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A capless pen: From the prototype to the finished pen...



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A year ago I "accidentally" transformed a pen I failed to finish into a prototype (kind of capless bulkfiller).

This pen had several issues like an uneven finish, flow issues, ink burping when retracting the nib, no clip, bad ebonite quality:  not the ideal workhorse.

Here is the journey to this prototype improvement...

 

Overal view of the 3 versions:

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All the pens have both an inkview and a view on the capless mechanism, an ebonite feed, and hold a large amount of ink.

V1 has a flexible size 2 eversharp gold nib, V2 an V3 have a cursive italic nib ground from an  Pelikan M100 B nib.

V3 has a stronger clip and a matching ebonite insert. 

V3 is made of german ebonite which seems to oxidize much less than V2 made of japanese ebonite.

 

Evolution of  the "capless" mechanism:

For those pens the nib unit is activated by rotating the pen grip section.

1985455512_Variousevolutions.png.84b0063d4f3789ef96c5e21a4ffedcc8.png

In V1 the nib unit screw (the "elevator screw") is directly set into the back of the ebonite feed which caused the feed channels to be deformed thus  preventing the  air to flow back to the  barrel which caused bad flow issues.

V1 "guts" are made of bronze and ebonite, V2 and V3 are made of stainless steel.

The V3 nib unit fixed this issue with the nib housing (green) friction fit and epoxy glued into the nib screw. A crescent hole into the nib screw allows ink to flow into the nib feed.

The V3 has also a modified screw shape which better regulates ink flow allowing the nib not to be too wet.

An issue from V2 feed was that when the nib was retracted the breather hole burped ink onto my fingers. This was corrected in V3 adding a second breather hole "the burping hole" (blue arrow) which is hidden behind the end of the grip section: the pen still burps ink when the nib is retracted... but inside the section preventing ink stains.

 

Evolution of the pen cap:

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V1 has the trap-cap mechanism directly inserted into the ebonite of the barrel with very fragile and sensitive to wear holes.

V2 has a stainless ring which supports the trap-cap mechanism, the main issue with this design was ink drying in the nib after 2 to 3 days without using the pen holding the nib upwards.

V3 fixed this issue inserting a friction fit bronze insert into the stainless steel ring, thus reducing the opening of the pen, preventing air to penetrate finally preventing the nib to dry.

 

Evolution of the barrel back end screw:

535117910_Backends.png.ed63dbe542ca37d34fc3e900129c32b2.png

The back on the barrel is closed by a double sided screw with a hole in it allowing the piston rod to glide.

In V1 this screw was made of ebonite which allowed free gliding but was not sufficient enough to precisely guide the piston rod the right way...

In V2 it was made of stainless steel with problems of piston rod gliding.

This was solved using a bronze insert into this double sided screw.

 

Exploded view and plans of V3:

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And here it is with its 30 parts and countless milling/turning operations!

 

Only one problem remains: the trap-cap is passively activated by the nib itself and goes back to its closing position with a spring blade. Had no problems with this but it appears to be fragile and... ulgly!

Any ideas on how to fix this?

 

Thanks and enjoy FPN back again!

 

 

 

 

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  • Hardy08

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Wow! What a great project, you have amazing skills!

“The proper definition of a man is an animal that writes letters.”


Lewis Carroll


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I loved V1 when you showed it -- and now the later versions are even more spectacular.  Thank you for sharing these, and especially for all the details about problems and solutions in the design! 

You have a different solution to the clip-vs-grip problem that other capless pens have only partially solved, but i wonder about carrying that pen with so much of it sticking out above the edge of one's pocket.  Is that working well for you?

Is there any sort of soft gasket material at the trap-cap closure? 

I'm vaguely imagining the trap-cap actuated by a pin or  nub on the nib unit or feed.  When the nib is retracted, it would press on an extension of the trap-cap hinged arm to hold it in the closed position.  Possible? 

 

Thank you again! 

 

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Hi OCArt!

Thank you for encouraging this project!

 

@BrassRatt, thank you again for supporting this project, using a device to both lift the cap and close it seems a very good idea, unfortunately the only place I could attach it is onto the nib feed which is quite fragile, for this I need to modify the feed itself adding a piece of metal inlay in it. I will try to do so, this would take a couple of months but is worth the try! Thank you!

16073320994244644834701354357968.jpg

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That's a bit more elaborate than what I had thought of, with a link connecting the feed-inlay to the cap.  It does eliminate the external spring of the trap-cap. Very positive locating the cap both in open and closed conditions.  Hope the feed inlay doesn't occupy too much of the collecting fins volume.  Bravo! 

 

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OK.  Most unusual!  

How many turns to extend or retract the nib?  That elevator screw has 3+ turns, but the engagement rods cost some axial spacing I guess ... Thanks!  

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Great work. I have two things to suggest.

  1. Consider using conical nibs so that the metal bottom of the nib can push against the cap. You can get them from China if you don't mind fine widths.
  2. Why not have the cap be something you flip open with the thumb before turning to extend the nib?
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@basterma do you mean by conical nib nibs like Sheaffer triumph nibs?

The solution with a "flip-opened-cap" seems good, but I would prefer to have a single action which combines nib extension and cap opening...

 

Thank you for your suggestions!

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Yes. I meant conical nibs like the Triumph nibs, or the nibs for Parker 51 clones. There may be enough metal on the non-nib part to strike the door instead of the feed. 

You could also look at some sort of a clutch mechanism like that used in thick lead pencils made by Staedtler. Like the Mars Technico

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  • 2 weeks later...
GeoffMartin

Really nice work!

 

But, more importantly, thank you for adding a the term "burping hole" to my daily vocabulary.

 

Cheers

-geoff

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BrassRatt

That linkage is a trip -- especially in the way it brings the cap up under the nib to allow low-angle writing.  Wow! 

 

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magna carta

My friend it is beautiful concept. i can imagine how much time and effort you spend on it. 

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