Fountain Pen Magic

[Pen Engineer]

Plastics have their problems. All the reasons you mentioned are absolutely valid.

 

ABS is one of the better ones but its clear version has a bit of a tinge to it. It also has the effect of self polishing. The chemicals on the skin surface and the handling of a plastic component polish it. ABS, when you bend it often turns white.

 

For testing I had my components made from PMMA, the most neutral material for ink, but brittle. It is the most common choice when selecting a clear plastic. It has a clicky sound.

 

Good clear ones, like PC and PMMA both have a tendency for stress cracking. Meaning, for example, when you screw to components together, the screw section is under permanent stress and one or both will crack there after time without doing anything else, fatigue. Once, I was faced with the alarming use that all pens (thousands) of a certain type had fallen apart while in storage and no one told me that they had changed material.

 

PMMA may not actually break but develope many tiny internal cracks. Sometimes, when the component had be cast rather than injected, heating the component, like annealing, can get rid of the internal stresses.

 

I love writing about this stuff.

 

Thank you so much for you support, it is really motivating.

 

Thank you too for your invitation. Melbourne is not on my list. Three, four times Sydney a year is as much as I can handle at the moment. Visiting my daughter and her family, love them all!

[milkb0at]

...

 

Just to clarify: ...e.g. plastics that won't crack like TWSBI... do you mean, the TWSBI does crack or it does not?

 

...

 

Have a look at this page, where I collected the components of an fp... perhaps tell me your second preference.

 

Yes, several TWSBIs have cracked (including mine). Otherwise nice pens.

 

If you're doing the barrel I had in mind that the cap and section go along with it, but you can keep them separate if you think they are sufficiently different. The more detail the better for me, but of course that's more work for you! But I appreciate your hard work.

 

Of the list, my next suggestion would be the ink reservoir. There must be enough interesting details in the more standard modern cartridge / converter / piston choices, let alone older bladders, vac fillers etc.

 

I enjoyed your design articles when I last read them. I will re-read them, and look forward to reading your new section on aesthetics.

[Drone]

Plastics have their problems... Good clear ones, like PC and PMMA both have a tendency for stress cracking. Meaning, for example, when you screw to components together, the screw section is under permanent stress and one or both will crack there after time without doing anything else, fatigue.

 

Yes - IMO the problem with the TWSBI pens is not user over-tightening (as TWSBI often claims), it is improper injection mold design - temperature control in-particular.

 

Building a good plastic injection mold is far more complex than just mechanical milling. Depending on the type of plastic being used, the thermodynamic design of the mold can be just as important, if not more!

 

After the plastic is injected it must be cooled to the point where it hardens before being ejected from the mold. The cooling must be carefully controlled and as uniform as possible. Cooling is often controlled by pumped cooling fluid circulating through channels milled within the mold. The positioning of these cooling fluid channels inside the mold is critical. If the cooling is not uniform, then some sections of the part being molded will harden before other sections. This uneven cooling and subsequent hardening creates permanent internal mechanical stress lines that are "frozen-in" to the hardened plastic.

 

It is along these frozen stress lines where cracking is most likely to occur. Most often these lines of stress occur at points in the mold where the part changes thickness and/or shape. One such point where internal stress is likely to occur is where the barrel of a pen thins and becomes the threaded section. Therefore it is not surprising that the section is where we often see TWSBI pens cracking. It is not only because the threaded section can be over-tightened by the user, it is because the section is already under internal stress from improper mold cooling.

 

The internal lines of mechanical stress in molded plastic can be visualized with a Polariscope, which reveals the Pholoelsasticity in a material. Plastics under stress exhibit Birefringence under polarized light which causes internal stresses to appear as a spectrum of colors within the material under observation when viewed with a polariscope.

 

For more on this:

 

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

 

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

 

http://www.testing-instruments.com/ppc/preform-strain-viewer/

 

It turns out you can actually see and photograph the stress lines in plastic with a home-made transmission polariscope. All you need is a typical LCD monitor (which is a source of polarized light), a specimen for examination (e.g., a TWSBI pen), and a circularly polarized filter (such as a screw on camera lens filter). Check out this link for more on how to do this:

 

http://hackaday.com/2014/01/07/homemade-polariscope-is-super-easy-to-make/

 

I have seen at least one polariscope image of a TWSBI 580 somewhere on the Web (I unfortunately don't have a copy), and the image showed obvious stress lines and pinning points around the section which in my opinion were unacceptable for a production part. Also, there are numerous cases of TWSBI pens cracking even when not being used; another sign of unwanted internal stress.

