Dumore AC/DC motor?

Ulma Doctor

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they are called universal motors if i'm not mistaken
i have an old skill saw from WW2 that my grandfather passed down to me
she doesn't see much service anymore, but it does have an ac and dc rating
 

matthewsx

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Nice, I just was reading about them. It would be nice to have speed control on the tool grinder:)
 

markba633csi

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Yep, it's a thing, as Mike said it's called a universal motor and the speed can be varied
 

Flyinfool

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As mentioned the AC/DC motors are called universal motors. Universal motors have carbon brushes and both the field and the armature are wound with wire. Most (Not all) universal motors will be less efficient when running on DC and will wear out carbon brushes much faster. This reduced efficiency means less power available to do work and/or more heat generated for the same load.

You can still vary the speed whether it is running on AC or DC. Harbor Freight sells an inexpensive speed control that will let you run on AC and have speed control of a universal motor. They call it a Router Speed Control, most routers are universal motors.
 

Janderso

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They made everything so robust back in those days.
I can see where the option of AC or DC would be beneficial in certain industrial/international applications.
 

matthewsx

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Yes, pretty standard brushes. I had to take it apart to attach new electric leads and for such a little guy it is very stout.

I'll try one of the HF variable speed units, no sense of sourcing a DC supply if AC will work.

Thanks,

John
 

matthewsx

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I had an old lamp dimmer extension cord laying around, it works great.
 

Superburban

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Remember, the voltage requirement is still the same, for AC or DC. 110-120 volts DC is not that common. There us to be adds in magazines like popular science, that had a box you could wire into your cars alternator, to produce 110 DC (had to get the engine rpms right). It would run drills, and other tools with brushes. I have one somewhere, after reading all the instructions, I decided an inverter was a better option.
 
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