I've mentioned in the past that I believed the 1960s 149 had a larger ink capacity than later models. I repaired two 149s yesterday, and took note of the piston (and internal barrel) diameters of each pen. The piston seal of the 1960s model is approximately 11mm in diameter, and the piston seal of the 1980s model is approx 9.5mm in diameter.

Click to view attachment

The length of each piston 'rod' is the same, but notice the differences in the seals as viewed from this angle.

Click to view attachment

The piston in each model moves 25mm from it's telescoped to its non-telescoped position. Using the simple volume formula for a cylinder, I calculated the 1960s model holds roughly 2.4ml of ink, and the 1980s model holds roughly 1.8ml of ink.

I compared the 1980s 149 piston seal to a 146 seal of a similar timeframe, and they are identical. The 146 is on the left, 149 on the right.

Click to view attachment

When I measured the 146, the piston moved about 22mm from it's telescoped to its non-telescoped position, and that would mean it would hold slightly more than 1.5ml of ink.

I'll add that these measurements were not made with calibrated instruments, and therefore my conclusions as to ink capacity are approximate at best.

Regards, Eric

Your approximate measurements are far more accurate than my subjective wild arsed guess. How much ink does a 149 hold? "A whole bunch."

Thanks. This info is very interesting. So, do you think the MB folks changed the size of the 149 seals to lessen production costs? Or is there a good technical reason that eludes me?

Very interesting to learn. The outer diameter didn't change, did it? Was the barrel wall thickness altered when the material changed ? Probably it did.
Would love to own such a 60s silverring model. I probably will in a million years time or so. Until then, I am very fond with my 80s model.

Good questions Frank & Ruud.

The barrel walls on the later 1980s model are indeed thicker with no change in exterior dimensions. I'm doing to make an assumption that this change in fabrication was about the same time that MB went from resin to the precious resin, but have nothing to substantiate that claim. The 60s model 149 has a friction fit mechanism, so maybe when they went to the current threaded piston mechanism, the engineers determined the barrel walls must be thicker.

I also assume that MB could get some efficiencies from producing a single nylon/plastic piston seal for both pens.

Regards, Eric

Thanks for the info, you've made me more comfortable in my thoughts -- I've generally preferred the 146's size to the 149, and I prefer white metal, so it's nice to know I won't lose that much capacity.

I only own MB from the 60's-70's, I am very happy of their ink capacity. Thanks for those precisions.