Edited November 14, 2016 by Drone

[Pen Engineer]

 

Yes - IMO the problem with the TWSBI pens is not user over-tightening (as TWSBI often claims), it is improper injection mold design - temperature control in-particular.

 

Building a good plastic injection mold is far more complex than just mechanical milling. Depending on the type of plastic being used, the thermodynamic design of the mold can be just as important, if not more!

 

After the plastic is injected it must be cooled to the point where it hardens before being ejected from the mold. The cooling must be carefully controlled and as uniform as possible. Cooling is often controlled by pumped cooling fluid circulating through channels milled within the mold. The positioning of these cooling fluid channels inside the mold is critical. If the cooling is not uniform, then some sections of the part being molded will harden before other sections. This uneven cooling and subsequent hardening creates permanent internal mechanical stress lines that are "frozen-in" to the hardened plastic.

 

It is along these frozen stress lines where cracking is most likely to occur. Most often these lines of stress occur at points in the mold where the part changes thickness and/or shape. One such point where internal stress is likely to occur is where the barrel of a pen thins and becomes the threaded section. Therefore it is not surprising that the section is where we often see TWSBI pens cracking. It is not only because the threaded section can be over-tightened by the user, it is because the section is already under internal stress from improper mold cooling.

 

The internal lines of mechanical stress in molded plastic can be visualized with a Polariscope, which reveals the Pholoelsasticity in a material. Plastics under stress exhibit Birefringence under polarized light which causes internal stresses to appear as a spectrum of colors within the material under observation when viewed with a polariscope.

 

For more on this:

 

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

 

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

 

http://www.testing-instruments.com/ppc/preform-strain-viewer/

 

It turns out you can actually see and photograph the stress lines in plastic with a home-made transmission polariscope. All you need is a typical LCD monitor (which is a source of polarized light), a specimen for examination (e.g., a TWSBI pen), and a circularly polarized filter (such as a screw on camera lens filter). Check out this link for more on how to do this:

 

http://hackaday.com/2014/01/07/homemade-polariscope-is-super-easy-to-make/

 

I have seen at least one polariscope image of a TWSBI 580 somewhere on the Web (I unfortunately don't have a copy), and the image showed obvious stress lines and pinning points around the section which in my opinion were unacceptable for a production part. Also, there are numerous cases of TWSBI pens cracking even when not being used; another sign of unwanted internal stress.

yep...

 

we used another trick to reduce the cycle time, let the component fall into a water or oil bath...

 

I used the polarisation method. When you deform the component gently you can see the coloured lines move. One could sort of measure it: whenever red would come up again (like in a rainbow) the stress was double. Coloured lines close together indicated danger zones

 

Love the computer in your picture. As a young ingeneer, I was part of the team that designed the first mobile computer... when it was shown at the Hannover Fair in 1972, they believed it was a hoax and the real computer was sitting behind the curtain... good old days.

[Pen Engineer]

 

Yes, several TWSBIs have cracked (including mine). Otherwise nice pens.

 

If you're doing the barrel I had in mind that the cap and section go along with it, but you can keep them separate if you think they are sufficiently different. The more detail the better for me, but of course that's more work for you! But I appreciate your hard work.

 

Of the list, my next suggestion would be the ink reservoir. There must be enough interesting details in the more standard modern cartridge / converter / piston choices, let alone older bladders, vac fillers etc.

 

I enjoyed your design articles when I last read them. I will re-read them, and look forward to reading your new section on aesthetics.

The plan is that I write about components first individually and then in interaction. Of course, that is not always possible. Have not started with the barrel, yet. The forums at FPN keep me away.

 

Thanks for your feedback on my design papers. From 88 to 96, I worked in design education. I find it incredible how much design attitude has changed, and the purpose of design. So much can be done, so many opportunities, but all I see is cosmetics, the driver is greed. Several of the products I have been involved with have been on the market for decades, and the companies still rake in fortunes.

[milkb0at]

I've read your page on aesthetics. You did a good job of explaining what is often unexplainable. I don't have the years of experience of making physical things to have any real clue on how to make something that's aesthetically pleasing, but I appreciate those masters who can tweak things "just so" - a flick here, a millimetre there - to make something beautiful. There aren't any useful algorithms to create something pleasing, not even the (in)famous golden ratio.

