigger that switches it
at the high pressure side.

The proper sequence valve may do it all. See Figure 2 on the page I
pointed to. Connect the IN port to a tee at the cylinder's port; the
OUT port resturns to tank. It'll act like a relief valve when the
pressure reaches the preset, but unlike a normal relief, won't reclose
until the pressure drops to a very low value.

--
Ned Simmons
-----------------------------------

I'll take your expert word for it. My brain is still in a primitive BC
state. (Before Coffee)
https://www.hydraulicspneumatics.com...equence-valves

"When flow stops, spring force closes the main poppet because pressure has
equalized."


I don't entirely follow that paragraph. See my reply to Richard.

Re a device with memory, a directional valve with two detented
solenoid actuators would do the trick. One solenoid controlled by a
pressure switch that closes at the high pressure setting, the other by
a pressure switch that closes at the low pressure setting. Or the
hydraulic equivalent.

https://www.festo-didactic.com/int-e...i4xMjMxLjY3Nzk

--
Ned Simmons

"Jim Wilkins" writes:

"Joe Gwinn" wrote in message
...
...
If the motor runs slow, so does the oscillation cycle, in direct
proportion.

Joe Gwinn
----------------------
If the expected fatigue life is 2 million cycles, the test time at 1
cycle per second is three weeks. I think a good solution would be a
closed loop based on a pressure sensor that shows when the high and
low limit pressures have been reached, so the controller can switch
between the fill and dump solenoid valves as rapidly as fluid flow
permits.

If I had to build a prototype of the tester the controller would be an
old laptop (or desktop) with a printer port, the data bits driving a
successive-approximation A/D converter to measure the pressure sensor
and two control bits operating the fill and dump solenoid valves.

QBasic running in DOS gives full unhindered access to all of the
printer port bits for input and output, unlike Windows. An Arduino
could also work but the laptop has the advantages of a huge hard drive
to store data, the keyboard for control, and the LCD on which QBasic
can display the cycle count and a graph of the pressure.
http://www.nicolasbize.com/blog/30-y...till-the-best/

This simple resistor network outputs a voltage proportional to the
binary code from the port bits:
https://www.tek.com/blog/tutorial-di...rsion-r-2r-dac

The other electronics are an analog comparator (LM311) driving a
printer port status bit that tells if the sensor output voltage is
more or less than the DAC output, and the two high current solenoid
valve drivers.

Stunning detail.
I see that with
* test method and hardware
* control and data acquisition
2million cycles would be a start. With well-performing welds, you'd
want to get out to 20million cycles or more
(200Million is something around what a ship or bridge gets in its
entire period of service, but can be a bit of an ask in test).
I've programmed in Basic. Access to devices / ports - hadn't thought
about it being that convenient and tailor-made.

Ned, Jim, everyone - massive thanks. Rich S

"Richard Smith" wrote in message ...
....
I've programmed in Basic. Access to devices / ports - hadn't thought
about it being that convenient and tailor-made.

----------------------

I can't claim credit for the idea, it was the engineer's suggestion when we
(Unitrode / Texas Instruments) wanted to design and operate evaluation
boards for new user-configurable ICs from customers' unmodified laboratory
computers, which at the time were typically former office desktops and
laptops running Win98. We started with Visual Basic but quickly found that
it lacks the hardware control instructions of QBasic, and Windows polls the
printer port to detect newly attached devices. DOS + QB give full read/write
access to the I/O address space, interrupted only to update the clock.

The only change to the computer was setting the BIOS to boot from a DOS
floppy if present, else to Windows. The same can be done with a USB flash
drive using HPUSBFW. FAT32 USB flash drives are big enough to store programs
and large data files without access to the NTFS internal drive though older
FAT32 hard drives could handle either DOS or Windows, up through XP.
https://www.handheldgroup.com/knowle...ble-usb-drive/

The computer boots normally with the flash drive removed and you can read
any data log files the QB program created, such as cycle intervals which
might increase when the sample began to stretch, and indicate the point of
failure if you can't otherwise sense it.

I had previously assembled one-time computer to hardware interfaces with
added plug-in boards, a purchased digital I/O card and a 16 bit A/D
converter for the Macintosh that I designed. The printer port and DOS/QB
method turned out to be easier for relatively simple tasks. I'm also very
familiar with relay ladder logic controls if you choose to go that way.

