More about submarines

[230RN]

OK, so you were just throwing out a data point without any referent. Understood, now.

I was comparing to a certain recent event

Thought I heard 5,800 somewhere. I could be wrong about that though

You may have confused a 3 for an 8.  I do that a lot with my little four-banger calculator.  That's a problem with "our" arabic numbering system.  Threes for 8s, 7s for 1s and 2s, 9s for 4s, Os for Øs...

Why, we'd be better off using IIIs for 3s, VIIIs for 8s, Vs for 5s, IVs for 4s...   This is the year MMXXIII, and there's no confusing that.

Me go now.

[MechAg94]

I was comparing to a certain recent event

Thought I heard 5,800 somewhere. I could be wrong about that though

Some reports were throwing out meters which was throwing me off.  Someone should have thrown in furlongs or fathoms. 

[WLJ]

Some reports were throwing out meters which was throwing me off.  Someone should have thrown in furlongs or fathoms.

Similar in many astronomy videos and whatnots where using parsecs will throw some off.

[WLJ]

Or how about this
How often have you seen 7.62x51 been stated to be at 50,000 psi?
It's actually 50,000 CUP not psi and some where along the line someone changed CUP to PSI in an army (I think) paper and thus the myth started that 308 will blow up your 7.62 NATO gun because, OMG "7.62 NATO is 50,000 psi and 308 is 62,000 psi" when in reality they're pretty much the same pressure, ~62,000 psi. Still get into that argument today.

[230RN]

Well, the way I undertand it, Copper  Units of Pressure were supposed to be related to PSI, the equivalent of the force required to duplicate the crushing of a standardized copper slug at so-and-so square inches of a standard-sized opening into the barrel of a "pressure gun."  Older pressure measurements with BP were made with standardized lead slugs.  There is a picture of a pressure gun on page 336 of Hatcher's Notebook.

CUPs were not yet used in Hatcher's day.

Then they started to use strain gauges around the barrel to measure distortion under pressure of firing and decided that should not really be called PSI since the relationship could only be established empirically, not theoretically.

That's the way I understood it, but I'm willing to be corrected.  I believe I gleaned this information from either an old reloading manual or perhaps a Q and A asked by a member to the NRA.  (K Frame, comments?)

Hopefully offered,

Terry, 230RN

[WLJ]

Well, the way I undertand it, Copper  Units of Pressure were supposed to be related to PSI, the equivalenr of the force required to duplicate the crushing of a copper slug at so-and-so square inches of an opening into the barrel in a "pressure gun."

Then they started to use strain gauges around the barrel to measure distortion under pressure of firing and decided thar should not really be called PSI since the relationship could only be established empirically, not theoretically.

That's the way I understood it, bur I'm willing to be corrected.  I believe I gleaned that from either an old reloading manual or perhaps a Q and A asked by a member to the NRA.

Kind of sort of but they really don't convert to one another directly because they actually represent, in cartridge testing at least and as shown with the 7.62 vs 308, two different ways of testing the pressure of cartridges and they curve differently as the pressure increases and the crush copper method's results are often effected by other factors not directly related to pressure.
The 7.62 was tested by the mil using the Crush Copper Method
308 was tested by SAAMI using the piezoelectric method.

I've seen online calculators that are promoted as being able to convert one to the other but the results I've seen in a little bit of testing they really don't because since again they represent two completely different methods of determining pressure they really don't convert back and forth that way. It's not like meters  = some many feet and so many feet = so many meters. That would make it too easy.

[230RN]

^ Exellent and thank you !

"They could only be related empirically..."

[WLJ]

^ Exellent and thank you !

"They could only be related empirically..."

Maybe that was the word I needed the whole time typing that. 

[230RN]

Maybe that was the word I needed the whole time typing that. 

Forgetting names and aphasia is the first sign of...  Wait a minute, I know this... watchamacallit... OH! Yes, ...senility.

Terry, 780BG

[WLJ]

Deleted
 

[K Frame]

Copper, and Lead, units of pressure were in use during Hatcher's time. I believe, but have been unable to determine conclusively, that the CUP method was developed in the early 1900s as a means of dealing with the new smokeless powders and the pressures that they developed.

I believe CUP testing began widespread use in the firearms industry in the 1930s and in the military somewhat before that, but again, I'm not 100% sure about that.

