Atlas/Tomix vacuum car problems

[Maletrain]

Peteski, That "CL" position is somehow related to "constant lighting" on a DC system.  My guess is that the constant lighting (in other types of cars, not these vacuum cars) is accomplished by an additional constant low-voltage AC potential - probably just enough to light LEDs.  With that available, a bit of additional power to the vacuum motor could probably be obtained by rectifying it and adding it to the DC potential.  But, I am not seeing that in the traces.  (I don't have the time right now to fool with something I can't use and am going to throw away.)

[peteski]

There already is a bridge rectifier permanent in the circuit. The cap likely just connects (like any filter cap in parallel with the bridge rectifier and with the motor (they will all be in parallel). Maybe that does take the advantage of the overlaid AC voltage providing constant power to the motor. If that cap is engaged during normal DC operation it would nto have any effect.  Again without knowing for sure how the switch wipers connect various copper pads on the PC board I;m just speculating.

Personally I think we are seriously over-analyzing this simple circuit. 

[Maletrain]

I played around with the motor, and I think that is the real problem.  It runs up to 12 volts without the impeller in it (so no load), but has now started getting a locked rotor when I run it at 12 volts with the impeller.  I thought maybe the impeller was the problem, and noted that the "housing" looked scored - like somebody had tried to vacuum rock ballast with the car.  But, the impeller was not what was locking - it was the motor rotor.  And, the locking was occurring at slightly reducing voltages as I tried various experiments.

When I took the motor out and spun the rotor by hand, it would unlock, and would then run again under power.  But each lockup event was tighter than the last - going from easy to unlock to pretty hard. And, it often made a short screech when starting up the first time after having been locked.  I had heard that screech on tests yesterday, but was thinking it was due to the impeller rubbing.  Apparently it is the motor making the sound because it will do it without the impeller being installed.   

I am not seeing anything that is impeding the rotor.  I used some thin card stock strips to see if I could pass them between the rotor and the permanent magnets. It is much easier to pass then through one side than the other.  But, I did not feel it hang up on any particular spot on the tight side.

So, this motor does not seem useable, unless somebody has an idea how to fix it.

[peteski]

Try putting little oil on the bearings. If that's not it then you would have to disassemble the motor to see what the problem is.  With some motors they can be taken apart easily , others  - not so much. You could also try getting a replacement motor from either Atlas or Tomix. Tomix does not send parts outside of Japan so you would have to try going through one of the Japanese online model RR dealers.

[Maletrain]

The motor housing has little tabs bent around the front piece.  Same with the cover for the commutator.  I really doubt that I could get those parts back on in the necessary alignment if I pry the tabs open.

Atlas says they don't have parts for this car.  And the motor body is different from the Tomix version - it uses the brush holder ends as both electrical contacts with the PCB and as physical supports for the PCB and motor in the car frame.  So, something Tomix or generic won't physically fit.  It isn't just a matter of soldering wires to the brush holders.  The best diagram I have found is here https://download.atlasrr.com/pdf/PartsPDFs/NTrackCleaner.pdf .

[mmagliaro]

Yeah... I know that kind of motor.  Sometimes you can pry the tabs back to get the end cap of the motor and the armature out, and then clean out any carbon junk and clean out the commutator slots.  It is tricky to get them back together and squeeze the tabs back down, but it can be done.  Of course, you can't do that very many times before the tabs will just break off.

That, and oiling the bearings SPARINGLY, as Peteski suggested, are about all you can do.

One thing I would definitely NOT do is put in a higher-current PTC, or take the PTC out.
That will just let the motor overheat and destroy itself more quickly.  Just the fact that they put that PTC in there at all belies the fact that they knew they were using a motor that wouldn't tolerate overloads or being stalled.

I think it's just a run of the mill little Mabuchi motor and you can probably find something like it on eBay.  Using a closed can one is probably very important so that all the dirt that flies around in there when it's vacuuming doesn't find its way into the motor.

Ah... if only Mashima were still around.  That would be a great upgrade for this.  But you could probably use something like the older circa 2000 Bachmann 2-8-0 motor if you can find one.  Those are really small, and very powerful for their size, and would probably do a good job.

