M800 ink capacity

[HDoug]

  southpaw said:

Might I suggest an alternative method to measuring the capacity and comment on another.

 

First, Blorgy's weight gain is an excellent idea provided you know the density of the ink. Knowing that ink is mostly water gives us a rough approximation, but only rough. If the density is 1, then it's 1.6 ml capacity; if 0.9, then 1.8 ml, and if 1.1, then 1.5. There's a little bit of variability there.

 

A better method - and the one which IIRC some of the pen companies themselves used - is to put water in a graduated cylinder, measure it, fill the pen, and measure what's left. The difference is the capacity of the pen.

 

Just my $0.01.

Not to be contentious, but Blorgy filled the pen with water, so the weight gain translates quite easily to volume. And the problem I detect from the "measure what's left" method, is that some of the liquid will be absorbed by the external feed/comb which is then "swaddled" off the nib. At any rate, that fluid should not be included in the calculation of the reservoir capacity.

 

But maybe it's not that big a deal. Even with the disagreement here on the method, we've established that Pel pistons hold a lot more than carts. Love my Pels!

 

Doug

[*david*]

For the weight method, just use water, whose density is 1 anyway.

 

Or, you could just use the pen, or else sell it to me.

[chemgeek]

The density of FP ink should be insignificantly different from that of water. Just for kicks, I measured the density of PR American Blue using a micropipettor and an analytical balance, and my sample is 1.02 g/mL. Close enough to 1 g/mL for government work! (And I know, I have worked for the government on occasion!)

 

Hey, I'm not the chemgeek for nothing!

 

Cheers.

[adallak]

  Blorgy said:

I measured the ink capacity by weighing the pen before and after filling with water. The weight gain was 1.62 grams.

That's the way doctors measure how much milk a baby got from the breast-feeding mom.

[adallak]

  fjf said:

Apparently, if you fill the whole barrel with ink, you'll also have a big bubble of air sooner or later, when you start emptying it. And air dilates with your hands heat, leading to a pen that leaks drops of ink when warm. One way to avoid this is to limit the volume of the ink chamber. Other would be using a heat-isolating material in the barrel. The big japanese eyedroppers are hard rubber (isolating) and use a shutoff valve. Pelikan uses small chambers in their pistons.

Okay, let me see. The expansion coefficient for air is 0.00343 at 20C and 0.00320 at 40C . It is probably 0.00330 at 30C. Let assume the room temperarure is 22C and the one of your body is 37C. That will make 15C difference. Let's take that 0.00330 coefficient and multiply by 15 to get the relative increase those 15 degrees would make. That is deltaV/V =0.0495. So, any initilal volume of air in the reservoir will expand by some 5%. Now, can someone measure the volume of a single drop of ink say, off a medium nib? A nice digital scale would help. I do not have one available right now. That would help me to estimate the critical volume of that air bulb inside the reservoir which would make the pen blot while warmed up with your fingers. Sure. we assume the fins ar not going to handle that extra ink.

 

EDIT: Let's assume you have got 2ml air bubble and your fingers warm the reservoir from 20C to 37C (which I do not believe will ever happen). 5% of 2ml is 100 cubic mm. That's the volume of a ball with R= 2.88 mm. That's a huge drop of ink or several smaller drops. I still believe fingers cannot affect the temperature of the reservoit that much and besides the fins of the feeder are probably designed to handle that extra volume of ink (if it ever happens). I personally do not think there will be a problem with say, 5mm reservoir.

Edited November 3, 2008 by adallak

[lapis]

(1) All of the above.

(2) It is much easier to get an exact measure of weight than a measure of volume. I measured the weights and thus densities of four inks: 1000µl of Florida Blue = 0.9649 g, Eclat der Saphir = 0.9754 g, Pelikan Black = 0.9581 g, and MB blue-black = 0.9605 g. Okay, there are many other inks out there but the average density of these four inks here is 0.9647 whereby the mean is at a stunning low of only ±0.44%. Thus, as Southpaw suggested, the ink volume is "about" 1.6-1.8 ml.

(3) BUT... the most important thing is whether or not the excess air has first been expelled or not. This has been described by MB's ink instruction sheets. IMO it is not necessary to get rid of a bit of ink so that the pen is no longer (harmfully) "100% full". If you really need to "fillerup", then just expell as much air as possible until you've already got ink on your fingers and refill accordingly.

 

Whew

[Orval]

I'm not an engineer but I try to add a few thoughts.

 

About the air dilatation when the pen is nearly empty: My experience with the Récife eyedropper is that a well designed collector-feed group can handle this increased pressure without ink overflow or blotting.

 

About measuring the ink capacity of a piston FP: It depends wich defintion you give to ink capacity.

 

If you define it as the capacity of the piston movement, you just calculate the cylinder capacity of the piston movement.

