I actually laughed out loud at this post. The fact that the clock faithfully kept time backwards for over a year and you and your wife just got used to it is hysterical, but I can totally relate. We humans are a strange breed--we get used to something and we make every concerted effort possible to work with it and make it last as long as possible.
I agree, Beth, this is a funny one. I'm just trying to imagine what it's like to learn to read a clock that runs backwards. Then you have to wonder if that talent affects your ability to read a clock that runs forward.
My wife and I have old friends who have a Hebrew clock, which of couse runs counter-clockwise! The answer to this puzzle is: the old-time electric clocks used small synchronous motors. Synchronous motors, unlike the more-common induction motors, (for those of you whose engineering education occured after the Motors and Power labs were removed from the required list of the EE curriculum) inherently are quite happy running in either direction in their most basic form. For specific applications like these mini clock motors, the trick was to put a small-gauge "shorted turn" winding on one side of the pole-piece gap. This would cause a small phase-shifted magnetic field which when vector-summed with the field from the main winding would result in a field that rotated synchronously (similar to that from a split-phase induction motor) that would induce a torque in tne rotor making the rotor accelerate and rotate synchronously with the field. I suspect this winding (or in the really cheap clocks, a brass screw near the gap) may have been displaced with all the rough handling. Thus until something made the clock start rotating in one direction or the other, it would continue in that direction as long as power was applied. Unless the clock was powered-down with the center of the rotor exactly in the cennter of the pole gap, that would be the direction the motor would run in the next time power was reapplied. If the rotor WAS centered, the odds were 50/50 for either direction on next power-up!
Synchronous motors are a big part of the old world of audio turntables. I've restored a bunch of them, and I've found that these motors are very prone to seizing up due to dried out lubricant. (Well, not really seizing in the way an auto engine does, but getting gunked up to the point that they can't run.) Maybe that played a role here. The other thing is that when you revive them, you can't just use any old standard oil, because that will drain away too quickly. You need stuff that's not so heavy it'll inhibit motion -- these tend to be low-torque motors -- but something that'll stick around and not leak out.
Good explanation, Ratsky. Does this mean that if you unplugged the clock and then plugged it back in, there is a 50/50 chance it would begin to run the right way? Could it be that this clock continued to run backwards simply because the power source continued, uninterrupted?
LOL! We call this a simple "workaround" in corporatedom. Sometimes you just sidestep the disconnected and loopy corporate bullschitte to achieve the ultimate goal that you know everyone wants anyway. No thanks for the workaround is ever granted and you don't admit it to anyone not onboard to your cause. You just hand them the results that you gained through nbo support by them in the least.
Essentially you are saving them from themselves while ensuring your own survival. Once we lose this boldness and individuality in the business world we'll be cooked by the clueless and over compensated above us. They then die too... so who is most important...hmmmm?
In politics, usually more known as a somewhat more subversive tactic employed by one side of the political spectrum moreso than the other, it is often called "justifying the means by the ends"...
Back in the service, one of the guys in our shop took apart one of the typical government clocks to get the motor running again. He put it together backwards. One seeing the result, he relettered the dial.
We enlisted took delight watching visiting brass check the time and then re-look with a strange lost expression.
There is no mystery at all why the clock ran backwards. There is a type of motor where the rotor is a permanent magnet inside an AC pole structure (like a "standard" synchronous motor). If the rotor is light enough, its vibration amplitude at 60 Hz will exceed a pole pitch. Such a synchronous motor will spontaneously start in a random direction. A ratchet mechanism forces it to reverse if it starts in the wrong direction. The drop damaged this mechanism, allowing the motor to start backwards.
2 stroke engines with reed valve intakes can run in either direction. One of my friends would start up model airplane engines, and they would sometimes get going the wrong way. He would throw a rag into the propeller to stop the engine so it could be restarted. So the bike engine running backwards is no mystery, if it's 2 stroke.
I assumed the DC adapter was for another appliance plugged into the same outlet as the clock.
I cannot imagine the adapter causing the grinding sound. My first thought is of a poor service connection. Plugging in the adapter caused an intermittant connect-disconnect (sparking) of the 110v service to the outlet. If you caught this motor just right, it could reverse it. You may also hear it as chatter or grinding in the clock. Not a safe condition.
As a newly minted electrical engineer (back when dinosaurs ruled the eath) I was asked to debug my grandmother's alarm clock, which exhibited the same backward running behavior discussed above. The motor was the same synchronous design, but instead of a shaded pole arrangement to provide the initial torque, this design had a small cam that acted as a one-way clutch that would mechanically stop the motor and kick it back in the right direction. After cleaning and lubricating, it worked fine. My folks were impressed.....
