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When dealing with the various vintage sewing machines we find ourselves constantly learning and expanding our understanding of the basic principles that affect the overall performance of our sewing machines. This being said I would like to explore a series of variables over the next few posts and include the common misconceptions that are all too often repeated until they become accepted as fact, even though they defy the physics of the concept they are defining.
Since I am in the USA and our common household electricity is single-phase, 115-volt nominal, AC current, I will be focusing my experiences based upon machines requiring this type of electricity. I don’t feel that my experience with commercial and industrial motors and circuits will readily transfer to the household sewing machines designed for other voltages or straight DC current.
Now on with the show and let’s talk a little about our sewing machine motors. The majority of vintage sewing machines use a pulley and belt system to turn the main shaft, which in turn operates all the other moving mechanical parts of the machine. From this majority, there are a few that are OEM (original equipment manufacturer) or specialty-built motors specific to brand or model sewing machine it serves. The rest of the belt driven machines use motors that were built to be easily removed, replaced, and retrofitted onto older bodies to upgrade the life of grandma’s old treadle. They were built by hundreds of motor manufacturers over the years. They are available with mounting hardware already attached or with mount bracket threaded holes or studs either on the sides of the motor or in some cases on the end bells(shaft end and opposite shaft ends )of the motor. Some are completely universal with all the necessary mounting to attach motor to the existing original bracket.
The second most commonly used vintage sewing machine motor drive system is called a friction drive . Friction drive systems utilize a rubber wheel in place of the motor pulley. The wheel rides the surface of the hand wheel or a special rim shoulder of the hand wheel with enough pressure for the friction of the rubber to spin the hand wheel and in turn the main shaft and all the subsequent mechanical movements of the machine. These motors are usually mounted to a hinged spring mount plate with the spring supplying the pressure to create the friction. The major difference using this type drive system versus a belt system is physics. While a belted system will spin the main shaft the same direction as the motor, a friction drive will spin the main shaft the opposite direction of the motor so there needs to be more care taken when choosing your replacement motor. This same care applies to belted systems also but most hand wheels rotate towards the sewing machine operator with few turning away from the operator making it a much more readily available drive system for replacement motors.
The final vintage sewing machine drive system is the gear driven systems, these systems are unique to the manufacturer of the machines, therefore making replacement or upgrades with a universal motor replacement virtually impossible. While I hesitate to say this type drive system is always an internal drive, I will speak truthfully to the fact that I personally have never seen any external gear motor driven system, yet. In my opinion, gear drives are the smoothest drive system available and by far one of my favorites.
Since we are almost finished with the drive systems and the last systems we covered are proprietary, We should also mention there are a very few specialized motors which are manufactured into the bodies of the machines. Whereas these motors can be disassembled and rebuilt they are not for the faint of heart or the amateur beginner. If these motors need more than a change of brushes and the armature cleaned up then the decision must be made as to the cost effectiveness of such an extensive repair. Generally, at this point, the machine becomes a donor machine so others can live on or it gets its replacement motor from some other unlucky donor machine.
This concludes the first part of the vintage sewing machine motor and drive systems break down. Next time we will get into the motor ratings, horsepower etc. and enlighten a little bit about why so many motors and stitch per minute differences with the same rated motors. Until then may your ruler never slip as the rotary cutter travels its length. Enjoy your machines.
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