As some of you know, I have a VERY early Atlas FP7 (from the 70s) with the early Roco drive. It has a silver flat can motor w/ one flywheel. A few months ago it stopped running. I was working on it last night and I got the motor to run by itself, but when I put the motor in the loco and hook up the driveshafts it won’t start on its own- I have to spin the flywheel and it starts moving, but if I stop it it wont start moving again unless I give the flywheel a spin. Seems to be a lack of power, as it doesn’t run as fast as it should, even on 20V DC.
Sounds like you have a broken winding. 4 of the 5 poles are good, but you have to hand spin the motor to get it started. Adding voltage will only burn out more windings…
dingoix, you just described the classic symptoms of a (DC) motor that has lost one or more of its windings; if you want to continue using this unit you’re going to have to take all that sound advice that has been tendered and install a $35.00 (replacement) motor in that $24.95 locomotive!!! Only motors I never burned out were Pittmans - and they lasted forever.
Sounds like a winding broke. That just happened to me recently with an Athearn motor, but somehow, it started working again when I accidently pushed the broken winding under the commutator.[%-)]
I just finished testing a new Roco motor from my Genesis F3 in my first production Roco SD24, which has the same motor and mounts as your FP7, and the new motor was a perfect fit![:D] The motors are nearly the same size, the mounting screw holes are in identicle locations, and I’m pretty sure the shafts are the same size.[:D] The performance was also a lot better, with very good low speed control and smooth running at all speeds.[:D]
So If you get a new motor, the new Roco motors are definately one of the best ways to go.[:D]
I don’t know if the FP7s use the same motor or not, but about 15 years ago I replaced all the motors in my Atlas SD24’s with NWSL Sagami #18351-9 motors. Wonderful runners ever since. It was well worth the $31.95 upgrade to a $20 locomotive.
This engine is old, but I bought it last December and I’m 99% sure it was new in box. It’s always been “sticky” requiring anywhere from 30 to 50% throttle to get rolling.
That’s interesting on the broken windings.
BTW, tomorrow I’ll post a pic of this motor just to make sure we’re all talking about the same one.
The only weak link in a otherwise fine drive system. Usually the motor gets very noisy and runs hot before it fails completely. Roco upgraded the motor when Con-Cor brought back the GP/SD models. I have used the Mashima motor in several of the GP models. The overall length of the drive train in your FP is the same as the Atlas/Roco GP models. The only difference is the FP uses a different flywheel than the GPs. The new part # for the PPW/A-line Mashima 1830 motor is now 40321. I wish I could find the electrical specifications for the Athearn motor Darth mentioned. The Kato motor would also be a fine choice.
They’re designed to work at the same voltage as most other HO motors (12 volts recommended, probably 16 maximum), draw less than 0.1 amps running free at 12 volts, and have a stall current near 1 amp (again, 12 volts). They’re also pretty powerful, and won’t stall if the engine is slipping, unlike Tyco motors, which will stall if you grab the coupler.
I also used a Kato HM-5 to remotor a first run FP7.
The Kato motor is just a little smaller with longer shafts. I cut the bottom off the old motor to make a cradle to mount the new motor to and get the height just right. I also had to trim just a little off the ends of the shafts to match the original shaft length. The flywheel and driveshafts are all 2mm so it goes together easily.
It runs very well now and is very close in speed to my newer run FP7’s.