Film-Tech Forum ARCHIVE: Century motor start resistor value?

This is topic Century motor start resistor value? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=008400

Posted by Scott Norwood (Member # 30) on 12-04-2006, 12:37 PM:

My Centurys (MSAs with MTR-3-67 soundheads) have neither flywheels nor starting resistors, nor can I afford inverters. They come up to speed quite quickly and I assume that this is not good for the mechanisms.

What is the value of the "standard" resistor that is found in the little box that is normally attached to the motor? Oddly, it is not listed in the R-3 soundhead manual on this site. Does the resistor go across the hot or neutral AC wire? Do I need the flywheels, too? These are my personal machines and will receive only occasional home use. In their previous lives, they were used occasionally in a screening room.

In case it matters, these have the 1725 RPM, 1/4 hp Westinghouse motors of whatever type was shipped with the machines circa 1970.

Posted by Gordon McLeod (Member # 33) on 12-04-2006, 02:58 PM:

Depends on the motor
usually it was around 40ohms and connected in serries with the start winding

Posted by Louis Bornwasser (Member # 3063) on 12-04-2006, 06:11 PM:

You absolutely need the flywheels; otherwise you will absolutely replace the main drive gear often.

The small resistor is wired only into the start winding. Value is unknown, but I think I have some in the shop.

My favorite resistor is wired into the hot wire and is a 150 watt, 2 ohm, adjustable resistor. Hard to find lately. Louis