When it comes to congenital defects, time always tells. This past week we have had four Parker pencils on the bench, and each had the same problem. And that problem was the result of a design flaw that would only reveal itself over time.
The Design
From the time Sampson Mordan first patented the propelling pencil, in the early 1800s, most pencils used a helix-driven shuttle to propel, and eventually repel and expel, the lead. Parker used this design extensively until the 1940s, when they adopted the (far superior, in my opinion) German dual-clutch mechanism in the 51 aerometric pencils. Even then, they still used the helix-driven mechanism in some models. This system was used in, at least: Duofold, Challenger, 51, 21, 45, 61, 75, &c &c. Also, Sheaffer. Also, Waterman. You get the idea.
In this design, the shuttle holds the lead, and travels up and down a slotted inner shaft. Two small knobs of brass protrude at right angles from the shuttle, and are long enough to pass through the slot in the long shaft and act as keys. (Note: “key” is the proper mechanical term. It sounds so much better than “knob” that I’m going to use it for the rest of this article.) This entire assembly fits inside a helical sleeve. When the helical sleeve is rotated, the keys from the shuttle are guided by it up and down the keyway (See? So much better than “knobway”!) that runs the length of the shaft.
Here is a photo of all of the parts, which will hopefully help you to imagine it all together:
And here, at the prompting of Apprentice Em, is a video to clarify further. The two spots I point out are the drive keys for the shuttle, inside the tube:
The First Problem
There are a couple of problems with this design, one minor and one major. First, the minor.
Everything you see is made of brass. Brass is an excellent material generally, and has been used in small machines for centuries. However, brass tends to wear out when it is abraded. This is one reason, as an aside, that watches use jewels as pivot points: brass would wear too quickly.
Also, like metals have an affinity for each other; they tend to stick. So, in very good designs, two parts which bear on each other tend to be made of unlike metals, like a steel shaft in a brass bushing. There is less material loss because the parts don’t want to stick together, and friction (thus wear) is minimized.
So, in our pencil mechanism, you have a brass shuttle sliding along a brass track, with a brass helix driving it. Can you see where there might be an issue?
The Second Problem
This brings us to the second, far more substantial issue: the way the shuttle is made.
In these pencils, the propel-repel-expel action was accomplished by means of a two-part shuttle. The shuttle consisted of an outer sleeve, with an inner shaft. The lead fits in the outer sleeve, and when the shuttle reaches the end of the action (when the lead is spent), the inner shaft is engaged, pushes forward, and pushes the last little bit of lead free. When the shuttle is retracted, the inner shaft retracts, allowing you to seat a new piece of lead in the now-empty socket.
The inner shaft is simply a brass rod with the last few millimeters bent sideways, forming one of the keys that is engaged by the helix drive. This is not bad.
The outer sleeve part of the shuttle is a flat piece of brass, about 0.25 mm thick. It is formed into a cylinder, into which the brass shaft fits (can you see the seam in the photo? It is all just press-fit into shape.) And this is the biggest issue: the main drive key is made of two flaps of this very thin sheet, pushed together. Now, a one millimeter piece of brass rod will take awhile to wear. But two 0.25 mm flats will wear much more quickly. And this is exactly what happens.
The front key is the main drive point for the shuttle. Remember, the rear one only engages when the lead is spent and needs to be ejected. This means that the tiny part taking the brunt of the wear, and without which the lead cannot move in and out, is also the weakest part of the pencil.
Here is a photo of a reasonably sound shuttle drive key, with a worn one above it (click to embiggen).
What you can’t see is that, when you take apart most pencils of this design, both sides have worn away. Then they fold over, inside the slot in the inner shaft. Then the ejection shaft key is the only one engaged, and the next time you try to replace the lead, the ejection shaft won’t retract properly and you can’t ever fit a new piece of lead in place, ever!
Hard Conclusions
How many pencils are affected by this kind of debilitating wear? About 80% of what we have handled, several hundreds of pencils.
Is there a repair? Nope. You can replace the worn part, if you can find a sound one. The only repair solution we can see is to use a micro-welder to weld on a new key: a nice, solid one. Which also means taking an hour to strip it all down, clean it, and assemble it again. But considering that the effort and equipment that would take is about the same as re-tipping a nib, or repairing a Waterman lever box, it’s not likely to happen, except as a labour of love. (Hmmm…$20, or $150? $20 and lovely, or $150, and also lovely? Such choices…)
The sad truth is that many of the beautiful old pencils, matching beautiful old pens, are worn out. Because of a bad engineering choice, which maybe, just maybe, was part of planned obsolescence.
Yard-o-led used a similar design, but far more robust parts. And the Germans, of course, used a completely different design with only one moving part, and no wear points. So if you want a good, beautiful, useful, robust vintage pencil, buy a Pelikan. ; )
