Fixed it a second time. It's definitely the thrust bearings. I pulled the motor and when I spun the armature with or without the brush plate the armature would bind up. I pulled the worm gear side bearing and and then spun the armature spun as freely as I have ever seen. Put the worm gear side bearing back on but flipped it over and made sure that I put the washers on so that the cleanest side was against the bearings. Armature spins freely no binding. Put the motor back in the chassis and now when I spin the wheels bu hand they continue to spin an extra two revolutions after my hands clears which is much easier than it was before. Final test, I ran it for a few laps pulling about 6 modern cars, no signs of binding and fairly quiet for a worm drive motor. Ran it both directions no problems. Put the body back on and I will give it a good run tomorrow when I don't have to worry about waking up the kids.
I will probably order a new set of bearings to be safe, but I'm sure this has been the problem, particularly the front bearing (worm gear end).
I'll post again in a few days or weeks if everything continues to operate correctly.
Thanks again for everybody's help, hope I don't need any more!
jsonova99Put the motor back in the chassis and now when I spin the wheels bu hand they continue to spin an extra two revolutions after my hands clears which is much easier than it was before.
I went in and checked my 681 and 736 locos with worm gears. Both engines were completely disassembled, cleaned, and lubricated when I purchased them. Both engines required considerable force to turn the wheels. If I push the engines by hand, the wheels will just slide. If I put some downward force on the engine while pushing the engine, the wheels will generally turn. Both engines run fine on the layout.
Earl
Earl,
My 671 does the same as you state.
The wheels turn when electric current is applied to the motor, not freely by hand.
I believe, because of the motor drive worm inter meshing with the drive gear, this will cause no free movement of the drive wheels, by hand and it is designed that way for a much more positive drive effort.
Ralph
I may have exaggerated in my excitement to see it working, but the wheels spin very easily and continue to turn if I spin them hard by hand another 3/4 of a turn more realistically. The only other worm drive engines I have are a 2032, 2245, and soon a 2343 project. The wheels move very easily on the 2245 and 2032, though they are a different setup than the 671. I guess "easy" is a relative term, it doesn't move as easily as some of my modern 2-4-2 engines do. If I push the 671 on the tracks, I have to put a little pressure to get the wheels to start to turn then they move pretty easily as I push it. I don't know, it feels really good and the short test run was really smooth, we'll see.
EIS2 jsonova99: Put the motor back in the chassis and now when I spin the wheels bu hand they continue to spin an extra two revolutions after my hands clears which is much easier than it was before. That doesn't sound right to me. The wheels on engines with worm gear drives should not spin freely with the worm gear engaged...
jsonova99: Put the motor back in the chassis and now when I spin the wheels bu hand they continue to spin an extra two revolutions after my hands clears which is much easier than it was before.
That doesn't sound right to me. The wheels on engines with worm gear drives should not spin freely with the worm gear engaged...
He didn't say they spin freely. I have 2 particular locos, a 726RR & a 671, that are set up so perfectly that they exhibit this same behavior - get the motor spinning and it coasts to a stop. They came that way for the most part, but I lubed them with synthetics to make them super slippery. You don't need excessive force to get the worm wheel to turn the worm if it's meshed and lubed properly. The motor bearings in this design play an important role in this design too. I have new Berkshires not broken in yet that won't roll quite as easily.
Which is why they don't slam to a stop when you cut the power - the motor armature and it's laminations/poles acts as a flywheel.
Also, the angle of the worm is critical on worm drives. Pittman(or other can) powered Williams locos have such a shallow pitch that it really is impossible to turn the worm with the wheel. Without a flywheel, these stop very abruptly when powered down.
Vertical motored postwar diesels - steep pitch much like the worm drive steamers - no problem.
Rob
Problem is back again. I even tried swapping in a different thrust bearing from another old motor to see if it made a difference. It didn't. Still can't find anything that points to the drivetrain as the issue, when the engine is running and the problem occurs you can hear it in the engine. The sound is not a grinding sound, but more of a rubbing sound when it happens like the motor is binding internally causing excessive friction on the armature, however the armature spins freely when not under load. The drivetrain still moves just as easily, unless you spin it really quickly, then you can get the problem to occur intermittently.
I think the problem has been narrowed down to the front and rear sleeve bearings. Recommend replacing them, as they may be worn enough to cause your problem, but not enough to show excessive play.
