I got this SD9 at a yard sale. Wheels are in need of a cleaning, but the dumb thing wil not run. This is the old flywheel motor. There is a brass clip on top and one on the bottom. If I touch leads to these the motor runs. Touch one rail and the top clip and it runs. Touch bottom clip and other rail no go.
So what would be a good way to clean the wheels? I will need to do it by hand so what do I use? Also how is the motor wired to the wheels?
Throw the metal clip away and using stranded wire, perhaps 20 AWG stranded, solder the posts to the motor connections directly.
You can clean the wheels with denatured alcohol and a small brush or pipe cleaner. The old sintered metal Athearn wheels are prone to collecting dirt due to the manufacturing process used, but replacement nickel silver wheels from Northwest Short Line stay clean much longer. If your SD9 has the newer plastic sideframes, the current machined wheels from Athearn will also work.
The power pickup design on the older Athearn models left a lot to be desired. It depends on contacts that can fail due to mechanical misalignment and/or corrosion. The motor bottom clip takes power from one side of the trucks through the frame, while the top clip connects to the metal tower extending from the other side of the trucks. Hard wiring from the trucks to the motor eliminates the potential for failure in either contact path. Google for Athearn five-wire tuneup and you’ll get some photos showing how to do it.
Sometimes there will be a failure within the motor. Oxidation or a too-short spring (held in place by the clip) can prevent current moving from the clips to the commutator. If it’s only oxidation, manually spinning the motor while applying power from clip leads usually does it. Otherwise you may have to disassemble the clip/spring/brush and check for problems.
Replacing the stock motor with a high-quality can motor, along with new wheels and other basic tune-up, can result in a loco that runs just about as well as anything you can buy new.
One truck connects to the frame of the locomotive. The motor bottom clip is supposed to touch the frame and so pick up juice. The other truck connects to that top clip. The truck has a metal strip that comes up vertically and then bends over and rubs on t he top strip. For a neat hardwire convertion, get 1/4 inch Fastons from your hardware store. These will slip over the strip coming up from the truck. Crimp a wire into the Faston and solder the other end to the top brush/top clip on the motor. The Fastons will slide off and allow you to disassembly the locomotive without unsoldering wires, a great benefit.
From what you say, the motor works when it gets juice. Since it runs when you bypass the strippy thing on top and doesn’t run when you bypass the frame, that says the strippy thing going to the top of the motor isn’t conducting. Dump the strippy thing, put a faston on the truck strip and solder to the top of the motor and it will run.
For wheel cleaning, I like GooGone. Get her working, put a paper towel moistened with GooGone on the track. Slide one truck over the paper towel and let the wheels spin. The wheel is clean when the paper towel stops picking up blackness from the wheels.
Alternate wheel clean. Use a wire brush in a Dremel. Get her running, and then touch the Dremel to the wheels.
While you have here apart you can make her look better by replacing the light bulb in the cab with smaller bulbs up inside the hoods to illuminate the headlamp lenses without shining light out the cab windows. You can be real fancy and install constant brightness lights, 1.5 volt bulbs in parallel with a pair of silicon diodes in series with the motor. A Radio Shack full wave bridge rectifier will furnish all four diodes (two for forward, two more for reverse).
If she is noisy, take the gear towers in the tru
CGW121,
About all the help you’ll need:
http://www.mcor-nmra.org/Publications/Articles/Athearn_TuneUp.html
Frank
Thanks for the info. It willl take me a while to get back to working on it and report.
You’ve already diagnosed the probem. Jumping rail power to that top clip makes it run. As other mention, that spring snapped on the top of motor is not making solid connetion to the trucks. Solder wires in place of it and you’re good to go. Another trouble sometimes overlooked, the truck bolster carries rail power to the frame. Many times too much grease/ gunk build up can affect the connection. If you remove the top motor clip to solder, be careful not to have the brush springs fly away.
Both trucks are six wheel pickup. One side of both trucks connect to the locos frame which carries power to the bottom clip on the motor. The other side of both trucks are connected the L shaped contact arms that connect to the metal spring clip that connects to the top of the motor.