This is like an "unloader valve" (?) - which does exist - but with
additional characteristics(?)

The need...

I've got a hypothetical on-paper hydraulic device.

For fatigue-testing
- while "the hydraulic cylinder is always bigger than the sample
you are trying to test"
* has always meant a machine with a frame and parts distributed along
a central axis, dwarfing the size of the sample it's testing
* it also means the sample will always fit *inside* the hydraulic
cylinder which is testing it

I cycled up a high hill to get that inspiration, by the way, if you
were wondering...

For fatigue testing samples - it has to tension and release millions
of times.

If I had this valve I mention, you connect the cylinder directly to a
pump - the higher its capacity the faster - more strokes per second -
it will go - "strokes per second" - with "the valve" at the outlet,
dumping the oil in the cylinder and flow of the pump for the time
being back to the tank.

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?

There are computer-controlled systems with a pressure transducer and
the "dump" valve opening on command.
These are the "servo-hydraulic" systems which are familiar to many.
That might be the option it would be necessary to use, in reality.

However - still curious if there is a stand-alone valve device which
does what's wanted.

For accurate pressure control, the only thing I could think of was to
use a balanced open-close valve (sliding "bobbin" ?) - but with one
end pressurised by a "reference pressure system" with its own small
pump, large accumulator and pressure relief valve returning to the
tank.
With the cylinder pressure routed to the other side of the "balanced
valve".
So when the cylinder pressure exceeds the reference pressure by only a
small amount, the valve moves over to rapidly fully open a big dump
line to tank.
Then there has to be another mechanism / valve which only trips for
the valve to return to closed when the cylinder pressure is about the
same as atmospheric.
If proven to work well, the almost constant pressure in the reference
system could be taken as the peak pressure the cylinder reaches.
That reference pressure is freely adjustable by turning the adjuster
squeezing the spring on the relief valve of the "reference" system.

Thanks for considering.

Rich Smith

"Richard Smith" wrote in message news:ly7djv9rgh.fsf@richards-air-2.home...

This is like an "unloader valve" (?) - which does exist - but with
additional characteristics(?)

The need...

I've got a hypothetical on-paper hydraulic device.

For fatigue-testing
- while "the hydraulic cylinder is always bigger than the sample
you are trying to test"
* has always meant a machine with a frame and parts distributed along
a central axis, dwarfing the size of the sample it's testing
* it also means the sample will always fit *inside* the hydraulic
cylinder which is testing it

I cycled up a high hill to get that inspiration, by the way, if you
were wondering...

For fatigue testing samples - it has to tension and release millions
of times.

If I had this valve I mention, you connect the cylinder directly to a
pump - the higher its capacity the faster - more strokes per second -
it will go - "strokes per second" - with "the valve" at the outlet,
dumping the oil in the cylinder and flow of the pump for the time
being back to the tank.

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?

There are computer-controlled systems with a pressure transducer and
the "dump" valve opening on command.
These are the "servo-hydraulic" systems which are familiar to many.
That might be the option it would be necessary to use, in reality.

However - still curious if there is a stand-alone valve device which
does what's wanted.

For accurate pressure control, the only thing I could think of was to
use a balanced open-close valve (sliding "bobbin" ?) - but with one
end pressurised by a "reference pressure system" with its own small
pump, large accumulator and pressure relief valve returning to the
tank.
With the cylinder pressure routed to the other side of the "balanced
valve".
So when the cylinder pressure exceeds the reference pressure by only a
small amount, the valve moves over to rapidly fully open a big dump
line to tank.
Then there has to be another mechanism / valve which only trips for
the valve to return to closed when the cylinder pressure is about the
same as atmospheric.
If proven to work well, the almost constant pressure in the reference
system could be taken as the peak pressure the cylinder reaches.
That reference pressure is freely adjustable by turning the adjuster
squeezing the spring on the relief valve of the "reference" system.

Thanks for considering.

Rich Smith

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

As I understand it, you want a bistable valve with variable hysteresis
between its opening and closing pressures.