Do you have the equipment or machinist friends to consider custom machining
as part of solutions? I couldn't do nearly as much without my lathe and
milling machine.

"Jim Wilkins" writes:

"Richard Smith" wrote in message ...
...
I've programmed in Basic. Access to devices / ports - hadn't thought
about it being that convenient and tailor-made.

----------------------

I can't claim credit for the idea, it was the engineer's suggestion
when we (Unitrode / Texas Instruments) wanted to design and operate
evaluation boards for new user-configurable ICs from customers'
unmodified laboratory computers, which at the time were typically
former office desktops and laptops running Win98. We started with
Visual Basic but quickly found that it lacks the hardware control
instructions of QBasic, and Windows polls the printer port to detect
newly attached devices. DOS + QB give full read/write access to the
I/O address space, interrupted only to update the clock.

The only change to the computer was setting the BIOS to boot from a
DOS floppy if present, else to Windows. The same can be done with a
USB flash drive using HPUSBFW. FAT32 USB flash drives are big enough
to store programs and large data files without access to the NTFS
internal drive though older FAT32 hard drives could handle either DOS
or Windows, up through XP.
https://www.handheldgroup.com/knowle...ble-usb-drive/

The computer boots normally with the flash drive removed and you can
read any data log files the QB program created, such as cycle
intervals which might increase when the sample began to stretch, and
indicate the point of failure if you can't otherwise sense it.

I had previously assembled one-time computer to hardware interfaces
with added plug-in boards, a purchased digital I/O card and a 16 bit
A/D converter for the Macintosh that I designed. The printer port and
DOS/QB method turned out to be easier for relatively simple tasks. I'm
also very familiar with relay ladder logic controls if you choose to
go that way.

Do you have the equipment or machinist friends to consider custom
machining as part of solutions? I couldn't do nearly as much without
my lathe and milling machine.

Machining, making parts and equipment... My cider-maker / cider
supplier could feature in that... Can see a need to trade favours...


Digression into computing.
I often put "emacs" on a CD-ROM, take it by IT-support and invite them
to check it (fully up-to-date virus check software, etc, etc.)
If it's a write-once CD-ROM, it can't be altered ever again.
So if they trust that is all I will ever put in the drive of "my"
networked computer, that's sound in terms of IT security.

The reason for this is;
I have a range of suites of functions for various engineering
tasks which run in the test-processor I am using now - the famous /
well-known "emacs".
They will inject the answer straight into the document you are
writing. You can quote the function and the values you fed to it, and
the answer it gave. Complete record.
"sketching" your way to often high-value decisions.
Plus I do most other text-based thing in emacs.
For examples I didn't just type
"
Thermo-Mechanically Controlled-Processed High-Strength Low-Alloy
"
I typed tmcpqc hslaqc
When you are typing documents with huge strings of standard quotes of
Standards, Company Specifications, etc, that can save a huge amount of
time and effort, and leave your mind clear to think of the big
picture.
Boot off a CD-ROM? Could do?

Ned Simmons writes:

On Thu, 20 May 2021 12:01:50 +0100, Richard Smith
wrote:

Ned Simmons writes:

On Wed, 19 May 2021 12:43:21 -0400, "Jim Wilkins"
wrote:

Ned Simmons" wrote in message
m...

On Wed, 19 May 2021 07:18:38 +0100, Richard Smith
wrote:



The set pressure of opening means you reach an aim maximum tension in
the sample.
That that valve stays fully open until the hydraulic pressure drops to
(very near) zero completely unloads the sample to no load.
The valve closes and the cycle repeats, etc.

Does such a valve exist?

Look at "sequence valves."

For example:
http://valveproducts.net/pressure-se...sequence-valve


Rich Smith

--
Ned Simmons
---------------------------

You need some bistable hydraulic, mechanical or electrical memory device
that remembers if the pressure should be increasing or decreasing after the
limit sensors stop signaling the limit condition, and operates the valves
accordingly, and that sequence valve could be the trigger that switches it
at the high pressure side.