CUP/LUP cannot be directly correlated to PSI, and the readings are NOT interchangeable.

Then there's also the problem that each batch of CUP/LUP slugs has to be calibrated individually, and the differences between batches can give different results, sometimes significantly so.

The first electronic testing was developed in the early 1960s and is now the defacto universal standard, but there are even differences there. European and US test methods are different in how the tests are set up, so the readings can be very different.

[WLJ]

Even NASA can mix units up.
In this case it lost them a $327 million dollar Mars orbiter

During insertion, the orbiter was intended to skim through Mars' upper atmosphere, gradually aerobraking for weeks, but post-failure calculations showed that the spacecraft's trajectory would have taken it within 57 km (35 miles) of the surface. At this altitude, the spacecraft would likely have skipped violently off the denser-than-expected atmosphere,[citation needed] and it was either destroyed in the atmosphere, or re-entered heliocentric space.[2]

The primary cause of this discrepancy was that one piece of ground software supplied by Lockheed Martin produced results in a United States customary unit, contrary to its Software Interface Specification (SIS), while a second system, supplied by NASA, expected those results to be in SI units, in accordance with the SIS. Specifically, software that calculated the total impulse produced by thruster firings produced results in pound-force seconds. The trajectory calculation software then used these results – expected to be in newton-seconds (incorrect by a factor of 4.45)[16] – to update the predicted position of the spacecraft.[17]

Still, NASA does not place the responsibility on Lockheed for the mission loss; instead, various officials at NASA have stated that NASA itself was at fault for failing to make the appropriate checks and tests that would have caught the discrepancy.[18]

https://en.wikipedia.org/wiki/Mars_Climate_Orbiter

[Hawkmoon]

Some reports were throwing out meters which was throwing me off.  Someone should have thrown in furlongs or fathoms.

But then we'd have to know if they were metric, imperial, or nautical fathoms or furlongs.

[230RN]

But then we'd have to know if they were metric, imperial, or nautical fathoms or furlongs.

LOL !

I got a little frosted over when I saw one table that started from 0,0, but the ordinate was in Pascals and the abscissa was in Kelvin.  Talk about hard core SI...

[BobR]

But then we'd have to know if they were metric, imperial, or nautical fathoms or furlongs.

Absolutely, like that Flex seal super glue commercial, I think they should differentiate between short tons and long tons when they say it will lift over "x" number of tons.   

bob

[230RN]

"Oodles of pressures?"

[K Frame]

But then we'd have to know if they were metric, imperial, or nautical fathoms or furlongs.

I measure pressure by hogsheads per fortnight, just like my patriotic Colonial ancestors! If it worked for them it works for me!

[230RN]

Absolutely, like that Flex seal super glue commercial, I think they should differentiate between short tons and long tons when they say it will lift over "x" number of tons.   

bob

Well, it's only 10% different.

The commercial:

https://youtu.be/CDq62bqb_cI

Besides, it's like having a very very very short plastic rope of about 3 or 4 inches diameter (my estimate by my micrometer-click eyeballs) holding that weight.

Not too amazing, looking at it that way.

There's another "cheater" either they or another outfit uses where they glue a close-fitting "piston" inside a cylinder and tout how strong their glue is, when the mating area of glue is actually in shear mode rather than tension mode.

Gotta watch them advertising rascals, they're almost as expert as the goobermink in producing desired incorrect perceptions.

Terry, 230RN

[Northwoods]

Some reports were throwing out meters which was throwing me off.  Someone should have thrown in furlongs or fathoms. 

A college professor (engineering) likes to make kids give velocity problem answers in furlongs per fortnight.  Part of his method of hammering the importance of unit consistency.

[K Frame]

A college professor (engineering) likes to make kids give velocity problem answers in furlongs per fortnight.  Part of his method of hammering the importance of unit consistency.

220 yards per 14 days.

Nice, steady pace for a snail...

[JTHunter]

The sub USED to be outdoors, but I think since the last time I was there they put up a building around it.

Yep.  It was outside when we were there in the early 60s.

[230RN]

Copper, and Lead, units of pressure were in use during Hatcher's time. I believe, but have been unable to determine conclusively, that the CUP method was developed in the early 1900s as a means of dealing with the new smokeless powders and the pressures that they developed.