I recently tricked up a relay for my solar panels that acts that way. Relays
do anyway but aren't adjustable, I have it switching resistance in or out of
series with the coil to set the pull-in and drop-out voltages. The reason is
to protect digital meters from the voltage range just below their minimum
supply requirement at dawn and dusk, where they operate strangely.

For your problem a second pilot cylinder could change the tension of the
relief valve spring that opposes the pressure. You might need a small
accumulator and restrictor orifice to delay the pressure change at the pilot
to ensure the valve completes each operation instead of chattering between
states.

The generic name for a bistable device with memory is "flip-flop".
https://www.hydraulicspneumatics.com/technologies/pneumatic-valves/article/21122363/basics-of-pneumatic-logic

The solution is easy with electrical control by relays and solenoid valves.
You can either sense pressure or use time delays.

https://en.wikipedia.org/wiki/Relay_logic
In the example STOP/START circuit CR1 (ControlRelay1) is bistable, it
remains in whichever state the last button press left it. The symbol that
looks like a capacitor is a relay contact and the circles are relay coils,
solenoids, motors, etc.

On Wed, 19 May 2021 07:18:38 +0100, Richard Smith <null@void.com>
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-sequence-valve/operation-principle-of-pressure-sequence-valve

>
>Rich Smith

--
Ned Simmons

"Ned Simmons" wrote in message
news:sp8aag549f0td31j70c1hv32ielqp4a6nq@4ax.com...

On Wed, 19 May 2021 07:18:38 +0100, Richard Smith <null@void.com>
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-sequence-valve/operation-principle-of-pressure-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.

Is this commercial or Heath Robinson?

On Wed, 19 May 2021 07:18:38 +0100, Richard Smith <null@void.com>
wrote:

>This is like an "unloader valve" (?) - which does exist - but with
>additional characteristics(?)
>
>The need...
>
>I've got a hypothetical on-paper hydraulic device.
>
>For fatigue-testing
> - while "the hydraulic cylinder is always bigger than the sample
>you are trying to test"
>* has always meant a machine with a frame and parts distributed along
> a central axis, dwarfing the size of the sample it's testing
>* it also means the sample will always fit *inside* the hydraulic
> cylinder which is testing it
>
>I cycled up a high hill to get that inspiration, by the way, if you
>were wondering...
>
>For fatigue testing samples - it has to tension and release millions
>of times.
>
>If I had this valve I mention, you connect the cylinder directly to a
>pump - the higher its capacity the faster - more strokes per second -
>it will go - "strokes per second" - with "the valve" at the outlet,
>dumping the oil in the cylinder and flow of the pump for the time
>being back to the tank.
>
>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?

This sounds very much like the mechanism of a hydraulic shake-table
driver, used for vibration testing of all kinds of equipment.

One manufacturer is Unholtz-Dickie. Look into their history, and
patents assigned to them and their predecessors.

Like "Fluid-operated vibration test exciter" to John Dickie, patent
US2773482A. This is basically a siren driving a shuttle piston back
and forth. If the shuttle piston is prevented from moving, it will
generate a cyclic stress. The addition of a dead weight to this
allows the cyclic stress to ride atop a static stress.

Joe Gwinn

"Joe Gwinn" wrote in message
news:3ksaagdrho7jolcviqf5ccfdrihtak0jgt@4ax.com...

On Wed, 19 May 2021 07:18:38 +0100, Richard Smith <null@void.com>
wrote:

>This is like an "unloader valve" (?) - which does exist - but with
>additional characteristics(?)
>
>The need...
>
>I've got a hypothetical on-paper hydraulic device.
>
>For fatigue-testing
> - while "the hydraulic cylinder is always bigger than the sample
>you are trying to test"
>* has always meant a machine with a frame and parts distributed along
> a central axis, dwarfing the size of the sample it's testing
>* it also means the sample will always fit *inside* the hydraulic
> cylinder which is testing it
>
>I cycled up a high hill to get that inspiration, by the way, if you
>were wondering...
>
>For fatigue testing samples - it has to tension and release millions
>of times.
>
>If I had this valve I mention, you connect the cylinder directly to a
>pump - the higher its capacity the faster - more strokes per second -
>it will go - "strokes per second" - with "the valve" at the outlet,
>dumping the oil in the cylinder and flow of the pump for the time
>being back to the tank.
>
>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?