[Pen Engineer]

I've read your page on aesthetics. You did a good job of explaining what is often unexplainable. I don't have the years of experience of making physical things to have any real clue on how to make something that's aesthetically pleasing, but I appreciate those masters who can tweak things "just so" - a flick here, a millimetre there - to make something beautiful. There aren't any useful algorithms to create something pleasing, not even the (in)famous golden ratio.

Thank you so much. Yes, there had been a lot of feeling, sensing and thinking, before the words came out.

 

When we tweaked pen designs, we made models that really felt like the final thing... even put metal weights inside...

 

and often the diameter variations would be 2 to 3 tenth of a millimeter, length variations around 2 mm and the barrel cap demarcation would move in steps of 1 mm. There would be 15 to 20 models laying next to each other.

 

Initially, there would be 5 guys with good eyes and the boss, unfortunately. We learned, that us 5 would meet before, and show the boss only the variations that we considered good.

[Drone]

Love the computer in your picture. As a young ingeneer, I was part of the team that designed the first mobile computer... when it was shown at the Hannover Fair in 1972, they believed it was a hoax and the real computer was sitting behind the curtain... good old days.

 

The device in my Avatar picture is not a computer, it is an IBM Model 029 card-punch/reader station which is used to program computers. The Model 029 was in the IBM product line from 1964 through the late 1980's. I first learned to program on IBM System/360 and IBM 1130 computers via Model 029 and earlier 026 punch/readers.

 

Slaving over a Model 029 for hours on end makes for an indelible experience. You will never forget the smell of the lubricants, feel of the electromechanical keyboard, and unmistakable clunking and clicking sound of cards feeding through the endlessly whirring machine.

 

Program development on a busy multi-user IBM System/360 academic and research mainframe computer went like this: 1. Punch your program on a deck of cards. 2. Submit your program deck to a systems operator by putting it into an empty numbered job box while taking the numbered card from the box to indicate it is occupied. Job boxes were essentially a wall of cubby-holes which are open on two sides. 3. Wait... 4. After your job is finished, a system operator puts your program deck and the printout from your job back into the numbered job box. 5. Take your program deck and printout from the job box and return the numbered card, which indicates the job box is no longer occupied. 6. Read the printout and debug the program. Repeat Steps-1-6 over and over again until your program works.

 

This modern YouTube video shows a refurbished Model 029 punch/reader in operation:

 

https://www.youtube.com/watch?v=YnnGbcM-H8c

 

Here is a vintage 4 minute tutorial video on the basic use of the Model 029:

 

https://www.youtube.com/watch?v=oaVwzYN6BP4

Edited November 15, 2016 by Drone

[Drone]

Question: What is the optimal shape for a nib slit breather hole when it come to preventing stress induced fatigue fractures?

Some claim the circle is the ideal shape. Others claim the heart shape is optimal because not only do the rounded lobes of the heart prevent stress concentration, but the thicker part of the heart shape between the lobes is diametrically opposite from the slit, which is the point where the circle shaped hole is most likely to crack.

So Pen Ingeneer, which is best from a strict Engineering standpoint? The circle, heart, or some other shape?

Ref.-1: "Nib Notes", http://www.nibs.com/NibNotes.html

"As experience has shown, there are both better and worse shapes for vent holes. Those with no sharp concave corners are much superior. Ideal is the round hole, but it is not very interesting. The heart-shape is even better. This is where engineering and emotion meet. For not only does it minimize cracking, but people grow very attached to their pens and nibs. What better way to express this affection than a heart?"

Thank You, David

Edited November 15, 2016 by Drone

[Pen Engineer]

Question: What is the optimal shape for a nib slit breather hole when it come to preventing stress induced fatigue fractures?

 

Some claim the circle is the ideal shape. Others claim the heart shape is optimal because not only do the rounded lobes of the heart prevent stress concentration, but the thicker part of the heart shape between the lobes is diametrically opposite from the slit, which is the point where the circle shaped hole is most likely to crack.

 

So Pen Ingeneer, which is best from a strict Engineering standpoint? The circle, heart, or some other shape?

 

Ref.-1: "Nib Notes", http://www.nibs.com/NibNotes.html

 

"As experience has shown, there are both better and worse shapes for vent holes. Those with no sharp concave corners are much superior. Ideal is the round hole, but it is not very interesting. The heart-shape is even better. This is where engineering and emotion meet. For not only does it minimize cracking, but people grow very attached to their pens and nibs. What better way to express this affection than a heart?"

