C&O 0-10-0 switcher

[Kentuckian]

Finally, it lives! Thanks to everyone who helped get me this far, especially @mmagliaro !

Since I posted the video, I have run it in some and it runs smoother.

[mmagliaro]

Yeah, the motor mount looks fine, but unless it smoothed out a LOT after this video, something is wrong.  With that 13mm Maxon in there, there is no way there should be any periodic bind in the motion like that.  That motor is a BEAST for power and torque.  It definitely looks like a mechanical bind - not an electrical pickup issue, since it is so repetitive and seems to hitch at one place around the driver rotation.

Like I said, maybe it runs way better now, per your comment.  But if you can't get it to run under 5 mph, uniformly, on straight DC with that motor, time to start working on the mechanism.  First, I'd put a mark on the idler gear under the motor worm when it binds, and then see if it always binds at that exact same tooth.  If it does, make sure the worm mesh isn't too tight.  Remember, the precision of these mechanisms isn't that great.  That idler will bob up and down a little as it turns, so if you have the worm mesh set very close, it might be binding right there.  If the worm isn't tight at that point, then it's time to take out the motor and look for the bind in the mechanism.     If the drivers always bind at the same spot (and it looks like they do), take the motor out, and turn the idler with your thumb, and see if you can feel the tight spot when the drivers come around. 

[Kentuckian]

Thanks, Max. I should have time to troubleshoot later in the week.

[mmagliaro]

Thanks, Max. I should have time to troubleshoot later in the week.

Not to worry, and I didn't mean to discourage you, by the way.  This is par for the course with these mechanisms.
Studying the video more, it clearly binds when the crank hole is at the top of rotation, every time around.
Since all the drivers are geared, the FIRST thing I'd do is pull all the rods and valve gear off and see how it runs.  I am betting it will smooth right out.   Then put a side rod on only ONE side, only attached to drivers #1 and #5, and see how that goes.

Because it's all geared, all the drivers will always run, and the rods are 100% for show.  So you have the luxury of just putting a rod on two drivers on one side, and testing.  Then put in another pin on that side, and test, etc, until you get all 5 drivers on one side pinned.  Unlike an engine where the rods actually propel the wheels, you should be able to get it to run smoothly with a rod on only one side, and then focus on the other side. 

Most likely, there is either one driver rotated a tooth off on its idler, causing its crank holes to not quite line up,
or there is one wheel rotated on its axle that is causing this - a common malady with these old Trix engines.

[ncbqguy]

Kentuckian...
Follow this link to the page in Railway Mechanical Engineer Volume XCIV 1920 that has a three page article on the C&O 0-10-0 that includes drawings of the locomotive and tender starting on page 11:

https://archive.org/details/railwaymechanica94newy/page/10/mode/2up

Charlie Vlk

[Kentuckian]

Max, thanks for the step by step. Removing rods will be another first for me.

Charlie, thanks for the link, very cool!

[mmagliaro]

Max, thanks for the step by step. Removing rods will be another first for me.

Charlie, thanks for the link, very cool!

Oh!  Okay.... 60 second primer.
1.  TAKE PHOTOS OF BOTHS SIDES before you start, so in case you get confused putting it back together,
you can refer to them.

The main crank, where the eccentric is attached, is a gray plastic crankpin that has a square post.   It's easy to break off when you try to pry it out.  Slip an Xacto behind all the rods, right up against the driver, and pry out gently, a little on each side, easing it out.  You want to pry on the ROD, not the plastic pin directly.  That spreads the pressure more evenly and should ease the plastic crank out.

The other 4 are metal pins that should just pry out the same way (but are not so prone to breaking off).  Get the Xacto behind the rod and pry gently.  Once the pin comes out part way, get some tiny needlenose pliers under the head (or tweezers) and gently pry/twist until it comes out.  But ALWAYS keep a finger on the head of the pin at all times, so if the tweezers slip, or the pin comes out suddenly, it doesn't go flying.

That's about it.  Once you have all the pins out, take the valve slider off, take off the siderod. 
Get a LOW drinking GLASS on the workbench and put all the pieces in it.  Don't use a plastic cup.  They tip over too easily.
(This may seem like a silly detail, but it comes from hard-learned experience)

If the slider won't easily come out, just leave it, but  position it somewhere against the engine boiler out of the way with a bit of tape so it won't get stuck in the wheels while you test the engine.

Putting the pins all back in is not hard on this engine.  Just hold the pin with tweezers on the hole and nudge it in with your thumb or fingernail.  Then grasp tweezers around the back of the driver, and over the top of the pin, and squeeze.  Do NOT just push on the pin from outside the driver.  That can make the driver push in on its axle, or turn on the axle.   Do the 4 metal pins on 1,2,4,5, and do the plastic eccentric crank last.  Use your photos to get the crank back in with the same orientation as before  (this is important).

As long as you have photos, you should be able to get all the parts back on the way they came off.

Did I mention to TAKE PHOTOS of both sides before you start!???   

[Kentuckian]

Gotcha. Take photos. Thanks.

[mmagliaro]

Just one final comment:
As a general rule, if you (meaning "anybody") are going to remotor, regear, or in any other way change the
driveline in a steam loco model, taking off all the rods and running without them is an absolute
must-have skill.  You can't possible know if you've got the motor and gears working right without doing this.  It's as fundamental as running a problem DCC loco with the decoder bypassed.  It's really just basic step-by-step system engineeing to confirm correct performance at each stage:

motor
motor + gears
motor + gears + drivetrain
motor + gears + drivetrain + drivers
motor + gears + drivetrain + drivers + siderods
motor + gears + drivetrain + drivers + siderods + valve gear
motor + gears + drivetrain + drivers + siderods + valve gear + DCC decoder

I know it seems tedious, but if you have binds in the motion and don't do this, you're just spinning your wheels (ha ha).

[Cajonpassfan]

I see what you did there Max...
But you’re right on. Which is why steam engines are such a pain/joy...
Otto