The proper sequence valve may do it all. See Figure 2 on the page I
pointed to. Connect the IN port to a tee at the cylinder's port; the
OUT port resturns to tank. It'll act like a relief valve when the
pressure reaches the preset, but unlike a normal relief, won't reclose
until the pressure drops to a very low value.

--
Ned Simmons

Ned - I thought this is it.

Then I realised (?) - the full flow of the pump will always be the
minimum flowing through valve - which will defeat the closing action
we are counting on? This device, the "kickdown valve", is for filling
say a hydraulic cylinder, where the flow comes to a definitive stop at
full stroke? It avoid the energy loss of pumping oil past in-effect
an "intermediate-pressure" relief valve.

I suspect that constant flow from the pump would defeat it ??

Good question, but I don't think so, as long as the valve and the
return piping are sized such that the pressure at the OUT port (at
full flow) is low enough that the "light spring" in Fig 2 can force
the spool closed.

In other words: the pressure rises to the set point; the "control
relief poppet" opens, releasing the balancing pressure on the back
side of the main spool; the spool shifts open, and the pressure at the
IN port drops; the control poppet closes, but; the "kickdown jet" is
now open and bleeds the balancing pressure from the back of the spool,
until; delta P across the spool * spool area spring force and the
valve closes.

I hope that's right. Whether this is a practical way to control your
device in the real world is another matter.


I'll try to do sketches.

I have thought of a circuit I believe would act quickly at the set
pressure - giving the set pressure and no more. I ran with the idea
of having "separate reference pressure system" where a small pump,
large accumulator and pressure in it freely set via an adjustable
pressure relief valve dumping back to the reference-system tank. I'll
try to sketch that too.

Rich S

--
Ned Simmons

Hi Ned.

Your real-world experience enables you to answer this question?

You've already raised the point

"... Whether this is a practical way to control your device in the real
world is another matter."

I was thinking of constancy of pressure at which it triggers.
This thing is perfect when sequencing.
For a fatigue test, hydraulic pressure at trigger = peak force.
This is crucial to the test - for the peak force to be known and constant.
Would this device settle down to triggering at a very constant
pressure, do you reckon?
Within reason, so long as it stays constant, what that pressure is is
just fine - plot the "F=PA" force on the "S-N curve / plot" for
comparability of data.

(That's why I designed a parallel small system "reference pressure"
concept - so the peak force / pressure is accurately at, but neither
more or less, than a constant reference pressure)

Rich Smith

"Richard Smith" wrote in message ...

"Jim Wilkins" writes:
....
Do you have the equipment or machinist friends to consider custom
machining as part of solutions? ...

Machining, making parts and equipment... My cider-maker / cider
supplier could feature in that... Can see a need to trade favours...

-----------
So not easily, perhaps shortening a bolt but not to the full custom extent I
would otherwise suggest, like the small piston in the cylinder end cap.
Experimenting is difficult when you are limited to only what you can afford
to buy. My shop is what an inventor would have dreamed of in 1960 though
perhaps not today, after 50~60 years of wear.

How about electronic test equipment? Capturing the brief peak value from an
analog pressure sensor during rapid cycling will be difficult without a
digital storage oscilloscope.

https://www.aliexpress.com/price/200...sor_price.html

"Richard Smith" wrote in message ...
Ned Simmons writes:

....
This is crucial to the test - for the peak force to be known and constant.
Would this device settle down to triggering at a very constant
pressure, do you reckon?

-----------------

I don't know about that valve but I do have lots of R&D experience on
difficult projects.

Generally you design and build what you predict (hope) will work, then
measure and correct until you run out of time, money or patience, and
declare it "good enough". The limit is how accurately you can measure.

If the valve is inconsistent you may simply need a better filter, or
different oil viscosity. A recording of cycle intervals and peak pressures
would show you if a problem develops and perhaps hint at why, i.e. was the
change sudden or gradual.

I save measurement data into text files that can be loaded into a
spreadsheet as *.csv for analysis.

"Richard Smith" wrote in message ...
...
Boot off a CD-ROM? Could do?

_____________
Can do easily.

Hit the key during startup that enters the BIOS setup and put the CD-ROM
ahead of the hard drive in the Boot Sequence. On my Dells it's F2 before the
self-test completes. F12 lets me select any bootable source for this session
only.