 

Thank You, David

That's right, our accounting section had one of those machines... or something similar looking, it had two huge floppy discs, 40 odd centimeters diameter.

 

The breather hole is not a breather hole. Nothing breathes there.

 

Slitting the nib is a tricky business, it used to be and perhaps still is semi automatic and still required a lot of operator skill. Important was, that the slit cut the tip in half, if the slit wandered off a bit does not really matter that much. The hole is there to give the operator a target and a definite point for the slit to end. The length of the slit determines the characteristics of the nib.

 

Stress reduction sounds technical, very sofisticated. Some nibs have no "breather hole" and don't crack. If you see crack lines at the end of the slit, it is for other reasons. We had the problem and it was caused by insufficient cooling during the cutting or having the cutting wheel run idle at the end of the slit. The "breather hole" prevents this problem. It happened only with steel nibs, not gold. If you like more info, I have written about all this on my website.

 

And who says that ingeneers have no feelings? If I were in charge and people want "breather holes" I would certainly give them a heart with the slit coming out of the pointy end. Just because it looks nice and give the feeling touch.

 

So, from a strict Engineering standpoint? Do whatever gets you going, makes you happy. I had so many discussions with the form designers about all other things where a more lenient viewpoint would have made things so much easier and better from a strict Ingeneering standpoint. Did they ever want to do anything with the nib? No! One wonders, one really does.

Edited November 15, 2016 by PenIngeneer

[Drone]

Stress reduction sounds technical, very sofisticated. Some nibs have no "breather hole" and don't crack. If you see crack lines at the end of the slit, it is for other reasons. We had the problem and it was caused by insufficient cooling during the cutting or having the cutting wheel run idle at the end of the slit. The "breather hole" prevents this problem. It happened only with steel nibs, not gold.

 

Go here:

 

http://www.nibs.com/NibNotes.html

 

Scroll down the page and look at the four pictures of different shaped vent holes in gold vintage nibs. Carefully examine the two pictures on the left with the star and crescent shaped vent holes. You can clearly see the stress induced cracking, especially the cracks radiating from the star points. These fatigue cracks are from the gold nib flexing over long periods of use. It typically has nothing to do the manufacturing process, unless there is something seriously wrong with the gold alloy or the way it was processed. I have handled and restored my share of vintage pens, and in my experience finding stress cracks in well used gold nibs is not uncommon.

[Pen Engineer]

 

Go here:

 

http://www.nibs.com/NibNotes.html

 

Scroll down the page and look at the four pictures of different shaped vent holes in gold vintage nibs. Carefully examine the two pictures on the left with the star and crescent shaped vent holes. You can clearly see the stress induced cracking, especially the cracks radiating from the star points. These fatigue cracks are from the gold nib flexing over long periods of use. It typically has nothing to do the manufacturing process, unless there is something seriously wrong with the gold alloy or the way it was processed. I have handled and restored my share of vintage pens, and in my experience finding stress cracks in well used gold nibs is not uncommon.

Bean there... had a look

 

I saw the cracks... if it's not manufacturing then I would see the cause to be stress beyond the capacity of the material, beyond the yield strength of the material. I would say the nib has been misused, or not designed for the intended use.

 

Fatigue, in a mechanical ingeneering sense, standpoint! ... is repeated stressing but remaining below the capacity of the material.

 

The cause for fatigue cracking is the high repetition and the frequency of the stressing, like in a jet turbine, when one of the blades is a bit out. After a thousand flight hours and millions of rotations, fatigue failures can cause the blade to break or a bearing to fail.

 

Fatigue is nothing mystical. I have designed products where components reciprocated 50 times per second. Once the preventative maintenance cycles are determined, hours of operation are known, one can calculate the parameters (and safety factors) so that components will not fail within those cycles.

[Drone]

That's right, our accounting section had one of those machines... or something similar looking, it had two huge floppy discs, 40 odd centimeters diameter.

 

If it was IBM and looked similar but had large removable discs, then there is a good chance the computer in your accounting section was an IBM 1130 system Model 2X or 3X depending on the cycle speed and amount of memory installed. The Model 2315 removable disc cartridges were 15 inches (38 cm) in diameter and stored a total of 2 MB per disc (1,024,000 bytes per side).

