Valve gear or connecting rod issue on steamer

[ATSF_Ron]

I recently acquired this nice SP MT-1.  It's a Swiss watch in terms of running in forward.  In reverse it has a bit of a bind at low speeds.  Nothing terrible, but it's noticeable.  I was doing some break in running on a test loop earlier and noticed quite a difference in the angle of one of the rods or valve gear (not sure about the correct term here) between the two sides.  The fireman's side seems to be what I'd call "normal."  But the engineer's side has what I call a "monkey motion" appearance.  In photo 1 on the fireman's side, the rods are in the "down" position.  In photo 2 they are in the same position but on the engineer's side.  The smaller rod that goes to the valve gear is clearly not in the same position as on the other side.  Photo 3 shows the main rod in what I'll call the "forward" position.  Also not in the same position as the fireman's side.  Could this be causing the binding while operating in reverse?  I have no clue how this could happen except maybe from the factory.  This was a mint loco.  Probably never run except for testing.  Does anyone have an idea about how to fix this?  I get VERY nervous when messing with brass steam loco side rods.  Any advice is greatly appreciated!

[ATSF_Ron]

OK, as I'm looking at the larger pics on my computer screen, it appears as though the piece which connects the shorter rod from the main rod to valve gear is rotated about 90 degrees towards the rear of the loco, if that makes sense.  It also appears as though this piece may be a press fit onto the main driver.  Are these fairly easy to pop loose gently with an exacto blade or small jeweler's type screwdriver?  Like I said, I'm VERY nervous to mess with steam loco rods.  No point screwing up a very smooth runner over a cosmetic issue, in my opinion.  Steam loco gurus, feel free to advise, thanks!

[Rasputen]

Yes, the offset crank pin should be pointing close to the center of the driver, like the left side does.  Usually they are just pressed in.

[ATSF_Ron]

Rasputen, do you think a #11 blade slid gently in there can pop it off without bending anything? 😬

[peteski]

I would not do that. The eccentric arm is usually soldered to the crank pin, which in turn is threaded and screwed into the hole in the driver.  When the crank pin is tightened in the hole in the driver, the eccentric arm should end up in a proper position.  Something here does not add up. Weird that the same issue is present on both sides.  To get an idea what the proper position should be, check your other steam locos.

Try to gently turn the eccentric arm clockwise (to tighten the crank pin connected to it).  Does it turn, or is it in tight?

[mmagliaro]

Peteski is correct.  DO NOT try to pry that crank pin out.  This is a brass loco.  They don't work that way.
All his other suggestions, I agree with.  (Except, Pete, notice, both sides are not the same.  The left side is
oriented correctly.  It's the right side only, that is messed up).

If you GENTLY try turning that crank about 1/4 turn clockwise to get it rotated back to the correct position, and it moves, then it might stay.   If you try to turn it and it feels tight already, you can just touch it with a hot iron while holding the crank with tweezers, and turn it about 1/4 turn to get it in the right place and let the solder cool.

If it just turns back to the correct position, it might just work its way back out again, which might be how it got out of whack in the first place.  Of course, it might just twist around the pin, or twist right off the pin so be prepared.  It's only held on by solder.   If that happens, just push it on at the correct position and give it a quick touch with a soldering iron.  A drop of flux really helps here.  Be quick.

Don't try to twist it hard.  If the pin shears off in the driver hole, that's a real mess.   Now you're drilling and tapping, making a new pin from a tiny threaded screw, etc.

And yes, that one is so far out of position, that it looks like it can't extend far enough at that really bad part of the rotation you photographed, so it can be causing a bind there.

[peteski]

Peteski is correct.   (Except, Pete, notice, both sides are not the same.  The left side is
oriented correctly.  It's the right side only, that is messed up).

You are correct of course. I just confused the photos.

[ATSF_Ron]

Thanks for the info Peteski and Max.  Oy vey!  I was afraid of that.  I think something like this is above my pay grade, lol!  Since it's a small bind and in reverse only, I think I'll let it ride for now.

