major surgery?

Model Railroader General Discussion (Model Railroader)
1

The patient, a 35 year old Mantua GP~40, was born with congenital defects, including riveted assembly and unspecified electrical problems. It never played or ran like other locomotives. Often you had to nudge it just to get it to move, and then it was still balky.

The unit recently underwent exploratory surgery, but no major defects were found. It was given a thorough cleaning and returned to service. The convalescent period was short, measured in tens of minutes, and not many of those. Immediately on return, the lights burned as bright as I’ve ever seen them, but it just lay there, unmoving. Reversing power incurred an astonishing recovery. The patient took off like a well oiled machine, running as smoothly and quietly as I’ve ever seen it run, easily the best on the table. After a couple laps on the mainline, power was reversed and with a gentle nudge, this performance was repeated in the normal direction.

Selecting a comfortable pace, I settled in to observe an extended “break-in” period, to get it warmed up, relubed, work out the kinks after the long period of inactivity. Within three laps around the mainline, disaster struck. The patient emitted an ugly CLUNK and stopped dead in its tracks.

The lights continued to burn brightly, forward or reverse, but it just lay there, unmoving. Undercarraige probing revealed an armature able to turn freely, and after replacing it on the track, it failed to move forward, attempted a halting feeble attempt to crawl in reverse, then gave up the ghost entirely, showing no further sign of life. The lights now come and go, either full on or not a glimmer, but sliding the unit down the track in either direction yields no apparant inclination to move under its own power.

The options at this point are limited to four:

  1. Retire the old bird gracefully to a display case.

  2. Retire the old bird less than gracefully to the pond.

  3. Bring in a team of specialists and spare no effort to resucitat

2

When my Mantua GP20 (first HO loco, has some sentimental value to me) did the same thing, I tried all of your repair options though no team was brought in… Eventually gave up the fight and placed the CN body on a newer can motored, flywheeled Mantua drive. Installed a decoder and she runs better than ever…

Jeff

3

try and try again…until all hope subsides…I had an athearn loco that gave me fits until i finally rebuilt the entire locomotive from the motor mounts up using spare parts from other old athearn loco’s that saw better days…it ran for about one more year and then gave up the ghost…it’s in the “spare parts” bin with the other athearn locos now…I give athearn about 6 -10 years of good service and then it’s time to retire them…chuck

4

Went through some of these things myself, I bought a GP-35 Athearn off ebay, this thing appeared to be new in the box, after careful inspection I noticed no wear on the wheels and perhaps no more than a test run on the motor. Everything looked new!! It was a little slow starting out but after a couple of nudges it bagan to run and pick up quite well. So, a couple drops of oil and back on the track, it ran like a champ!! So I took a little time to do the break in; about 30 minutes at half throttel in each direction—all was well and I was very happy about the $21.50 spent for it. I felt so good about it I decided to give it some track time… if thirty min is good how about an hour?? So I left it running and came back??? Much to my suprise there it sat, light burning brightly and not moving. I tried several times to get it going it would crawl a little and stop again ect ect, I finally gave up and found one of my athearn motors that need brushes and made the necessary changes. It runs great now.
Sometimes we just get a bad one because bobodys nerfect!!

5

There’s another option which has proven to be a good one for me. I removed the motor and any gears connected to the wheels on a couple of old Athearns (vintage 1960,) and now they run as dummies in consists. I thought about replacing the motor, headlights and old brass wheels, but when I found a new P2K GP-9 at M.B. Klein for much less than the replacement parts, I knew what I had to do.

I now think of these old relics as “honorary” locomotives, kind of like the venerable seniors that get to be “Grand Marshall” in small town parades. All they have to do is ride around in a convertible with a couple of cheerleaders. Not a bad life…

6

Weather it up really good, lots of rust, excellent way to practice your skills. Place it next to your engine service area, and consider it scenery. Much more constructive than making it fish food.[swg]

7

In a way, this is a sad story. For a brief moment, you saw all its promise, and then it resumed its truculent behaviour. After all that work!

From what you describe, and from what others have said, the motors are poorly constructed or designed. However, I wonder if there is a connecitivity problem right at the pick-ups, or somwhere after them up to, and including, the motor solders. Poor connections exhibit that behaviour; they work for a few minutes, and then hear or vibration or insulation torsion breaks the contact.

However, I am certain you have ruled these possibilities out.

8

The “Clunk” you described leads me to belive the drive mechanism jammed, and then the contacts burned up trying to force said jammed mechanism to work. dont quote me though, Never had a Mantua open, so I wouldnt even know what it looks like inside.

9

Might I reccomend a Transplant?

Bear Locomotive Company owns the old “Hobbytown” line of frames and drives and they include a drive kit for your locomotive.

http://bearlocomo.zoovy.com/product/K049

Should have everything you need to get her running good again.

James

10

Since I am assuming that you have taken the oath that all surgeons take to do no harm I do not see that option 2 is a viable alterative. Option 4 is for corpses only and would require an official time of death pronouncement (which may be forthcomming). Option 1 seems to me to be taking the low road for such a learned man as yourself, while option 3 would present itself as the high road.

