Lionel PW 726 Stall Problem......need some ideas

CW,

Well.......we finally found something that IS wrong with it. Whether it is causing the stall is another story. I looked to see if the wheels were rubbing. I did a cursory check of that the other day and didn't notice anything amiss. But there is. One of the rear wheels can slide over and is contacting the wheel in front of it. And was worn away a line around the base of the flange. Not major, but under my magnifier, it's clear. 

George,

I normally do rebuild bad e-units, but I'm all out of parts. I was thinking of jerry rigging a spare e-unit in there. Problem is.....it's a bottom mounted lever. I'd have to elevate it and then ground it with an alligator.    I will try the tender jumpers later this afternoon and get back to you. As for the wheels.....I don't have a gear puller or a press. If I were to take the slack out of those rear wheels, I'd have to  use my vise.....which I've done before, but is iffy.

What constitutes an E-unit rebuild?
For the e-unit to cycle, it has to be loosing power.
It's not a fast, intermittent short because Roger uses #91 breakers.

In order for an e-unit rebuild to have any effect, I think he'd have to break down the top section to tighten or remove/reinstall the e-unit lever, and resolder the wires from the e-unit coil to the terminals.

Here is another thought:
On your 726, are the smoke unit wires attached to the e-unit hot terminal or to the terminal coming up from the collector?
If they are soldered to the terminal coming up from the collector, then you could have a bad wire or loose connection from the collector terminal to the e-unit. I did not think of this before because most locos have the headlight and smoke unit wired to the e-unit terminal.
And if everything is wired to the e-unit terminal, you could have a good connection between the wires, but a poor connection to the terminal itself.
In either of these scenarios, the e-unit cycling problem should be random, not happening in specific places.

CW,

The lamp and smoke are connected to the roller terminal (which I desoldered). I'll wire them up to the e-unit and see if there's a difference.

C W Burfle posted:

For the e-unit to cycle, it has to be loosing power.
Agreed, either losing power or a short, and I think the consensus is there's no short

 

In order for an e-unit rebuild to have any effect, I think he'd have to break down the top section to tighten or remove/reinstall the e-unit lever, and resolder the wires from the e-unit coil to the terminals.

Which is why I prefer swapping instead of repairing - it gets rid of variables like the possibility that there's an intermittent connection being jostled every time the engine bounces over a specific switch or bounces side-to-side in a turn. Granted, I'm stretching on this theory, but I have actually had it occur. E-unit ground leads are either soldered to the e-unit frame (rare) or spot welded in places where you cannot see them. And a hot lead can appear for all the world to have a good solder connection, yet be intermittent - had that about a month ago.

 

In either of these scenarios, the e-unit cycling problem should be random, not happening in specific places.

I like the bouncing theory!  That could explain why it's not random

This may not fix anything, but at least you will have eliminated the e-unit as a root cause. I would use double sided tape or tye wraps to hold and old working e-unit in there as a substitute.

E-unit ground leads are either soldered to the e-unit frame (rare) or spot welded in places where you cannot see them.

Don't think I've seen this. The wires from the e-unit coil are soldered to the terminals on the fiber plate.
What parts of an E-unit are soldered or welded? The only exception might be the e-units that don't have a lever.

And a hot lead can appear for all the world to have a good solder connection, yet be intermittent - had that about a month ago.

I've seen that too.

Hey Guys,

I think we've got a wiff of success here (finger's crossed). I spent the last hour and a half rewiring the wires to the lamp, smoke, rollers, and e-unit connections. Fired it back up and......no change. Of course.               How many possibilities can there be?     But then I remembered I hadn't  done the test that George suggested.....running jumpers from an open tender. I ran tender rollers to e-unit incoming and frame to frame. Fired it up and......it didn't stall........anyplace. I ran it for about 5 minutes, varying the speed and it went smoothly through all the suspect spots. 

So, it feels good to have some positive news, but now what?  How can this be in light of the fact that I put a relatively new collector assembly from a 736 on there and it didn't correct it?  Wheel play moving the chassis?  I could run a wire from this engine's tender as a permanent solution, but not if this can be corrected otherwise.  Should I try and squeeze that rear drive wheels together to try and eliminate the play?  Or is there another way around this?

