Reader solves mystery hidden inside Acme Semaphore Traffic Signal

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Subscriber Jeff Schiedegger was able to provide Robert Rentzer with answers concerning his Acme Semaphore Traffic Signal.

In the April 6, April 20 and May 4, 2011 editions Antique Trader honored me by breaking tradition and for the first time in their history ran an article over three editions. The article was titled, “One Collector’s Holy Grail” and was the complete (actually, almost complete) story of the rise and fall of the Acme Semaphore Traffic Signal Company. For those who missed any part, and even for those who read it all, the article can now be found in a full-color download posted online.

FREE DOWNLOAD: The Holy Grail of Traffic Signals – One collector’s quest to find and restore an iconic 1924 Acme traffic signal

Why do I say “almost complete?” Well, that’s why this post script is being offered.
In Part 3 of the article mention was made of what I described as an, “anomaly.” To quote the relevant paragraph:

“The oil trough, which contained saturated horsehair padding to retain the oil, had a strange pinhole at the top lip of its wall, which ran down inside the entire length of that wall and let out to the exterior. There was no discernible purpose for this, unless it was some sort of breathing shaft. But even more curious were two holes where the trough sat mounted on a gasket above the worm gear. Oddly, those two holes were not accessible once the trough was mounted in place. Perhaps one of Antique Trader’s readers can explain this odd setup.”

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Well, as the title to this article reveals, one of those two mysteries has been solved thanks to an Antique Trader subscriber who wrote: “I saw your article in Antique Trader … the small hole that runs down the side wall of the oil well on this model has a small piece of string passing through from the interior of the well to the exterior lower port. There is a small lead crimp on each end of the string. I assumed it was for wicking oil to the end of the worm gear but I’m not positive.”

That Antique Trader subscriber was also kind enough to provide some photos (one showing the string resting inside the oil trough with its weight attached is printed here).

Using those photos and and the subscriber’s information, John Long, the electronic engineer who assisted in the restoration and whose technical contribution was featured in Part 3, was reminded of some photos which had been run on eBay when the first of the Acmes had been put up for auction (also included with this article). John was then able to then extrapolate the answer to the first of the two questions, that being the purpose the hollow shaft served. John now shares that answer with us, so, in his words:

“I looked thru all the other images I have from other Acmes etc, and I can see the string in at least 2 other signals. Apparently, what it does is wick the oil out of the reservoir then down the vertical hole. As it does some drips off and leaks down the inside of the housing onto a bearing, then drips onto the worm gear. The rest is wicked to the outside of the housing, which is tapered downwards so as to funnel the drips onto the same gear. I should have thought of that as the motor oilers do the same wicking action with felt.”

This is all revealed in the various photos and captions. But there is yet one more mystery which remains and that relates to the two larger holes which are over the worm shaft and are found just below the trough when it is removed (also seen in the photo with a caption related to this). According to John, “the current configuration of the trough and wick string could not provide any lubrication access through to the inner holes over the worm shaft that could have originally been intended as a way to lubricate it. Additionally, there is a gasket between the trough and base, which further isolates the drip flow from the shaft holes. Furthermore, it is a very low wear part of the system. I believe they are larger holes with the purpose of serving as mini reservoirs on their own, so I simply added a few drops of 20-50 oil to them.

The worm and worm gear action is the highest friction part in the Acme and therefore it deserves the best in lubrication. Originally, what I did was to lubricate all moving parts with either lithium grease or 20-50 oil. For the worm gear I added a liberal amount of auto caliper grease (which is a combination of graphite, teflon and molybdenum). I did this because it is a far superior lube than the original way of doing it with dripping oil. It will not result in a bunch of gunk at the bottom of the housing.

I envision their original function was to provide a means of flushing the dirt off the gear while giving some fresh lube at the same time. This is because the Acmes were intended to be outside in the weather and dusty wind. In our case it is now a museum piece and will be inside in a much cleaner environment, therefore grease would be a better choice.”

As for what John was making reference to when he says “…the motor oilers do the same wicking action with felt,” those oilers are the cylinders which are screwed in so as to hang below both ends of the motor shaft, one of which is also seen in the photo depicting this setup.

And so, unless and until someone has a better explanation for the two “hidden holes” above the worm shaft and the fact that there is a gasket around them which serves no discernable purpose, we are left with John’s thought that these may have served as mini reservoirs or my guess, which is that maybe these were packed with grease and the gasket was to prevent the grease from oozing out below the trough. So, for now, it seems we know all there is to be known about the working parts and design of the Acme Semaphore Traffic Signal.

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Robert Rentzer started his career as a television actor under the name Bob Dennis and later joined Broadway productions. While raising a family, he launched a successful law career and formerly served as a deputy district  attorney and prosecutor in Los Angeles. Now in private practice, Rentzer is credited with taking on high profile cases, including representing Rodney King and participating in both the Los Angeles and Las Vegas O.J. Simpson cases. Rentzer is also an author whose latest book stands ready and waiting for a publisher. He may be contacted via his website,

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