Bearing this in mind, only options 3 and 4 are worthy of concideration.

I would have to say that IMHO option 3 must be concidered the better of the two, although one must realize that option 4 may become a real possibility somewhere in the middle of exploring option 3.

That is my “second opinion”.

11

Selector, you see it. For a long time, I thought of it as a pretty boy, all show and no go. If it didn’t look as good as it does, it would be long gone. But now I know what it can do and that changes the equation.

Josh, I thought the drive train ate a tooth or piece of debris too, but the armature spun freely right afterward. I had the power off quickly so if something burned through it would have had to be quick. My best guess is that one or both brushes are improperly seated or not mating well wit the commutator. If the edge of a brush caught on the gap between commutator sections, that would explain the sound I heard. If the lip of the brush snapped off and wedged between commutator plates, shorting them out, then it explains the attempt to crawl in the face of a radically reduced torque field generated by a single pole fuctioning. If a brush got bent away from the armature, then that explains all of the above too.

I think there’s probably another issue at play here too. As long as the light stays on bright, I have to assume that the contacts with the track are good, but after the “clunk” the light was intermittant as I slid the loco along the track. It’s not just the motor that’s locked up with rivets. The power truck is a solid casting, and there are no wipers for the live wheels. Whatever contact is taking place is happening inside the casting at the axles, where I can’t see it. I could back it up with wipers without dissasembly though. Before I tackle that, I need to see it move when the lights are bright. No sense fixing a balky contact when the motor itself has problems. One possibility is to apply power directly to the brushes and see what happens. A good response there means problems upstream, and if the motor still won’t work, the problem is internal.

Pcarrel, Option 2 never was a real option, but writing it out did relieve some frustration. The mental image, the windup, the release, the arcing trajectory, the splash, the ignominious cloud of silt, the curious fi

12

I like this thread, its right up my alley, to raise the dead back to life, no matter the make or model, I will try to the bitter end. Even if failure is in the sky’s I march on to try again! Sad part is, the pond is getting pretty full of the old mantua and Tyco engines from many years back. I always remember them running good for awhile, but would die a sad death of total heart failure. And we cannot forget the cheap Bachmann diesels that only had 4 wheel drive with this tiny little motor that could hardly pull more than 7 cars down a grade. I had quite a few of those years ago. Most of the dead got there place on the shelf of honor, to show there colors and stand proud as over worked, under powered loco’s that will hold silent all the $#@%$& words I threw at them. Man do I miss them!

13

Option 7: Use as a flat car “load” in a freight train with a spiffy new paint job for the “new” engine being delivered!! Or park it on the siding, as previously suggested. I can visualize the GP-40 sitting on one of those supersized ‘lowered’ flat cars…what a piece of rolling stock!!

14

Success!

I broke down the brush assembly, which is the only part of the motor you can get to without drilling rivets. A screw holds a tiny circuit board to the top of the engine, and there are a pair of brass posts acting as contacts and pivots for the brush springs. The armature runs horizontally, fore and aft. The brush design is not encouraging, each arm acts as a lever. There is a jog in the brush arm that acts as the fulcrum, pressing against the edge of a slot in the circuit board. The spring acts against one end of the lever, pressing outward at the upper end, the circuit board pivot pushes inward in the middle of the brush arm, and the contact between the brush and the commutator resists the spring’s force.

The problem is that the jog in the brush arm is not a very precise way to keep the brushes where they need to be, and this turned out to be the problem. On disassembly, it was clear that one brush had been mis-positioned, probably from the factory. The “cup” worn into the face of the brush was centered on the upper edge of the brush, with the edge of the cup across the center of the brush. Clearly the brush and arm had slipped downward at some point early on, making the contact point too low too small, and allowing the upper edge of the bru***o (probably) catch between plates in the commutator.

I brightened all the components and re-knapped both brushes to a dead flat face with a tiny piece of 220 grit sandpaper. Reassembly wasn’t too difficult, after a couple of false starts it all slid back together with less hair-pulling than I expected.

Back on the track, both trucks alone, without the bodywork holding them together, it still wouldn’t move. But by applying about a quarter throttle, and making minute adjustments in brush position with a jeweler’s screwdriver, it lurched, (in reverse) and then took off, the contact truck being pulled along by the heavy wire connecting it to the motor.

It still wouldn’t move in the forward direction, but

15

I would recommend changing that motor. That old motor has a known problem and it is probably a straight three pole, and you would see definite improvement with a new 5 pole skew wound motor.
I have a brass steam engine that had a Canon motor that was never quite right from the start. I tinkered around with it and could never get it perfect although it ran good enough 95% of the time. Finally, after 20 years of screwing around, I got a new motor and will always wish I had done it 19 years before I did.

16

Option 3

Congats!!!

17

I know the feeling. Spent a bunch of time getting my dads old Chat choo choo to run again for under the tree this year. Finally got traction tires that work…got the light to work…got the smoke to work…got it to run nice and smooth…weighted it to keep it from jumping off the track…set it up under the tree and it ran PERFECT…for about an hour. Then the fatal death weeze of a plastic gear loosing it’s teeth…[xx(][:(]. oh well…
At least YOU have the option of repowering.