[peteski]

I found  my car.  I bough it back in 2002 and it has Atlas-Tomix embossed on the bottom. I'm pretty sure it is the initial run of that model.  It has a typical Tomix construction, including the Japanese prototype trucks.  The jewel box itself is also what Tomix uses.



The motor is exactly as shown in the exploded diagram you pointed to. Again, this is is typical Tomix motor, similar to some motors Kato uses,  but each company makes their own motors.  And as in your example, the PC board touches the brush holders to power the motor.



Are you saying that the motor in your model is different? Why not post a photo of it?

The screetchign sound seems typical of dry bearings, but I don't think I have ever seen it so severe to lock the rotor. As Max and I mentioned, sparingly oil the bearings and see if that makes the motor run better and quieter.  Also pull and push on the motor shaft to see if it has a little play - it should, and mine does.

To clean the commutator I have sometimes removed the brushes by pulling the brush holders out - they are press-fit. Make sure not to lose the springs and brushes.  Are the brushes still long enough to work properly?  With the brushes out the motor shaft and the armature should spin very freely.

Now take a wooden toothpick  - flat ones work the best, and sharped the end to a thin flat shape. Like a tiny screwdriver for slotted screws.  Thin enough to fit in the commutator gaps.  Wood works the best because it is soft enough not to scratch or damage the copper commutator segments.  Then you can clean the commutator gaps through the openings for the brush holders.  I have successfully done that many times.  To do that I need strong light and Optivisor for magnification.

Oh, and I checked  that in CL mode the big cap simply gets connected in parallel with the motor.  I would leave it out of the circuit when the motor is to be powered from a DCC decoder.  For that matter the bridge rectifier is nto needed either and the tiny RFI suppression cap might interfere with the decoder BEMF (if that was used).

[MK]

Peteski, is that the original coupler?  I've only seen Rapidos on them out of the box.  If not, how did you convert?

[peteski]

Peteski, is that the original coupler?  I've only seen Rapidos on them out of the box.  If not, how did you convert?

I converted. I used standard MTL short T-shank adapter I used in dozens of Bachman and Atlas cars back in the day when they all came with rapido couplers.  I don't recall the part number.  I had to leave some play in the Tomix metal bottom coupler cover when I bent the tabs so the coupler could swing freely.

[Maletrain]

Peteski, that is the same motor that I have. 

The only issues for replacing it with something not physically identical is that I would need to wire the brushes and somehow "mount" the motor in the correct position.  As it is now, the motor position is determined by a slight recess in the solvent tube plus the opening in the top of the car body that fits around the bearing housing.

I am going to try oiling it, sparingly.  Then I might attempt the brush removal.  If all of that fails, I may as well try to take it apart.  At least I might find out why it is acting up, even if I never get it back to usable condition.

Much thanks to Max and Peteski for the interest and help.

My train room becomes a guest bedroom today, so it may be a while after Easter before I can get back to this.

[peteski]

As Max mentioned there could be some small debris (like grains of ballast) in the motor.

Make sure to first remove the brushes (or keep them out of they are already out) before taking the motor apart.  I use a silver sharpie or paint marker (or even a black one), to mark the orientation of the brush end in relation to the main body. Or I have also scratched a mark across the metal and plastic parts to do that.  But in this case the orientation doesn't really matter since the motor can be installed either way and the running direction doesn't matter.

[mmagliaro]

I must racant my description of the motor!  I took mine apart again, after seeing Peteski's photos, and that is exactly the motor in mine.
I incorrectly thought I remembered it as a little metal closed can.  You can forget all that "Mabuchi" stuff.

When I run mine, in the car, it only draws about 90 mA at 12v.  So you measuring 310 mA indicates the motor has a problem.

So yeah, I'd try to clean the slots and put a tiny drop of oil on each bearing.  You might be able to clean the comm slots using a toothpick and some alcohol through the brush holder holes after you get the brushes out.

[peteski]

As I mentioned I has success clearing the commutator gaps using a sharpened wooden toothpick through the brush holder holes.

Looking at the closeup photo I took of my motor I see that he plastic end is covered with fine (ground foam?) dust.  I'm thinking that maybe covering the openings in the motor hosing with some aluminum duct tape might keep the dust out of the motor.