Poles in the Can

[jacon12]

What is meant by the following:
"Powerful 5-pole can motor with flywheel "

How many poles does a motor usually have?
Is it helpful to have more poles?
Why is it called a 'can' motor?
How many flywheels are good enough?
Why are they called poles?
Why more than one motor on a model?

Thanks,
Jarrell
P.S. Pardon the 'basic' questions but it's the best way for me to learn..[:)][:D][:)]

[jrbernier]

Jarrell,

DC 'permag' motors usually have an odd number of 'poles' that the windings are wrapped around. Usually more poles the better, Really cheap train set engines have had 3 pole motors, most HO engines have 5 pole motors(and some have had 7 pole 'skew wound' motors. Basically more poles will be smoother.
A 'can' motor can vary from a basic DC motor in 'can' to some very pricy coreless motors.
Flywheels help smooth out motor operation, it is the 'mass' of the flywheel, not the number of flywheels. Most diesel models will have a pair of flywheels to increase the total mass in the confines of a narrow hood.
Some models have two motors. Sometimes it is to split the load, other times it is due to mounting limitations.

Jim Bernier

[jrbarney]

Jarrell,
Back in the "dark ages" of early model railroading, some craftsmen made their own motors, cutting out the individual armature laminations, then stacking them on a shaft and winding them with magnet wire. Depending on the tools used, three poles were easier and faster to cut than five. If I'm correct, an odd number of poles prevents "cogging" whereas even poles would hesitate opposite the brushes on the commutator.
Bob
NMRA Life 0543
P.S. I'm glad that nobody has seen fit to make a bad pun on your topic heading. [:D]

[jacon12]

Thanks for the insight Jim and Bob. Lol... Bob I see what you mean now about the topic heading! I had to reread it a couple of times myself..
Jarrell

[cacole]

Okay, now that someone brought up that aspect of the Subject line, how many Poles in the Can does it take to change a light bulb?

[Javern]

and then some of the elder modelers of the forum probably recall the rubber band pole motors

[andrechapelon]

Every time I see this subject, I think of Porta potties at a Warsaw construction site.

You've heard of L.D. Porta of course, probably best known as the inventor of the gas producer fire box http://www.trainweb.org/tusp/porta.html.

What's not generally known is that Se#241hor Porta was such an advocate of reduced back pressure that he invented the portable toilet so that relief could be had at any time anywhere. Hence the Porta Potty. [(-D]

Incidentally, I also have some 1st rate agricultural property for sale cheap in Central Florida.

Andre

[Anonymous]

So far there has been a few good answers to the pole question, the summary of it being that the armature of a motor has shapes protruding out of it that are called "poles" and the wire is wound around them. Poles have to be an odd number or the motor will vibrate but not rotate. The more poles you have, the smoother the motor will run.

But nobody as yet has answered your second question "why is it called a can motor" -- this has to do with the shape of the casing. Originally DC motors were square shaped open-frame things, with the top and bottom of the frame forming a bridge from the permanent magnet at the end of frame so that a magnetic field existed around the armature. This is hard to say in words - I wish I could include drawing. Anyway, the point is that a superior construction method was found where the frame and the magnet could completely surround the armature instead of being just at the top and bottom. This gave better efficiency, and it converted the old open frame motor into something that was now fully enclosed in a can. That's where the name comes from.

And they are called "poles" because they represent magnetic poles. The permanent magnet at the end of the frame exerts a magnetic pull on each pole in turn when current flows through it and that causes the motor to turn. For that reason poles have to be an odd number, or the north magnetic pull would balance the south magnetic pull and the motor would just vibrate.