I believe CUP testing began widespread use in the firearms industry in the 1930s and in the military somewhat before that, but again, I'm not 100% sure about that.

CUP/LUP cannot be directly correlated to PSI, and the readings are NOT interchangeable.

Then there's also the problem that each batch of CUP/LUP slugs has to be calibrated individually, and the differences between batches can give different results, sometimes significantly so.

The first electronic testing was developed in the early 1960s and is now the defacto universal standard, but there are even differences there. European and US test methods are different in how the tests are set up, so the readings can be very different.

I believe I'm confused here between the CUP and "Copper Slug Crushing" method.

My understanding is that Copper (or lead, for black powder tests) Slug Crushing was a direct physical measurement of pressure by means of the force developed through a standardised hole in the barrel through a standardized  piston to the amount of crushing of a standardized copper slug.

This amount of deformation was related directly to the force developed by an hydraulic (or other) compression tester to match the deformation of the test slug.  Given standardized materials and methods, this gave a direct numerical comparison to the pressure developed in the barrel of the pressure gun.

Copper Units of Pressure (to my understanding), CUP,  are units derived from the calculated deformation of the barrel material as shown by either strain gauge deformation or piezoelectric voltage generation due to barrel deformation during firing. 

They are only called "Copper Units of Pressure" (CUP) to keep people happy, but are actually a derived number and not a direct "force per unit area" measurement that the actual copper slug squashing method gives.

It's obviously neater and cheaper since no mechanical fussing around between shots is involved, but lots messier in its theory since different assumptions for strength of materials ( e.g. stainless barrel or regular old iron barrel), temperature, bore diameter, transducer output calibration, etc. etc., are required for each caliber test.

Help.  If this is wrong, someone say so, so I can delete this post in order to avoid further confusion.

Terry, 230RN
EDITED TO ADD:

 " « Reply #72 on: Today at 06:14:34 AM »

Terry,

I believe you are mistaken.  CUP (and LUP) are the units that are used to describe the pressure derived from the slug crushing method.  So if the calibrated copper slug were to be crushed 10mm (or whatever) that pressure would be described as 50,000 CUP.  So they were the units used to describe the direct measurement of the crushed slug.

Now that folks almost universally use piezoelectric strain gauges, the units are kinda anachronistic and most folks use PSI for the units.  If you'd care to go back and forth, the formula is PSI=-17,902+1.516*CUP"

And a big THANK YOU to dogmush ! !

[dogmush]

Terry,

I believe you are mistaken.  CUP (and LUP) are the units that are used to describe the pressure derived from the slug crushing method.  So if the calibrated copper slug were to be crushed 10mm (or whatever) that pressure would be described as 50,000 CUP.  So they were the units used to describe the direct measurement of the crushed slug.

Now that folks almost universally use piezoelectric strain gauges, the units are kinda anachronistic and most folks use PSI for the units.  If you'd care to go back and forth, the formula is PSI=-17,902+1.516*CUP

[K Frame]

"Copper Units of Pressure (to my understanding), CUP,  are units derived from the calculated deformation of the barrel material as shown by either strain gauge deformation or piezoelectric voltage generation due to barrel deformation during firing."

No.

CUP are the units of estimated chamber pressure derived from use of a crusher gun and the copper slugs that are actually crushed in the test.

The term CUP and the copper crusher method far predate the development of strain gauges or pizoelectric measurements and was in common usage in the industry well before World War II.

As far as I know, the term CUP didn't come into standard consumer usage until the late 1950s early 1960s when strain gauges or pizoelectric measurements started to be used and that information started to filter into the market as the various ammo manufacturers began to use it.

There needed to be some distinction between the measurements because the readings derived from all three methods can be quite different and there is no direct method of converting CUP/LUP to PSI or PSI to CUP/LUP.

Lead Units of Pressure testing have been around about as long, or perhaps longer, than CUP testing, and was used both for black powder cartridges and for black and smokeless powder shotshell loads.

[K Frame]

"If you'd care to go back and forth, the formula is PSI=-17,902+1.516*CUP"

I've seen that before, and I've never understood where it came from. It was never used in the industry because while it might work as a conversion method for one cartridge it can provide WILDLY different numbers for other cartridges.