[ATSF_Ron]

I dunno.  I was just looking at things again with the strongest set of optivisors I have.  In the 3rd pic the pin end almost looks like a pentagon shape., but that must be a trick of the lighting or something.  Under optivisor magnification it's circular.  Same with the other side.  In pic #2 with the main driving rod in the "down" position is where the binding occurs.  It doesn't do it with every rotation, but often enough to easily observe it when creeping along in reverse.  In forward, like I said before, there is zero binding.  I tried moving the pin gently with tweezers.  Nope.  I MAY try the quick touch with a hot iron later, if I get the nerve!  Thanks again for the tips!

[peteski]

If you look at the other crank pins they have hexagonal shape. Just like other brass locos, that almost certainly indicates that they are threaded and screwed into the drivers.  Again, it is almost certain that the misaligned crank pin is also screwed in.  Try turning it with a bit more force to see if the eccentric arm will move towards the center of the driver. It is hard to believe that someone would actually heat it up until the solder melted just to leave it positioned incorrectly, but then again, some people do some strange things.

[ATSF_Ron]

OK this is gonna be a few pics, lol!  But for comparison's sake...
Pic 1 is my Oriental UP 2-8-0.  Pic 2 is my Key C9.  These both use a hexagonal mini bolt/screw which is different from my MT1.





The next two are the MT1 in question.  You can see the glob of solder on the correctly positioned crank on the left side of the loco. (pic 3). These are the closest I can get with my old phone and still remain in focus.





The last pic is my unstreamlined MT1.  Much nicer soldering job on this loco.



I have a needle tip adjustable temp soldering iron that will melt solder very quickly, especially using flux.  I just need to think it through a few more times and get the nerves calmed before I venture forth, lol!

[mmagliaro]

It doesn't look like any hex to me, just a pin that the crank is popped over and soldered.  Since you say you could not turn it with tweezers,
I think you have no choice but to hold it with tweezers, touch a hot soldering iron on there, turn it, pull the iron off, wait for it to cool,
THEN let go with the tweezers.

With a little dab of flux and a drop of solder on the tip of the iron, it will let go surprisingly quickly, so you definitely want to be holding it with tweezers when you apply the heat, or it will move, turn, cock down at a weird angle, etc.   You want to have a grip on that little crank at all
times and hold it for a few seconds after you remove the heat to be 100% it is cooled and set again.

Take heart... you might not get it in right spot the first time you try it, but with a few attempts, it's not too bad.   It's scary the first time, not scary the 10th time.  Somewhere in between, it gradually stops being scary.  LOL.

[peteski]

It doesn't look like any hex to me, just a pin that the crank is popped over and soldered.  Since you say you could not turn it with tweezers,
I think you have no choice but to hold it with tweezers, touch a hot soldering iron on there, turn it, pull the iron off, wait for it to cool,
THEN let go with the tweezers.

That is not it. I was saying that since the *OTHER* crank pins have hex heads, the main crank pin is also most likely threaded.  While I have not seen dozens of brass steam locos, all the ones I recall had threaded crank pins (on all drivers).  The main crank pin is not made like the others since it also holds the eccentric arm. So no, it would not have hex end, but it would still screw on.  However I suspect Max is more seasoned in brass loco repairs, so follow his advice.

[ATSF_Ron]

Max, I was just getting ready to ask about what you just answered.  Thanks!  Now, knowing my jittery right hand, I'll have to try this tomorrow after a day with no morning coffee!!  And yes, flux and a VERY quick touch with the iron.

I just had the loco on a Kato Unitrack test loop at 15" radius.  With the "bad side" facing the outside of the curve, it binds almost every turn of the wheels as the rods go into the down position.  Again, not a lot and ONLY in reverse.  On straight track it's barely noticeable.  Hopefully this fixes it!

[ATSF_Ron]

Peteski, I know what you mean.  Thank you for your input as well.