Is there a steam locomotive doctor in the house?

[R L Smith]

I have a Life Like Heritage 0-8-0 that has been in the box for about 5 years or so. I recently took it out of the box and re-connected the tender to the loco to give it some exercise, and it ran fine until...  the first right-hand curve.

It runs fine in reverse throughout the layout.  It runs fine in forward on straights and on left-hand curves.  (NASCAR anyone?) But as soon as it enters a right-hand curve going forward, it locks up.  The motor is trying to run, but the wheels are locked. Putting it in reverse frees up the wheels, and it will then go forward again until a right-hand curve.

Using an optivisor, i don't see anything in the linkage that would appear to be out of place and creating the bind. Any thoughts on what to look for?

Ron

[wazzou]

Sounds like the only explanation is some kind of a bind in the side rods.   

[nickelplate759]

I have one that does this.  The side rods are hanging up on the valve gear.  I wish I knew how to fix it.

[peteski]

What does "motor tries to run" mean exactly?  The loco is stopped but you are hearing the motor spinning? Or the motor is also not running but it makes a sound like it tries to spin?

I agree with wazzou:  something is likely jamming (siderods, main rod, or cross slide).  After the loco is in a jammed state, take it to your workbench and (under strong light and magnification), using pointy tweezers try to very, very gently grab each piece of running gear.  There should be slight slop to all the moving parts.  The one that is causing the jam will not budge.

[R L Smith]

OK, thanks Peteski - that gives me a place to start.

When the binding occurs, the loco's motor is still trying to drive the wheels, as in the electrons are still doing their thing. As opposed to, stopped and no motor sound.

[peteski]

OK, thanks Peteski - that gives me a place to start.

When the binding occurs, the loco's motor is still trying to drive the wheels, as in the electrons are still doing their thing. As opposed to, stopped and no motor sound.

Ok, but it is not like the motor is spinning (slipping)?  The armature is locked but the electricity is still flowing through the armature windings?  If the motor is powered by a pulse DC throttle, or a DCC decoder then some buzzing is likely audiable.

[up1950s]

It's the trailing truck 

[mmagliaro]

Can you take a close-up photo of each side when it locks? 
I'll take an educated guess...
It sounds like a case of either the siderod crankpin jamming
in the crosshead (gets hooked behind the slider), or the main rod jamming on the front side of the crosshead. 

Happening only in one direction, on only one direction of curve, is not surprising.  It happens because the drivers slide over to one side on a curve.  So your rods and crankpins are arranged such that when the drivers move over, they push the rods in or out to jam on the crosshead.
It is not too hard to fix if we can see a picture of it when it is jammed.

[randgust]

I think we all think that you've got a hit between something and something else in the running gear.

Peteski almost told you what you need to do, but this is where a cushion cradle of foam or bubble wrap that can hold everything upside down, and some alligator clips to pickup points (tender wheels?) so you can see it run under power will find it.

I'd look at the lateral movement on the front drivers.  If they can slop around enough horizontally, the crankpin can catch on the crosshead, or the main rod, etc.   Main rod goes to #3 driver so same thing can happen to #2 driver and crankpin against main rod.

Mark's photo:  http://www.spookshow.net/loco/files/ll080mech2.jpg

If you're lucky, a crankpin just needs pushed back in.   If it's really hanging and banging (and I've had that happen) with no other fix one approach is to put "C" shaped washers (MT delrin truck washers cut a favorite) on the axle between the frame and back of driver (just trim and push on, don't take apart wheels) to take up the lateral movement on the drivers that whack stuff.  If it causes more problems than it solves, pop them back off.   I've had to do that to several steamers with a lot of unnecessary lateral slop on the lead set.

But flipping upside down and power running in a cradle, and moving things around with your finger will spot the problem anyway.

[peteski]

In my experience running upside down (or even on the side) might not result in the jamming, but if it does,  it will make troubleshooting easier.

[R L Smith]

Had a chance to look at this a bit more this evening.  Observations:

- it takes a few minutes for the bind to occur. (Faked me out at first, because I thought it was miraculously healed.)  Although I don't believe run time contributes anything to the problem.

- once it occurs, it occurs consistently regardless of speed. From slow creep to mid-range, she'll bind up in a right-hand turn.
 
- switching to reverse, it will move under it's own power after a small voltage is applied, without any help from the 0-5-0. Said another way - prior to binding, this engine will creep at very low voltage. After it binds, put it in reverse, and it takes more voltage to get it to move but it breaks free on its own. with a bit of a lurch.

Upside down in a cradle, I cannot detect a specific part that is jammed and it's corresponding part on the opposite side moves freely. I note that the front driver set has a lot of lateral play. The rear driver set has less lateral play. The third driver set has a tiny amount of play. The second driver set has none at all - very tight.

Back on the layout, I made 15 observations of the left side of the engine. In every case, when it bound up, the main crankpin on the third driver was between the 12:00 and 1:00 position on the driver.  Every time.

Next step, later this week, will be to get some alligator clips and power it in the cradle as suggested above. And will get a couple of photos showing the crankpin position.

Thanks again,

Ron

[mmagliaro]

I will assume that if the crankpin on the third driver is between 12 and 1 o'clock, that ALL the crankpins are about there.  The one to be suspicious of is the one BEHIND the crosshead (the valve slider) that you can't see.

[R L Smith]

Well, it seems to be fixed. But I don't know specifically what cured it...

Since my last post, I observed that occasionally - not often, but occasionally - the bind would occur while passing through the guardrails of a turnout (when going through the turnout from the frog end, not the point end), and also when passing over an Atlas Code 55 60° crossing.

Back in the cradle after getting bound up, the #2 driver has no lateral play. I poked and prodded with a dental pick and tweezers but did not observe anything specific. Back on the layout, ran it in reverse to free it up, and back to the cradle. Now, the #2 driver set has lateral movement. I pushed the drivers to one side and poked and prodded the crankpins on the opposite side. Then I pushed the drivers to the other side and moved each of the rods on the opposite side. Everything seemed to move freely, and I couldn't see or feel a bind.  Now back to the layout, and...

MAGIC

The engine has run for over one hour without binding. I ran it at top speed for two laps, cut it back to half speed for a lot of laps (about 45 minutes), and then cut it back to speed step 8 (out of 128).   It took more than 16 minutes to make one lap, crawling along smoothly. 

"One lap" equals 2.75 complete circles in the right-hand direction, 0.75 of a circle in the left-hand direction, and through two #7 crossovers - one LH and one RH. It includes grades of 1.5% (both ascending and descending). Not. One. Burp.

I plan to repeat the test a couple times more. If it still runs fine after that, then I will (a) buy some lottery tickets, and (b) put it up for sale as originally planned.  With a 95% clear conscience.  (I will always wonder...)

RLS

[randgust]

Wow.   Ballast particle?

Well, when I used to do IT client computer repairs on-site, and magically found a solution that I couldn't necessarily explain or understand myself, I had a stock answer:

Q: "Well, what was wrong with it?  What did you do?"

A: "If I have to explain it to you, I'm going to charge you more".

[Maletrain]

Wow.   Ballast particle?

Well, when I used to do IT client computer repairs on-site, and magically found a solution that I couldn't necessarily explain or understand myself, I had a stock answer:

Q: "Well, what was wrong with it?  What did you do?"

A: "If I have to explain it to you, I'm going to charge you more".

That would be when I said, "OK, if you can explain it to me, then I will know how to fix it myself, next time it happens."