Questions about lack of wheel conductivity and metals

[Jim Starbuck]

As you talked your way through this , you said "but all 4 wheels?".  Seems very unlikely 4 wheels would loose contact simultaneously.
That tells me that the intermittent contact is farther downstream. Have you tried touching the whisker to one of the contact strips instead of the wheels?
Could there be a cold solder joint between the contact strip and the motor lead or the lead joint at the motor?

[mmagliaro]

Everyone, I thank you all for chiming in, but let's recap all the things that we know are not the problem based on my original post.

1. When it stalls, if I touch a whisker to any wheel, it runs.  Therefore, there cannot be a broken connection, wire,
loss of contact in the axle point cones, etc.  If there was anything wrong there, then touching the wheel would not help.

I also touched the wheel with a "dead" whisker and the engine never starts.  That means that my whisker is not moving anything physically to cause the engine to start moving again.  i.e. it is not moving the wheel, the sprung contact strip, or anything else.  It only moves when I touch the wheel with a live whisker.

Therefore, the wheel has simply lost contact with the rail.

And yes, I find it amazing that I don't have pickup from at least one of the four when these stalls occur.

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2. As for the track.. remember, I run other other engines over this same trackwork and they do not have this problem.
So I am not going to look for new ways to clean or polish railheads.  What I'm after is a way to make THIS engine as
robust and trouble-free as all the others.  Remember, real-world track is always dirty, it's always non-level.
There are always problems with it.  Engines have to be made robust enough to tolerate at least a modicum of imperfect track conditions.

---------------------------------------------

To answer some questions:
The draw bar is very free.  It is not lifting the tender.
I did try adding 30g of extra weight and that did not help.
The trucks are free to swivel AND to rock from side.  That is, the tender can rock side to side without lifting the trucks.

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Yeah... it's a bloody weird mystery.
And I really want to solve it because man... when this thing runs, it runs like the cat's meow.  I don't want some goofy
intermittent electrical pickup issue to plague this engine.

[u18b]

I would try taking the loco, turn it upside down, apply power and gently touch the treads with very very fine sandpaper.

There may be some kind of glazed build-up.

[mmagliaro]

I would try taking the loco, turn it upside down, apply power and gently touch the treads with very very fine sandpaper.

There may be some kind of glazed build-up.

Good thought.  But I already did that.  In fact, after I made my wheels, I polished them with 2000 grit on the treads.
And I have since tried spinning them and polishing with autobody polishing compound, which got them like mirrors!
But it made no difference.

[Kisatchie]

Cue the creepy science fiction music...


Hmm... there is no earthly
explanation for this
phenomenon...

[Maletrain]

This means, to me anyway, that the lost contact cannot possibly be in the axle points, cones, the "thumbs" that go up into the tender or the tender floor strips or anywhere else.  If hot-wiring to a wheel makes it go, that means that the wheel
has lost contact with the rail.  And in fact, since I tried this over and over with different wheels,  it means that ALL FOUR wheels on one side have lost contact with the rail.

I did try to address your question with this in mind in reply #9.  It tells me that either the wheels have lifted away from the rail or there is something coming between the wheels and the rail.  Or, you have made an assumption somewhere that is incorrect.  Your reference to the Kato trucks having the same issues might be something involving a wrong assumption.  Did you do the exact same tests with the Kato wheels and your own home-brew wheels, or were the detailed tests only on the home-brew wheels?  And, it would be nice if you would tell us what rail size is used for the the track with the problem.  And whether the rails are painted or otherwise colored

The only other thing I can suggest is that you perform an additional test on the stalled situation.  Push down on individual wheels with a NON-conductive probe to see if the will move downward and create electrical contact.  If not, try pushing laterally (both ways) on the wheels to see if that works.  The idea is to determine if there is an air gap, or something physically obstructing the contact. 

[Cajonpassfan]

[quote author=mmagliaro link=topic=39602.msg484509#msg484509 date=1468702929

To answer some questions:
The draw bar is very free.  It is not lifting the tender.
I did try adding 30g of extra weight and that did not help.

Yeah... it's a bloody weird mystery.
And I really want to solve it because man... when this thing runs, it runs like the cat's meow.  I don't want some goofy
intermittent electrical pickup issue to plague this engine.
[/quote]

Max, adding weight to the tender *should* help, but an ounce spread over eight wheels is only 7 grams each, not really that much. Have you tried loading up the tender externally to see if it helps? Without the need for a decoder or sound, you should be able to add a lot more weight? (In my experience, if tender is free-rolling, the extra weight shouldn't affect the pull as much as one would think).
Beautiful engine BTW...
Otto K.

[mmagliaro]

Okay, to answer questions.

First, I really do appreciate people trying to help, and I also appreciate the insistence on scientific method.
Without repeated trials under the same conditions, and problem like this will run you in circles forever.
So I really have tried to do that.