 

If you define it as the total capacity of a FP from full until running dry you have to add the capacity of the feed-collector group and this is more complicated. When the piston chamber is completely empty and you turn the piston completely down counterclockwise, you can still write many pages with the M800. When the pen runs dry you weigh the pen. The pen has then a lot of air in the feed-collector group, wich remains inside the pen when you suck up ink from the bottle. You have therefore to turn the nib upwards after filling and pull that air outside by turning counterclockwise again until the space between the fins of the nib fill completely with ink. Then you suck a second time. After this operation, you have to turn again counterclockwise to eliminate some drops and then with the nib upwards once more clockwise to eliminate the superficious ink from between the fins. After you've cleaned the nib and section you weight again the pen. The difference between the 2 measurements is the ink capacity.

 

My opinion: even 2ml is terrible poor for such a big and good writer. For me, this means 2 stops a week at least at the ink bottle with a medium nib. The ancient pistonfillers have much more capacity. The piston movement of my old Pelikan and of my Aurora 88 vintage edition is +/-2,5cm. Thats near twice the M800's one while they are more tiny.

Conclusion: The starter of this topic is right. M800 is designed for show and signature more than for writing. YMMV

Edited November 2, 2008 by Orval

[fountainbel]

Hi all,

Ive just disassembled both a Pelikan 800 & a vintage Pelikan 400 aiming to compare their "potential" ink intake.

I've first measured the piston bores, and to my astonishment de piston bore of the 800 is smaller !

Pelikan 400 : 9mm piston bore

Pelikan 800 : 8.2mm piston bore

I then measured the effective piston stroke : removed the nib unit, turned the piston fully to the section stop, installed a steel pin through the nib bore contacting the piston top & measured over the pin top to the the rear barrel edge.

Same measurement was done with the piston fully retracted, difference between both measurements being the effective stroke.

Pelikan 400 : 31 mm stroke

Pelikan 800 : 26 mm stroke !

I was rather surprised with the shorter stroke of the 800, so I thought the piston lead screw was not engaged properly;

So I dis assembled the piston mechanism and engaged the lead screw obtaining a maximum stroke backwards.

In fact the lead screw was engaged so it axially contacts the bore end in the filling knob.

Repeating the stroke measurement with this setting confirmed however the disappointing 26 mm stroke.

These measurements result in the following "potential" ink intake figures :

Pelikan 400 : 1.97 ml

Pelikan 800 : 1.37 ml

Conclusion : Contrary to what one should expect, the Pelikan 800 has 30% less "potential" ink intake capacity compared to a (vintage) Pelikan 400.

Regards, Francis

Edited November 3, 2008 by fountainbel

[RLTodd]

Just as a matter or curiosity..............

 

Did the Vintage 400 have the double extension screw mechanism?

[adallak]

  fountainbel said:

Hi all,

Ive just disassembled both a Pelikan 800 & a vintage Pelikan 400 aiming to compare their "potential" ink intake.

I've first measured the piston bores, and to my astonishment de piston bore of the 800 is smaller !

Pelikan 400 : 9mm piston bore

Pelikan 800 : 8.2mm piston bore

I then measured the effective piston stroke : removed the nib unit, turned the piston fully to the section stop, installed a steel pin through the nib bore contacting the piston top & measured over the pin top to the the rear barrel edge.

Same measurement was done with the piston fully retracted, difference between both measurements being the effective stroke.

Pelikan 400 : 31 mm stroke

Pelikan 800 : 26 mm stroke !

I was rather surprised with the shorter stroke of the 800, so I thought the piston lead screw was not engaged properly;

So I dis assembled the piston mechanism and engaged the lead screw obtaining a maximum stroke backwards.

In fact the lead screw was engaged so it axially contacts the bore end in the filling knob.

Repeating the stroke measurement with this setting confirmed however the disappointing 26 mm stroke.

These measurements result in the following "potential" ink intake figures :

Pelikan 400 : 1.97 ml

Pelikan 800 : 1.37 ml

Conclusion : Contrary to what one should expect, the Pelikan 800 has 30% less "potential" ink intake capacity compared to a (vintage) Pelikan 400.

Regards, Francis

Fountainbel,

Thank you for taking measurements. That says it all. Talking about the stroke and the piston bore sections, that's the latter which actually counts most since V=3.14 x R^2 x L. In other words, if you increase the stoke L by 10% your volume will increase by 10%, but if you increase the bore radius R by 10% your volume will increase by 21%.

Edited November 3, 2008 by adallak

[fountainbel]

Hi Todd,

No just the standard piston mechanism.

I was even not aware Pelikan ever made a double extension screw piston, do these exist?

Never seen them, except on vintage Montblanc's !

 

  RLTodd said:

Just as a matter or curiosity..............

 

Did the Vintage 400 have the double extension screw mechanism?

[RLTodd]

Don't know, thought I heard it mentioned once, but may not have.

 

I was only curious.

 

I don't attend closely to these capacity piston mechanism topics.

 

 

[fountainbel]

Being surprised on finding the smaller stroke on the M800, I decided to compare the design of the 400 & 800 filling systems.