With everything you have done, this seems like a geometry issue that is causing the rollers to pull up and cause a loss of power. That free play in the rear wheels seems like a likely culprit (not sure how to correct that, leave that to other experts), but I suspect that is the cause, not the roller assembly/springs (the 736 would have corrected that). It is going to take observation of the engine going over the switch, and probably trial and error, to figure this out. 

I would remove just one of the jumpers and run it. If it still works, that narrows down whether its the wheels or the rollers that are causing the problem (depending on which jumper you chose to remove .) Quite easy to do!!!!

George,

To each his own, but to me, THIS is the real fun part of this hobby. Troubleshooting, fixing, modifying. Unraveling the cause of something like this is a journey. Can be frustrating, but you can't beat it when you figure it out. And it helps to have a great Forum like this.

And speaking of 91 breakers, I'm probably preaching to the choir on this one, but I've been using them for 6 years and they are terrific. What pushed me over the edge to try them was CW and Rob, proponents of their use. I've wired mine in series with a friend's PH-180 brick and the 91s trip first. Incredible.      Provided your amp load is under 6

George,

Ok, I removed the jumpers one at a time and here's what happened. First I ran it again with both jumpers on just to make sure it wasn't a fluke. I got no stalls. Then I removed the jumpers between the rollers.......stall.    Put that one back on and removed the frame jumper.....no stall. So....it appears it's a roller issue. But, seems to me it is either because the wheels are shifting with that play we discussed or......maybe the rollers themselves need to be replaced. They don't have a groove in them, but they can't be new. 

I'm tempted to squeeze those rear wheels. 

Setting up a permanent jumper in and of itself is not a problem.  I've done it with my 3 PW Alco sets........I added a motor to the dummy unit and tethered it to the e-unit in front. They pull like F3s now. But that was to get an improvement. If I can correct this without a tether, I'd prefer it, but, I know it would work if I can't fix this. 

Roger

First, clean all the wheels, track and pickup rollers with Naphtha. If the rollers, wheels or track are rusty, clean them with fine emery paper. If the entire roller pickup assembly is rusted, replace it. Once everything is new and clean, you should not have any stalling issue.

Thank you, I was beginning to think that Postwar never had any problems.  Little clean, little lube, little love, good for another 50 years.

Chris Sheldon

Chris,

Well, in this case, cleaning wasn't going to help. It wasn't the issue. It was/is a real puzzle. But the tether corrected it, but I think we're reaching consensus that wheel play in the rear drivers is causing a chassis shift. We'll see

C W Burfle posted:

E-unit ground leads are either soldered to the e-unit frame (rare) or spot welded in places where you cannot see them.

Don't think I've seen this. The wires from the e-unit coil are soldered to the terminals on the fiber plate.
What parts of an E-unit are soldered or welded? The only exception might be the e-units that don't have a lever.

Ooops! Brain fart! You are of course, correct. One end of the coil goes to the hot terminal, the other to the ground switch. I've been working on the 3356 horse car below, and that coil is what my brain was still seeing!

ROGER1 posted:

Chris,

Well, in this case, cleaning wasn't going to help. It wasn't the issue. It was/is a real puzzle. But the tether corrected it, but I think we're reaching consensus that wheel play in the rear drivers is causing a chassis shift. We'll see

"Wheel play in the rear...." - you are referring to the rear drivers I presume? So to clarify, the thought is that the back end of the engine is allowed to swing right or left due to drivers that are gauged too narrow, correct? Could this possibly result in the contact roller sliding off to one side of the center rail, juuuuuuust barely losing contact for one of two nano-jiffies?

George,

Yes, the rear drivers appear to have a bit too much play. CW said that "too much" occurs when it rubs on frame or other wheels.  So, I went back and looked closer. The rear pair has 1/16 inch of lateral movement. Enough movement to cause one of the rear wheels to contact the wheel in front of it. Observing it with my magnifier shows a groove being worn in it near the flange base. 

