Lionel Pre-War Motor Issue

[NNJRailfan]

I purchased an early 1920s Lionel #158 boxcab, which has a motor identical to the #150's "humpback" (type 2 or 3 according to the diagrams I got from Olsen's).  One of the brush holders was broken, and I replaced both for good measure.  Power is getting from the holders to the commutator but it won't turn - my guess is that there is a short circuit somewhere but I've examined the motor as thoroughly as I can and can't find one.  It doesn't look like the commutator is touching the electromagnets; it's not due to wiring because I've removed all wires except the original that goes from the roller plate to the headlight, and I encased that one with shrink tubing; all the insulators on the motor plate cover are solid and in place.  Anyone have suggestions on where else to look?

[rrswede]

You indicate you are getting power to the commutator plates of the armature. How did you perform that test? Do you get any movement of the armature at all when power is applied? Have you tested the armature, itself?

Thanks, swede

[lionelsoni]

What does this mean:  "It doesn't look like the commutator is touching the electromagnets"?  What electromagnets?  Are the brushes and the field wired in series?

[rrswede]

I think he is using "commutator" to mean "armature".

If the motor does not have a manual reversing switch, one brush is connected to the field and one brush is connected to the pickups.

swede

[TrainLarry]

Disconnect all wiring from the motor. Wire one transformer lead to one brush. The other brush gets a jumper to one field lead. The second field lead should be grounded. Hook the other transformer lead to motor ground and the motor should run.

If it does not, check for continuity between each of the commutator segements to the others. The readings should be identical. Also check for continuity of the field winding.

If all this checks out and the motor is wired as described, it should run.

Larry

[NNJRailfan]

rrswede:  I am using commutator in lieu of armature; please correct me if I am wrong, but aren't they the same thing?

Lionelsoni: I may have misinterpreted what the plates are surrounding the armature, I guess that is what you referred to as the "field"?

Larry: The only wire currently on the motor leads from the roller plate to the light and is currently disconnected.  Can you please confirm my interpretation of where the field leads are connected to - both soldered to the field winding (assuming that I have correctly identified the "field"), then one then connected to a motor brush and the other to the frame?  The field winding looks OK.

[lionelsoni]

One brush should be connected to one end of the field winding.  The other brush should be connected to the pickup.  The other end of the field winding should be connected to the locomotive frame.

The armature is the rotating iron lump with windings on it, in the middle of the motor.  The brass or copper plates at one end of the armature that the brushes rub on are the commutator.

[TrainLarry]

The wire from one brush gets connected to one field winding. The other field winding is grounded. Power gets connected to the other brush and ground.

[NNJRailfan]

Bob, thanks for the clarification.

Larry, I believe you provided a link to a wiring diagram, but it didn't come through on the forum message.  I PM'd you my email address, can you please provide the link or attachment to it?

[rrswede]

See tjcruisers post and photos. 

http://www.modeltrainforum.com/showthread.php?t=125778&highlight=humpback

swede

[lionelsoni]

|  |  |
|  |  |wheels
|  |  |(----field winding-----
|  |  |                      |
|  |  |                      |
|  |  | brush          brush |
|  |(-+--->o--armature--o<----
|  |pickup
|  |  |
|  |  |

[NNJRailfan]

After reviewing everyone's instructions, I saw that the key thing I was missing was that I wasn't providing a connection between the field winding and the motor brush, so without power flowing through the field winding there was no electrical field to act upon the field from the armature to make it spin.  Once I made that connection the motor came to life. Thanks to all for your advice!

[lionelsoni]

Now make sure that the two elements--field and armature--are wired in series, not in parallel.  A series motor works far better over a wide range of speeds.  Series connection is especially important for a universal motor (which is what was used in toy trains) because it generates the two magnetic fields from the exact same current waveform, making any relative phase shift absolutely impossible.

[NNJRailfan]

How would I tell if it's wired in series or parallel?  My current setup:

a. rollers to upper brush

b. bottom end of winding to motor body (how it was manufactured)

c. upper end of winding to lower brush

[lionelsoni]

That's series--you're good to go.

In a series circuit, the same current flows through all the circuit elements.  So terminal 2 of element A connects to terminal 1 of element B, terminal 2 of element B connects to terminal 1 of element C, and so on.

In a parallel circuit, all the elements see the same voltage.  So all of the elements' terminals 1 are connected together; and all of the elements' terminals 2 are connected together.

These aren't the only possibilities.  For example, a commonly used voltage-dropping circuit has pairs of diodes connected in parallel.  Then those parallel pairs are connected in series to make the full circuit.  In this case, the two diodes in each parallel pair are connected with their polarities opposite from each other, so they are said to be connected in antiparallel.