# American Models 4-8-4 Northern



## rjcaster (4 mo ago)

Immediately this locomotive throws sparks from the front drive wheels and gets extremely hot around that area. Also, if it does move, it will slow down, stop and you can hear "humming."

I took the unit and put it on its back. I connected the wire to it and it runs perfectly!

Does anyone have any idea as to what is going wrong?


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## AmFlyer (Mar 16, 2012)

The front truck on an AM Northern is not a power pickup. The wheels are metal but there should be no continuity between any two wheels. Each axle between wheels is a plastic insulator. I included a picture of the front truck for reference. Check with an Ohmmeter to identify the conduction path from one side to the other. As long as the front wheels are not on the track there will be no short.


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## flyernut (Oct 31, 2010)

As Tom said, there's a short somewhere in the truck.. If it was a AF engine, I would say the white plastic insulators are loose or broken. I'm not familiar with AM engines, sorry. That's my best guess.,


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## mopac (Feb 24, 2011)

Tom, it is FRONT driver wheels sparking, not Front pilot wheels. I do not have such a steamer so I have no idea.


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## Yard King (4 mo ago)

A picture of it on its back showing the offending wheels might help to see what the problem is.


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## AmFlyer (Mar 16, 2012)

You are right, I read the first post incorrectly.


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## AmFlyer (Mar 16, 2012)

Conceptually Flyernut is on the right track. All eight AM Northern drivers are pressed on the axles using a nylon insulator, they are visible in the picture. These should preclude a short unless one has failed. The only difference in the front pair of drivers is the traction tires, again visible (barely) in the picture. Even if the engine has thrown a traction tire it should not cause a short.


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## rjcaster (4 mo ago)

To all,

Thanks for the information. The one post did correct the first error in that the sparks were coming from the front two drive wheels, not the leading truck. I will check the insulators but I am still dumbfounded at how it runs perfectly when set upside down and power is supplied,


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## AmFlyer (Mar 16, 2012)

There is no short when the drive wheels are not on the rails, so it will run perfectly upside down when tested. I recommend using an ohmmeter with the engine upside down to see where there is continuity between the drive wheel tire and either the chassis or the opposite drive wheel.


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## AmFlyer (Mar 16, 2012)

This is an AM Northern, Lackawanna pictured.


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## rjcaster (4 mo ago)

AmFlyer said:


> There is no short when the drive wheels are not on the rails, so it will run perfectly upside down when tested. I recommend using an ohmmeter with the engine upside down to see where there is continuity between the drive wheel tire and either the chassis or the opposite drive wheel.


Tom,

Thank you.


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## flyernut (Oct 31, 2010)

AmFlyer said:


> There is no short when the drive wheels are not on the rails, so it will run perfectly upside down when tested. I recommend using an ohmmeter with the engine upside down to see where there is continuity between the drive wheel tire and either the chassis or the opposite drive wheel.


Yes sir..Whenever I do a repair for someone, the engine MUST run at least 1000' without any interruptions, forward and reverse.Many times the engine runs perfectly on the test bench but shorts out on the track.. To me, a easy fix as 1 or more of the drive wheel insulators are loose, broken, or sometimes missing...A short every time. I just had this happen to me the other night. I was running a 312 pulling 4 passenger cars and noticed a few sparks coming from the engine chassis.I pulled the engine and checked it and sure enough, the center blind driver was loose on the axle and the insulator was loose and coming off the wheel.. I can't explain how I missed that while servicing it, but miss it I did.


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## rjcaster (4 mo ago)

flyernut said:


> Yes sir..Whenever I do a repair for someone, the engine MUST run at least 1000' without any interruptions, forward and reverse.Many times the engine runs perfectly on the test bench but shorts out on the track.. To me, a easy fix as 1 or more of the drive wheel insulators are loose, broken, or sometimes missing...A short every time. I just had this happen to me the other night. I was running a 312 pulling 4 passenger cars and noticed a few sparks coming from the engine chassis.I pulled the engine and checked it and sure enough, the center blind driver was loose on the axle and the insulator was loose and coming off the wheel.. I can't explain how I missed that while servicing it, but miss it I did.


Truly great stuff. Thank you!


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## rjcaster (4 mo ago)

rjcaster said:


> Truly great stuff. Thank you!


Do you do any repair on American Models?


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## flyernut (Oct 31, 2010)

rjcaster said:


> Do you do any repair on American Models?


If you're asking me, the answer is no, I only work on 3 digit steam locos, and occasionally a diesel or two.


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## AmFlyer (Mar 16, 2012)

Rjcaster, I send all my AM engine work to Ed at Goldinhands.com. He is in Schaumberg, Il, I am in SoCal. Ed has installed TMCC and Railsounds in all my AM engines. In the steam engines, in addition, he has installed fan driven smoke units and electrocouplers. I have had some of the gear towers fail in the diesels and he repairs those. He can also add lighting and strobes. Take a look at his website for examples.


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## AmFlyer (Mar 16, 2012)

Ed has also done DCC installs in RRM engines. Not his favorite jobs since the RRM engines are harder to work with than the AM engines. He has also done a TMCC/Railsounds install in a RRM steam engine. I recall him saying "never again."


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