 

The IBM 1130 is generally considered to be the first widely available "Mini-Computer". A typical 1130 system with removable disc storage sold in 1965-75 for around $40,000 USD ($40,000 in 1968 is worth $278,000 in 2016).

 

As there were usually removable disc drives in an 1130 system, punched cards would not be used. An IBM 1130 in an accounting department would most likely be programmed in COBOL. The 1130 I had the most experience with was used to control and process data to/from a large radio telescope and was programmed in a mixture of Fortran and Assembler.

 

See here for info and pictures of the IBM 1130 system, including pictures of the Model 2315 removable disc packs.

 

https://en.wikipedia.org/wiki/IBM_1130

Edited November 15, 2016 by Drone

[Pickwick]

Bean there... had a look

 

I saw the cracks... if it's not manufacturing then I would see the cause to be stress beyond the capacity of the material, beyond the yield strength of the material. I would say the nib has been misused, or not designed for the intended use.

 

Fatigue, in a mechanical ingeneering sense, standpoint! ... is repeated stressing but remaining below the capacity of the material.

 

The cause for fatigue cracking is the high repetition and the frequency of the stressing, like in a jet turbine, when one of the blades is a bit out. After a thousand flight hours and millions of rotations, fatigue failures can cause the blade to break or a bearing to fail.

 

Fatigue is nothing mystical. I have designed products where components reciprocated 50 times per second. Once the preventative maintenance cycles are determined, hours of operation are known, one can calculate the parameters (and safety factors) so that components will not fail within those cycles.

 

"No Highway", a novel by Nevil Shute is worth reading. It uncannily predicted what happened to the very first jet airliner, the De Havilland Comet which crashed, and investigations revealed it was metal fatigue in the fuselage was the cause.

[Drone]

"No Highway", a novel by Nevil Shute is worth reading. It uncannily predicted what happened to the very first jet airliner, the De Havilland Comet which crashed, and investigations revealed it was metal fatigue in the fuselage was the cause.

 

The fatigue cracking that led to the Comet crashes started at the corners of the large square windows cut out of the fuselage. This was bad design. In the late 1940's when the Comet was on the drawing board, it was already well known that squared corners were dangerous pinning sites for stress fractures. For example, Waterman stopped using keyhole shaped nib vent holes back in the 1930's when they found them cracking at the squared corners. The Comet's window cut-outs should have been oval shaped, not square.

Edited November 15, 2016 by Drone

[Pickwick]

 

The fatigue cracking that led to the Comet crashes started at the corners of the large square windows cut out of the fuselage. This was bad design. In the late 1940's when the Comet was on the drawing board, it was already well known that squared corners were dangerous pinning sites for stress fractures. For example, Waterman stopped using keyhole shaped nib vent holes back in the 1930's when they found them cracking at the squared corners. The Comet's window cut-outs should have been oval shaped, not square.

 

This is still an ongoing problem in other areas of any aircraft undergoing air pressure changes and other stresses, and during routine maintenance certain structural parts need to be especially checked for signs of cracking.

 

I notice some FPN members show photos of flexible nibs on the fountain pens they own spreading the tines far beyond acceptable limits. If this is kept up on an overextended time, it's inevitable that they will fail.

[istvang]

This can actually be a nice book.

[Pen Engineer]

And since we are in aircrafts, now... I know I am not allowed to do this, however, I have written a very long article on why Aeroplanes can't fly. don't tell anyone.

 

 

I agree with Pickwick. Flexible nibs require good skills from the writer. They can be bent beyond the yield strength. Just had an idea: "What about adding a movement limiter onto a flexible nib, to prevent overbending?"

[Pickwick]

And since we are in aircrafts, now... I know I am not allowed to do this, however, I have written a very long article on why Aeroplanes can't fly. don't tell anyone.

 

 

I agree with Pickwick. Flexible nibs require good skills from the writer. They can be bent beyond the yield strength. Just had an idea: "What about adding a movement limiter onto a flexible nib, to prevent overbending?"

 

An interesting concept. Do you think you might come up with a solution?

[Pen Engineer]

 

An interesting concept. Do you think you might come up with a solution?

what are you referring to?

 

If I can make aeroplanes fly? Don't think so.

 

the bent limiter? sure. It could be like a double decker, where the lower, soft wing can flap but the upper is strong enough to limit the range. Just one shorter hard nib on top of another, soft one. I wish I still could draw the way I could...