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MU Plug - USA Trains GP-7/9

by Paul Norton

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INTRODUCTION

Aristo-Craft, Plug and Play diesels are sold with battery car plugs on each end. This project shows how to add the same plugs to a USA Trains GP-9 so you can use a power car to run it. While this project deals with a specific locomotive, the principles should be the same for most USA Trains four-axle diesels.

Nothing in this project prevents this locomotive from being restored to track power for re-sale at a later date. As the locomotive’s track power wiring will be unplugged during this project however, it will require a power car to run it. A power car is simply a battery car with a receiver added for on-board, radio control. To view an article on how to build a Power Car, just click on the link.

Four, 2-pin plug sets are required for this project. They are available from All Electronics under part number CON-240. OVGRS member can purchase them by contacting Paul Norton. See the Items For sale Section for details.

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REMOVING THE TRACK POWER SLIDERS

Remove the railings from the sides and ends of the locomotive to prevent possible damage and set them aside for now.

HINT: A small, flat screwdriver can be used to pry the stanchions from their holes in the frame. A Post-It Note placed between the locomotive and the screwdriver may prevent the paint from being scratched.

Place the locomotive upside down in a soft cradle taking care not to damage the horns. Remove the six screws (circled in red) from the bottom of each motor block and remove the bottom covers.

Remove the small chrome screw (circled in red) from each track slider bracket. Lift out the track sliders and the pieces of piano wire (indicated with yellow arrows) sprung between the axles.

The track sliders and axle wipers are the only components removed during this project. Mark a Ziploc bag with the road name, diesel model and road number. Place the sliders and wipers in the bag, and tape it in a pocket of the locomotive's Styrofoam packaging.

Fasten the track slider brackets back in place with the small chrome screws. Fasten the covers back on the bottom of each motor block with their six screws.

HINT: Do not fully tighten any of the screws until all the screws have been inserted and turned down some. If you tighten the screws as you go, the last few may be hard to insert and may strip the threads in the plastic motor block.

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REMOVING THE SHELL

Remove the screws holding the coupler brackets and couplers to the frame. Set the couplers aside for now. Install the coupler bracket screws back in the frame so they do not get lost.

Unplug the four wires from the center of a motor block.

Pull the stirrup from one of the side frames. Remove the three small screws, and slide the side frame off the ends of the axles.

Remove the motor block and wipe the excess black grease from the ends of the axles. Set the motor block aside for now. Fasten the side frame back on the A frame, and push the stirrup back in place.

Repeat the process for the other motor block. Wash the black grease from your hands when you are done.

Remove the two small screws from the base of the fuel tank. Remove the fuel tank and set aside for now. Install the fuel tank screws back in the frame so they do not get lost.

Remove the four short screws, indicated with yellow arrows, that hold the battery boxes to the frame.

Remove the ten screws, circled in yellow, which hold the shell to the frame. These are hidden in deep holes and require a long, number 1 Phillips screwdriver to extract them.

• Four are in the long hood truck area.
• Four are in the fuel tank area.
• Two are in the short hood truck area.

Turn the locomotive over. Carefully lift the shell from the front of the long hood. The whole shell (long hood, cab, battery boxes and short hood) will lift off as one piece. Do not lift the shell off too far or the wiring may unplug.

Install the four screws back in the battery boxes and the ten screws back in the shell so they do not get lost.

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DISCONNECTING THE TRACK POWER PICK-UPS

It is imperative that the track power pick-ups be disconnected so that the locomotive can not pick up track power or feed battery power into the tracks. The result could be electronically catastrophic.

There should be two plugs from the motor block under the short hood, but only one plug has two red wires and two black wires attached to one side of it. This plug provides the power distribution board with track power from the short hood truck. Unplug it to disconnect these track power pick-ups.

There should be two plugs from the motor block under the long hood, but only one plug has two red wires and two black wires attached to one side of it. This plug provides the power distribution board with track power from the long hood truck. Unplug it to disconnect these track power pick-ups.

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INSTALLING THE POWER CAR PLUGS

Drill a 1/8th inch hole in the center of the short hood pilot between the coupler cut-bar and the grab rail.

Drill a 1/8th inch hole in the top of the frame opposite the screw holding the coupler return spring.

CAUTION: The 2-pin plug sets sold by All Electronics are not always colour coded the same as the plugs in USA Trains diesels. If the colour coding is not the same, just click on the following link to see how to change the AE Plug Set Wiring so that proper polarity is maintained.

As only the male halves of the four All Electronics plug sets are needed for this project, unplug the females halves and set them aside. They can be used for power car plugs or lithium-ion battery pack charging plugs in other projects. Hereafter the male halves of the sets will be referred to as the AE plug.

Slide a 1/2 inch length of shrink wrap over the wires of an AE plug until it reaches the back of the plug. With the tab of the plug facing up, feed the wires over the coupler cut bar on the short hood, through the holes in the pilot and the frame. The shrink wrap will provide the proper spacing for the plug and the coupler cut bar will prevent it from falling on the coupler.

Insert another AE plug into the plug (indicated with a yellow arrow) that leads from the short hood to the power distribution board.

Gather the ends of the wires of this AE plug and the AE plug installed on the short hood pilot. Trim the wires to the proper length and strip 1/4 inch of insulation off all four wires. Slip a 3/4 inch length of shrink wrap over one of the red wires, and over one of the black wires. Solder the red wires together. Slip the shrink wrap down over the joint and warm until it seals. Repeat for the black wire.

Using the instructions for the short hood as a guide, drill holes in the long hood pilot and frame, and thread another AE plug through the holes.

Insert the last AE plug into the plug (indicated with a yellow arrow) that leads from the long hood to the power distribution board.

Gather the ends of the wires of this AE plug and the ends of the wires of the AE plug installed on the long hood pilot. Trim the wires to the proper length and strip 1/4 inch of insulation off all four wires. Slip a 3/4 inch piece of shrink wrap over one of the red wires, and over one of the black wires. Solder the red wires together. Slip the shrink wrap down over the joint and warm until it seals. Repeat for the black wire.

THAT'S IT! You have completed the installation of power cars plugs on your USA Trains GP-9. All that's left to do is test to ensure the unit is wired correctly before re-installing the shell.

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TESTING THE POWER CAR PLUGS

Pull the stirrup from one of the side frames. Remove the three small screws and the side frame.

Grease the ends of the axles and slide a motor block and the side frame back in place. Fasten the side frame back on the A frame, and push the stirrup back in place.

Repeat the process for the other motor block. Wash the black grease from your hands when you are done.

Slip the four wiring connectors back on the pins of each motor block. The outside wires are the unplugged track power wires soldered to the side frames. The next two are the motor wires. The two in the center are unplugged track power wires from the sliders and axle wipers which were removed earlier.

NOTE: The colour coding of the wires alternates across each motor block.

Plug a power car into either of the power car plugs. If a power car is not available, connect the female portion of an All Electronics plug set to a small power pack for testing. Test to ensure the headlights and motors are both operating in the proper direction.

Repeat the test for the plug on the other end of the locomotive.

If the headlights and motors are not operating in the same direction, check the colour coding of the wires of the four AE plugs to ensure they line up with the USA Trains plugs.

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ASSEMBLING THE LOCOMOTIVE

Once the power plugs have been tested; the shell, fuel tank and couplers can be replaced using the disassembly instructions as a guide.

CAUTION: When installing the shell to the frame, all the wires should be inside the mounting posts so they do not get pinched between shell and the lip of the frame.

CONGRATULATIONS! These new plugs will allow you to run your GP-9 with a power car and enjoy all the benefits of battery power and radio control.