[Tutorial] Modifying a 9V Train Motor

[codefox421]

This is a tutorial detailing how to modify a LEGO 9V train motor so that it may be powered independently of the track. This effort is part of a larger project inspired by Thorsten Benter’s article in Railbricks Issue 7 titled “PF and 9V Trains: The Best of Both Worlds”.

Step 1) Open the 9V motor. This has been covered elsewhere, so it should suffice to say you carefully remove the 12 tabs holding the bottom cover on with an xacto blade or something similar. There is enough friction to hold the bottom cover in place later even without the tabs.

Step 2) Remove all internal parts. Ignore the fact that I took this photo after completing step 3.

Step 3) Use a rotary tool with a cutoff disk to bisect the metal strips in the top of the motor enclosure. These strips are exposed in the top studs, and we will later use them to pull power from the track and apply power to the motor.

Very important: Be sure to apply NO PRESSURE when using the rotary tool. Instead, just lightly touch the spinning cutoff disk against the metal strip, and let the tool do the work. It will take some time, so be patient and careful. If you apply pressure, the metal strips will heat up and deform the plastic. If the plastic deforms, it will be impossible to interface with LEGO bricks and PCB adapters (like the one in the upper-right corner of the picture). Keep it light and easy. You will thank yourself later when you haven’t ruined your motor’s plastic housing.

Step 4) Desolder the metal pieces from the electric motor.

I don’t have a picture of this exact step because I used the electric motor from a Power Functions train motor. If replacing the 9V motor with a Power Functions motor, open up the PF train motor using a T6 bit, remove the electric motor, and desolder it from the wires.

Step 5) Solder a short length of wire to each tab on the electric motor (do this outside the housing to avoid accidently melting it). I used 32 gauge DCC decoder wire, but you can use whatever you have that will fit inside the motor. Reassemble the motor with exception of the wheels and the bottom cover.

Step 6) Attach the wires to the outermost halves of the metal strips; the innermost halves are connected to the wheels through the wipers. I used a silver epoxy for this. I chose silver epoxy for two reasons: 1) I didn’t want to risk melting the studs by soldering the wires to the metal strips, and 2) silver epoxy has a lower resistance than graphite epoxy.

Step 7) Reinstall the wheels and make sure everything is running smoothly. This would also be a good time to lubricate the gears if you want to. Make sure you don’t get any lubricant on the electrical parts! Press the bottom cover onto what remains of the tabs, and you’re done!

If you ever want to run the motor directly from track power, simply use a PCB adapter with a loopback connector or connect a LEGO wire (9V or light gray end of PF).

This is what a PCB adapter looks like when installed on the motor. (I’ve updated the design since taking the previous photo.)

And here is a connector leading up to the electronics (currently just a Power Functions battery box, soon to include a Bluetooth receiver) in my Horizon Express.

The connector plugs into the PCB adapter.

The PCB adapter is attached to the electrical studs on the motor.

And the motor is pinned to the bottom plate of the locomotive.

Now I can charge the battery in my train without taking it off the track, run it indefinitely on a mixed metal and plastic layout, and have non-line-of-sight control when I add the Bluetooth receiver. It really is the best of both worlds!

[THERIZE]

Whaaat. That is so cool!

[fred67]

I like this idea a lot - I've heard people talk about doing it, and there's probably and old thread on EB that describes how to do it, but I like the step by step pictures.

[garethjellis]

This is a really neat and tidy solution, What I would love is a 9v pick up solution.... this would make all my dreams come true

[Rail Co]

can you still use the 9v motor when not powered by the battery box and if you wanted to use it just by itself like a normal 9v motor could you still use it for those purposes?

Great tutorial

-RailCo

[dr_spock]

Cool, this works well for small shunter that can only have one motor bogie. If you have room for two bogies, I think converting a dead 9V train motor for power pick up only would be an easier solution.

can you still use the 9v motor when not powered by the battery box and if you wanted to use it just by itself like a normal 9v motor could you still use it for those purposes?

Great tutorial

-RailCo

He has a loopback plug that permits that function.

[Lazarus]

. pointless post after looking closer.

Edited September 6, 2015 by Lazarus

[spzero]

Awesome work thank you for sharing, it's good to know I can use the PF motor to run my 9V's when they eventually run out life

[AlmightyArjen]

Nice tutorial, thanks! I was always wondering if it could be done.

[zephyr1934]

Now I can charge the battery in my train without taking it off the track, run it indefinitely on a mixed metal and plastic layout, and have non-line-of-sight control when I add the Bluetooth receiver. It really is the best of both worlds!

If I follow correctly, you are using the 9v motor for pickup, but are you then powering it too from the PF output?

On the battery side, are you using the LiPo battery and just using the output port to also charge when on powered 9v track? If so, does the battery like that solution?

Just one quibble, when you add the bluetooth receiver you are doing better than either world (grin).