Valve gear or connecting rod issue on steamer

[ATSF_Ron]

OK this is surprising.  Since I had my other (unstreamlined) MT1 out for the pics, I decided to run it on the test loop again.  As I was watching the rotation of the rods, the exact same issue happened right in front of my eyes!  The left side crankpin solder must be loose, because it slipped out of position and went into that "monkey motion" I described in the initial post!  I stopped it and reversed direction.  Bam.  It slipped right back into position.  Looks like I'm touching up the solder joint on THIS loco as well.  No, the pin does not move with gentle pressure from tweezers.

I wonder if this is a common issue with these locos?  Any other owners of these (made by Key, Custom Series #29, mid 1980s) have similar issues?  I also thought it might be that the solder joints are 30 years old.  Who knows?  The adventure continues...

[peteski]

Ron, are you absolutely sure it is the solder joint and not the threaded crank pin rotating and loosening, then tightening?  I still have a feeling that those crank pins are threaded.

[ATSF_Ron]

Peteski, I'm not sure at all.  I'm far from a brass expert.  I see where that could be a possibility.  As I think about it, I tend to think it's the solder joint.  If it was the crank pin loosening, wouldn't it continue to loosen??  I'm not sure what to think on this one.

[peteski]

You mentioned that it loosened when going on one direction and tightened when going in the other direction?  Sounds like possibly thread that loosens and tightens.  If you take tweezers and try to adjust the eccentric arm on the crank pin, if it does move you should be able to observe (using magnification) if just the eccentric arm is moving, or the entire crank pin is turning.  That's what I would do.

[ATSF_Ron]

Ok I’ll try that. Looks like the optivisor is coming back out. Thanks!

[mmagliaro]

Peteski's point is well taken.  The way brass locos are put together varies a lot. That pin could certainly be threaded, and be
screwing in and out as you run in forward and reverse.   That would certainly make sense since you are seeing the phenomenon
in two engines - it could be an assembly or design flaw where that pin just isn't tight enough to stay put.  Saying the pin isn't loose
could be a function of how "bold" you are willing to get with it when you try to turn it.  It might be too tight to turn with tweezers, but still not very tight.

It will be very important to know if that pin is turning.  If you decide to try resolding the crank, I think I would first touch it with the iron and pull it off.  Then you can grip the end of the pin with little needlenose pliers and try turning it, and you can fix that problem before resoldering the crank.

[peteski]

Ok I’ll try that. Looks like the optivisor is coming back out. Thanks!

Mine is permanently chained to my work bench (couldn't model without it).  Optivisor with the #7 lens plate.

[ATSF_Ron]

Fixed it!  At least I think so...


I tried turning the loose piece again but with a different set of tweezers and a stronger set of lenses on my optivisor.  It rotated fairly easily 90 degrees forward, then stopped.  It's now on my test loop in reverse.  I'll be keeping an eye on it for some time - in both directions.  Hopefully I won't need to resolder this one.  Now for the other one...the one that slipped out of alignment right in front of me yesterday.  I doubt I'll get away quite so easily with this one!

[ATSF_Ron]

The streamlined MT1 is fixed as far as I'm concerned.  Over an hour on the test loop in different directions and speeds has been nothing but flawless operation.  The screw still feels tight to me after all that.  Now the Shasta version?  Well, I put that one on the rails for a bit and within seconds it was doing the flip flop in position-out of position thing it did yesterday.  In fact, as it passed directly in front of me it did it twice, back to back.  I stopped it, took it off the rails, and took this pic.  It makes a lot of sense after what I saw.  I think this outside part is barely hanging on with a weak/failing solder joint.  Notice the large space between the outer rod attachment and the other inner rods.  It could also easily be a loose pin, as Peteski and Max have suggested.  I think I'll start with the easier fix and do a quick touch with a hot iron and press it gently farther down onto the pin.  If that doesn't do it, then I'll be taking it off and tightening the pin!

[ATSF_Ron]

This is one giant pain in the arse!  I can get the solder loose in a quick second but can’t hold the damn part still or at the correct angle long enough to get things in position. I do have a pair of self-closing tweezers, but they are too thick for the job. I have some needlepoint tweezers, but they aren’t self closing. Super tight clearances in there! I’m going to quit while I’m ahead and walk away from it for a bit. Soldering brass steamers isn’t my forte! 🤦🏻‍♂️

[peteski]

Ron, the space you see between the eccentric arm and the rods is not excessive.  Also I don't think the eccentric arm will go in any further.  It doesn't seem to be sitting too far from the end of the crank pin.  I'm pretty sure the end of the crank pin on which the arm is sitting is smaller diameter than the rest of the rod, so you can't get the arm to sit further in. 

So you can grasp the eccentric arm and freely rotate it on the crank pin without the crank pin also rotating? Just remelting the solder joint (with tiny amount of flux applied) should fix the problem. Just make sure to locate the eccentric arm in the correct position.

[ATSF_Ron]

Peteski, that space I’m referring to is a LOT larger than the other side by a large margin. The other side appears to be nearly flush against the rods. Same with my other locomotive. I attempted to rotate it a bit the first time, and it went off center in the vertical plane, if that makes sense. The second time I tried it, I got it closer to vertical alignment, but I still need to rotate it clockwise a bit more. My hands were starting to shake a bit again, so I stepped away for a couple of hours. I’ll give it another shot later. I think I’ve got this. I’m not going to try and push it up against the other rods though. If you think that’s within the realm of normal, then I will leave it.

[ATSF_Ron]

All finished and operating 100% normal!  Thank you to Peteski and Max for the soldering/crankpin tips.  I took it completely off the pin, tightened it up maybe a 1/4 turn, then resoldered it in the proper orientation.  Luckily it all went back together perfectly.  This particular loco had no binding at all and still doesn't.  Max, you are correct.  It does get less scary after several attempts. LOL!
Pic 1 shows the rod desoldered and resting in position, waiting to be soldered back in the correct orientation.  Pic 2 is the finished product. WHEW!

[peteski]

Excellent Ron!

[mmagliaro]

Very good, Ron!  You did everything right, including walking away from it for a while if you feel fatigued.
Yes, it's trickier than you might think to actually hold that thing in the correct, straight position while you solder it!

And yes, once you do it a few times, as brass steamer repairs go, this one isn't so bad.  Really, the only way you
can screw it up is if you:

1. Use too much flux or solder and get solder on the pivots or rods or on the lower part of the pin near the wheel.

2. Hold the iron on there long enough to start heating up the driver.  Here's a thing about brass steam that isn't
at all obvious.  And this is true of every brass steam loco I've worked on, so I think it's a universal property.
The brass axle is pressed into two brass drivers.  Have you ever wondered why that doesn't cause a dead short
across the rails?  It's because the nickel plated tires that are pressed on around the wheel centers are actually
INSULATED from the wheel center by a super thin sheet of stuff that's kind of like wax paper.  You usually can't even see it between the wheel center's outer edge and the rim, but it's there.  They use that on only one side.

So if you happen to be soldering on an insulated side, and you hold that iron on there for too long, you can melt and destroy that paper insulator, and then you WILL have a short and the engine is pretty much ruined unless you
can find another driver for it.

Fortunately, a small pencil soldering iron would probably take 30 seconds or more to heat that wheel up enough
to damage it.