What is an easy and quick way to determine if a motor is too old; or, worn out to use in a DCC equipped locomotive?
NP 2626 "Northern Pacific, really terrific"
Northern Pacific Railway Historical Association: http://www.nprha.org/
If the motor is in an engine, I'd say if it runs well in DC it will run well in DCC. If a motor seems to be weak, sometimes you can revive it by adding new magnets - IIRC, you can get them from MicroMark.
Hi Mark
A motor that doesn't have much power could be suffering from a couple of different problems. Weak magnets are one cause. The other is friction due to worn parts or lack of lubrication.
I would suggest that you do an amp draw test on any old motor before attaching it to a decoder. Before doing the test you should service the locomotive to make sure it is properly lubricated and running smoothly. If it doesn't run well on DC there is no use putting a decoder into it. I'm sure you were aware of that.
If you have a multi meter the test is easy:
- Set up a short piece of test track. Make sure it is clean.
- Hook up your power pack but insert the multi meter leads between one of the power pack leads and the track. Set your meter to measure amps. On some meters you have to use a different socket for one of the leads in order to measure the amp draw properly, otherwise you will get bogus readings.
- Put the locomotive on the track, hold it so that it can't move, and crank the power up to 14 volts or so. The wheels will spin.
- Next, push down on the locomotive until it stalls and then read the ammeter. Don't hold the locomotive down for more than a couple of seconds or you could smoke things.
- The meter will tell you what the maximum draw of the motor is, and that draw has to be less than the rated maximum amps of the decoder.
If the draw is high, or even if it is low but the engine won't pull, you can replace the magnet. That is assuming it is an open sided Pitman style motor. You will be replacing the single old cast magnet with a stack of new Neodymium magnets. You may have to put a small steel shim in with the magnets to make them fit properly.
Micro Mark sells the replacement magnets. I get mine from here:
http://www.forcefieldmagnets.com/catalog/index.php?cPath=23_37&sort=0a&page=3&osCsid=9421e594d526d832ef6116c77e9d48fe
Replacing the magnet makes a big difference in the motor performance. You get both lower draw and higher power.
The other issue of course is wear. A worn out motor isn't likely to run very smoothly so no amount of work will fix that problem. Best to replace it.
Regards
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
I should have given more specifics, I'm talking can motors and not open frame.
Key is the current draw - as the magnets get weak the current draw goes up. So test the current draw on DC, running free, slipping, and briefly hold the flywheel if possible to get a stall current. If you're within limits of the decoder, it should be good. ALso see how it runs on DC, even if the current is within spec, if it runs slowly even at full throttle and it's not supposed to be slow, or if the motor heats up from just the loco running around and there's no problems with the drive train, the motor is suspect. It's helpful to have the original specs, for example if the original rating was .2 amps and now it draws .5 amps - it's still fine for a DCC decoder, but the motor is drawing over twice the original current and probably has weak magnets. This will also show up as poor DC performance and lack of power, in case the motor info is unknown.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Shorted pole windings can also cause a high current draw as the resistance is lowered. This occurs due to heat melting the thin coating off the windings which allows amature wire to come in contact.
Jim
HUMPH (sayeth the camel).
LION was trying to make photographs from moving train of him and thought to use some old Atheran Blue Box locomotives (shell removed to fit tunnels of subway), but would not work on layout of LION.
Apparently these older motors draw more current, which means that the track resistors approaching and departing the stations stop the poor thing dead. Newer motors (or leastwise better motors) have no problems with design of LION. To Bad, LION was planning on using these motors in some of the train sets that were not powered. Now think again, him must, and the old locomotives will go to the static display at Penn Station.
So what od electro-math-heads think of that. Is my analysis correct or is the LION all wet?
ROAR
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
I have to say that I have a very difficult time trying to understand lion speak.
It's a Lion thing. You get used to it. Everyone knows cats are strange beasts. (well, if you have cats, you know)
Lion is correct, though the reason is more the resistence of the motor windings (which is of course directly related to the current draw). You can have the same problem in reverse if you take an old HO power pack (the rheostat kind, not a transistor one) and try to control one of the new low current locos - as soon as you move off the stop position, the thing will take off at max speed, because itr draws so little current that there is almost no voltage drop in the rheostat. It's also why before transistor packs were the norm, there were HO and N scale versions - sticking with MRC, there 770 and the 770N for N scale - the difference being the rating of the rheostat, since N scale locos draw a lot less power, there are pretty much uncontrollable with an HO pack. And if you tried an HO loco on the N pack, at full throttle you'd be lucky if it moved, all the voltage is being dropped in the rheostat. Transistor throttles solve all this and there is no fundamental difference for scales, because the voltage drop is not accomplished by running through a resistence.
I guess we need to know if you are experiencing an issue with a particular loco?
The below meter would help a lot checking a loco. I have used them regularly when checking a suspect loco.
http://www.trainelectronics.com/Meter_Workshop/index.htm
Checking for current and voltage at the same time.
http://www.trainelectronics.com/Meter_HF/index.htm
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.