This sounds very much like the mechanism of a hydraulic shake-table
driver, used for vibration testing of all kinds of equipment.

One manufacturer is Unholtz-Dickie. Look into their history, and
patents assigned to them and their predecessors.

Like "Fluid-operated vibration test exciter" to John Dickie, patent
US2773482A. This is basically a siren driving a shuttle piston back
and forth. If the shuttle piston is prevented from moving, it will
generate a cyclic stress. The addition of a dead weight to this
allows the cyclic stress to ride atop a static stress.

Joe Gwinn

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

I considered an oscillator-based solution but didn't suggest it because they
may require specialized instruments, dataloggers, digital storage
oscilloscopes and spectrum analyzers, to test and debug. It's much easier to
test a system that can be stopped or run slowly.

"Richard Smith" wrote in message news:ly7djv9rgh.fsf@richards-air-2.home...
....
For fatigue testing samples - it has to tension and release millions
of times.
....
----------------------

If you want simple, a 3-port rotary valve would alternately let oil in and
out of the cylinder. You could run it slowly until you determine how fast
you can spin it and still attain full and minimum pressure. The valve could
operate a revolution or cycle counter. If you can tolerate a little leakage
it's simple enough for a model engineer to make. ( I have too many machining
jobs for the sawmill and its gantry hoist in the queue to offer. )

On Wed, 19 May 2021 12:43:21 -0400, "Jim Wilkins"
<muratlanne@gmail.com> wrote:

>Ned Simmons" wrote in message
>news:sp8aag549f0td31j70c1hv32ielqp4a6nq@4ax.com...
>
>On Wed, 19 May 2021 07:18:38 +0100, Richard Smith <null@void.com>
>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-sequence-valve/operation-principle-of-pressure-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

Hi to everyone.
You folk are amazing!
I've been here on my own, and you come along knowing lots of solutions.
I'm in information-overload with all the great leads you've given.
Plus I've just done a week and a half of calculations on testing
methods and really really need to give my head time-out.

You asked about this device.
I'll share with you
http://www.weldsmith.co.uk/tech/fatgres/210511_fatgt_hyd_inner/210511_fatgt_hyd_inner.html
It's an idea for a metal fatigue test, particularly of welds.

So in this rig, the sample is inaccessible, inside the hydraulic
cylinder immersed in the hydraulic fluid.

For the advantages you get, the disadvantages are "nothing".
This test could be running for days to 10's of days, by the way.
It's "high stakes".

Even where you can stop the test and approach the sample, you don't,
in reality. Gets you nothing additional.

The test stops when the sample breaks...

Welding the sample to the "pistons" has more advantages than
disadvantages (one would reckon).
Small and stiff.

A "contraption"? Yes. However - so long as you do a "scattergun"
approach, you have a significant likelihood that some try will work.
You have to be very open-minded, because you can have "dead-certs"
which don't work, and "shouldn't work" which delivers and then some.
You can find the science was wrong, or incomplete, and by giving it a
try anyway you find that out, as well as getting results.

I'll get my head around the info - the links and hints.

Like be back in a little while...

Best wishes all,
Rich S

Ned Simmons <news@nedsim.com> writes:

> On Wed, 19 May 2021 12:43:21 -0400, "Jim Wilkins"
> <muratlanne@gmail.com> wrote:
>
>>Ned Simmons" wrote in message
>>news:sp8aag549f0td31j70c1hv32ielqp4a6nq@4ax.com...
>>
>>On Wed, 19 May 2021 07:18:38 +0100, Richard Smith <null@void.com>
>>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-sequence-valve/operation-principle-of-pressure-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 ??

