Can-motors come in 3,5 and 7-pole cofigurations. The more poles, the better the slow speed performance. I know a typical HO can-motor has 5 poles. Are there aftermarket 7-pole motors that will work in my BLI’s and if so, how do I remove the flywheels from my old motor in order to use them and the mount on my new motor?
It sounds like you have never done this before. NWSL has tools for this. I have seen 7 pole motors before but there was only a small gear on the end of the motor. The motor did not have a shaft on both ends. There was no place to mount a flywheel. You might check with the motorman also. He has coreless motors and matching gear boxes. I have one of his motors. This process is not for the faint of heart.
http://www.nwsl.com/Catalog/CatalogSect2.htm
http://www.micro-loco-motion.com/canmotors.html
Good luck.
Rich
You could very well be opening up Pandora’s box with attempting to remotor any of the newer drives. I’m not suggesting that you may find a perfect motor to suit your needs, but finding one that will physically fit and have the specs needed to outperform the BLI may be a challenge. I would hate to see you experiment with an otherwise decent running piece only to revert to reinstalling the origional motor. Amp draw, torque, and overall motor shaft speeds are all as critical as the physical dimensions for optimum performance. Many manufactures aren’t always using the best quality, however the motors used are speced out the the needs for the drive.
I don’t think that a 7 pole would offer that much more performance for all your efforts. Just my thoughts.
I’m not sure you are going to see the gains you are looking for, considered against the effort of putting in a new 7 pole motor.
The primary benefit of increasing the number of poles is the reduction in the “cogging” effect. The fewer the number of poles, the more uneven the torque as the distances between the center point of the armature and field magnetic fields vary during rotation. Switching from open frame motors with pole pieces on either side to can motors with the field magnets wrapped around the armature already id a lot to reduce cogging. Use of skewed armatures also reduced cogging. Cogging of an older open frame motor is quite noticeable when rotating the shaft by hand. It’s much harder to detect in a modern 5 pole can motor, so the benefits of going to 7 poles are less.
Modern controls, including good DCC decoders, use the back EMF (BEMF) of a motor to sense the cogging and apply brief pulses to assist a motor in overcoming cogging and maintain a steady slow speed. Even without BEMF detection, applying pulses of the right frequency, shape, and duration could make a model locomotive with a typical 5 pole motor move at seconds per tie speeds. DCC has a slight advantage in the very slow speed arena due to higher track voltage to help maintain good electrical contact. With traditional DC, any increased resistance in the path at these very low voltages creates problems.
Back to your post. The underlying assumption to your question is that the current slow speed performance of your BLIs (I believe you implied plural) is unacceptable. I’m also assuming you are talking steam and not diesel. I don’t own a BLI, so my answers are rather generic.
For outstanding slow speed operation the following is needed:
- sufficient gear reduction. The greater the gear reduction, the greater the range of slow speeds available. However, top speed will be limited with large gear ratios bec
As a custom builder/painter myself, I totally agree with fwright’s excellent comments. I agree that only marginal improvements, if any benefits would be achieved in switching to 7 pole motors. It would be much more cost/time effective to tune up the mechanical parts of a drive to gain a lot more in overall performance, including smoother, slower slow speed.
Friction is one key, less is better. Anything that binds or rubs impedes the drive. While today’s modern drive designs are pretty good, they suffer from mass production. The tough enineering plastics used for gears today, (steam or diesel), never really “wear in” and often have small defects that affect smoothness of movement. A few swipes of every gear tooth and all bearing surfaces with some 600 grit will help greatly in softening hard edges and minimizing flash and imperfections and thus “wearing in” the gear train.
Lubrication is another key, here less is more, do not over do it. Use only hobby types, LaBelle, HobbyLube, etc. Oil for motor and worm gear bearings, most wheel bearings are self-lubricating bronze and shouldn’t be oiled, (too close to dirt). Teflon grease for the gear teeth, dry teflon powdered lube for the gear bearings, (won’t attract dirt).
My [2c]
In addition to all of the above, brass flywheels are fairly soft and the act of removing them from a motor shaft, even with a puller, can deform the ID of the mounting hole. It’s not easy to be perfectly on-center with the press screw while removing them.
When you put the flywheels back on the new motor, they may not be completely true, causing vibration you didn’t have before with the factory installation. I agree that you should eliminate as much friction in the drive train as possible before attempting something more radical.