Converting a spin-start electric clock to a self-starting clock

[Bud]

Hi, I have a spin-start advertising clock that is mounted high on my wall and it is a pain to restart after every power failure. We have had several power failures recently. I was wondering if there is a simple adaptation to make the clock self starting, perhaps adding a capacitor? Thanks in advance.

 

[R. Croswell]

Hi, I have a spin-start advertising clock that is mounted high on my wall and it is a pain to restart after every power failure. We have had several power failures recently. I was wondering if there is a simple adaptation to make the clock self starting, perhaps adding a capacitor? Thanks in advance.

The simple "adaptation" is replace the movement with a new self-starting movement which will also be safer. Just adding a capacitor won't do it.

 

[Willie X]

It takes a copper wire loop through the stator leaves, in just the right place to make it start. I have no clue about how to do that, or what else it might take.

I like RC's answer.

Willie X

 

[Dick Feldman]

Many of those clocks ran hot and over the last 80 years or so, the insulation has broken down. You can bet on that.
If it has the original cord, It is probably not in good shape.
At the very least the cord should be replaced with a phased cord (one with one fatter contact) and an inline fuse should be added so the thing does not turn into a ball of fire on your wall.
Especially since is inconvenient to reach.
That is what I think,
Dick

 

[Bud]

I replaced the cord when I cleaned and relubricated the movement. It keeps fairly good time. I don't really like that it stops after a power failure and then just hums when the power comes back on. I may just unplug it and leave it that way. The clock is on a circuit with a circuit breaker, but I may consider some type of fuse. What fuse rating should I use, 5 amps?

 

[Dick Feldman]

What fuse rating should I use, 5 amps?

5 or less amps. Make sure the fuse is on the power side of the cord/plug and not on the neutral side of the plug.
Inspect the internal wiring for faults/cracks, etc.
The clock would likely be on fire before it tripped a 15 or 20 amp breaker.
If you unplug the clock it will be correct twice per day.
Dick

 

[R. Croswell]

I replaced the cord when I cleaned and relubricated the movement. It keeps fairly good time. I don't really like that it stops after a power failure and then just hums when the power comes back on. I may just unplug it and leave it that way. The clock is on a circuit with a circuit breaker, but I may consider some type of fuse. What fuse rating should I use, 5 amps?

If you decide to run the clock and add a fuse, the fuse should be about 0.1 amp. (1/10 amp) which is available from electronics supply stores as a small glass fuse. The motor typically draws about 2 or 3 watts of power - amps x volts = watts. You will also need an in-line fuse holder that should be available from the same source. The motor is not polarized so the fuse can go in line with either wire from the motor. (If the fuse were placed at the plug it would go in the "hot" wire, but at the motor it doesn't matter.) The insulation on the cord is only part of the story. The motor has a coil of many feet of very fine copper wire wound in several layers. The wire is only insulated by a thin layer of enamel that's almost 100 years old. and each layer is separated by a thin layer of paper that's equally old. The fine wire is terminated at the short wires that exit the motor and the whole coil is wrapped in heavy paper and typically varnished. If the insulation between the coils or the layers fail and some of the coils are shorted out the motor will begin to overheat. The hotter it gets the more insulation will fail and the hotter it gets. Yes, it would be on fire before the home circuit breaker would trip.

It is synchronous motor that runs at some multiple of 60 rpm. Being a single phase motor, there is no specific phase rotation so it just tries to turn in one direction then the other and fails to start. If you want to play with it and add the copper wire loop that Willie referred to, it must be a closed loop (the ends need to be connected so current can flow through the loop). The loop would typically be placed off center around one of the pole pieces. The magnetic field generated by the main coil induces a current in the loop that, if setup correctly, will oppose the rotation in one direction and helping in the other to get it started. It is called a shading coil and typically found in shaded pole motors. I doubt that you can make it work without some serious redesign of the motors pole pieces.

During my lifetime, I know of two house fires - one was "determined" to have been caused by an electric clock, and the other was possibly caused by an electric clock (an electric clock was at the source ignition and no other verifiable ignition source).

