Standard Electric Standard Electric - diodes and power reserve

[Thurmond]

From a prior post, I was deciding upon a diode to mitigate arcing on the contacts. I ended up using a Schottky 1N5817, rated at 1A and 20V. My clock seems to run fine on a 12V source, and draws about 0.5A during contact. No more arcing.

Now, onto the power reserve of the clock's spring. Fully wound, the clock will run about 50 minutes or so, which is apparently correctly. If I let the clock run down (as I do to measure the power reserve), and then wind it manually for approximately 10 min of power reserve. And then apply electrical power to allow it to run normally. After several days of operation, the power reserve is max'ed out again (around 50 minutes).

I've checked the 'kicker' that winds the main spring. It is advancing one tooth every minute.

I'm curious as if this is normal operation, or do other's Standard Electric clock's power reserve remain somewhere between completely wound and completely unwound?

I would think that the clock was designed so that the power reserve would stay about 50%, but maybe there is a bias in the design to slightly wind the clock over time, with the thought that a clock fully wound is better than one that gravitates to an unwound (and stopped) state.

Just wondering out loud, as this is my first Standard Electric.

Thurmond

PS Coming from the watch world (when the eyes were young), I use the term 'power reserve'. I don't know if this is the correct terminology in the clock world or not.

 

[mxfrank]

I think you'll find the winding ratchet has 59 teeth.

 

[novicetimekeeper]

I thought it was capacitors that were used to prevent arcing on contacts. Is the arc in this case a back emf?

 

[mxfrank]

Yes, the inductive kick is what kills the contacts. There are many ways to shunt spark current. A TVS diode is probably the most effective and least fussy solution for a self winder. Capacitor works best in series with a resistor, and the size of the components matters. A resistor is the simplest solution, but decreases battery life. Here's a comparison of various shunt circuits:

https://jaxxeninc.com/pdfs/pcb-relays/tech_info.pdf

 

[novicetimekeeper]

Yes, the inductive kick is what kills the contacts. There are many ways to shunt spark current. A TVS diode is probably the most effective and least fussy solution for a self winder. Capacitor works best in series with a resistor, and the size of the components matters. A resistor is the simplest solution, but decreases battery life. Here's a comparison of various shunt circuits:

https://jaxxeninc.com/pdfs/pcb-relays/tech_info.pdf

Thank you. I'm only really familiar with them from induction coils

 

[Toughtool]

I would think that the clock was designed so that the power reserve would stay about 50%, but maybe there is a bias in the design to slightly wind the clock over time, with the thought that a clock fully wound is better than one that gravitates to an unwound (and stopped) state.

The clock will run more accurately if it is kept fully wound. In the case of an IBM master, the pulse to the wind magnet is 80 pulses per hour, but it only needs about 60 pulses per hour to keep it wound. The drive pawl is prevented from engaging the next tooth until the clock has run down enough for the drive pawl to engage. This prevents damage from overwinding. The extra 20 pulses is for rewinding a run down mainspring after a power loss. Remember, in the early 1900's, power line service was not as reliable as it is now. I would think the Standard Electric would do the same.

 

[John Sidlauskas]

Having the clock wound is normal, atleast for my clock! Some clocks had 59 teeth on the winding wheel, this was due to the fact of having frequent power line failure, Standard thought that having this reduced amount of teeth would prolong the clock incase the power went out, this was proved to be a very bad way since it puts more stress on the gear train and could prove other problems, but most case scenario it is fine. If you have moved the contacts on the escapment I would try to refer to a Service manual from the 1960s, If the clock is winding before the swing of the pendulum is at its end, it will cause the rewind to engage early and put more stress on the gear train. I have my clock rewind set to set off a little after most of the pendelum has swung, having the escapement fully engaged with the pallet.

 

[svenedin]

Interesting. I know nothing about electric clocks but TVS diodes are used on old SU electric motor car fuel pumps to reduce arcing. Zener diodes can also be used but in the case of the fuel pump the contact frequency is high enough that the Zener can fail so the TVS is a better solution