A Vernier Watch

I lost the minute hand on my pocket watch recently. (Yes, I wear a pocket watch. I use slide rules, too.) Rather than buy a new watch, I just adapted to telling time without a minute hand.

Use it up, wear it out,
make it do, or do without.

Using the minute marks - five between each hour mark - I could tell time to within 12.5 minutes, which is good enough. Instead of "quarter of seven" or "quarter after seven", it became "fifth of seven" or "two-fifths after seven". ("At the sound of the tone, the time will be seven and three-fifths.") Since most people round the exact minute to the nearest fifteen minutes anyway, this isn't really any less accurate, and is actually more precise.

"You don't have enough hands on your time." - Paul Neuhaus

After thinking about it for a while, I realized I could do better than 12.5 minutes - in fact, I could read it to within a minute!


A Vernier Watch Face

Replacing the hour hand with a dial upon which is engraved a vernier scale allows the clock to be read to within a minute. I'm not going to go into how to read a vernier scale here - maybe in the future.

"What time is it?"
"You mean right now?"
- Steven Wright

However, because verniers usually divide a single length onto smaller units, and this one is spread out over 12 lengths (hours), there is a complication: it actually gives six answers. Examine the image above, and you'll see that it indicates 0, 12, 24, 36, 48 and 60 minutes. 0 and 60 are, of course the same, in the sense that 5:60 is also 6:00. To differentiate the others, you can do one of two things:

Lowell Scott's Vernier Clock

Shortly after adding this web page to my site, I received an e-mail from Lowell Scott, who actually built a vernier clock.

I spent three sleepless nights thinking and working on this thing. And this is all I have to show for it.

Note that the hour hand doesn't even line up with 12 in the 12 position. That's so I can see all of the minute lines. Also, I have yet to actually put any numbers on it.

Guess I should have glued the vernier dial on the outside of the hour hand... That's for VernClock v2.0 I suppose.

I need to sleep now. Maybe I can, after I've finally got it out of my head...

I think he did an excellent job, especially since it appears he drew the lines by hand.

I Finally Made One

It took me a few months to get around to it, but I've finally built my own Vernier Pocket Watch.


6:00 exactly.

Someone (I'll be damned if I can remember who) pointed out to me that it wasn't necessary for the vernier to go all the way around the dial; all it needs to do is cover the space of 9 lines. These lines would normally number four between each hour mark, each marking off the minutes for the minute hand. Instead, I drew FIVE lines between each hour mark, each marking off ten minutes for the hour hand.

I drew the clock face and the vernier in AutoCAD, and printed them with a laser printer. I attached the vernier to the hour hand with a the world's smallest drop of rubber cement - it's not quite right, but pretty close. In this image, the vernier is twisted ever so slightly counter-clockwise (don't think about it), which slightly misaligns some of the lines.

The spacing of the marks isn't quite regular, either. I think this is a result of my watch being only 3/4" in diameter: at 600 DPI printer resolution, that is only 400 dots across, and such tiny marks really need more resolution.

Then I Made Another One


Horologist's Nightmare at 5:28

This one is a tad different - the vernier is split into two sections, one on either side of the hour hand. It's not any harder to read than any of the above designs, and I think it looks much nicer.

I made this pretty much the same way as the pocket watch - I started with a regular, battery-powered clock with an ugly frame, and replaced the dial with one I designed in AutoCAD and printed on a laser printer. It says "Vernier" on the dial, but the vernier has covered it up.

What good is it?

Hmm. Good question.

By the way...

Before you laugh too hard, know that Ben Franklin invented a three-dial clock that only had an hour hand. The three dials were numbered 12-8 (outside), 9-5 (middle), and 6-12 (inside). (Horologists, feel free to correct me if I've got that wrong.) Just like how we can tell AM from PM, we could also have told first shift, from second shift, from third shift, in order to know which dial to read.

References

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© 2003 W. E. Johns