The original 400 filling system - successfully used for decades by Pelikan - features an axially sliding & radially fixed nut and a rotating screw spindle ( friction fitted in the filling knob) Rotation of screw nut is prevented by a axial key groove in the piston sleeve & a mating key in the filling system housing., in other words both the screw nut & its anti rotation feature are radially offset to each other

Advantage being that the threads in the piston tube & the key groove are in the same axial plane, resulting lengthwise in the shortest possible design.

The new M800 filling system to the contrary features an axially sliding & rotating nut and a radially fixed screw spindle.

The nut sleeve slides axially in the anti rotation slots in the filling knob bore. The screw spindle moves axially in the anti rotation bushing which is press fitted in the brass housing .Drawback is that the nut and the anti rotation bushing are axially offset to each other - in other words length wise behind each other - leading to a lengthwise less compact design, hence shortening the potential filling stroke.

So the new filler mechanism design is in my opinion the main reason of the shorter M800 filling stroke compared to the M400.Attached the link to a sketch showing the differences between the 2 filling systems :

http://i62.photobucket.com/albums/h89/foun...omparison-1.jpg

Hope this clarifies the differences between the two filling systems;

Francis

(edited for adding sketch)

Edited November 5, 2008 by fountainbel

[adallak]

  fountainbel said:

Being surprised on finding the smaller stroke on the M800, I decided to compare the design of the 400 & 800 filling systems.

The original 400 filling system - successfully used for decades by Pelikan - features an axially sliding & radially fixed nut and a rotating screw spindle ( friction fitted in the filling knob) Rotation of screw nut is prevented by a axial key groove in the piston sleeve & a mating key in the filling system housing., in other words both the screw nut & its anti rotation feature are radially offset to each other

Advantage being that the threads in the piston tube & the key groove are in the same axial plane, resulting lengthwise in the shortest possible design.

The new M800 filling system to the contrary features an axially sliding & rotating nut and a radially fixed screw spindle.

The nut sleeve slides axially in the anti rotation slots in the filling knob bore. The screw spindle moves axially in the anti rotation bushing which is press fitted in the brass housing .Drawback is that the nut and the anti rotation bushing are axially offset to each other - in other words length wise behind each other - leading to a lengthwise less compact design, hence shortening the potential filling stroke.

So the new filler mechanism design is in my opinion the main reason of the shorter M800 filling stroke compared to the M400.Attached the link to a sketch showing the differences between the 2 filling systems :

http://i62.photobucket.com/albums/h89/foun...omparison-1.jpg

Hope this clarifies the differences between the two filling systems;

Francis

(edited for adding sketch)

Fountainbel,

 

Thank you for the description and the nice scetch. The question is why have they switched from more efficient in any respect design to the new one? Pelikan seems to be the first pen manufacturer which used double-screw (telescope?) filling approach mentioned earlier. Unfortunatelly, I was not able to find any related diagram. Have you seen one? It would be great if someone could provide a graphical information about that early Pelikan pen filling system while on the subject.

 

[fountainbel]

Hi adallak,

To my knowledge Pelikan never made a telescopic piston filling system.

Montblanc did, from the thirties till the fifties of last century.

This really is a beautiful & efficient filling system.

Being confronted with the repair of such pens I could not find any drawing, so I've made a rough sketch some time ago:

http://i62.photobucket.com/albums/h89/foun...FillerMB136.jpg

 

Francis

 

PS edited for adding proper link, sorry

Edited November 6, 2008 by fountainbel

[adallak]

  fountainbel said:

Hi adallak,

To my knowledge Pelikan never made a telescopic piston filling system.

Montblanc did, from the thirties till the fifties of last century.

This really is a beautiful & efficient filling system.

Being confronted with the repair of such pens I could not find any drawing, so I've made a rough sketch some time ago:

http://i62.photobucket.com/albums/h89/foun...FillerMB136.jpg

 

Francis

 

PS edited for adding proper link, sorry

thank you, Francis.

I seem to find the related patent. You can download PDF file. EDIT:

http://www.google.com/patents?id=KdxQAAAAEBAJ&dq=2167815

Edited November 6, 2008 by adallak

[fountainbel]

Thanks adallak.

This looks however the standard MB piston filler used from the sixties, not the earlier telescopic version;

I would surely appreciate if you could find anything on this earlier "telescopic" system !

Regards, Francis

 

[adallak]

  fountainbel said:

Thanks adallak.

This looks however the standard MB piston filler used from the sixties, not the earlier telescopic version;

I would surely appreciate if you could find anything on this earlier "telescopic" system !

Regards, Francis

Francis, I have edited my previous post. Please find the correct patent link in the edited post! Sorry for confusion.

[Titivillus]

  JRG said:

Now, if you could manage to eliminate that little bubble (i.e., achieve a 100% fill), which is impractical, you might raise the load to 1.4mL.

 

Try using a Visconti travelling inkpot and you'll get a full fill

 

[fountainbel]

  adallak said:

Francis, I have edited my previous post. Please find the correct patent link in the edited post! Sorry for confusion.

 

That's it !

Thank you very much adalak !