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

"Jim Wilkins" <muratlanne@gmail.com> writes:

> "Joe Gwinn" wrote in message
> news:3ksaagdrho7jolcviqf5ccfdrihtak0jgt@4ax.com...
>
> On Wed, 19 May 2021 07:18:38 +0100, Richard Smith <null@void.com>
> wrote:
>
>>This is like an "unloader valve" (?) - which does exist - but with
>>additional characteristics(?)
>>
>>The need...
>>
>>I've got a hypothetical on-paper hydraulic device.
>>
>>For fatigue-testing
>> - while "the hydraulic cylinder is always bigger than the sample
>>you are trying to test"
>>* has always meant a machine with a frame and parts distributed along
>> a central axis, dwarfing the size of the sample it's testing
>>* it also means the sample will always fit *inside* the hydraulic
>> cylinder which is testing it
>>
>>I cycled up a high hill to get that inspiration, by the way, if you
>>were wondering...
>>
>>For fatigue testing samples - it has to tension and release millions
>>of times.
>>
>>If I had this valve I mention, you connect the cylinder directly to a
>>pump - the higher its capacity the faster - more strokes per second -
>>it will go - "strokes per second" - with "the valve" at the outlet,
>>dumping the oil in the cylinder and flow of the pump for the time
>>being back to the tank.
>>
>>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?
>
> This sounds very much like the mechanism of a hydraulic shake-table
> driver, used for vibration testing of all kinds of equipment.
>
> One manufacturer is Unholtz-Dickie. Look into their history, and
> patents assigned to them and their predecessors.
>
> Like "Fluid-operated vibration test exciter" to John Dickie, patent
> US2773482A. This is basically a siren driving a shuttle piston back
> and forth. If the shuttle piston is prevented from moving, it will
> generate a cyclic stress. The addition of a dead weight to this
> allows the cyclic stress to ride atop a static stress.
>
> Joe Gwinn
>
> ----------------------------
>
> I considered an oscillator-based solution but didn't suggest it
> because they may require specialized instruments, dataloggers, digital
> storage oscilloscopes and spectrum analyzers, to test and debug. It's
> much easier to test a system that can be stopped or run slowly.

That's a "vibrophore", isn't it, if you apply that conept ot fatigue
testing machines?

Electro-mechanical device.

You would always use one of these if you could, for the project I'm
planning (?) Test rates to 150Hz and higher. Energy consumption so low
many will plug into a "domestic" wall socket.

Never met one in real life. Would desperately like to.
Idea of running a sample to 20 Million cycles no problem is like a
dream come true.

But the problem is when you go beyond "research test samples" to
testing representations of full-sized welds.

The biggest machines are 100Tonnes-force (1000kN; 1MN).

I've indicated the discussions would get very favourable if a 250kN
(25Tonne-force) "vibrophore" were available.

The rig I've sketched is for if say you needed to test a weld to
hundreds of tonnes cyclic stress range.

Rich S

"Ned Simmons" wrote in message
news:lfebagpisbrgqd6b60jmm5saarkf1fmaes@4ax.com...

On Wed, 19 May 2021 12:43:21 -0400, "Jim Wilkins"
<muratlanne@gmail.com> wrote:

>Ned Simmons" wrote in message
>news:sp8aag549f0td31j70c1hv32ielqp4a6nq@4ax.com...
>
>On Wed, 19 May 2021 07:18:38 +0100, Richard Smith <null@void.com>
>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-sequence-valve/operation-principle-of-pressure-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/technologies/hydraulic-valves/article/21885033/are-you-taking-advantage-of-sequence-valves

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

"Richard Smith" wrote in message news:ly5yzdvpap.fsf@richards-air-2.home...
....
You asked about this device.
I'll share with you
http://www.weldsmith.co.uk/tech/fatgres/210511_fatgt_hyd_inner/210511_fatgt_hyd_inner.html
It's an idea for a metal fatigue test, particularly of welds.

So in this rig, the sample is inaccessible, inside the hydraulic
cylinder immersed in the hydraulic fluid.

For the advantages you get, the disadvantages are "nothing".
This test could be running for days to 10's of days, by the way.
It's "high stakes".
---------------------------

You might be able to significantly reduce the 80KW power demand if the
pressure source is a small flywheel-driven piston built into the fixed end
of the cylinder to minimize flow friction loss, that absorbs the pressure
energy as it retracts. You'd add oil/bleed air until a pressure sensor
signal peaks at the desired pressure.

This could require some custom machining and knowledge of using an
oscilloscope. Are those acceptable for you?

