mostlytechnic

New Option for Dual Motor PF Locomotives

28 posts in this topic

I wanted to dual-motor some of my locomotives, but didn't want the expense or space to add the pole reverser to do it the "official" way. Given that, I tried opening up a motor and found that it's actually pretty simple to make it run reverse.

First, you need a tiny Torx T-6 driver:

6510723151_c104617acb.jpg

IMG_7822 by mostlytechnic, on Flickr

Flip the motor over, and there's 6 screws to remove. Once in each corner, and two in the center area.

6510725461_500129e786.jpg

IMG_7827 by mostlytechnic, on Flickr

Inside, you see the motor, some gears, and that's about it.

6510727745_bdb1fe1b10.jpg

IMG_7829 by mostlytechnic, on Flickr

On one side, there's a small brown disc. I believe that's the thermistor that'll shut things down if it gets too warm in here. Keep that attached to the wire (doesn't matter which side of the motor it's wired to) but disconnect the two wires from the motor.

6510729691_12fea0aa4d.jpg

IMG_7832 by mostlytechnic, on Flickr

There's not enough slack in the wires to cross them and wire to the opposite terminals of the motor, so I added a couple extra bits of wire and covered it with heatshrink tubing. Solder the wires back onto the motor (crossed, of course).

6510731611_6983663d15.jpg

IMG_7838 by mostlytechnic, on Flickr

One last thing to do. There's a diagonal ridge inside the cover that holds the motor in place. With the wires crossed over the motor, that's in the way. I used a knife to weaken the ridge a bit, and then grabbed it with pliers and wiggled till it came off. Reassemble, and the motor is now reversed. Probably oughta mark it somehow so you know which motor is which.

6510733043_0b2a0794c9.jpg

IMG_7842 by mostlytechnic, on Flickr

Now, put this and a regular motor on your loco, wire them to the IR receiver, and the dual motor locomotive is ready to run.

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Cool idea but if you're going to cross wires wouldn't it be better to make a few "reversing cables" from the PF > 9v extension and use that with a RC Train Motor? I know it's said to be weaker than the PF Train Motor but we're talking about adding power so in most cases you'd be okay.

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I thought about that, but that's another wire to stuff into the loco - this is completely contained. But sure, crossing wires in an extension would do the exact same thing.

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That indeed is a very nice find! So at last we can service motors without destroying notches etc. huh!!!

You can also do other neat tricks now. Thanks for your small tutorial.

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Thanks indeed!

Very informative, I had looked at the bottom of the PF motors but couldn't work out how to open them, Torx T-6 driver ordered!

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I thought about that, but that's another wire to stuff into the loco - this is completely contained. But sure, crossing wires in an extension would do the exact same thing.

As I described it (using the RC Train Motor with PF > 9v Extension) would have the same footprint as the PF Train Motor just a less powerful 2nd motor.

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As I described it (using the RC Train Motor with PF > 9v Extension) would have the same footprint as the PF Train Motor just a less powerful 2nd motor.

You are correct. However, I have a stack of PF motors and no RC motors, so I went this route :)

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As I described it (using the RC Train Motor with PF > 9v Extension) would have the same footprint as the PF Train Motor just a less powerful 2nd motor.

It could also cause some problems if you use one PF motor and one RC motor, since they may not run at the same speed (from the same source). I think Philo did some testing and posted results that show the PF motor takes a train around a test circuit faster than the RC motor on a full charge. Once the charge starts running down, I think the difference is quite dramatic. Not sure what kind of problems that would cause.

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is there room in there to fit a micro DPDT change over slide switch of the type used on PCB's?? this would make it easy to switch it back and forth depending on which direction you wanted the bogie to travel. also why not just butcher a power lead to reverse the polarity?? perhaps lego should make a proper one a different colour to the norm for those that want it?

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There is room at the end of the motor where I bet you could add a switch, with the switch lever sticking out the end of the motor (under the power cord, so it'd be towards the center of a loco and not interfere with adding a buffer and such to the other end of the motor).

(look at my 3rd photo, with the motor open showing the orange axles. Picture putting a switch in there at the right hand end of the motor. It'd take cutting a hole in the end and mounting the switch, but should be doable)

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Instead of changing the wires around and seeing you have to remove the axles & gears to do this - a simpler method would be to reverse the axles and gears in there bearings - simple.

Edited by Doug72

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Instead of changing the wires around and seeing you have to remove the axles & gears to do this - a simpler method would be to reverse the axles and gears in there bearings - simple.

I think I tried that and they (the white gears) wouldn't fit on the other side. I'll double check though... if that works, it would definitely be the simple solution!

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Nope, no luck. I thought at first it would. There are two tabs that need removed, marked with the red circles. Only the "vertical" part needs removed. I did it by just grabbing it with a pair of needlenose pliers and twisting and the tab tore right out.

