RailPro User Group
RailPro => RailPro Specific Help & Discussion => Topic started by: ON28 on July 22, 2020, 04:46:36 PM
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I have an older DC Kato/Stewart F3 with original motor. It ran for some time on DC until I installed a used (but working) LM3-S and used KA-3. It functioned well until one day it stopped and the HC showed a Motor Over Peak Voltage message. I tore it down, the motor tested fine on DC, then reassembled. Worked for awhile, then got the same message. Tore it down again, saw no binding in the trucks, motor fine. Reassembled with different LM3-S and KA. When I auto-set the voltage, it ran up to 680mAh from around 380 the previous time. Ran for a couple of hours until it shut down and I got yet another Over Voltage message. HC is fine and operates my other RP locos without issues. So I am throwing it out to the group for advice here, and thanking you in advance. I use NCE for track power.
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Motor getting hot?
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Not really. Or the LM.
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Spray the brushes and commutator with contact cleaner. Carbon dust may be partially shorting the windings.
The 680mA reading is kinda high. Sure there is no mechanical issue?
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It's run normally for hours, down to crawling speed, most recently and then just stopped. I wonder if it's the TCS KA-3 reacting for some reason with the Kato motor. I have KA-3s and -4s in my Intermountain F3, Atlas GP7 and Proto 2000 BL2, with no operating problems. I tried swapping one KA-3 for another but came up with the same result. (I will note that I purchased my KAs used from a well-known RailPro operator who is switching to RP keep-alives...)
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Easy enough to find out for sure. Take out the KA altogether and run the loco.
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To the surprise of no one, the loco seems to function well without the KA. However, when I reset voltage it maxed out at 770 mAh. I only have a headlight LED in the circuit bvut still seems high even for an old Kato.
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To the surprise of no one, the loco seems to function well without the KA. However, when I reset voltage it maxed out at 770 mAh. I only have a headlight LED in the circuit bvut still seems high even for an old Kato.
Agreed. You have an issue somewhere. 770 is too high. Did you try cleaning up the commutator and brushes?
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Yes, another teardown. Along with drilling holes for grabirons, my favorite part of the hobby! Any tips for cleaning the comm/brushes? Thanks!
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Just for my curiosity, how are the power from the trucks routed to the LM? Is it like the newer Kato with hard wires? Can you post pictures of insides?
Thx
Kevin
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Yes, another teardown. Along with drilling holes for grabirons, my favorite part of the hobby! Any tips for cleaning the comm/brushes? Thanks!
Aerosol contact cleaner
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I have used isopropyl alcohol on a swab in a pinch and it seemed to work well. One must rotate the armature to ensure complete coverage and one must be alert to ensure no stray wisps of cotton attach themselves to any motor part.
Alan, as our resident electronics guy, do you see a problem with my method?
Cecil
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Sure, IPA will work. Contact cleaner is faster evaporating so you can really blast it. Just make sure everything is dry before applying juice.
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Thanks for the advice. I found a tutorial online restoring an Arnold N scale steamer, had lots of good info. The author used CRC 2-26, a bit of mineral spirits, and IPA. Also 2000 grit sandlpaper to clean the commutator. He ran the motor with CRC in it to clean the can, among other things. His methodology lowered draw by a full volt. Here's a link to the PDF:
https://www.nscale.net/forums/downloads/Arnold%20Tutorial.pdf (https://www.nscale.net/forums/downloads/Arnold%20Tutorial.pdf)
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Just for my curiosity, how are the power from the trucks routed to the LM? Is it like the newer Kato with hard wires? Can you post pictures of insides?
Thx
Kevin
I hardwired directly to the LM.
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Update: After running the loco without the KA for about 20 minutes today, it crapped out again with a Motor Over Voltage alert. I disassembled the loco, and bench-tested the motor with my multimeter, finding a draw of more than 700mah, as per the module reading. The stall current was nearly 1 amp. Also, the motor got overly warm in less than a minute under power.
I disassembled the motor. There wasn't a lot of carbon buildup. I didn't see any obvious stray winding wires. The magnets seemed strong. The commutator was fairly clean. I removed the brushes and cleaned them with a q-tip and IPA. As I was trying to reseat one brush with a tweezer, IT BROKE IN HALF. I have never heard of this happening, but maybe deterioration of the brushes was causing excessive current draw? Could the brush springs have been too weak to begin with? Anyway, I'll be looking for replacement brushes or, more likely, an entire motor. I've got a trio of Atlas/Kato GP7s and maybe get a donor motor there.
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I suspected such. That's why my first question to you was is the motor hot? Find a nice place in the backyard to bury the motor. It is in the final throws of dying from old age. Get a new motor.
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I'm no motor savant, but it looked to be in excellent condition, no damage, magnets still strong, windings intact. Thought new brushes. I only paid $60 for the custom-painted loco. Still, only $20 for a new motor so yes, replacement indicated.
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I suspect the insulation on the windings is failing. Explains the heat and the rising amperage measurements. The insulation is a varnish that gets brittle and cracks when it is old.
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Thanks for that explanation. I have a sister unit about the same age I haven't RP'ed yet.