Hello All,
Thank you for this opportunity to post about a recent acquisition, an International Time Recorder Master Clock. The device appears to be in excellent condition although it did not come with the original power supply. I am not sure of the model – there are no tags or markings on the clock – but it was the time keeper for the San Francisco-Oakland Bay Bridge which was built in 1936 and I believe that it is a Model 13. I have poured over all the posts regarding power supplies and want to acknowledge the extremely generous contributions of many people including the late Harold Bain, eskmill, swolf and recently, Toughtool.
I am trying to use the existing impulse mechanism on the clock to create the simplest way of winding the clock. At this time, I have no intention of driving any slave clocks, though that could be a fun step for later on. My inclination would be to create a basic circuit with a 24 volt power supply where the power is switched on and off to the wind coil using the minute contact switch on the clock. But I have read in the forum that when the power is cut off from the winding coil, the electromagnetic field it creates collapses and causes the contacts (on the minute switch) to arc and wear out. The suggestion was made to use a "damping resistor" rated for 10x the resistance of the wind coil. I measured the resistance of the coil and it was 144.5 ohms. Therefore, I would like to use a 1500 ohm resistor. I have posted my design for a circuit and would sincerely welcome any comments or advise from this community. Also, I traced the wires from the contact switches to the terminal block on the top of the clock and have labeled them in the attached image. I have also included the clock face for help dating it. Thank you very much.
Thank you for this opportunity to post about a recent acquisition, an International Time Recorder Master Clock. The device appears to be in excellent condition although it did not come with the original power supply. I am not sure of the model – there are no tags or markings on the clock – but it was the time keeper for the San Francisco-Oakland Bay Bridge which was built in 1936 and I believe that it is a Model 13. I have poured over all the posts regarding power supplies and want to acknowledge the extremely generous contributions of many people including the late Harold Bain, eskmill, swolf and recently, Toughtool.
I am trying to use the existing impulse mechanism on the clock to create the simplest way of winding the clock. At this time, I have no intention of driving any slave clocks, though that could be a fun step for later on. My inclination would be to create a basic circuit with a 24 volt power supply where the power is switched on and off to the wind coil using the minute contact switch on the clock. But I have read in the forum that when the power is cut off from the winding coil, the electromagnetic field it creates collapses and causes the contacts (on the minute switch) to arc and wear out. The suggestion was made to use a "damping resistor" rated for 10x the resistance of the wind coil. I measured the resistance of the coil and it was 144.5 ohms. Therefore, I would like to use a 1500 ohm resistor. I have posted my design for a circuit and would sincerely welcome any comments or advise from this community. Also, I traced the wires from the contact switches to the terminal block on the top of the clock and have labeled them in the attached image. I have also included the clock face for help dating it. Thank you very much.