6522340273_fc7d8b41b4.jpg

motor-marked by mostlytechnic, on Flickr

However, with those out, the white gear at the non-wire end goes right in, but the wire end has extra plastic for the wiring under the white gear, so it won't fit reversed. So I tried making it have just 1 driven axle. Still no go - worked while the motor was open, but there's actually little notches in the cover for the orange gear - once you put the lid back on, it binds against the reversed orange gear and it won't turn.

So alas, what I thought would be the easiest way doesn't work at all. It'd take serious mods to make the gears work backwards...

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Nope, no luck. I thought at first it would. There are two tabs that need removed, marked with the red circles. Only the "vertical" part needs removed. I did it by just grabbing it with a pair of needlenose pliers and twisting and the tab tore right out.

6522340273_fc7d8b41b4.jpg

motor-marked by mostlytechnic, on Flickr

However, with those out, the white gear at the non-wire end goes right in, but the wire end has extra plastic for the wiring under the white gear, so it won't fit reversed. So I tried making it have just 1 driven axle. Still no go - worked while the motor was open, but there's actually little notches in the cover for the orange gear - once you put the lid back on, it binds against the reversed orange gear and it won't turn.

So alas, what I thought would be the easiest way doesn't work at all. It'd take serious mods to make the gears work backwards...

I pulled the wire clip out, and removed the outer two wires for about an inch or so longer, and seperated the middle two, which effectively gave me enough wire to not have to solder in another piece, doing away with the heat shrink. Then I swapped the wires on the motor and tucked it all around the left side of the R in the photos above. No modifications necessary to the housing, which means it's a simple case of pull the motor apart and reverse the wires again if I want to go back to normal. The lead going into the motor is now about one inch shorter, which serves as a way to identify reversed motors, and lets face it, mostly the leads are eccessively long anyway, so it is a win win situation :classic:

So now my Maersk has two motor.... I'll have to buy some more to do the same to my Cargo trains!

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If possible, -why not just flip the motor? (so that the buttom is on the top) That would reverse the direction without changing gears or cutting wires...default_classic.gif

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If possible, -why not just flip the motor? (so that the buttom is on the top) That would reverse the direction without changing gears or cutting wires...default_classic.gif

Yeah, I thought of that, and almost posted that suggestion, and figured I may as well try it first.... not possible, as the little bulges on each end of the motor are different sizes, so the motor only fits one way.

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What is that yellow thing? a self-resetting fuse I guess?!: I guess it is indeed a thermistor (never mind ;)).

But phillipe says: "The train motors also contain thermistor limitations. For the PF train motor, this protection trips too fast and prevents direct measure of the stalled current. These values were obtained by extrapolation." so we could maybe also modify it a bit. Although I didn't run into problems with it.

I also think crossing the wires is the best option to reverse the motor.

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Revised my method. If you pull out the wire clip (where the wire comes into the case, under the motor), you can then pull the wire that doesn't have the thermistor completely out of the clip, slide the thermistor wire over, and put the bare wire back thru the clip. Basically cross them right in the clip. Then just reattach them to the motor on the swapped sides. No lengthening or anything needed.

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Sorry to bump this if its an old post.

That PF internal motor looks just like the 9v ones. I have to dead 9v ones i might buy some pf ones and take the motors out.

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This should be stickied somehow, as it is incredibly useful. I'm going to try the method posted in post #19 on one of my motors.

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My E9 has 2 motors, I just flipped the front one around and ran the wire through a whole in the front of the base of the locomotive. Works great, no moding. Tthe only issue is having enough wire, my E9 is 42 studs long and I think it reached, if not I just added a PF extesion cable. I haven't tried it in my GP38, but since it is shorter, wire length should not be an issue. I brick build my train bases so adding the hole in the front for the second motors wire is no big issue.

Sal

WFB, WI

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Would these be the same motor as the 9V motor? For instance, replacing a burnt out 9V with this for a new life on metal wheels?

I see Lazarus asked the same question :blush:

I am, though, also curious as to if this is a solution. I have no broken 9V's that I know of, so trying this is out of the question for now, but if it works, believe I will be buying a bunch of these :grin::classic:

Edited by LEGO Guy Bri

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My E9 has 2 motors, I just flipped the front one around and ran the wire through a whole in the front of the base of the locomotive. Works great, no moding. Tthe only issue is having enough wire, my E9 is 42 studs long and I think it reached, if not I just added a PF extesion cable. I haven't tried it in my GP38, but since it is shorter, wire length should not be an issue. I brick build my train bases so adding the hole in the front for the second motors wire is no big issue.

Sal

WFB, WI

I did the same thing on my F40 (Railbricks #10, p42 for a detail shot). Works great (though I too had to use an extension wire). You can fit a plate or a tile under the PF wire leaving the motor, something you can't do with the stud based power connector on the RC and 9v motors.

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