All tests, Kato trucks and mine, are

1. Run engine back and forth at 7.5v over a certain 24" long stretch of track that I have cleaned with alcohol and a paper towel
2. Confirm that a Kato F unit running over that same stretch as slow as I can run it never stalls.
3. Run the engine around the entire layout at 7.5v and count how many times it stalls (typically it stalls 2 or 3 times).
It tends to stall over a switch and on a stretch of straight track that I know has a little undulation in the rails.
But remember... my other engines all negotiate this trackwork fine, and I don't want to insist that track be "perfect"
to make this engine work.

I did test the switch with meter probes to make sure it doesn't have dead frog or point rail.

The rail is Atlas code 55.  It is painted on the sides, but very clean on top.  And yes, the top "edges" on the sides don't have paint on them.  But even if they did, again, other engines don't have any problems with this.

Maletrain:
To address your concern about the flanges.  My home-made wheels have pretty fine-scale flanges.  They are smaller than Kato's and definitely do not bottom out on the ties.   But you are right about one thing, the Kato tender truck flanges do
graze Atlas code 55 spikeheads unless they are sanded down a little, which mine are.

Pushing down on a wheel with stick makes the engine move, but it's very hard to do that without physically jarring
or otherwise moving the tender, ever so slightly.    So even though the stick makes the engine move, it could easily be
making the axle points touch the insides of the cones, for example.  It wouldn't tell me that the problem is lost contact between wheel and rail.  Touching the wheel with a wire whisker, that is not connected to anything, and seeing the engine not move, and then connecting the other end of the whisker to the rail, then touching the wheel, and seeing it move,
and doing this same test on different wheels dozens of times, is awfully convincing evidence that the wheels
are not picking up from the rails.

Weight:
This tender has no body, so I can stack on as much weight as I want.  I have tried 30 grams.  I suppose I could put more.
I will try that.

[svedblen]

What about track gauge vs wheel set gauge? Is it a tight fit or not? Trucks with problems vs trucks with no problems? The spot where it most often stalls vs other stretches of track?

Maybe these trucks have the same problem more or less everywhere? And you are nearly always running with just one or two wheels making contact? So when it stalls it is "just" the last wheel that looses contact? That would make the "all four wheels at the SAME TIME" oddity not that odd.

Have you tried with track of another brand?

[nkalanaga]

I doubt that the brand of track would make much difference, but "running with just one or two wheels making contact" does.  Is there any way to test the wheels individually, when it is sitting still, but supposedly making contact, to see how many are actually in contact?  With axle-end pickups, I can't think of one, because both axles in a truck are always connected.

[sp org div]

The rail is Atlas code 55.  It is painted on the sides, but very clean on top.  And yes, the top "edges" on the sides don't have paint on them.  But even if they did, again, other engines don't have any problems with this.

Take a three foot section, rub the edge of a bright boy or 600 grit to thoroughly clean the inside of the railheads, then wipe off with clean rag in alcohol.

[Chris333]

What about those electronic track cleaners the Z scale guys use? 

http://zscaletrack.com/ga1-hf1

I think they work by bridging any gap between wheel and track. (never used one myself)

[svedblen]

I doubt that the brand of track would make much difference

I still think this in some way is about not running on the top of the rails. Track with a slightly different gauge could then give another behaviour.

[mmagliaro]

It would be possible to test the wheelsets individually, while on a flat piece of track.  I had thought of this and may
make a jig to test it.

Take a flat piece of track with gaps cut so that each wheel rests on an isolated piece of rail.  Run feeders to each
piece of rail.  Then it would be possible to power little mini-sections of only about 1/2" in length, to see if that particular wheel
is working.  The wheels all definitely work well when it's flipped on its back in a cradle.

Yes... it is possible that most of the time, when it's running, only 1 or 2 wheels are really doing the work.
Although all the wheelsets consistently roll perfectly.  I have never ever seen any drag along or not roll.  But that could be caused by the wheel on the opposite side of a wheelset making good contact, while the wheel in question does not.  The axle would still roll.

I really don't think any strategy for doing any super cleaning of the track is the way to address this problem.  If I've got a bunch of engines that work fine on this track, and this one doesn't, the problem is the engine.  I need to make this engine more robust so that it works on this track.

Oh.. wheel gauge.  Yes, it is correct.  I have checked it many times.  It's dead-center in the notches on an NMRA plate.

[nkalanaga]

OK, it IS possible to test each wheel individually.  I hadn't though of cutting that many gaps in the rails...

As for some not rolling, you've probably watched very carefully, so this won't help.  The D&RGW, and possibly others, used to paint white lines on the wheels so they could see if one was dragging.  It looked a little odd, but worked, and they didn't care what it looked like.