Changing the polarity of PowerFunction train motors

[legotownlinz]

Today’s Lego City train sets include a PowerFunctions motor that works very well for short trains. However, if you add additional wagons, the traction of a single motor is not sufficient. An obvious way to fix this issue is adding a second motor. Another option is adding weight to the engine as the motor has power for some additional wagons but there is not enough friction between wheels and rails.

In this posting I discuss an issue with the first approach: While adding a second motor sounds like a straightforward task, you will encounter a problem: The motor of the second bogie must be rotated so that the cables of both motors point towards the holes at the center of the engines base plate. Due to the rotation, the motors move in different directions.

To make the second motor go in the same direction, the polarity of the motor must be changed. This can either be achieved by swapping the cable leads either in the plug, in the middle of the cable or inside the motor housing.

I prefer the last approach – swapping the leads directly at the motor – because its easier to open the motor housing than the plug and the modification will not be visible.

What you need:

• PowerFunctions train motor
• Soldering iron
• Torx T6 screwdriver
• Tweezers (optional, helps with getting the gears in place again)

Instructions:

1. Remove all six screws at the bottom of the motor and open the motor housing.
2. Remove the gears and axles. You can just take them out, they are not fixed once the housing is open.
3. Remove the motor and the clamp piece that is used as strain relief.
4. Unsolder the leads from motor.
5. Put the motor back into the housing at its original position.
6. Cross the wires and arrange the wires and the yellow inductor. It is possible to cross the leads below the clamp piece, it still snaps in with the crossed leads below it.
7. Solder the leads to the motor.
8. Restore the gears and axles. This works best with tweezers.
9. Close and screw down the housing.

Motor after opening the housing:

 

Motor removed from the housing, leads crossed:

 

Unsoldered motor:

 

Motor back in the housing:

 

A folIow-up on how to change the polarity of Powered Up motors can be found here.

Edited October 24, 2018 by legotownlinz
Added link to Powered Up topic.

[dr_spock]

Nice work. Don't forget to mark/label the motor has been "reversed" for future reference. 

[coaster]

While this is neat, couldn't you just use the polarity switch to reverse it?

[legotownlinz]

21 minutes ago, coaster said:

While this is neat, couldn't you just use the polarity switch to reverse it?

Sure, but soldering is cheaper, more elegant and saves space in the engine.

[fred67]

Would be nice to be able to buy a single connector piece only that reverses the polarity.  You could then stack the connections to the IR receiver with the polarity reverser in the middle.

I agree that adding the switch would be difficult - it's already bad enough with the battery box and receiver being built into the train to have to add something else that large.  At the same time, it would be a lot easier for those less electronically inclined 

[justinwebb]

I cut the wire as normally there is a ton left over in the cab so it helps hide and I flip the 2 middle wires to reverse polarity. 

[MAB]

12 hours ago, legotownlinz said:

Sure, but soldering is cheaper, more elegant and saves space in the engine.

You have extra wagons to hide it in. :-)

[Paulbricks]

I had the same dilemma last week, wanted to put two motors in the 60052 fright engine, but one is always in reverse. Not got around to reversing one, and thought about breaking into the motor and reversing the polarity. I'm quite good with soldering iron, anyway, and might do it. Just now I might just.

As for the reversing switch, they are hard to obtain, especially here in the UK, and never seen one for sale on ebay or whatever, so far...so soldering is the way to go.

 

[legotownlinz]

1 hour ago, Paulbricks said:

As for the reversing switch, they are hard to obtain, especially here in the UK, and never seen one for sale on ebay or whatever, so far...so soldering is the way to go.

The reversing switch is part of 8293 Power Functions Tuning Set, and can probably be purchased separately in the Lego web store.

Anyway, the soldering solution is cheaper and looks better. It takes less than 10 minutes per motor for people with average soldering skills.

[Paperballpark]

Polarity switches are cheap, easy to buy from the LEGO website or any of the 12 or so Brand stores in the UK, and actually quite small, so easy to fit into a train - especially if it's large enough to be able to take two train motors.

I managed to fit two motors, two battery boxes, two IR Receivers and a polarity switch into my Horizon Express cab. Given the small size of the polarity switch, I don't really see the issue with the size of it.

