No flow on Up Stroke

[Bristol24]

Hi all;

 

I'm working on a recently acquired 1938 Parker Parkette Deluxe with a nice somewhat flexible stainless steel nib.  I have the pen 90% "there" but have one small issue.  The nib delivers a nice, somewhat wet flow with just the lightest pressure except on the up-stroke.  If an up-stoke follows a down-stroke then there is flow but even then, it appears to be residual from ink already on the tip.  If I press down a bit on an up-stroke, then there is flow of ink.  This is not a serious issue as the pen writes quite nicely but it does go quite light of line if a line begins on the up-stroke.  I'm almost of the opinion that the tines are touching and are less likely to spread a little on an up-stroke but are inclined to separate on an upward or sideways stroke.  Could it be that I need to separate the tines slightly?  Any input from your experiences would be appreciated.

 

Cliff

[dipper]

Below is my first guess .....

 

There are two forces acting on the nib tip when writing that affect the flexing of the nib tines. The first force is a reaction force that acts perpendicular to the paper surface - and always acts upwards on the nib tip - causing the tines to flex upwards.

The second force is the friction force that acts parallel to the paper surface - and always acts in the opposite direction to the direction of movement of the pen over the paper. Usually that friction force is so small that we don't think about its effect on nib tine bending.

 

Though I have never considered this before now, it is theoretically possible that on an upstroke those two forces could sum to give a nett force directed along the axis of the pen (so zero flexing) or even directed such that the tines flex downwards. That would be an extreme worst case scenario, with the pen axis held at an unnaturally high angle, and a high friction coefficient at the nib tip to paper sliding contact.

The result could be that the tines actually flex downwards on an upstroke, closing the tine slit gap and also closing the small space between underside of the nib and the top face of the feed. Either effect would reduce ink flow to the nib tip.

 

I was about to sketch a force vector diagram to justify this unexpected crazy idea... but  have now thought of a more practical demonstration - something familiar to users of pointed dip pens:

If a sharp pointed dip pen is used to make an upstroke, held pointing forward in the direction of movement - like a farmer's plough, then the tip can dig into the paper. Result is a sudden massive increase in the force opposing sliding movement - the tines close tighter together and plunge deeper into the paper, flexing "the wrong way", before tearing free, springing upwards again, and spattering ink over the upper area of the page!

 

Does my guess explain why this Parker pen writes dry on upstokes? Only close observation of the pen in action could answer that. A good loupe and a bright light source helps with that.

A comparison using smooth glossy low-friction paper could be tried.

 

But how to adjust feed or nib to cure the problem? That depends on the existing form of the tines slit taper, and the existing gap between nib and feed tip.

My "idea" is only a possible explanation of how the effect is occuring. Always good to have an explanation.

However, by itself, and assuming test do confirm that my idea is in fact what is happening, the idea does not tell us what is the most appropriate adjustment to prevent the dry upstroke effect.

[MidSouthern-Dad]

Look at the point with a loupe.  There should be a tiny gap at the point between the tines.  Ink will flow by capillary action to the point.  Flex nibs should just touch at the point, but without undue pressure.  You can lift up one tine with a fingernail to see how much force is required to get the point to open up.  If the tines are tightly pressed against each other, then gradually lift up the tine on each side until the desired gap or closing force is achieved.   If the nib point is now lifted up from the feed by a few millimeters, heat set the feed when nib adjustment is done.

[Bristol24]

3 hours ago, dipper said:

Below is my first guess .....

Wow!  As guesses go that is a virtual thesis.  Thank you.  I believe you may be on to something.  What you theorize is essentially what I sense is happening.  The tines indeed close up.  I will investigate this further tomorrow.  Thanks!

 

Cliff

[Bristol24]

12 minutes ago, MidSouthern-Dad said:

Look at the point with a loupe.  There should be a tiny gap at the point between the tines.  Ink will flow by capillary action to the point.  Flex nibs should just touch at the point, but without undue pressure.  You can lift up one tine with a fingernail to see how much force is required to get the point to open up.  If the tines are tightly pressed against each other, then gradually lift up the tine on each side until the desired gap or closing force is achieved.   If the nib point is now lifted up from the feed by a few millimeters, heat set the feed when nib adjustment is done.

This goes along with what dipper suggested.  At rest the times are touching.  I checked.  Thank you for the input.

 

Cliff

[Bristol24]

20 hours ago, dipper said:

it is theoretically possible that on an upstroke those two forces could sum to give a nett force directed along the axis of the pen (so zero flexing) or even directed such that the tines flex downwards.

This has been confirmed.  Because the tines were actually touching at rest, any upward stroke worked to keep them closed even more tightly, hence no flow.

 

17 hours ago, MidSouthern-Dad said:

heat set the feed when nib adjustment is done

Actually, in looking at the nib and feed from the side with the pen held level, it was evident the nib was actually angled downward slightly.  Also, the tines were touching in this condition.  I assume this is because, after 84 years of the nib pressing downward on the feed, the feed had given way.  I merely heated the nib and feed in near boiling water and applied pressure enough to move the nib and feed back into the axis of the pen's barrel, then moved quickly to hold it under the faucet to cool it down.  I re-inked the pen and it now writes like a dream.  There is flow on the upstroke and, because the nib is flexible, the upstroke flow and line width is less than the down-stroke but that is what makes for line variation and shading.  Thank you both for your input.  This was certainly worth posting and seeking advice!

 

Best regards,

 

Cliff

[MidSouthern-Dad]

Glad it worked out.  If your pen seems little used, it may have been set incorrectly at the factory.  It still happens today.

I picked up a “final drop” Pilot Vanishing Point 14k gold 1 mm italic nib from Goulet Pens for around $60.   It wrote very dry and skipped.   Looking under magnification, and after adjusting the tines and heat setting the nib- it now writes “like a dream “!