Parameterizing Flex Nibs

[Guest Denis Richard]

Antonios, it seems to me that you could easily derive for a given geometry and alloy, at which writing speed the transition between the first and second regime occurs. right ?

[antoniosz]

Antonios, it seems to me that you could easily derive for a given geometry and alloy, at which writing speed the transition between the first and second regime occurs. right ?

Yes. For inertia to take over the release time should be of the order of a milisecond. (k=100 gram-f/mm, m=10 grams).

I am not sure yet if our release times are so fast. We need some experiments

[Guest Denis Richard]

Got a high speed video camera ?

[Stylo]

Just to get bring back into this thread our non techie friends: someone mentioned in this thread or elsewhere that one of the concerns with a "slow return" flex nib was that certain caligraphy styles that use sharp transitions from thick to thin lines produce letters with a smeared look with such nibs. But I wonder how much of that is due to the flexing mechanics of the nib and how much of it is due to what happens to the ink when the nib flexes back into its original position. I can easily imagine how the tines coming back together could momentarily increase ink flow substantially, resulting in these "smeared" thick/thin transitions.

 

[edited for typos]

Edited March 25, 2005 by Stylo

[Guest Denis Richard]

Interesting sugegstion Stylo... see ? we're getting at hydro after all....

[antoniosz]

Just to get bring back into this thread our non techie friends: someone mentioned in this thread or elsewhere that one of the concerns with a "slow return" flex nib was that certain caligraphy styles that use sharp transitions from thick to thin lines produce letters with a smeared look with such nibs.  But I wonder how much of that is due to the flexing mechanics of the nib and how much of it is due to what happens to the ink when the nib flexes back into its original position.  I can easily imagine how the tines coming back together could momentarily increase ink flow substantially, resulting in these "smeared" thick/thin transitions.

 

In my first post about this (item 5a), I was saying this problem may depend on "how well the feed and the nib "cooperate". I.e., although we need a generous feed to coop with the high ink requirements when flexing, the feed should not flood the nib during thick-to-thin returns."

 

So it is your turn to analyse the basics of the feed. I would mostly rely on intuition rather than knowledge in that area. What feed design characteristics would make the return of the nib to be able to push the ink "up" the feed. Would the ink play any role?

 

Yes I conceed some problems need fluid mechanics So the ball is in your court Stylo Dust off that supercomputer account... or pick up your favorite FP to jot down some equations....

 

AZ

[Stylo]

In my first post about this (item 5a), I was saying this problem may depend on "how well the feed and the nib "cooperate". I.e., although we need a generous feed to coop with the high ink requirements when flexing, the feed should not flood the nib during thick-to-thin returns."

 

Thanks to the discussions that followed it, I have re-read your post with an increased level of appreciation and unerstanding.

 

So it is your turn to analyse the basics of the feed.  I would mostly rely on intuition rather than knowledge in that area.  What feed design characteristics would make the return of the nib to be able to push the ink "up" the feed.  Would the ink play any role?

 

I took your suggestion to rely on intuition, and to pick up my M200, not to write down equations, but to flex its nib and observe what happens. After thinking about it a little, my first guess is that it is rather unlikely that the nib could push the ink back up the feed fast enough in relation to the speed at which the tines rejoin each other. So then what happens to the excess ink that is present when the tines are apart? Well, pressing and releasing my M200 nib, I can immediately see a small ball of ink form under the nib, right above the ball of the tip. So my first guess is that the geometry at the back of the tip has to have a small indentation or protrusion of some sort to hold the excess ink there with the help of surface tension. In the case of the typical pen, that indentation is provided by the "irridium" ball tip. What do you folks think?

 

Yes I conceed some problems need fluid mechanics   So the ball is in your court Stylo 

 

But here is the catch. While a lot of my coursework was indeed in computational fluid mechanics, I strayed during my doctoral research into the field of time domain computational electromagnetics, and I have been working in that area ever since graduating (I am not counting my small coding/numerical algorithm contributions to my CFD coworkers). So guess in whose court the ball really is: Denis' !!! :bunny1:

 

(Edited to remove duplicate quotes)

Edited March 25, 2005 by Stylo

[Guest Denis Richard]

I can take a look, but I'm really more of an unbounded flow / turbulence modelling / cosmochemistry kind of guy.

[antoniosz]

I do not know Denis, now that Stylo put you on the spot you brought the whole FPN down for ... maintenance. Coincidence?

[wimg]

Hi Antonios,

 

I do not know Denis, now that Stylo put you on the spot you brought the whole FPN down for ... maintenance. Coincidence?

Obviously not . Just that Denis seems to think we suffer from a very short term memory .

 

Kind regards, Wim