Larry
This is my thought, too. What is involved in this job and what tools are required? I was also curious if the 671 and 681 motors are the same? As I stated before, mine has the brush plate of that of a 681 or the 671RR, although I have not identified mine as a 671RR. I have a source for motors with very low run time or even NOS, had luck with another engine going this route, but I want to make sure the 681 motor is the same first although I don't see why it would be different, but i'll refer to those with more knowledge on this than me. I would keep this one as a spare to fix later.
Knocking out the first bearing will be the hardest. You need a steel rod of slightly smaller diameter than the armature shaft. Slide the rod in through one bearing at an angle until it touches the other bearing away from the hole, near the circumference of the bearing. Give a tap with a hammer. Move the rod around to the other side of the bearing circumference and give another tap. Keep moving the rod and tapping it until the bearing comes out. The other bearing requires a rod bigger than the armature shaft. Give a few taps straight down and the bearing will come out.
When installing the new bearings, put them in loosely, get a rod the diameter of the armature shaft, and insert the rod through both bearings before slowly pressing the bearings home to insure that they line up properly.
Sounds like we have this figured out. I sent the motor off to Dennis Waldron at Just Trains to let him rebuild it. Anyway when they removed the bushings, they found pieces of another lower bushing in the middle of the block. Somebody replaced the bushings at some point and when they put the top one in, it was cocked slightly and rather than fix it they ran a drill bit through the bushings allowing the armature to flop around. Anyway, Dennis has a fix, but he's not sure if the armature was damaged or not. Anyway, sounds like the problem has been found. Waiting to hear back if I'm better off with a replacement motor.
Glad the problem was found and repairable. The first bushing is the hardest to take out, like I posted before. Sounds like rather than do it properly, the first bushing was pressed inside the motor, instead of being punched out, and left there. If the bearings can be installed properly, the worst you could need is an armature, not the whole motor.
I have three 726s and all of them will back drive the motor easily when you turn the wheels. The worm is a triple cut worm, not a single cut worm. This allows the wheels to back drive the motor. If you have a 726/736 or one of the turbines and the wheels will not back drive the motor, you better get it fixed before something is damaged. If you push the loco while it is on the track, the wheels should turn without you putting any downward pressure on the loco.
Just got the motor back, can somebody explain the ins and outs of shimming these motors. The motor was not shimmers, however before the rebuild the mesh between the two gears felt perfect, moved easily. Is it typical for these to not require shims? Just want to make sure I get this right from the start.
Not aware of any shimming of these motors, but you need to tighten the bolts alternately, checking for proper mesh as you tighten.
Engine seems to run well, only did a single slow lap since the kids are sleeping. Wheels spins as easily as before. I am a bit curious about the motor shimming though, Dennis sent me a an old Lionel tip about how to properly shim these motors, and I'm curious if it would free it up even more with a little shim. I did notice that it take a little bit of throttle to get started, and then you can dial it back slightly while it runs, maybe I'm just being paranoid. I'll give it a good test run when I get home from work tomorrow which will give it a chance to to let everything settle back in. Great to see this old engine alive again though, very satisfying to bring an old PW engine back into service.
jsonova99 Engine seems to run well, only did a single slow lap since the kids are sleeping. Wheels spins as easily as before. I am a bit curious about the motor shimming though, Dennis sent me a an old Lionel tip about how to properly shim these motors, and I'm curious if it would free it up even more with a little shim. I did notice that it take a little bit of throttle to get started, and then you can dial it back slightly while it runs, maybe I'm just being paranoid. I'll give it a good test run when I get home from work tomorrow which will give it a chance to to let everything settle back in. Great to see this old engine alive again though, very satisfying to bring an old PW engine back into service.
Lionel did mention using washers as shims between the motor and frame in the 736 documentation, but I've never seen a Berk or Turbine with a shimmed motor. I used to deal quite extensively with a guy in the Pittsburgh area ( now out of business) who was a Lionel parts dealer and authorized Lionel service center, and he said that he never saw the need for the shims.
If you do try shimming a motor, be careful that you don't run with too shallow of of a mesh as that will lead to excessive wear of the teeth on the worm wheel. You should see an improvement in performance as the new bearings are run in though regardless of shimming since the clearances are tighter on fresh bearings.
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