I’ve heard the term “cogging” and I wonder if that’s what my loco is doing. Now don’t laugh just because the loco is a Mehano 0-4-0 Old Timer (HO) about 12 years old. For the first few years it ran perfectly - smooth and a very strong puller. Much better than it should have. I guess I just got a good one. It had only a few “miles” on it when we moved. Then the loco was in storage (in a cool dry place) for 3-4 years.
I ran it today and it sort of surged forward, almost paused, then lurched forward again, and the cycle continues to repeat. Pulling a load minimzes this, but it’s still noticable.
Does this sound like cogging? I really don’t know what cogging is, I’ve just heard it mentioned. If so, why would storage cause this problem? It can’t be wear and tear. Would lube help? If so, what kind should I use? Thanks.
Harry…the loco being in storage would probably have dirty wheels and /or contacts. Non-use has a tendency to do that. Clean the wheels, check the wipers. Motor brushes, and the armature’s commutator can also get corroded. Also, lubricants do dry up over time. Try a good cleaning and lube. If you can get to the motor’s commutator, try cleaning it . If not, try to get the thing running, and it should eventually sluff the crap build-up off the com.
Now I’m sure some of the self proclaimed “experts” will have other opinions, but I’d try these as a start.
‘Cogging’ refers to the uneven torque of an un-skewed permanent magnet motor that does not have field magnets around most of the armature. The worst performers are ancient three-pole vertical-mount open frame motors that were common in cheap low-priced semi-scale products from some Japanese manufacturers of 50 or so years ago.
The herky-jerky movement you describe sounds like either seriously dirty wheels or a dirty armature. If the surge covers an inch or so, check the wheels. If the loco sort of shudders forward, check the armature.
Some engines with crappy drive trains will “Buck” a train shoving on the engine while the thing is downgrade. I recall very old open frame motors that would cog across every single one of the three magnets as they rotated between the poles. These were the non skewed ones.
HH:
Hey, don’t feel bad. I had a loco which I remotored, and it still wouldn’t run, so for a few years I would gripe about this whenever that particular loco came up in RMR discussions. Then I tried tweaking the pickup wipers and boom! it worked perfectly. Oops.
On cogging - I have discovered an interesting thing. Some of my old PM-1s, a non-skew, open-frame, 5-pole motor, cog quite noticeably, but others do not. I have found that at some point, the gap between armature poles was made much wider…about double…and this caused the increased cogging. I have also found that increasing the strength of the magnet, by replacing it with a rare-earth type, increases this cogging. At the same time, however, the increased torque completely overcomes it as a problem. It still occurs, but it doesn’t matter; the loco will creep at extremely low speeds, despite the noticeable cogging when the shaft is hand-rotated. I find this interesting.