Kaweco Dia 85 piston.

[RevAaron]

I do have those O-rings on their way to you too. I tried them in a green marble 85A, and they worked well. The same size appears to work quite well in my Pelikan 100 as well. I don't know what size they are- originally, I just went to the farm and fleet store and looked through every little tin of O-rings that they had, taking two of each, four of those that were especially promising.

 

In my 85A, three rings would be too much. They compress vertically, which forces them out radially, and allows no squish-room when in the pen. Technical terms, I'm sure! The seal held fine with two rings and some wiggle room, but obviously it's a sloppy way to go about things. So, I put a smaller, thinner and tighter O-ring beneath the other two. I tried a few before I got there.

 

ASCII art-wise, it looked something like this:

 

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On another, older Kaweco, I was just able to use two- the top of the piston rod is friction fit, so I was just able to tap it down a smidgen.

 

Aaron

[Ondina]

Most useful info, Francis, thank you. It will be an invaluable reference for the future.

 

Thank you Aaron, much appreciated. I hope some carts of De Atramentis Sapphire will please you in return for the kindness. They will get to me next Friday night. New pics and updated results to follow when done.

[fountainbel]

Or to a cork, which may be even better.

Installing a nylon washer will be an issue: the "free" lower end has a ridge and the "long" lower one that extends to the rod, as a washer already that is the one that serves as a stopper. I don't see the way to getting anything non elastic in there, but for cutting it and re-gluing it once installed.

 

Thanks for the input, and excuse my inexperience in such tasks.

 

Having a cork installed always implies the front piston collar can be removed.

Kaweco uses a collar pin, which is axially/ radially secured with a dowel pin.

When you look just behind the rear piston collar, you will see a small transversal hole.

Using a small pin -diameter 0.7mm- you can drive the pin through and remove the cork holding collar pin.

Francis

Edited June 13, 2009 by fountainbel

[Ondina]

Francis, el que sabe, sabe ( Those Who know, know) After reading your last post, some natural light was needed as previous close inspections have shown no pin holes. Everything seemed carved out of a solid rod but for the washer.

http://i348.photobucket.com/albums/q347/Ondina_2008/Kaweco011.jpg

So how on earth did the washer get in there? No pin holes, nothing. Wait. There is more gunk around the head's ridge? And what is this upper notch for?

http://i348.photobucket.com/albums/q347/Ondina_2008/Kaweco013.jpg

A slight screwdriver's twist, and voilà. There is a big world in there......

http://i348.photobucket.com/albums/q347/Ondina_2008/Kaweco015.jpg

http://i348.photobucket.com/albums/q347/Ondina_2008/Kaweco017.jpg

 

This opens the range of possibilities and simplifies the repair so much. Thanks for the tip.

Edited June 14, 2009 by Ondina

[fountainbel]

Glad you managed to get the cork enclosure pen out ,well done !

I did not remark the screw driver slot on top of the piston on your earlier pictures, seeing this its obvious a threaded fixation

Never seen a Kaweco with screw thread there, most Kaweco's use a transversal dowel pin to fix the cork enclosure pen.

Good luck with the further repair !

Making a cork seal is not so difficult, just give it a try !

Francis

 

 

[fountainbel]

Hi Ondina,

 

Just made and tested an O-ring set-up for the Kaweco 85 piston.

 

 

Directly seated on the original cork seat, the ideal standard O ring (Buna N- 70 Shore) is 4.5x 2.0mm (0.177" x0;078") or alternatively 4.7 x2.0 mm ( 0.185" x 0.078")

 

This set up ensures an optimum radial O ring pretension of 0.2-0.3mm in the barrel

 

Coping with the width difference of the cork & O ring,the O ring should be backed-up by a nylon ring diameter 4.7 x7.5mm, having a width of 3.8mm.

 

On the attached picture you can see the set-up.

 

Avoiding the necessity to disassemble the collared piston enclosure pin ( specially on the transversal pinned piston heads) I've provided a slot in the ring , so one can slide the ring behind the O ring..

 

Personally I would not mount more then one O-ring, avoiding excessive friction, hence unneccesary increasing the actuating torque.

 

Regards, Francis

 

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

Edited June 14, 2009 by fountainbel

[paolino_paperino]

Sorry for the necro-post, but I felt necessary to thank everyone involved for the help this thread has given me.