Question about MR DCC article

[gondola1988]

Try a helix humper fron Robs trains in Alliance Ohio.1-888-313-4048 Tues thru Sat noon til 8,   they are made to your specs if need be I've used them for years for Atheran locos,good luck,Jim.

 

[fwright]

hwolf

Existing motor was a Open Frame.  That is why I want to replace it.

There seems to be an assumption in these forums that:

• open frame motor = bad
• can motor = great

While those statements may be true, they are from universally true.  First off, in a permanent magnet motor, the strength of the magnetic field at the armature has a lot to do with the efficiency of the motor.  The stronger the magnetic field, the more efficient (using less current for the same torque) the motor can be.  The stronger the field, and the more of a point source for the magnetic field through the armature, the greater the cogging action of the motor at low speeds.  Cogging is why 2 and 4 pole motors are not used.  With 2 or 4 poles, it is too easy for the magnetic forces to balance, and the motor lock up.

Another point is that shaft diameter for motors has decreased over the years.  This means swapping out a new can motor for an old open frame usually means bushing the shaft of the can motor or replacing the gear box.  The smaller shaft and lighter duty bearings of the new motors also means the worm should not be placed directly on the motor shaft.  Universals are highly recommended for the small shaft diameter motors, even to the flywheel, to reduce the load on the motor bearings.

Open frame motor:  The magnet is in a block, usually at one end of the motor.  Or, it can be at the top or bottom of a U off to the side of the motor.  The magnetic force is transmitted to the armature (the iron with the copper windings) by the motor frame, which is usually made of steel.  Pros/cons of open frame motors:

• the magnetic path is long and relatively narrow (like using small wire).  It is more difficult to get a strong magnetic field at the armature.  Rare earth and ceramic magnets were not available at reasonable prices in the open frame motor heyday.  Magnets were made from Alnico, which loses magnetic strength when the magnetic circuit is broken - like removing the armature.  Alnico magnets could be "recharged", but it was not simple.  Result is that open frame motors draw more current for the same torque than other types.
• the motor bearings are easily accessible to clean and lube.  The commutator is also generally easily accessible for cleaning and dressing, and brushes and brush springs are easily replaced.
• the small pole pieces which conduct the magnetic field into the armature make the cogging action stronger, especially with 3 pole motors.  Noticeable cogging can be done away by going to 7 pole motors or skewing the armature axially along its length.
• replacement of the Alnico magnet with a rare earth magnet stack will usually give as much magnetic force as the frame and pole pieces are capable of transmitting.  This will give a good open frame motor permanent new life.  Efficiency will be improved, current draw reduced, heat reduced, and top RPM reduced.  Cogging may be increased.

 Can motors have ceramic (typical) or rare earth (better) magnets that are shaped to surround the armature.  The magnets are then enclosed in a can.  Pros/cons:

• early can motors used in some Korean brass locomotives did not have sufficiently strong magnets for the load they were expected to pull.
• the ceramic and rare earth magnets hold their magnetism much better over time in comparison to Alnico.
• cogging is reduced because of the magnetic field is spread out over the rotation of the armature.
• the motor may or may not be easily removed from the can for maintenance.  Bearings tend to be of the sealed variety.  Can motors tend to be disposable in comparison to open frame motors.
• internal heat may be higher because of the can enclosure.  However, can motors generally draw half the current of a comparable open frame motor under the same load.

Coreless motors do away with the iron in the armature.  The armature is just a bundle of wire held in place by plastic spacers.  The armature can be placed inside the magnets like a can motor, or it can be made to rotate around the outside of the magnet, or the magnet placed on the shaft and rotated inside the armature.  The lighter the rotating mass of the motor, the faster the response to the driving signal.  It the armature does not rotate, the commutator and brushes can be done away with.  Pros/cons:

• coreless motors are very low current/high efficiency devices. 
• coreless motors are more susceptible to overheating due to the lack of iron mass to absorb and dissipate the heat.
• they can be made smaller than can motors.
• they are much more expensive than can or open frame motors.

just my thoughts and experiences, your choices

Fred W

[modelmaker51]

NWSL will respond to emails. It is a small company and this is also show season, but I'm sure he'll get back to you.

An alternative might be http://www.alliancelink.com/alp/  They produce the "Helix Humper" series of motors and drop-in replacement drives. Click on: "Photos Of Products & Instruction Sheets"

[hwolf]

Existing motor was a Open Frame.  That is why I want to replace it.

[maxman]

I think you should be a little more patient and keep trying to contact NWSL.  I think they're a small operation, and with the holidays and all they might just be taking some time off.  I had some questions regarding gears for a Roundhouse HOn3 mudhen, and they were very helpful.

Plus, if you think you are capable of doing the remotoring, then I think you should be capable of making some rudimentary measurements of the existing motor.  NWSL has an on-line catalog that gives the different available motor sizes and configurations, so you could do some initial research before you contact them. 

[hwolf]

Rich

I wish I could.  This is my first attempt at anything like this.  That is why I am looking for a supplier that can go more by Make  & Model. The engine looks exactly like the one in the article.

[richg1998]

Get yourself a dial or digital caliper and spec out your present motor gear arrangement.

Go to the NWSL site and spec out the motors. Specs are there. The only possible issue will be for the older motor shaft diameter and the replacement motor shaft diameter.

I did that over ten years ago and found what I wanted for some motor/gear upgrades from NWSL

You just have to do some homework.

There is also plenty of gear info.

There are also some good motor replacements on ebay as one motor seller I have bought from also sells on ebay. I believe his company name is Micro Loco Motion. He did a custom gear motor for me for a 4-2-4 loco.

Rich

[hwolf]

Any idea on another source for the motor?

[jrbernier]

Harold,

  The reason he was installing two decoders was to sepeate the wiring.  The motor decoder is in the engine, and the sound decoder is in the tender with the speaker.  Basically, that picture in Fig 1 is all you really need for a quick & dirty install.  The problem with this kind of install is that the decoder is getting power from the RH drivers(3) and returning power via the LH tender wheels(4).  Adding pickup shoes(like Tomar) would help with electrical pickup(especially with sound engines).  In your case the existing electrical pickup may be OK.

  Make sure that both motor brushes are NOT making any contact with the frame of the engine.  Use a multi-meter and check it out.  You do not want to let the 'magic smoke' out of that decoder!

Jim

[hwolf]

I am changing a 35 year old brass engine to DCC. Two question. I am trying to change the motor from the Open Frame to a Can motor.  I have tried to reach NWSL as I do not have a clue of which one I need but I have been unable to contact them. Any other suppliers you guys might know?

I am going to install Motor control only with no lights. In the DCC Articile on Pg 78 Jan 2011 MR. I understand except for two things.

1. Why is he using TWO decoders?

2. With my install do I just connect the four wires shown ? The wire he is talking about that runs to the tender. Is that for the other decoder?

Thanks in Advance

Harold