I’ve seen a lot of information about electric motors for remotoring model locomotives. But I’d like for someone to explain, preferrably in simple, non-engineering terms, what the different terms that you encounter mean. I’m sure that there are more, but for instance…
skew wound
5-pole (are there others?)
can vs. open frame… I know the difference but what is the advantage / disadvantage?
ceramic magnet
coreless
As I said, I’m sure that there are more, but this list is a good start.
Now, to be specific, I’m thinking of remotoring an old Mantua / Tyco 4-6-0 engine that I have. Armed with the information I’m requesting, I may be a little more knowledgeable when I go “motor shopping.”
This is when the arms on the armature core (the spinning thing in the center of the motor) are not sticking straight out from the center shaft. They’re skew at an angle. This reduces “cogging” (That herky-jerky motion that is caused by the interaction between the permanent magnets and the rotor’s teeth, and is undesirable in terms of a smooth operation, and this cogging can be suppressed by skewing at a certain angle.) when running the motor slowly.
Here’s a regular armature (these are like 15 pole armatures)…
And here’s a skewed pole armature…
This means it has five wound points coming off of the center shaft. Older design motors had three shafts and didn’t run as smoothly (Remember the cogging I talked about?) at slower speeds. This is because there is more open space between the arms (rotors) on the armature. The less open space you have, the smoother the motor tends to run. There are 7 pole motors and many others, but they are usually more expensive and larger, so you don’t see them in models much.
If one looks at the pictures pcarrol posted, it will be noticed that there is a quite massive amount of metal that the wires on the armature are wrapped around. That metal is the “core”. So obviously a coreless motor doesn’t have these. The armature turns strictly based on the magnetic field it generates rather than the magnetic field it generates in the core.
With this design the permanent magnet can be inside the armature instead of like normal. This allows the armature to turn around the magnet (with all the normal brushes etc.) or the magnet rotates inside the armature. In the later case the polarity of the electricity is electronically “reversed” instead of depending on mechanical brushes to do that.
The first can motors I was exposed to (around 1970?) were coreless. For the longest time my definition of a can motor was synonymous with coreless. At that time the motor could not handle any thrust torque on the shaft. This left model railroaders in a quandary developing slip shafts and the like to prevent back force from the wheels from ripping out the guts of the motor. And they were way expensive back then to. As I recall about $30 (twice the price of a powered Athearn blue box).
AC ‘squirrel cage’ motors are brushless, depending on the reversing magnetic force of the field windings to induce torque in the armature - which has no electrically-connected windings. With DC and permanent magnet fields, this is not an option.
The advantage of AC diesel-electric locos is that there are no brushes to wear, get shorted out or arc over. The traction motors are squirrel cage type. (The complication is in the electronic inverters which supply those traction motors with precisely-tailored special waveform AC.)
They are brushless, but resemble a backwards can motor. A steel core with windings around it that resembles a DC armature with 4 poles is static in the center, while a rubberized ring magnet lines the inside of the center of the fan. I’m not sure what keeps the fan in rotation, since no switching of the stator poles occurs.
I just had to tear one in my Dell apart and clean and relube the bearings because it was getting noisy, and it has some ridiculously high CFM rating that makes it equally as expensive to replace.
Nikola Tesla’s induction motor. MOST motors working non-stop in appliances running modern life are induction motors. The electricity in the armature is created in the same way a transformer works. The wires in the armature are the like the secondary winding. When the electricity flows in them they create the magnetic field that turns the motor.
Coreless motors that have the perminant magnet turning inside of the fixed wire windings field. Depending on how the power is applied to the windings the magnet adjusts its position accordingly. Many submersible fish tank filter motors work this way from simple 60Khz AC power. The power to the windings can be controlled digitally creating exact movements of the armature so one can create things like stepper motors, and variable speed based on frequency.
Yes, I’ve been copying the mail at the Yardbirds Yahoo group for a while now. But if I remember correctly, they don’t have a really good conversion motor for the 4-6-0. I think it has something to do with the small boiler size not being able to house the motor & flywheel that I’d like to have.
As to the answers on the varied motor terminology, thanks to all of you. One learns all of the time…
Any flywheel that you could fit in these small locos doesn’t have enough mass to overcome the friction in the drivetrain, so you’ll not miss it. I removed the flywheel from my Proto USRA 0-8-0, and replaced it with a block of lead - it still runs well, but now it can actually pull something.
When I wanted to replace the motor in the ex-B&M Mogul shown below, any can motors that would fit between the sides of the narrow firebox were so small that I didn’t think they’d be of much use. Instead, I opted for the biggest motor that would fit inside of the boiler and mounted it in the boiler, with a sliding coupling in the driveshaft. A pair of tweezers takes care of aligning the driveshaft anytime the loco needs to be re-assembled. She’s a super smooth runner and a good puller for her size. [swg]
Thanks, too, to the various posters for the explanations on the motors.
I always love your photos, Wayne. I really like the electrical junction box and wires to the number boards and headlight. I assume you just used some fine gauge wire?
Thanks, Nelson. [:)] If I recall correctly, the junction box was punched out of some .020" sheet styrene, and the wires are individual strands pull from some light-gauge wire. This is an easy-to-add detail that can be used on almost any steamer.
That’s one type of coreless motor. The other type has the windings wound into a cup shape with a sort of epoxy holding them together, and they’re mounted to the armature with the usual DC motor commutator at one end. The permanent magnet is a cylinder shape and has a hole going through the middle for the motor’s shaft. The cup-shaped windings turn around the cylinder-shaped magnet.
