# Weak motor in my Athearn :(



## Green River (Dec 19, 2009)

I have basically brand new blue box Athearn SD-40-2 that the motor seems pretty week to me, at least compared to the other blue boxes I have. I took both gear boxes apart, cleaned and lubed with LaBelle's oil and cleaned the contact points and still no luck. I figured with the 12 wheel drive I should be able to pull stumps with this thing but it struggles with 8-10 good pulling cars, sometimes it needs help pulling itself out of its tracks to get going. Am I missing something, will brushes cause problems like this? I know the blue boxes can be hit or miss at times but surely there is something else I can do, I don't mind tinkering with it as long as I have to if I just knew what to do. Maybe I will have to get a new motor?? Thanks for looking.


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## DonR (Oct 18, 2012)

I note that you cleaned and lubed the trucks, but did you notice
that the wheels and gears were free turning? The same
question about the motor, free turning? Binding is always
a first suspicion when a loco is not pulling strongly.

While apart, you might do a stall test on the motor only by putting
a meter set to amps in series with one power lead. Run it at around
10 to 12 volts DC. If it is drawing
a big part of an amp free running, I'd say the motor has
an ailment. It should be less than .5 amp. It would also run
high if it's shaft is binding.

Don


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## Green River (Dec 19, 2009)

I checked for binding and everything is smooth even the motor turns free. So I did a motor swap with another loco and confirmed the bad motor, also ran both motors out of the chassis and I could definitely tell the difference in the sound and RPM. I guess there is not much you can do to a bad motor to fix it?


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## DonR (Oct 18, 2012)

You did right.
Not many are repairable. Likely has a shorted winding.

Don


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## Green River (Dec 19, 2009)

Wonder if there would be an increase in performance if I re-motored the SD-40 with a Genesis motor? What is the difference between a 2 axle motor and a 3 axle motor? The motor swap I did was from a GP-38 (2 axle) to a SD-40 (3 axle) and the motors fit and run well due to slip drive shafts and they have different part numbers. The only difference that I could see with the eye was that the SD-40 motor was a bit longer due to larger flywheels. I'm thinking maybe a blue box SD-40 with a Genesis motor may be a real stump puller....what do you think?:dunno:


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## wvgca (Jan 21, 2013)

as far as i know, the genesis motor is around the same power, but has a lower current draw, and runs quieter for around 40 dollars, i had looked at these before but they require shaft updates as they are the newer hex drive ... i got some new old stock origional motors for about half that ...


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## ggnlars (Aug 6, 2013)

Really no difference in motors for 4 axle and 6 axle engines. Another problem may be lack of magnet flux or strength. This can happen if the motor sees a lot òf sudden high powér polarity reverses or if the motor magnets and windings are taken apart. While the engine may be new, but Blue box engines are now at least 10 years old. Correśiòn can also reduce the torque capability". 

Expect the Genesis motor to be ok, but not as good a puller as a good blue box. Recent motors are focused on low current draw, good low śpeed characteristics and low noise. The power and thus torque will be lower. 

You would be as well off with a Kato or Atlas motor. They will mount easily in the chasśis. You may need to change the spline.
Larry
www.llxlocomotives.com


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## Green River (Dec 19, 2009)

Well I made the trip to Louisville and took my locomotive back where it came from so they could take a look at it. The gentleman removed the shell and put it on the test track and ran it for about 1 minute forwards and backwards, he to could tell there was a problem with the power and speed, the motor had already gotten hot in that short amount of time. Even thought the engine was at 20 years old (but NIB) he did a motor swap for free and it now runs smooth an quiet as it could be. 3 cheers for Roundhouse electric trains!! I picked up a couple of old Roundhouse box cars while I was there so the trip was well worth it.


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## mikek (Dec 29, 2013)

A good example of why to shop locally. The local hobby shop will value your business, and he knows it pays off in the long run. That gives me a good idea, I will check mine to see if he may have the Athearn rubber band drive motors I want...I plan to fix my old shells up with old drives, I actually like them, they are quiet and dependable.


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## riogrande (Apr 28, 2012)

mikek said:


> A good example of why to shop locally. The local hobby shop will value your business, and he knows it pays off in the long run. That gives me a good idea, I will check mine to see if he may have the Athearn rubber band drive motors I want...I plan to fix my old shells up with old drives, I actually like them, they are quiet and dependable.


Helps if you have a local hobby shop of course. Not an option for many of us. However, in that case, all is not lost of course. Many can re-motor.


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## Green River (Dec 19, 2009)

This train shop is 1hr 15min drive one way for me but worth the trip every time. They have a full staff and do repairs on almost any size trains. I have an expert evaluate my locos problem and fixed it right on the spot no question asked, can't get that service on the internet!


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## ggnlars (Aug 6, 2013)

Mikek,
Are you serious? If so, how many drives are you looking for?
Larry
www.llxlocomotives.com


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