Hacking The Kaweco Cartridge Interface

[James]

I really like Kaweco Liliput pocket pens – they are simple, robust and beautifully machined fountain pens. However, the Liliput’s small size mandates that ink cartridges need to used instead of a cartridge converter. I became frustrated with what I perceived as ink starvation when writing for extended periods of time with the pen, so I decided to look into this phenomenon in more detail.

 

The picture below shows a cross-section view of the interface between the ink cartridge and the Kaweco (Bock) 060 nib. This 060 nib is used on all Kaweco fountain pens, except the Elite and Supra models. It shows that the plastic ball that originally sealed the ink cartridge sits nicely on top of the feed tube when the pen is orientated upright – which is the opposite of what’s desirable from an ink flow perspective.

 

 

The feed tube length for the Kaweco (Bock) 250 nib (used on the Elite and Supra pens) extends about twice as far into the ink cartridge, so the mechanism for the plastic ball to obstruct the feed tube is largely mitigated for this design.

 

My solution to this perceived problem is to prevent the plastic ball from being pushed into the cartridge. I use crimp pliers (i.e. smooth jaws) to squeeze the cartridge and eject the plastic ball from a new ink cartridge. Its a bit messy, but only needs to done when a replacement cartridge is required. I empty the cartridge and dry it out – then fill it with my favorite (Monblanc permanent blue) ink using a 0.2ml disposable transfer pipette. A photo of a (truly) empty ink cartridge and pipette is shown below. The 0.2ml pipette is small enough to be inserted into the ink cartridge, and represents a very compact and inexpensive approach to fill cartridges. I reuse the pipettes numerous times, so I have a lifetime supply from the minimum quantity of 200 that I bought from Amazon for about $20.

 

 

If you find that you’ve experienced similar ink flow problems with your Kaweco cartridge pens, you may wish to consider the above approach to hacking the Kaweco cartridge interface.

 

[TheDutchGuy]

Wow. That's very informative and very helpful, thanks! I'm going to try this right away.

[Bo Bo Olson]

Tip the pen, the ball rolls away...if the pen is tilted for real use, the ball can not block like vertical.....my WAG.

The ball is an improvement over no ball and vapor lock.

Could cut a bit from a ball point spring and put that in after you take the ball out.

 

I'm more a piston head.....but do have some C/C pens, and bought some Kaweco cartridges to test their ink, before buying a bottle and I've not had problem with a plastic ball in Kaweco nor in Pelikan cartridges.

Edited January 5, 2019 by Bo Bo Olson

[James]

It is very possible that the cartridge ball is not responsible for ink starvation, and the real culprit is a temperamental nib and my preference for extra fine width. I've found the performance of the Kaweco 060 nibs to be quite variable out-of-the-box.

 

I haven't experienced vapor lock problems with Montblanc permanent blue ink, but I like the solution of adding a spring if vapor lock was a problem.

[LizEF]

I tested several ballpoint springs by letting them sit in water for a couple days - every one of them rusted. I concluded that gold keyboard springs were the only solution (as others here have suggested), but I don't have enough of a problem to overcome my reluctance to open an account at yet another store. If I could buy them on Amazon, I'd probably have a bag of them.

[Bo Bo Olson]

LisEF.....is right, though some have said, their steel BP nibs didn't rust that fast......are there 'stainless' steel springs for Ball points?..............would a Jotter spring be better than dime a dozen?

 

That is gold plated springs, and where one cuts is no longer gold plated. Humm. (I suffer from UC........universal cheapness. The price of Stamps is thought provoking. Wonder what would do in a big hardware store....do go to one of them a couple times a year...........There is a difference between thrifty and cheap.............but I'm too cheap to see a shrink about it.)

 

There I was sitting back all snug....having a couple cartridges with a plastic ball, so I could cut them open and put them in a converter.

Being a Piston Head, seldom use my converter fitted pens.