When I was in the automated testing business we had to figure times for high
count operations such as testing each cell on a memory chip wafer, often in
conversation without a calculator. There are 86,400 seconds in a day. 1
million seconds (cycles?) is 11.57 days. A micro-year is 31.5 seconds. 1 US
billion (10^9) seconds is 31.7 years.

https://www.youtube.com/watch?v=hj7LRuusFqo

"Jim Wilkins" <muratlanne@gmail.com> writes:

> "Richard Smith" wrote in message news:ly5yzdvpap.fsf@richards-air-2.home...
> ...
> You asked about this device.
> I'll share with you
> http://www.weldsmith.co.uk/tech/fatgres/210511_fatgt_hyd_inner/210511_fatgt_hyd_inner.html
> It's an idea for a metal fatigue test, particularly of welds.
>
> So in this rig, the sample is inaccessible, inside the hydraulic
> cylinder immersed in the hydraulic fluid.
>
> For the advantages you get, the disadvantages are "nothing".
> This test could be running for days to 10's of days, by the way.
> It's "high stakes".
> ---------------------------
>
> You might be able to significantly reduce the 80KW power demand if the
> pressure source is a small flywheel-driven piston built into the fixed
> end of the cylinder to minimize flow friction loss, that absorbs the
> pressure energy as it retracts. You'd add oil/bleed air until a
> pressure sensor signal peaks at the desired pressure.
>
> This could require some custom machining and knowledge of using an
> oscilloscope. Are those acceptable for you?
>
> When I was in the automated testing business we had to figure times
> for high count operations such as testing each cell on a memory chip
> wafer, often in conversation without a calculator. There are 86,400
> seconds in a day. 1 million seconds (cycles?) is 11.57 days. A
> micro-year is 31.5 seconds. 1 US billion (10^9) seconds is 31.7 years.
>
> https://www.youtube.com/watch?v=hj7LRuusFqo

Exactly so.

I have already done these calculations for my "beam configuration"
fatigue test.
Static version of it - tensile test
http://www.weldsmith.co.uk/tech/struct/210122_fwtest_rig/210122_fwtest_testrig.html

The benefit you have there are the highly predictable Euler-Bernoulli
beam calculations for long sections.
I found one fixed stroke actuator would cover every need.

The problem with the "hydraulic inner fatigue test" is it is difficult
to know with much accuracy how much hydraulic oil it is going to take
per stroke to reach the intended force on the sample.
The end pistons seem to be the design challenge. Flexing. Cylinder
analysed by "hoop stress" no problem.

Also - adjusting it so you can arrive at different forces...
Because you need to explore the shape of the fatigue "S-N curve".

That's why took thought of servo-hydraulic.
With "catalog" equipment you could quickly get started.
Connect it up and off you go.
You'd probably use a pressure transducer and servo valves, wth digital
logic linking them. In reality. As the equipment would be already
there and familiar.

I've drawn the servo-hydraulic drive system.
Mechanical logic though.
Drawn as best I can.
Sorry about any offence to familiar conventions.

http://www.weldsmith.co.uk/tech/fatgres/210511_fatgt_hyd_inner/210520_fatgt_servo-hyd_drive.pdf

There's two "bobbin" valves.

The big one dumps the main power system oil to the tank.
It opens when the cylinder pressure exceeds the reference pressure.
That cylinder oil comes through a check-valve, so once pressurised and
vlave open, it stays open.
Until...
The other "bobbin" valve opens when the cylinder pressure is so low it
cannot overcome a spring - that opening dumping the ex cylinder
pressure holding open the main bobbin valve against the reference
pressure - that reference pressure reopening the main valve.

All this mechanism could be on one "pallet" - reference system and
power system adjacent, with one pipe to the test-rig atking
back-and-forth flows.

Sorry that's "reference pressure re-closes the main valve" - to start the next cycle.

It would be good if this system could cycle very quickly and the bigger the pump, the faster it cycles.

