Got to messing about with my two black Parker 21s (Mk II and Super) for a friend of mine to try out -- seems he's in the auto collision repair business now and needs water resistant ink, so I suggested Noodler's black.
Anyway, I noticed that the super filled up to about 1/4" from the end of the sac (both have clear sacs, a wonder!) but the Mk II didn't seem to have much more than 1/4" of ink in it.
Finally gave up and removed the hood and nib, and sure enough, the breather tube was adrift. Seems to be either much shorter than the Super 21's or someone has put a longer tube in the Super at some time in the past. I pushed it back into the feed and re-assembled the pen, so it will fill better.
Can I safely lenghten the tube, or should I leave it a factory size and put up with a smaller ink fill? More ink would be nice, but not a the cost of ruined clothes if it overwhelms the aerometric system a burbs out.
Thanks!
Peter
Full Version: Breather tube length on Parker 21
You will likely want to wait for a more expert opinion, but from my back room tinkerer perspective, I can't see how a correctly fitting but longer tube could hurt, and would surely better fill the sac. Remember to drill/burn/poke the Aero-style bleeder hole in the section end of the breather tube while you're in there! 
The breather tube should be relatively short. A squeeze-filling pen with a breather tube will take up enough ink to cover the distal end of the breather tube plus one suck more.
A true aerometric pen (e.g., the "51" Mark I) has a breather tube that extends to just short of the distal end of the sac. This gives a very complete fill, and the lateral hole in the breather tube allows the pen to expel air when you carry it capped, nib upward, in a climbing aircraft. Were the lateral hole not present, the pressure differential would force ink up the breather tube, and the pen would spew that ink into the cap and thence, when you uncapped the pen, onto you or your clothes, or both. Messy, messy.
But the "21", like the "51" Special, is not a true aerometric pen; it lacks a lateral hole in its breather tube. Parker's patented filler design for these pens features a breather tube that is short enough that with a full fill (as much as the pen will take in, as described above), the distal end of the breather tube is not immersed in ink when the pen is held with the nib upward. This allow these pens to expel air. With a longer breather tube, they will take in more ink, the breather tube will be immersed, and the pens will hork up ink instead of air. Don't go there.
A true aerometric pen (e.g., the "51" Mark I) has a breather tube that extends to just short of the distal end of the sac. This gives a very complete fill, and the lateral hole in the breather tube allows the pen to expel air when you carry it capped, nib upward, in a climbing aircraft. Were the lateral hole not present, the pressure differential would force ink up the breather tube, and the pen would spew that ink into the cap and thence, when you uncapped the pen, onto you or your clothes, or both. Messy, messy.
But the "21", like the "51" Special, is not a true aerometric pen; it lacks a lateral hole in its breather tube. Parker's patented filler design for these pens features a breather tube that is short enough that with a full fill (as much as the pen will take in, as described above), the distal end of the breather tube is not immersed in ink when the pen is held with the nib upward. This allow these pens to expel air. With a longer breather tube, they will take in more ink, the breather tube will be immersed, and the pens will hork up ink instead of air. Don't go there.
Thank you Richard, that's what I suspected.
I put the original tube back in on that assumption. I was just curious because the 21 Super I got at the same time has a much longer breather tube, and is therefore either a true aerometric or is going to burp ink on me because someone put a longer tube in.
There is quite a bit of difference in the amount of ink -- the super holds much more.
Peter
I put the original tube back in on that assumption. I was just curious because the 21 Super I got at the same time has a much longer breather tube, and is therefore either a true aerometric or is going to burp ink on me because someone put a longer tube in.
There is quite a bit of difference in the amount of ink -- the super holds much more.
Peter
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