Optimising A Le Rötring 1928

[fountainbel]

Hi all,

 

Just acquired a brand new boxed Rötring 1928 , a limited edition made at the occasion of Rötring's 70 years existence in 1928 pieces in 1998.

 

Extremely beautiful and large blue marbled celluloid pen, however the plunger filling system proved to be a very poor design.

 

The filling system is very similar to the Visconti plunger filler, and some knowledgeable people even claim the pen was completely made by Visconti;

 

Given the size of the pen (barrel diameter 15mm, cap diameter 17mm , capped length 149mm) one would expect the filling system would be able to take in a huge amountof ink.

 

Astonishly the filling system only allowed a 0.52ml ink intake ( medium value of 10 fillings)

 

After disassembling and measuring I found the barrel bore is only 5.8mm, while the filling stroke is 38mm.

 

The potential ink intake being 0.87 ml using these figures, the filling system was clearly not efficient.

 

Approximately a year ago Ihad already optimized this filling system for FPN member Inka, who posted on this repair earlier, see :

 

https://www.fountainpennetwork.com/forum/index.php?/topic/138580-repairingmaking-of-the-rotringgoossens-limited-edition-uber-vac/page__p__1373199__hl__%2Brotring+%2B1928__fromsearch__1&do=findComment&comment=1373199

 

I knew from this earlier experience the filling efficiency was lowered by the "permanent set" of the telfon piston cup seal.

 

Contrary to a rubber cup seal( as actually used by Visconti) a Teflon cup seal is not flexible enough to ensure the necessary sealing pretension in the barrel over time.

 

While the cup seal was most probably made having an external sealing lip diameter of 6.0mm - having 0.2 mm radial pretension in the 5.8mm barrel bore - the seal lips will gradually "set permanently" to the 5.8mm barrel bore, hence loosing their sealing efficiency.

 

So I decided to introduce my proven "shifting O ring" plunger seal , used on my own Fountainbel plungerfillers and also used on the Rötring 1928 pen from FPN member Inka.

 

This system features a floating/shifting O ring on a conical seat.

 

When pulling the plunger rodout, the O ring- having some radial pretension in the barrel bore- shifts to the smaller diameter of the cone , allowing the ink to flow back underneath theO ring.

 

When pushing the plunger in,the O ring - having some radial pretension in the barrel bore shifts directly to the larger diameter of the seat cone, ensuring a perfect vacuum seal

 

In fact the floating/shifting O ring works as a check valve.

 

Doing so I obtained a filling of 0.75ml, or a filling efficiency of 86 %

 

Not bad, but I was still frustrated by the low potential ink intake -inherent to the pen design- of such a huge pen.

 

After examining the pen further, I concluded I could easily enlarge the barrel bore from 5.8mm to 6.9mm, while I could also enlarge the filling stroke from 38 to 45mm

 

Doing so the potential inkintake would increase from 0.87ml to 1.58ml, which looks to me -given the size of the pen- an acceptable figure for such a huge pen

 

I took also this step and obtained an effective ink intake of 1.4ml ( medium value of 10 fillings)

 

In fact only the barrel bore was adapted, and a new HR back-up ring was shellacked in the rod seal chamber..

 

On the attached sketch youcan see the changes I've made.

 

 

Best regards, Francis

 

http://i62.photobuck...ring1928004.jpg

http://i62.photobuck...ring1928003.jpg

 

 

 

Edited August 30, 2011 by fountainbel

[mana]

Wow, nice! Do you do commission work? If I ever get one I will be sure to send it your way...

[yus2001fr]

Really amazing job as usual ! :clap1:

[fountainbel]

Hi Mana,

Thanks for your comments mana and yus 2001fr !

And yes,mana if you ever buy one of these beauties, I can improve the poor filling system for you!

Francis

 

 

 

<br />Wow, nice! <img src='https://www.fountainpennetwork.com/forum/public/style_emoticons/default/smile.gif' class='bbc_emoticon' alt='' /> Do you do commission work? If I ever get one I will be sure to send it your way... <img src='https://www.fountainpennetwork.com/forum/public/style_emoticons/default/wink.gif' class='bbc_emoticon' alt='' /><br />

<br /><br /><br />

[stevlight]

I am continually in awe of your engineering and fabrication skills.

[markiv]

Fascinating work as expected from Francis.

Hmmm.. now I am wondering if the Homo Sapiens can go under your knife?

[fountainbel]

Hi Markiv,

Thanks for your nice comment!

As for the HS, do you mean the beautiful Homo Sapiens is sick in the same bed??

Thanks, Francis

 

Fascinating work as expected from Francis.

Hmmm.. now I am wondering if the Homo Sapiens can go under your knife?