Electrical: 6v to 12v conversion. Self winding clock

[Timothy Barr]

I have a 48 Land Cruiser in which I am converting to 12 volts. I got the Randy Rundle set up. It mentions that the Runtz dash guage voltage reducer is good, except for the self winding clocks. Another 48 Studebaker owner thought his was self winding. Does anybody know if mine might be. If so, where would I go to find out what I have to do instead of the Runtz? Not sure if it does work. How do I find out?

[altair]

I can't help you with much, else but if your clock is self winding you will hear it about every 15 minutes, a click and a buss.

[gordr]

Unless your clock has a key or some other means to wind it, it is self-winding. All they are is a pretty ordinary mechanical clock movement, like a wind-up alarm clock, except the mainspring, instead of being a very long steel ribbon in a cup, capable of running the clock for more than 24 hours, is a short coil spring, wrapped around a small drum, which is linked to a steel tab set over an electromagnet. As the mainspring unwinds, driving the clockwork, the metal tab slowly pulls away from the electromagnet, and an electrical contact carried on that tab eventually meets another one, and sends a jolt of current through the coil of the electromagnet, which pulls hard on that tab, winding up the mainspring, and also breaking the circuit that feeds it. And the cycle repeats. In my recollection, it cycles a lot faster than every 15 minutes, but that could depend upon the model of clock.

Incidentally, car clocks are so designed that the act of setting them also adjusts the regulator that controls how fast they run. So, if the clock is 10 minutes slow, and you set it ahead to the right time, it speeds up a tiny amount, and maybe the next time you notice it is "wrong" it is only 6 minutes slow. So you slowly approach having a clock that keeps perfect time. So all of you that put a switch in the clock power lead, or who disconnect your battery on a stored car, are defeating that little feature. Say the clock was keeping perfect time; you disconnect the battery, and a week later, reconnect it, but at 8:00 A.M., instead of the 4:00 P.M. it was showing when you disconnected the battery. So you set the clock's hands ahead 4 hours to make it show the right time, and now you have made it run too fast! These clocks were designed to work properly in cars that saw more or less daily use, and they worked fine for that. The design is incompatible with the typical pattern of use seen by collector cars.

Now to run that six volt clock on twelve volts, the best answer would be a resistor with the same value as the resistance of the solenoid coil, which you could measure with an accurate multimeter. The solenoid is to all intents and purposes a resistive load, and a momentary one at that. I would actually suggest using a resistor with maybe 80% of the resistance of the solenoid coil. It won't mind a little extra current. What usually kills electric car clocks is letting the battery run down. The clock goes to wind itself on a nearly-dead battery, and there isn't enough oomph there to wind the clock spring, so it just sits and buzzes, and the contacts burn out.

IMHO, the best solution for a clock in a collector car is to replace the old movement with a modern quartz movement, and hide an easily-accessible battery holder someplace under the dash. And it will run for a year on one AA cell. And eagle eye can spot that the second hand moves differently, but so what? Car companies bought in their clocks, anyway. The only part of the clock's design that the stylist was responsible for is the look of the face and hands.

[RDWEAVER]

Unless your clock has a key or some other means to wind it, it is self-winding. All they are is a pretty ordinary mechanical clock movement, like a wind-up alarm clock, except the mainspring, instead of being a very long steel ribbon in a cup, capable of running the clock for more than 24 hours, is a short coil spring, wrapped around a small drum, which is linked to a steel tab set over an electromagnet. As the mainspring unwinds, driving the clockwork, the metal tab slowly pulls away from the electromagnet, and an electrical contact carried on that tab eventually meets another one, and sends a jolt of current through the coil of the electromagnet, which pulls hard on that tab, winding up the mainspring, and also breaking the circuit that feeds it. And the cycle repeats. In my recollection, it cycles a lot faster than every 15 minutes, but that could depend upon the model of clock.

Incidentally, car clocks are so designed that the act of setting them also adjusts the regulator that controls how fast they run. So, if the clock is 10 minutes slow, and you set it ahead to the right time, it speeds up a tiny amount, and maybe the next time you notice it is "wrong" it is only 6 minutes slow. So you slowly approach having a clock that keeps perfect time. So all of you that put a switch in the clock power lead, or who disconnect your battery on a stored car, are defeating that little feature. Say the clock was keeping perfect time; you disconnect the battery, and a week later, reconnect it, but at 8:00 A.M., instead of the 4:00 P.M. it was showing when you disconnected the battery. So you set the clock's hands ahead 4 hours to make it show the right time, and now you have made it run too fast! These clocks were designed to work properly in cars that saw more or less daily use, and they worked fine for that. The design is incompatible with the typical pattern of use seen by collector cars.

