Hi All,
Last night, I was told that the open field USH motors were not compatible with DCC decoders, i.e., they burned them out.
Has anyone had a problem using a large O Scale decoder with these USH motors?
I use an NCE D408SR.
Thanks,
Ed

Open frame motors and DCC decoders generally do not work and play well with each other. I suppose if you had a decoder of sufficient capacity it would work. But high capacity decoders are quite expensive.

This is because an open frame motor can draw high amperage in operation and especially at a stall. Also, if the magnet in an open frame motor weakens with age, its current draw increases along with the ambient operating temperature. The speed and power decrease as well. Back in the 1950's there was an article on how to restore the magnetism using a transfomer and coil from a junked TV set. We've moved far past that now.

I've found a few early USH motors unsuitable when new even for straight DC,
barely able to move the locomotive let alone draw a train.

So if it's an open frame motor, even one that might draw only 4-5 amps at stall, it would still be better to replace it with a more efficient, high torque, low amperage motor. In the long run it would be less expensive than replacing a fried decoder.

Ed Bommer

Hi,
Thanks Ed B.
I have two Pittman #9514 12 vdc motors from 1981. Are these suitable replacements? Any other recommendations?
Thanks,
Ed

Ed:

The big P'man cans should work fine. To add to B'rer Bommer's comments, the real killer about large open frames from the '50s and '60s is that they are notorious for huge transient amperage spikes under load, in the three-figure order but of very short duration. In my early and frustrating DCC days, I measured these with an old HP scope, and was amazed at the amplitude of these spikes. They'd religiously kill a decoder, even the hi-amp ones of the day (remember folks are grounded against static electricity when they assemble these things, and for good reason!).

While the newer decoders today are usually much more robust (like the D408), these motors are dirty and sparky, so even the new decoders will suffer over time. Might not be the first spike or even the second, but sooner or later...


...pffffft

Ed

I recommend replacing the USH open frame motors for several reasons. The first is the risk to DCC decoders as Brian discussed. The second is that a good Pittman can motor will have superior starting torque for better low speed performance on the layout. The last reason is to minimize cumulative current draw on the layout - especially during heavy operating sessions. Hopefully that will minimize or avoid the need for additional ten amp boosters & transformers - they aren't cheap.

Some of the same reasons I replace USH open frame motors explain why I dislike the China drives in recent O scale diesels.

Ed Rappe

Hi All,
You have convinced me that I should remotor.
What brand and model # of motor would you use for the USH PRR L and M class locos?
Thanks,
Ed K.

Ed
I don't believe your 9514's will fit in the USH L1 on the existing motor mount due to the overall length of the motor and rear mounted brush contacts. That motor will probably fit in the longer M1a firebox. I think you can directly mount the 9xxx series motors to the USH/KTM motor mount bracket. My recommendation is unbolt the old motors and do trial fits in the boiler shells (before worrying about connecting the shaft). I suspect you'll need a shorter 94x3 series motor for the L1.

Over on the MTJ Forum there was a lengthy exchange between members on the selection of Pittman motors. Bob Turner favors 8xxx series motors and is particularly concerned about RPM and ball bearings (a Pittman option). I and several others are more concerned with starting torque. Bob does continuous running on a flatland circle - I run 25 heavy train movements under 1000' in a monthly operating session - I know I'll never wear out a motor, but I hate lurching starts. To that end I've had to replace the 8xxx series motors in all my Overland diesels and the Overland M1a/b's. They ran nicely on light moves, but poorly on 25-30 car trains.

Ed Rappe

As usual, I have an opposite experience with a open frame USH F40 using NCE 408. Ran fine, never a problem, loco was traded, and the other owner had no problems.

I guess I just lead a charmed life?????

Ed R