My Lenovo laptop is a little different. It came in a Fastboot mode that
bypassed the chance to enter the BIOS.
https://support.lenovo.com/us/en/sol...n-windows-1081

On Fri, 21 May 2021 16:05:45 +0100, Richard Smith
wrote:

Ned Simmons writes:

On Thu, 20 May 2021 12:01:50 +0100, Richard Smith
wrote:

Ned Simmons writes:

On Wed, 19 May 2021 12:43:21 -0400, "Jim Wilkins"
wrote:

Ned Simmons" wrote in message
om...

On Wed, 19 May 2021 07:18:38 +0100, Richard Smith
wrote:



The set pressure of opening means you reach an aim maximum tension in
the sample.
That that valve stays fully open until the hydraulic pressure drops to
(very near) zero completely unloads the sample to no load.
The valve closes and the cycle repeats, etc.

Does such a valve exist?

Look at "sequence valves."

For example:
http://valveproducts.net/pressure-se...sequence-valve


Rich Smith

--
Ned Simmons
---------------------------

You need some bistable hydraulic, mechanical or electrical memory device
that remembers if the pressure should be increasing or decreasing after the
limit sensors stop signaling the limit condition, and operates the valves
accordingly, and that sequence valve could be the trigger that switches it
at the high pressure side.

The proper sequence valve may do it all. See Figure 2 on the page I
pointed to. Connect the IN port to a tee at the cylinder's port; the
OUT port resturns to tank. It'll act like a relief valve when the
pressure reaches the preset, but unlike a normal relief, won't reclose
until the pressure drops to a very low value.

--
Ned Simmons

Ned - I thought this is it.

Then I realised (?) - the full flow of the pump will always be the
minimum flowing through valve - which will defeat the closing action
we are counting on? This device, the "kickdown valve", is for filling
say a hydraulic cylinder, where the flow comes to a definitive stop at
full stroke? It avoid the energy loss of pumping oil past in-effect
an "intermediate-pressure" relief valve.

I suspect that constant flow from the pump would defeat it ??

Good question, but I don't think so, as long as the valve and the
return piping are sized such that the pressure at the OUT port (at
full flow) is low enough that the "light spring" in Fig 2 can force
the spool closed.

In other words: the pressure rises to the set point; the "control
relief poppet" opens, releasing the balancing pressure on the back
side of the main spool; the spool shifts open, and the pressure at the
IN port drops; the control poppet closes, but; the "kickdown jet" is
now open and bleeds the balancing pressure from the back of the spool,
until; delta P across the spool * spool area spring force and the
valve closes.

I hope that's right. Whether this is a practical way to control your
device in the real world is another matter.


I'll try to do sketches.

I have thought of a circuit I believe would act quickly at the set
pressure - giving the set pressure and no more. I ran with the idea
of having "separate reference pressure system" where a small pump,
large accumulator and pressure in it freely set via an adjustable
pressure relief valve dumping back to the reference-system tank. I'll
try to sketch that too.

Rich S

--
Ned Simmons

Hi Ned.

Your real-world experience enables you to answer this question?

You've already raised the point

"... Whether this is a practical way to control your device in the real
world is another matter."

I was thinking of constancy of pressure at which it triggers.
This thing is perfect when sequencing.
For a fatigue test, hydraulic pressure at trigger = peak force.
This is crucial to the test - for the peak force to be known and constant.
Would this device settle down to triggering at a very constant
pressure, do you reckon?
Within reason, so long as it stays constant, what that pressure is is
just fine - plot the "F=PA" force on the "S-N curve / plot" for
comparability of data.

(That's why I designed a parallel small system "reference pressure"
concept - so the peak force / pressure is accurately at, but neither
more or less, than a constant reference pressure)

Rich Smith

I've designed hydraulic systems that included sequence valves, but I
wouldn't want to make a prediction on how repeatable the cracking
pressure might be, especially at high cycle rates relative to the size
of the device. It's also likely to drift with oil temp, though that's
a slow-changing parameter that could be compensated for manually.
Probably best to speak to manufacturers, Eaton/Vickers, for example.

--
Ned Simmons