Back in 1972 at Cornell, we still had motors and electrical machinery courses. The text said cheap clock movements (no one had the ubiquitous battery operated quartz analog movements until the 80's?) used shaded pole synchronous motors - the shading was a loop of copper around one of the armatures.
I took my clock and moved the loop around the opposite armature and sure enough it ran backwards. I could not use the alarm function because of the way it engaged it would be going the wrong way. I pried the plastic face off and made a new face with the numbers labeled counterclockwise and I had that around for many years. At the time i just had drafting tools and made the face of paper, it looked a bit rough. Maybe I should make a new face now that I have CAD stuff... Have to dig the clock out, I'm sure its still somewhere around. Too bad the case is a hideous 1970's green color.
I've got a cheap quartz alarm clock thats doing the same trick. I can actually get it to change direction at will by removing and inserting the battery at the time the alarm function is tripped. I don't dare take it apart to see how it got to this state, because knowing a thing or two about how these things are put together, I know it's designed to be a one-way process.
Well, that's an old issue with 100% symetrical synchronous motors as they can rotate and lock to 60Hz in either direction. I believe GE Telechron clock motors had sufficent armature asymetry to put the armature at rest slightly in the clockwise magnetic aligment with the stator poles to make them always start in the correct direction. As for some 1960's vintage turntables, I believe at least one model from AR (Acoustic Reseach) used two motors, a small induction motor to accelerate the platter in the correct direction and a synchronous motor to lock it to 60Hz.
Ampex used fairly powerful hysteresis synchronous motors in their commercial audio tape recorders designed in the 1950's. They'd always start up in the correct direction. And they had two sets of windings to provide two speeds to pull tape at 7.5 or 15 inches per second. The one idiosynchracy of these motors was a cogging problem. If you switched motor speed windings while it was energized and turning, you would get temporary magnetization of the rotor such that it would cog sufficiently to be heard as tape flutter. Merely powering down the motor would void the magnetic memory and the flutter would go away. Easy to do since a spring loaded tape guide lever (tape break switch) controlled the capstan motor to stop transport motion if the tape snapped or slipped off of the take-up reel.
My father had one of these syncronous clocks on our fireplace mantel back in the 40s. It had a small knob on the back you would turn after plugging it in to get the motor spinning. Once it got going, it would stay in sync with the AC. If you turned the knob in the opposite direction of the arrow printed on it, the clock would run backward. I used to drive my dad nuts by changing its direction whenever possible.
The AC-powered clock. The power grid requires full synchronization of the entire grid, and there is no master. Thus once the grid is accurately sync'ed to exactly 60Hz, if any one generator starts to lag or lead, the power flows from the many other grid generators will pull the "offender" back into sync; if that fails, it will be cut off from the grid because the reverse power flows attempting to force it back will trip all its breakers! The conventional quartz-based timepieces at best can hold a few PPM considering temperature, aging, etc. Interesting sidepoint, though: those tiny cyindrical 32.768 KHz "watch" crystals have an interesting property. They have an inverted-U shaped temperature vs. frequency curve. The peak is generally very close to the average human body temp (37C or 98.6F). This happy accident has 2 consequences: as long as you wear a wristwatch (and don't leave it sitting on you dresser most of the time!) it will be most accurate. The other: at higher OR lower temperatures, the frequency DROPS, so your watch will lose time, rarely gain it!
HOWEVER... there is now a very common and even more accurate time source: your cell phone! The cell and hand-off structures of the networks require nanosecond-level sync (generally provided at each site by several GPS receivers in a "voting" redundancy configuration). Unfortunately, not ALL cell networks 'cooperate' properly, leading to (for example) my AT&T Blackberry to lag "real" time by as much as 2 minutes! My Verizon basic cell phone is dead on.
Of course there are also the so called "atomic" clocks and wrist watches that use miniature WWVB receivers to lock to the slow 60 kHz carrier AM modulated time code from Boulder CO. I have a bunch of different time sources in my home lab from a WWVB comparator with hoola hoop loop antenna, a rubidium oscillator, a GPS timing receiver, a shortwave receiver tuned to WWV on 10 MHz and my computers that periodically sync to Internet time servers. that said, I no longer wear a wrist watch as my cell phone provides a sufficient time check for my purposes. When it comes time. twice a year to reset those hidden real time clocks that cannot auto correct for daylight savings versus standard time, it becomes an adventure. I now have a list of over 60 devices that require such attention from me!
You mean you don't just keep everything on GMT <vbg>? I only have about 6 or 7 "conventional" clocks (microwave, oven, coffe maker, cordless phones, ancient clock radio and an old VCR, etc.) and I just take my cellphone (the Verizon one, the AT&T Blackberry is way off) around with me.
the quartz analog clocks rely on an inexpensive quartz crystal which is probably+/-100 ppm, typically probably 20 ppm.