Now to run that six volt clock on twelve volts, the best answer would be a resistor with the same value as the resistance of the solenoid coil, which you could measure with an accurate multimeter. The solenoid is to all intents and purposes a resistive load, and a momentary one at that. I would actually suggest using a resistor with maybe 80% of the resistance of the solenoid coil. It won't mind a little extra current. What usually kills electric car clocks is letting the battery run down. The clock goes to wind itself on a nearly-dead battery, and there isn't enough oomph there to wind the clock spring, so it just sits and buzzes, and the contacts burn out.

IMHO, the best solution for a clock in a collector car is to replace the old movement with a modern quartz movement, and hide an easily-accessible battery holder someplace under the dash. And it will run for a year on one AA cell. And eagle eye can spot that the second hand moves differently, but so what? Car companies bought in their clocks, anyway. The only part of the clock's design that the stylist was responsible for is the look of the face and hands.

I was not aware of the self adjusting feature you explained in this post. Our Studebaker clock when we first got the car did not wind all of the time so we always had to set the clock. Once when adjusting the knob unscrewed from the shaft while I was backing up the time so I made a note to always set hands in a clockwise rotation. Come to think of it now the clock always runs fast..... it gains about 9 min. per hour now but it seems to always wind itself. Could you guess how many hrs. counterclockwise I might need to turn it to get it correct?

[TWChamp]

Gord, good point about the self adjusting fast/slow time set.
I put a NOS clock in my 50 Champion, so to save wear I also use a toggle switch and only turn it on for the days I drive the car.

[rockne10]

... where would I go to find out what I have to do instead of the Runtz?

I hope someone will correct me but, I am under the impression the short zap that winds the spring when the points close is so quick that 12-volts probably won't damage the 6-volt clock; much as 12 volts don't damage 6-volt horns if they are just honked and not blasted.
These are called "electrically wound", not self wound. As the spring loosens, a set of points closes and an electric jolt rewinds the spring. The clock itself is mechanical; you can hear the tick-tick-tick if you listen. You can also hear the tiny "zip" every five or six minutes when the points close and it rewinds. In this way the clock uses only the tiniest amount of battery when the car is not running.

[gordr]

Gord, good point about the self adjusting fast/slow time set.
I put a NOS clock in my 50 Champion, so to save wear I also use a toggle switch and only turn it on for the days I drive the car.

Yeah. My '64 convertible came to me that way; clock on a switch. So you get in, start the engine, turn on the clock, and set it to read the current time. The poor dumb clock doesn't know how many hours it sat with no power; all it knows is that you set it forward or back X hours and Y minutes, so it speeds up or slows down by some unknowable increment to compensate for its self-perceived failings. When you put the clock on a switch like that, you are basically resetting the iterative regulating process back to Square One each time. If you must put the clock on a switch, just wait until the the actual time is whatever shows on the clock before turning it on again.

[TWChamp]

On the subject of electric contacts on clocks, in the 80's I was in a welding supply store in Watertown, South Dakota, and saw a picture of a blown up mid 50's Chevrolet. The owner carried home a tank of acetylene in the back seat, and the valve was leaking or partially open. The gas built up overnight, and sometime during the night a spark from the clock resetting ignited the gas, and that was the end of his car.

[altair]

In my other life I used to investigate fires and explosions and one particular explosion comes to mind. A chap on a farm owned a Ford Mustang with an electrical winding clock, he had placed an empty acetylene cylinder in the trunk to return to town (acetylene cylinders are never really empty) and was told by another learned farmer to always ship acetylene cylinders with the valve open, which he did. The evening was cool the night before he had loaded the cylinder, however during the nest day before he returned to town the temperature increased sufficient to allow the gas to escape and fill the vehicle. The owner was in his house looking out the window only to watch his vehicle explode into thousands of pieces leaving nothing recognizable as a vehicle. There was pieces scattered all over the yard and in the trees. It was determined that a spark from the self (electrically wound) clock was the source of ignition. Lesson learned do not ship acetylene cylinders in your car, and if you do, do not leave the valve open.

[Jerry Forrester]

Incidentally, car clocks are so designed that the act of setting them also adjusts the regulator that controls how fast they run. So, if the clock is 10 minutes slow, and you set it ahead to the right time, it speeds up a tiny amount, and maybe the next time you notice it is "wrong" it is only 6 minutes slow. So you slowly approach having a clock that keeps perfect time.

Wow! I like to learn something new every day.
Thanks Gord, I can go back to bed now. Today's task is complete.