21 December 2015

Astra Piston

(Note added on January 8th: This text has been amended on this date to correct some inaccuracies and eliminate some uncertain data.)

… or how to make a piston with little hassle.

… or the evolutionary ancestors of Conid’s Bulkfiller.

For many, the piston filler, so dear to German makers, is the filling system of choice, however, it does not come without disadvantages, the most clear being the large space needed to harbor the piston mechanism inside the barrel. All that space, needless to say, is dead space in terms of ink capacity. To minimize this problem several technical solutions have been suggested. The better known of which is the telescopic piston. A more modern strategy is that of Conid for its Bulkfiller model: a piston whose plunger rod is decoupled from the seal and is stored inside the ink deposit once the filling process had been completed.

Maker Astra tried a similar –but not equal— approach in the early 1940s: the plunger that moves the piston seal up and down in the barrel can be unscrewed from it and removed altogether from the pen. And, in fact, it MUST be removed once the pen was filled up and, therefore, the cork seal was at the top of the ink deposit.

The disadvantage of this system is clear: there is the need to keep the plunger rod stored while the pen is in use. Without it, filling the pen is not possible. But there are advantages too:

If compared to a standard piston, this system clearly takes a lot less space in the barrel and the ink deposit is a lot bigger.

The closing piece of the barrel has this particular shape to keep the piston seal from rotating and allowing the rod to be unscrewed.

If compared to the Bulkfiller by Conid, the metal rod is not in contact at all with the ink, and there is not need to create any seal between the rod and the seal itself. In the Bulkfiller, the rod literally moves across the piston seal, and there can be leaks through seal along the rod.

The engraving on the nib reads "DURFLEX / FPT / 4 / EXTRA".

As for the rest of the pen, the Astra is made of ebonite (section) and celluloid (barrel), and implements a steel nib. The dimensions of the pen are as follows:

Length closed: 124 mm
Length open: 116 mm
Length posted: 151 mm
Diameter: 12 mm (barrel)
Weight (dry): 15.5 g
Ink deposit: 2.5 ml.

No filling system is perfect, and this “detachable plunger” is no exception, but there are great advantages to it. The large ink capacity is indeed a powerful argument on its side.

It is not clear where this Astra pen was made. The inscription on the nib suggest an Italian origin. As an anonymous commentator pointed out, Durflex was the brand of the Pecco brothers, and FPT meant "Fratelli Pecco Torino". The owner of the pen bought it at a flea market in Warsaw, and a selling argument was that Polish soldiers used this pen during the Second World War and kept the detachable rod in their breast pocket. Probably an exaggerated claim... Any information on the origin of the brand Astra would be gladly appreciated.

Very special thanks to KDENA.

Inoxcrom Corinthian – Sailor Yama-dori

Bruno Taut
Madrid, December 19th, 2015. Nakano, January 8th, 2016.
etiquetas: Astra, Conid, soluciones técnicas


Anonymous said...

Interesting pen!
Is it really polish? the nib seems to be italian.
Durflex, used on Pecco's production. FPT stands for " Fratelli Pecco Torino"...Pecco brothers Turin.
May not be the original nib.

Unknown said...

But burping is always a problem on high capacity fillers when the ink is getting low. The beauty of the CONID is that the writer can avoid it by regularing the safety valve. And thanks to its clever design using O-rings, ink would never get behind the piston even though the rod is moving up and down through it.

Thanks for sharing this interesting filler. Great post.

Bruno Taut said...


Strictly speaking I cannot say it wa smade in Poland. It was bought in Warsaw with the, perhaps optimistic, claim that that was the pen used by Polish soldiers during the war.

Thanks for your notes--you have a very powerful point. Perhaps the nib is not original, perhapes the pen is just Italiam. Thanks.

And thanks again for passing by an dcommenting.

Tony Rex,

Blurping can be minimized and even avoided by a careful design of the neck connecting the feed and the deposit. Some eyedropper pens manage to do that.

I have no doubt the Conid pen works well, but it ceratinly has several potential weak spots and they need to be carefully analyzed in search for effective and durable solutions.

Thanks for passing by and commenting.


Pedro Haddock said...

A unique system all new to me. Quite intriguing why it did not came along in some other models. Thanks a lot for sharing.

rfueris said...

I presume that this kind of pen had a lot of "orphan rods" forgotten all over the world!
Been detachable of his body turned the plungers into expendable items. Maybe this is the reason because this system didn't succeeded.

Best regards, and congratulations for your work -and sorry for my english-.

Saltire Turquoise said...

Excellent article. All the best for 2016.

If you happen to see any of the innovative nib makers, modifiers and mechanics, could you ask them if they have any new projects they'd like to share with us?

Bruno Taut said...

Gracias, Pedro y rfueris, por la visita y por los comentarios.

El argumento de rfueris me parece muy plausible: una varilla alejada de la pluma es muy dada a perderse o quedarse olvidada en algún cajón oscuro. No obstante, es este un sistema que merece más oportunidades.

Como ve, rfueris, siempre nos queda otro idioma en el que hablar. No se sienta obligado a escrinbir en inglés. Los comentarios son siempre bien recibidos, en inglés, castellano o swahili.

Thanks, Saltire Turquoise, for your comment and for your best wishes for 2016. I also wish all of you readers the best for this new year.

Re projects for the new year in the hands of pen makers and nibmeisters, I am all for hearing them, and on these pages I simply write what I see and hear.

Than you all for your comments. They are always welcome.


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