The AC synchronous motor clocks rely on the power company. I think most of the major AC power grids litteraly count the number of cycles in an hour and speed up or slow down slightly every hour to make the long term stability way better even than the short term stability. So that there are exactly 5,184,000 cycles in a day (60 Hz US standard).
A thought problem, not a trick question: Assume two identical 12 hour clocks set accurately to the current time. One runs normally and the other backwards. In a 24 hour period, how many times will the hand positions of the two clocks exactly match? (Answer is the same whether a second hand is included or not).
Answer is 4x per 24 hour period. 6am, noon, 6pm and midnight. The answer would be the same if only the hour hand is present.
Reminds me of the ubiquitous AA battery-powered clocks. They were invented in Japan. During postwar reconstruction, eastern Japan including Tokyo ended up 50Hz generator from Europe and the western part including Osaka with 60Hz from American hardware. The battery powered clock eliminated the pain of having to buy an AC powered clock with the appropriate motor or gearing. The dual line frequency exists in Japan today; rather backwards for a modern industrial nation. At least modern power supplies will accept either frequency.
Back in the late 80's I built some custom equipment for a small clock mfg that had just received a shipment of clock faces with the numbers and text printed on the back of the clear laminate by a contract printing company. This was done to reduce costs as the laminate could be applied to several different clock face base colors. The printing company didn't notice that the laminate had been printed as viewed from the adhesive side thus creating reversed mirror image of the numbers/text when the laminate was applied its intended for use. While the clock company owner was greatly displeased at some of his employees assembling a few backwards-running mirror-image clocks, the clocks were a big hit at the local watering hole and it wasn't long before the new line of "novelty" clocks were selling more volume than the "normal" clocks.
This sounds like either a Bizarro cartoon, the beginning of a Twilight Zone episode, or a ghost story. I also laughed out loud, for the same reasons Beth did. Like Rob, I'm also trying to figure out how it could be used in real life: how the heck does that work?
...LOL...Bizarro Cartoon...clocks, and calendars... There's a Bizarro cartoon from a couple years ago...Two mayans are standing near this 4 foot diameter stone...calandar...filled completely with symbols...the one guy, with a mallet and chisel in his hands... says to the other..."I ran out of room, this will really freak someone out later.."
The "1" was in place of "11", "2" in place of "10", ect. The motors were changed to run in reverse so the hands turned CCW to correspond to the CCW number layout. The somewhat confusing part was that the numbers themselves were in reverse as if looking at lettering on a storefront window from inside the store.
I saw the same Bizarro cartoon after I posted about them: the strip reran this one last Sunday. The Mayan calendar carver actually says "I ran out of room after 2012." The other guy says something like "This will really freak someone out some day."
And thanks to fire-iron.biz for the reading instructions. Sounds really confusing in practice. Glad I wasn't one of their guests.
Not the same company but the page linked below has a similar type clock. It's actually quite funny to see people's reaction when they see it for the first time. You don't even need a novelty clock, just turn any standard wall clock upside down and watch how many people get confused.
This brings back great memories! When I was about 10 years old I started working with my dad, an electrician. One summer we were changing a house service and dad asked if I wanted to go up on the roof and cut off the utility power. I ran up the ladder and cut the wires and yelled down "Okay, its off!" He yelled back "So why are the light still on?" It was a city row home, and I had cut the neighbors power! We reconnected it and left the home owner a note. The next day the lady called and said everything seemed to be okay, but her kitchen closk was running backwards. Dad told her to unplug it and push the hands forward slightly, then plug it back in. It did restart in the right direction this time.
Our microwave oven is no more than a few years old. It has one of those turntables designed to provide uniform heating all the way around whatever is in the oven. One day I noticed that the direction of rotation of the turntable is completely random - some times it turns clockwise, sometimes counter-clockwise.
In regard to AC clocks versus quartz crystal clocks: Last year the Programmable Controller class I teach built a digital clock with an Allen-Bradley SLC-5/04 controller and six very large 7-segment displays - hours, minutes, and seconds. It is using a one second timer for its time base. Except for having no provision to account for Daylight Savings Time, it has been keeping very accurate time since May 2010.
I've experienced the same thing with my microwave, RonChownyk. When I'm not sure how long to zap something, I'll open the door and check the heat. If it needs more time, it invariably re-starts in the the reverse rotation. That happens consistently.
I had an analog alarm clock that developed a similar tendancy to run the wrong way. What I found is that it had a synchronous motor that was equally comfortable starting and running in either direction, and it used a rachet mechanism to force it to only run in the desired direction. When the grease on the rachet mechanism thickened a bit it kept the rachet dog from engaging the wheel, and so the motor could now rotate in either direction.
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