I did your jumper test and it appears like the rollers are the issue as then the jumper from tender rollers to e-unit is in place......no stall. So.....somehow the engine rollers are losing contact momentarily. CW seems to think that the rear wheels moving laterally, could cause the chassis to move laterally.  In  light of the fact that swapping the collector assembly out for a 736 one doesn't correct the issue on this engine.....I guess it's possible. So, now I have to decide if I'm going to try and squeeze those rear wheels a bit closer together. 

Or just use a tether.       But that wouldn't correct the wheel contact

So cool to read the thread from top to bottom from the statement of the problem all the way through some great analysis and recommendations to an eventual solution, we hope.  The Postwar stuff is pretty easy to work on when stuff goes wrong, especially with the help of this forum.

Chris Sheldon 

Is the problem with the rear drivers that the axle bearings are worn which is causing the drivers to make contact with the ones in front?

I could be wrong, but I don't think they are worn, I think they are gauged a bit off.There is no fore and aft movement. It's all lateral

If there is too much lateral movement then could it be that the hubs on the back of the wheels are worn down to give this excessive movement?

Moving the wheels in will remove the lateral movement but then will take the wheels out of gauge.

Answer could be to change wheels to a good pair either new or used or alternatively take them off and add some shim washers.

So to clarify, the thought is that the back end of the engine is allowed to swing right or left due to drivers that are gauged too narrow, correct?

I don't think so. As has already been said, the worm gear arrangement produces side pressure, causing the back of the wheel to rub hard against the face of the bearing, causing wear.

If there is too much lateral movement then could it be that the hubs on the back of the wheels are worn down to give this excessive movement?

I think it's the bearing that wears.
Regardless, replacing or resetting the bearing will address the problem, as would adding spacers between the wheel and bearing.

On Berkshires and turbines the flanges of the end wheels extend behind the next blind wheel, so it is possible for the bearing to wear to the point that the flange can rub on the next wheel.

Another type of wear is when the axle holes wear, making the axles sloppy in the bearing.

I have seem locomotives with both types of wear, and locomotives that had reasonably tight bores (axle holes), but worn ends.

If it's just a worn end, I usually will install 671M-23 or 671M-19 washers. The trick is to guess whether to use one or two. It is a whole lot easier than replacing bearings, especially since many of the bearings available today require reaming after installation.

I have the tools to remove and replace wheels.
For those who do not, some people report success using horse shoe washers, or bread tie plastic to make a ring with a slot that will snap over the axle.
I forget the exact application. Somewhere in the Lionel manual they recommended cutting a slot in a washer to snap over a shaft or axle.

Something similar can be done to fix a loose e-unit lever. I think some folks put the washer behind the spring washer. I have put the washer between the fiber plate and the metal e-unit frame when I don't feel like taking apart the top of the e-unit to get to the back of the eyelet.

CW,

So, it looks like we're back to square one. If the lateral movement is not causing the stalling from the e-unit, then what could possibly be going on under there?  The jumper test seems to indicate that the rollers are the issue.   It's looking like a tether would have to be the solution.  But I'd have to get those wheels repaired as that's not something I could do. But I'll see if I can find the description of the washer mod in the manual.

Roger

Not very likely the cause but were the roller pins cleaned and polished when the pickup rollers were replaced?

Not very likely the cause but were the roller pins cleaned and polished when the pickup rollers were replaced? 

The rollers were nubbed. They are completely cleaned. And.....I swapped out the whole assembly for one on one of my 736s and it made no difference.

So, it looks like we're back to square one. If the lateral movement is not causing the stalling from the e-unit, then what could possibly be going on under there?

How do you know the lateral movement isn't causing the e-unit to cycle (by causing a circuit interruption)?

I assumed you tried a single jumper, just for the center rail, to isolate the problem to the pick-up?

Did you check your 671-200 collector terminal?
the part that contacts the collector should have a little curve to it, which provides pressure for firm contact against the collector. Often they get flattened over time.
Maybe you have a contact problem.

The picture of the part is fairly accurate in the service manual.

CW,

Yes, I mentioned above, the test I did. Two jumpers and then removed them one at a time. With the tender roller to engine roller jumper in place....no stall. Taking it out.....stall. 

Did you check your 671-200 collector terminal?
the part that contacts the collector should have a little curve to it, which provides pressure for firm contact against the collector. Often they get flattened over time.