On Wed, 19 May 2021 17:42:41 -0400, "Jim Wilkins"
<muratlanne@gmail.com> wrote:

>"Joe Gwinn" wrote in message
>news:3ksaagdrho7jolcviqf5ccfdrihtak0jgt@4ax.com...
>
>On Wed, 19 May 2021 07:18:38 +0100, Richard Smith <null@void.com>
>wrote:
>
[snip]
>
>Like "Fluid-operated vibration test exciter" to John Dickie, patent
>US2773482A. This is basically a siren driving a shuttle piston back
>and forth. If the shuttle piston is prevented from moving, it will
>generate a cyclic stress. The addition of a dead weight to this
>allows the cyclic stress to ride atop a static stress.
>
>Joe Gwinn
>
>----------------------------
>
>I considered an oscillator-based solution but didn't suggest it because they
>may require specialized instruments, dataloggers, digital storage
>oscilloscopes and spectrum analyzers, to test and debug. It's much easier to
>test a system that can be stopped or run slowly.

In the patent reference above, the oscillation cycle is controlled by
an external "variable speed motor" of unspecified kind, designated is
item 25 in the figures and accompanying text.

If the motor runs slow, so does the oscillation cycle, in direct
proportion.

Joe Gwinn

there's other errors.
Reference pressure must hold main dump valve closed, until cylinder pressure exceeds refernce pressure.
Sure there will be other errors.
Got to head off now. Thanks for everything
Rich S

"Joe Gwinn" wrote in message
news:6pqcagdkqotlr92aj6ma5rtum3q18eqnmb@4ax.com...
....
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-years-later-qbasic-is-still-the-best/

This simple resistor network outputs a voltage proportional to the binary
code from the port bits:
https://www.tek.com/blog/tutorial-digital-analog-conversion-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.

On Thu, 20 May 2021 12:01:50 +0100, Richard Smith <null@void.com>
wrote:

>Ned Simmons <news@nedsim.com> writes:
>
>> On Wed, 19 May 2021 12:43:21 -0400, "Jim Wilkins"
>> <muratlanne@gmail.com> wrote:
>>
>>>Ned Simmons" wrote in message
>>>news:sp8aag549f0td31j70c1hv32ielqp4a6nq@4ax.com...
>>>
>>>On Wed, 19 May 2021 07:18:38 +0100, Richard Smith <null@void.com>
>>>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-sequence-valve/operation-principle-of-pressure-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

On Thu, 20 May 2021 07:22:42 -0400, "Jim Wilkins"
<muratlanne@gmail.com> wrote:

>"Ned Simmons" wrote in message
>news:lfebagpisbrgqd6b60jmm5saarkf1fmaes@4ax.com...
>
>On Wed, 19 May 2021 12:43:21 -0400, "Jim Wilkins"
><muratlanne@gmail.com> wrote:
>
>>Ned Simmons" wrote in message
>>news:sp8aag549f0td31j70c1hv32ielqp4a6nq@4ax.com...
>>
>>On Wed, 19 May 2021 07:18:38 +0100, Richard Smith <null@void.com>
>>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-sequence-valve/operation-principle-of-pressure-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/technologies/hydraulic-valves/article/21885033/are-you-taking-advantage-of-sequence-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-en/services/symbols/fluid-power-hydraulic/valves/directional-control-valves-4-2-way-valve-with-two-solenoid-coils,directly-actuated,with-detent-pulse-valve.htm?fbid=aW50LmVuLjU1Ny4xNy4zMi4xMjMxLjY3Nzk

--
Ned Simmons

"Jim Wilkins" <muratlanne@gmail.com> writes:

> "Joe Gwinn" wrote in message
> news:6pqcagdkqotlr92aj6ma5rtum3q18eqnmb@4ax.com...
> ...
> 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-years-later-qbasic-is-still-the-best/
>
> This simple resistor network outputs a voltage proportional to the
> binary code from the port bits:
> https://www.tek.com/blog/tutorial-digital-analog-conversion-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 news:ly8s48mo4z.fsf@void.com...
....
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/knowledge-base/create-a-bootable-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" <muratlanne@gmail.com> writes:

> "Richard Smith" wrote in message news:ly8s48mo4z.fsf@void.com...
> ...
> 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/knowledge-base/create-a-bootable-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?