OK, here is the deal. Last year I had 3 PK 1000 F 3's with 400 plus hours eat decoders. I have bought new motors and they are on there way. Before I install the new motors I need a refresher on testing the old motors to make sure they are bad. If they are not bad, I have other engines that could use the new motors.
My first big question is about the only DC power supply I have to do the test with. It is a small MRC 1100 with the following rating. Output 15V DC-19V AC/ Total-5 VA, is this sufficient power to do a good test?
Motors will be out of the chassis when I do the test.
What amp should they pull freewheeling?
On stall, should I just drag my finger on the flywheel to add drag, or bring motor to a complete stop? If I remember correctly I don't want over 1.35 amps, am I right?
Thanks for the coming answers!
On a side note, one motors was making a racket like it was losing a bearing. The other two I think I messed up. I have 2 Monon F 3 A's and 2 F 3b's that where speed match going one way. Front forward. I changed the direction using the decoder but did not think to speed match them going backwards.
Ken
I hate Rust
Your old power pack should be fine.
Bring the motor to a complete stop. But don't hold it there for an extended period of time, just enough for the meter to settle and read, since it's not really good for the motor Free-running current draw should be pretty low, and mostly meaningless, unless it draws over an amp runnign free. Stalled current that is acceptable depends on the decoders you are using, some can take 2 amp peaks, others only 1.5. If the stalled current is 1.3 ams or less you are safe for all but the smallest decoders. If the motor draws less than 1.3 amps stalled and under 1 amp free, and you're still blowing decoders, something else is wrong with the loco, like the motor isn;t truly isolated.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Thanks Randy. If the new motors work out will be getting some of the older engines going.
Far as decoders, I will run DH 123's for the MU F-3's or NCE D15SR's. I really like the NCE for Athearn RTR's
Testing a motor that has not been installed into a locomotive is going to be pretty meaningless if your locomotive's mechanism need lubrication or has a lot of internal drag.
A motor may draw less than 1/4 Amp outside the locomotive because your measurement is for a very short duration of stall, but draw over 2 Amps when installed in a poorly functioning mechanism that places a continuous load on it that causes both the motor and the decoder to overheat.
Using a different brand and type of decoder that is rated for a higher Amp output may be easier than changing a motor.
With modern motors and decoders I'd try to stay under an amp stall if using a small sized decoder. I think you'll find that you are fine with room to spare.
Springfield PA
Stalled is stalled, in or out of the mechanism. If the stalled current doesn't exceed the continuous rating of the decoder, it won't overload the decoder even if the mechanism is sticky since in the worst possible case it won;t draw more than the decoder can handle.
Please check my homework to be sure I'm doing this correctly.
I’m testing an IHC 2-6-0 with an old analog meter.
· The DC Amp feature on the meter has three setting 250m, 2.5m and 50u
· The meter's DC V mA scale reads 0 thru 5 or 0 thru 25
· Wired in series and set at 250m, the meter reads 2.0 on the 0-5 scale (or 10 on the 0-25 scale) pulling a train up a grade and 1.5 at stall.
· The 2.0 reading translates to 100 mA or 0.1 amp.
· The decoder rating must be comfortably higher than .1 amp.
Thanks!
Jim
10 on the 0-25 scale with the option set to 250ma would be 100ma, you are correct. That it goes down at stall - that's not normal. If it reads 100ma running free is shouldn;t drop on stall, but should rise. Other than some really top quality motors, most HO size motors stall at greater than 250ma, which would put the meter off the scale.