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 Trouble Shooting a Varney NW2
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Author Previous Topic: BAR Switcher Topic Next Topic: Diesels in action on your layout  

wstrouse
New Hire

Posted - 10/03/2018 :  11:51:21 AM  Show Profile  Reply with Quote
I picked up what I believe to be a Varney NW2. I took it apart, cleaned and lubed everything, and replaced the wiring with modern silicon insulated wire. The loco runs great at first, but after a few minutes begins to gradually slow to a stop and the motor gets hot. Is this a symptom of degraded magnets? All the gearing seems to turn easy, no binding, and no apparent shorts. If I let it sit for an hour or so the process repeats. Does it with or without the shell on (I soldered the lead to the opposite truck frame for a more reliable contact than screwing it to the shell. Any suggestions would be appreciated.

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Ray46
Engine Wiper

Posted - 10/03/2018 :  1:15:24 PM  Show Profile  Reply with Quote
Re-motor.


Country: USA | Posts: 259 Go to Top of Page

wstrouse
New Hire

Posted - 10/03/2018 :  1:51:16 PM  Show Profile  Reply with Quote
Are replacing the magnets worth it, or am I better off adapting a more modern motor to it?


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desertdrover
Engineer



Posted - 10/03/2018 :  3:00:54 PM  Show Profile  Reply with Quote
I'm guessing that it is a early 1960's Pittman DC-60 motor installed in your NW2. If it is a locomotive you like, I'd go with a re-motor instead of replacing magnets and tiring to get it to run well.


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jbvb
Fireman

Premium Member


Posted - 10/03/2018 :  3:25:13 PM  Show Profile  Visit jbvb's Homepage  Reply with Quote
If you have a voltmeter/multitester it would be worth watching how the voltage and current change as it slows and gets hot. I'd expect weak magnets to cause a large current draw right from the outset, so the only explanation I can think of for the gradual slowing would be something getting hot, expanding and creating extra friction. Of course, a moderate-resistance armature or commutator short could work the same way. Have you cleaned the commutator, including gently digging out the slots?

I recall a 1970s MR article explaining how to build a magnetizing/demagnetizing rig for open frame motors. It used a couple of old transformer coils.



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wstrouse
New Hire

Posted - 10/04/2018 :  2:36:28 PM  Show Profile  Reply with Quote
I removed the brushes and used denatured alcohol on q tips to clean the commutator, didn't concentrate on the slots. It gets too hot to touch, but doesn't seem to bind anything even hot. Put it in the refrigerator and it repeats the process in an hour.

I've been looking for time to hook up my multi meter. I like fixing old stuff rather than buying the latest and greatest.

I've picked up a few older loco's off Ebay recently. This is going on the shelf until my old time MDC 2-8-0 is done, but I'll get back to it. Thanks for the replys.



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