Ncore

12V motor running the opposite direction to other engines

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Hi, new member here, from Finland.

Long story short:
I recently visited Vanha-Palikka in Kyrö, Finland, and after looking at the trains there I realized I have a rarity in my hands (or rather, in the attic) - 7750 steam locomotive. So I digged up my old stuff and got many donations from friends who had similar stuff lying around. I had one dead motor on my own (shell cracked thanks to repair attempts at youth), and got another already neatly opened from a friend's treasure pile.

After numerous youtube videos, getting proper gear (silicone grease, right kind of plastic glue) and reading up on stuff I after much headscratching got to work to make one functioning motor out of the two dead ones I had. It was eventually a great success, it worked perfectly and didn't make any excess noise.

And then I set it on a locomotive and started driving with another locomotive on the track.
They were going opposite directions.

I am quite sure I returned all parts as they originally were - except maybe the axles, but their gearing is such that it shouldn't matter.
[Edit: As I was re-reading this, I realized there is a 50% chance I flipped the motor unit itself upside down... but that shouldn't matter, should it?] 

Has anyone ever seen anything like this? Any idea what could be causing this, or if there is something that could be done to reverse the direction?
(Not sure I'd reverse the direction even if it were easy, I might actually enjoy having one engine on its own loop going the opposite direction, but anyway...)

Edited by Ncore

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Hi,

there is quite a puzzle as I cannot imagine how to reverse the motor even if I wanted to!

Did you slide the motor armature out of the magnets?  Maybe putting the magnets on back to front will cause the motor to run the other way.......I am not sure.

 

John

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Well, not completely, since the small plastic plates that will hold the motor in place in the chassis were in the way, so I couldn't get the motor coil part out of the magnet chassis.

Might it be that I have the first and only 12V motor to run the opposite way? That would be an achievement. The magician himself is astonished as well...

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No idea about the workings of the motor, but having 2 locos going in opposite directions on separate loops is always fun, and this way you can run 2 with only one power supply. 

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Indeed. Once I have enough space (get the proper room renovated and emptied of useless stuff) I'm planning to make at least three separate loops - God knows I have the tracks and switches to do it... 

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I think that it's possible that the motor could run backwards if the armature assembly had been removed from the chassis, and replaced with the fixed magnet the other way up. I have a vague recollection of that happening to me, when I was experimenting with a dismantled motor.

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That's where it gets suspicious - I didn't remove the armature assembly from inside the motor, since the plastic clips (around the main axle) holding it to the base were in the way (it wouldn't slide through).

Or do you mean removing the entire armature + surrounding shell from between "A" and "B" blocks? That I did do, of course - can't really clean and lubricate everything without doing that.

Edited by Ncore

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I believe SDLgo9 is right. I'm pretty sure it's running backwards because the DC motor casing is backwards. I've opened these motors and have experimented with this, and I found that when you flip the motor casing around it runs backwards (it's not symmetrical, so the current is going through differently than normal). If you're able to reopen it, try reversing the direction of the casing.

The central axle (with worm gears, commutator, rotating plastic brackets) can indeed be removed from the cylindrical casing with enough wiggling.

I posted a video about repairing a red motor a while back and I believe I address this issue in it, take a look - I hope it's helpful!

Good luck fixing it, and I must say that a 7750 in the attic is a great (and expensive) find! I own a boxed copy and really like it.

Edited by Reker1000000

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Well, I sure didn't remove the black metal casing from around the armature (because the plastic axle holders were in the way and I didn't really need to get it out), and since the main axle can only go one way (due to the contact pins touching the axle having a very specific place), I can't imagine how I could have turned it around.

Or I am mistaking something? 

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I have actually watched that video multiple times while figuring out what to do and how!

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9 hours ago, Ncore said:

Well, I sure didn't remove the black metal casing from around the armature (because the plastic axle holders were in the way and I didn't really need to get it out), and since the main axle can only go one way (due to the contact pins touching the axle having a very specific place), I can't imagine how I could have turned it around.