My only issue with soldering would be if I eventually took that train apart, I'd then have a motor which ran in the opposite direction to everything else!

As for the first problem of not enough traction, I found that putting the battery box directly above the train motor really helps with that, as it's easily the heaviest (and densest) part of the whole train. Obviously in some cases you can't do that, but I found those to be quite rare.

[Paulbricks]

I suppose if you were to use a "reversed" motor normally, that won't be a problem, as you can reverse a single motor either on the battery box or controller, so it can stay reversed to use use where you like, but mark is as discussed so you know which is a "special".

[legotownlinz]

43 minutes ago, Paperballpark said:

My only issue with soldering would be if I eventually took that train apart, I'd then have a motor which ran in the opposite direction to everything else!

I managed to fit two motors, two battery boxes, two IR Receivers and a polarity switch into my Horizon Express cab. Given the small size of the polarity switch, I don't really see the issue with the size of it.

You can either label reversed motors or just test the motors whenever building a new model. Of course it is also possible to restore the old polarity. I'm using two motors in all engines and rarely take trains apart, so it's not an issue for me.

A switch that must not be switched feels wrong for me, thus I'd never use the switch in my trains.

A single IR receiver is better than two because separate receivers may run out of sync if one of them misses a command. This sometimes happens with my high speed trains where a motor is located in each engine.

Edited January 23, 2018 by legotownlinz

[Paperballpark]

1 minute ago, legotownlinz said:

Imho a switch that must not be switched feels wrong for me, thus I'd never use the switch in my trains.

But you do switch it - right at the start! ;)

[zephyr1934]

If you build your own base for the train there is an even simpler solution, put a hole for the motor wires behind each of trhe motors and run both forward. The wires leave the motor at one plate above the studs so you can even do this when you have a buffer plate on the wire side of the motor. But you might need an extension wire in this case, which is only slightly cheaper than the polarity switch.

Of course reversing the polarity is still eloquent, all a matter of the particular design and what will fit.

[Paperballpark]

10 hours ago, legotownlinz said:

A single IR receiver is better than two because separate receivers may run out of sync if one of them misses a command. This sometimes happens with my high speed trains where a motor is located in each engine.

I got around this issue by putting them back-to-back right next to each other. I figured that by doing so it would be very unlikely that one picked up the signal but the other didn't.

Plus, the very nature of needing two motors means that you're likely to run it at full speed anyway, so I just turned the dial a lot, so both were bound to be at full speed anyway, even if one somehow missed one of the signals.

[SuperChiefer84]

I have 2 60052 locomotives and wanted to run them in a back to back lash-up via a single controller. I did this by removing the seat and dashboard in the trailing locomotive's cab and putting the polarity switch in the cab. I also had to remove the gray 2x2 slope for the polarity switch wire to come through to the cab area. It works great and the locomotive is not altered from the exterior perspective. 

Edited January 24, 2018 by SuperChiefer84

[legoboy3998]

@legotownlinz, is there enough wire within the train motor body to simply rotate the actual motor 180 degrees, so the wire connections to the internal motor would be on the right side in you pictures in stead of the left?

 

Sal

[Grrr]

Dumb question - looking at those axle/gear assemblies; would it be possible to simply flip them so the gear is now on the opposite side of the motor; and therefore the rotation occurs in the opposite direction? (This presumes that the motor is exactly centred, and the gears/axles and parts holding them are symetrical).

[legotownlinz]

5 hours ago, legoboy3998 said:

@legotownlinz, is there enough wire within the train motor body to simply rotate the actual motor 180 degrees, so the wire connections to the internal motor would be on the right side in you pictures in stead of the left?

I've investigated several options but none of them worked. I could not find any easier solution than swapping the wires, which is actually very simple because the soldering points are big.

As far as I remember the motor cannot be rotated, it is not symmetric and would not fit.

Flipping the gears is not possible, there is no space for the gears on the other side. The chassis is not symmetric.

[sed6]

Fantastic write up! I just completed this mod myself and it was super easy, and effective!

[Toastie]

52 minutes ago, Blk69 said:

Ok, I would just cut the motor cable and splice wires as needed (swap the "+" and ground).  Do I need to turn in my AFOL card?  

Hmmm - why not. Haven't seen such a card ...

Would do (have done) the same thing.

Best,
Thorsten.