RC

 

[Dick Feldman]

The fuse should go on the wire that is hot on the cord, not the wire lead (neutral) having the fat plug prong.
Fusing the neutral on an AC circuit is of little or no use.
Maybe the best solution is to replace the clock motor with a quartz movement with a battery.
You should be able to find some period hands to match the originals.
Then you will have no possible electric hazard and will not have to deal with any electric cords or electrical outages.
JMHO
Dick

 

[Mike Mall]

If you can find the proper physical size (.1 amp) fuse to fit in a typical Christmas light set plug, that would be easy.
That fuse would give you 11 to 12 watts, which should be plenty, but still be quite sensitive.
An old useless set would probably be easy to find.
The fuses that come in them are usually rated at 5 amps (I've read), that's 600 watts - not real sensitive.
Both sides are usually fused, and the cord could be shortened to eliminate all the light sockets.

 

[R. Croswell]

Sorry for any confusion (post # 7), "The motor is not polarized so the fuse can go in line with either wire from the motor. (If the fuse were placed at the plug it would go in the "hot" wire, but at the motor it doesn't matter.)". This IS correct but perhaps did not go far enough.

In the day these motors had two black wires and did not designate one as "hot" and the other "neutral". Therefore, if an in-line fuse is added, it may be connected to either motor lead. If the original non-polarized power cord and plug is being replaced with a polarized power cord and plug (plug with one wide prong and one narrow), the "hot" lead from the narrow plug prong should connect to the supply end of the fuse holder. If the original cord or a non-polarized replacement cord is used it obviously does not matter which wire is connected to the supply end of the fuse holder.

The placement of the fuse holder relative to the polarization of the line cord is not for fire protection purposes but as an added protection from electrical shock. In a nonpolarized installation if the fuse opens in the neutral lead voltage is still supplied to the motor and if there is any leakage to the motor case, touching the motor while the fuse is blown and the cord still plugged in could result in an electrical shock under some conditions.

A suitable fuse holder is available here: https://www.jameco.com/z/JEF-702B-R...-In-Line-Fuseholder-22AWG-3-Wires_109322.html

A selection of fuses from 0.125 amp (125 milliamp) and up is available here: https://www.jameco.com/shop/Keyword...=10001&storeId=10001&langId=-1&freeText=fuses

RC

 

[shutterbug]

Have you considered adding something like a power back up to the circuit? Most are good for a couple of hours on a computer, and probably a lot more on a clock.

 

[RODALCO]

You still need to get to the clock after the power outage to adjust the time.

The idea behind these non-starting clocks was, that after a power outage the time stood still, avoiding the issue that a clock was half an hour slow, if gone unnoticed and the time was wrong.

A stopped clock gets noticed that something was wrong.

 

[R. Croswell]

You still need to get to the clock after the power outage to adjust the time.

The idea behind these non-starting clocks was, that after a power outage the time stood still, avoiding the issue that a clock was half an hour slow, if gone unnoticed and the time was wrong.

A stopped clock gets noticed that something was wrong.

I grew up with one of these non-self-starting clocks. Ours, and most of the ones I have seen, both self-starters and non-starters, have an indicator on the face to indicate if the power has been off. The one in our living room had a little round hole in the face and behind the hole was a rotating disk that was half black and half white. If the clock was running the hole appeared to rapidly blink, black, white, black, white, black..... When the power went off and the motor stopped, and the blinking stopped and did not resume until the motor was spun to restart it. Our kitchen clock was a self-starter but had a similar hole in the dial where a little red flag would drop behind the hole when the power went off making the hole turn red to say the time needs to be reset. A few years ago I sold a Dutch mill clock that was not a self-starter. When power had been off the windmill blades stopped. If one checked the time and the blades were not turning one knew the time was incorrect.

I do not believe that non-starting clocks were made that way intentionally to call attention to the fact that the power had been off, otherwise clock makers would have continued to make them that way into modern times. And yes, you still need to get to the clock after the power outage to adjust the time whether it self starts or not. There are several types of single-phase AC motors that have been use in numerous household applications and they all have one thing in common, they require some means to start them rotating the right direction. (These non-starting clocks will happily run backwards if started that way). The AC motors used in clocks have to run at synchronous speed, which is some factor of 3600 (3600 rpm being the synchronous speed for a 2-pole motor on 60 Hz AC power). The challenge the early electric clock makers faced was devising a means that would start the clock motor running in the right direction but would not interfere with the motor attaining synchronous speed, otherwise the clock would not keep time. In other applications AC motors typically run at slightly less than synchronous speeds, which really doesn't matter for most applications. Once the self-starting synchronous AC clock motor was perfected, everyone quickly jumped on the wagon and abandoned the old spin start clocks. When I was little, I rather enjoyed restarting the clock when the power went off which happened more frequently then.

RC