Yes, I have that opened up about 5 times. It had a curve to start with. I bent it a bit more. I also sanded the brass contact and underside of the roller assembly

I like CW's discussion about taking end play out of the axle/driver combo. I have done similar on a 2024 diesel with tons of slop, and it was a good solution. As I recall, I added shims (washers) to just one side to effectively move the worm gear to one side, exposing fresh metal where it mates with the worm.

If you have a horseshoe clip (or two) handy, it would only take a couple of minutes to test this theory. Stick a clip on one end of the driver axle and run the train. If no difference, put it on the other end of the axle. If you have room, put clips on both ends. If it fixes the problem, then you can either leave them in place or pursue a more elegant solution with wheel removal, new parts, washers, etc.

Hook up the tender roller to the engine and use a small connector to separate them when needed. Unless I am misunderstanding (and I certainly could be ), the slop in the drivers should not cause a loss of power. If the tender pickup resolves the issue, schedule driver maintenance at your conveniance and enjoy running you engine.

George,

Im going to try the horseshoe clip  I have nothing to lose  if it doesn’t work, I’ll have the wheels repaired. I’ve got 1/16 inch of slop. Plenty of room for washers  That’s close to twice what some of my other steamers have

Mike,

I’d prefer to remedy the stall issue rather than use a tether. I’ll see what happens after the washers are in....whether it helps with the stalls. Lots of things happen under there as it rolls over those 1122s.  Something is losing contact somewhere.  I must be missing something

I would not put clips on both sides.
The wheel set is pushed to one side going forward, and the opposite side going backwards.
Unless that loco has been run backwards a whole lot, the wear is going to be on the side which has the wheel rubbing against the bearing going foward.

By the way, it's my impression we have been discussing a 1947-49 Berk, making it approximately 70 years old. It's going to have a little wear here and there.

C.W.,

Would you happen to know the diameter of those axles?  I think I have clips and some thrust washers but I might want to Drexel a slot into a slightly thicker washer to take up more of that 1/16 inch slop on the one side

Have you tried running the engine with jumpers with the drive wheels off the track and  suspended, if it runs put pressure on the side of the drive wheel(s) to see what happens.

Nairb,

I’m not following that.   ???  What is the intent of that?

CW,

I just now read an old thread in Classic Toy Trains Forum. Bunch of guys with 726s that had play in rear wheel pair. They used the method I considered.....cutting a slot in a washer. The thickness of it was ..04.    Two questions.....they put it in the gear well.....between the worm and frame. Do you recommend that or putting it between the wheel and the frame?  I'm thinking it's easier to put the washer on the axle in the well (or remove it if it doesn't work out).  I also need the diameter of the axle so as to pick the right size washer I.D. 

Roger, while it should have nothing to do with your stalling problem you might want to check to ensure both rear drivers are tight on their axles.

I've serviced many Berks and Turbines that were poor runners because one rear driver became loose on the axle.  The wheel won't fall off because the flange rubs on the 3rd blind driver.  In one direction the rear driver rubs on the frame, and in the other it rubs on the driver. 

Worth a check, John. Thanks!  Pretty sure it's real tight, though.

Engineering manual says the axle diameter is .1875
Put the spacers in the well for the worm gear? .
I don't know. I wonder whether the spacers might catch on the splines for the worm gear.
You could try it and remove them if they bind.
It would likely be much easier to get the washers snapped over the axle by the worm gear, as opposed to behind the wheels.

I remove the wheels and either use solid washers (671M-19 or 671M-23) as spacers, or reset / replace the bearings.

I just now read an old thread in Classic Toy Trains Forum. Bunch of guys with 726s that had play in rear wheel pair.

I'd be interested in reading the thread. How about a link?

CW,

Thanks for that info up above.  I've got a .04 washer that I'll cut a slot in a bit smaller than the axle.  And yes.....I think it will be easier to get the washer on in the "well". And more importantly.....get it off it it goes South.  That thickness washer should get rid of all of the extra slop in that wheel set. 

Here's the link to the article.....interesting

http://cs.trains.com/ctt/f/95/t/88765.aspx

Roger