Or I am mistaking something? 

I mean removing the entire armature + fixed magnet assembly, and putting it back the other way up. That way, if I remember my DC motor theory aright, the direction of current flow is the same but the poles of the fixed magnet are swapped, so the motor will turn in the other direction.

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13 hours ago, Ncore said:

Well, I sure didn't remove the black metal casing from around the armature (because the plastic axle holders were in the way and I didn't really need to get it out), and since the main axle can only go one way (due to the contact pins touching the axle having a very specific place), I can't imagine how I could have turned it around.

I think flipping the black casing is what will fix it. It can be removed by tilting the metal shaft with the magnets a little bit and wiggling it out. Yes, the main axle can go only one way because of the placing of the commutator, but you can reverse the direction of the black housing (which should make it run correctly). You may not have removed the axle assembly from the housing during your repairs, but I would guess that if the motor block you used was the one you got from a friend and it was already opened then it was probably switched. It's also possible that when assembling the motor during manufacturing they put the housing in backwards, but I've never seen a post about an unopened motor running backwards so I think this is very unlikely.

Glad to know you watched my video, hopefully it was at least a little helpful.

4 hours ago, SDLgo9 said:

I mean removing the entire armature + fixed magnet assembly, and putting it back the other way up. That way, if I remember my DC motor theory aright, the direction of current flow is the same but the poles of the fixed magnet are swapped, so the motor will turn in the other direction.

I think this is another way of phrasing the solution that I'm speaking of.

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I wish there was a possibility to give +1 to helpful posts. You guys certainly earned it!

Yes, during the dark hours of the night I came to the same realization... the motor inner parts in fact were from a friend who had gotten it from a friend, and were already opened when I got it... therefore someone must have reversed the polarity (Hah! Got to say it!) inadvertently before I got it.

I accidentally glued the motor in a way I think it will be a hard job to re-open it... all of the glue is inward.

Oh well, I guess I'll use this engine for an assembly locomotive. I'll have I guess... five engines in addition to this, so there's plenty of them anyway.

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17 hours ago, Ncore said:

I wish there was a possibility to give +1 to helpful posts. You guys certainly earned it!

Yes, during the dark hours of the night I came to the same realization... the motor inner parts in fact were from a friend who had gotten it from a friend, and were already opened when I got it... therefore someone must have reversed the polarity (Hah! Got to say it!) inadvertently before I got it.

I accidentally glued the motor in a way I think it will be a hard job to re-open it... all of the glue is inward.

Oh well, I guess I'll use this engine for an assembly locomotive. I'll have I guess... five engines in addition to this, so there's plenty of them anyway.

I also have a red re-built motor going backwards, so this thread is very useful. :thumbup:

It is a sort of "Frankensteeeen": A/B metal parts,  upper hull and wheels are from a broken red motor (got in a bulk 12v sale many many years ago), while the rotor, metal contacts and lower hull are from a black motor (always in the same sale). The red lower hull was broken, so I replaced it completely (it cannot be seen from outside). I made the same error, mounting it in the wrong way...et voila - "suicide train"!  :excited::ugh:

I repaired other motors in those years, and figured out to remount them correctly - testing them in comparison to a working one (just putting tape instead of glue for keeping the lower hull  in place during the test).

But the red hull plastic is too weak to re-open the motor, so I'll wait for the glue to loose and then I'll repair it. It's a peculiarity of that poor motor and in some way I like it :wub: 

Ciao!

Davide

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Turn the train motor unit 180 Degs,it will then run the same way as the other train motor

Edited by doug72

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Well well.

Now I opened another motor, black one this time.

It drove in "the standard direction" before opening.
I did not remove the coil from the armature.
I might have switched tire axles.
I might have turned the armature upside down during the process.

And now it drives in the opposite direction.

Interesting.

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