Can I fix it? Brass B&O P7 Pacific by Key

[wm3798]

I recently acquired this beauty of a locomotive, and out of the box it ran smoothly after a brief warm up.


After about 30 minutes of run time, it bucked and stalled, something having seized up in the drive train.

Opening it up, I found there is a  multi part universal joint that had popped apart..
I tried reinstalling it, but the problem persisted.
In an attempt to get it operational again I tried replacing the U joint with a simpler Lifelike spring drive.

Everything fits well enough, but something is still seizing up.
I was hoping to avoid a complete tear down, but it looks like that may be required.

Any advice from the master mechanics here at the wire?
Lee

[Chris333]

NWSL makes a U joint set with a short tiny dong bone. I bet it would pop right in.

https://nwsl.com/collections/shaft-couplings-driveline-universals

BTW my photos are gone, but I found this still at eBay from when I sold it. Same number as yours:
https://photos.app.goo.gl/hbSYYaP9YgCMBcTV7

Sold it to Cibolo TX for $473.

[Rasputen]

I would take the worm out of the gear box, you can then roll the mechanism around and see what is hitting.
Is the right hand main rod hitting the valve gear?  Your image is a little fuzzy in that area.  Anyway, find out what is hitting before you spend a lot of time with the motor coupling.

[u18b]

I recently acquired this beauty of a locomotive, and out of the box it ran smoothly after a brief warm up.


After about 30 minutes of run time, it bucked and stalled, something having seized up in the drive train.

Opening it up, I found there is a  multi part universal joint that had popped apart..
I tried reinstalling it, but the problem persisted.
In an attempt to get it operational again I tried replacing the U joint with a simpler Lifelike spring drive.

Everything fits well enough, but something is still seizing up.
I was hoping to avoid a complete tear down, but it looks like that may be required.

Any advice from the master mechanics here at the wire?
Lee

Lee,
I concur.  The problem is in the valve gear or the wheel gears.  Not the coupling.

Look at your two photos of the rear drivers.  On the left side is a typical hex.  But on the right is a slotted screw.
This indicates a previous owner had trouble with this locomotive and had been messing with it.

There is a bind somewhere.

How hard would it me to remove the worm so you can push the chassis?

[wm3798]

Good call on the valve gear.  I'll inspect that more closely.
There was a hex head screw driver in the box.  Not sure if it was factory supplied or left behind.
No hex screw, though.

I suspect that the prior owner lost the OEM screw when changing out the traction tire driver.

I'll have time later today to futz with it hopefully.

In the meantime, anyone have a hex head screw they can spare?

Lee

[Dave V]

Good luck, man... One thing terrifies me more than anything in model railroading, and that's disassembling brass with the expectation of putting it back together.

[mmagliaro]

On that hex screw it could be M1.0, or M... something... smaller... than...that.  I do have little hex metric screws, but
it will not match in thickness or profile.  You would probably have to file it down to make it look good.  For now,
I would not obsess over the screw until the jam is fixed. 

As for the tool in the box, it was probably provided by Key.  They used to do that on engines with a swappable driver.
It won't be a quartering problem.  These things
are driven on one gear with all the rest driven by the rods, and the drivers are super tight on the axles, so they don't slip out.

I would not expect the problem to be in the gear box.  #1 place to expect this is in the rods.  I would look for any rod that can hook itself on something as it goes around. 

Look at where the piston rod pushes in and out of the cylinders in the front.  See if one of them can actually pull ALL THE WAY OUT
of the cylinder hole at some point in the rotation.  Brass steam is notorious for this.  The rod pulls out and then magically finds
its way back into the hole, over and over, and the engine runs great... until one time it doesn't quite find its way back into the hole,
jams against the cylinder face, and the whole engine locks up.

[peteski]

Good luck, man... One thing terrifies me more than anything in model railroading, and that's disassembling brass with the expectation of putting it back together.

LOL, to me *THAT* is the fun part of model railroading,  But OTOH, don't even ask me to attempt some rolling stock or structure weathering.    I'm all thumbs on that!

Max, as usual has given some good and detailed  advice.

[garethashenden]

I'm not sure if its distortion from the camera or if the main rod on the right side has a curve to it?

[mmagliaro]

I'm not sure if its distortion from the camera or if the main rod on the right side has a curve to it?

I see that too.  The right side is my prime candidate anyway, because of that screw, and because the solder blob holding the eccentric on
the main crank pin on the center driver is noticeably sloppier than the solder on the left side.  Somebody definitely has been messing around with the right side. 

Lee, that spring coupling isn't a bad idea at all.  It will probably work once you get the jam fixed.  But if you can find a set of the NWSL cup-and-dogbone couplings, that would be better.   

Can you give me some more info?  Does it run part of a rotation now?  Does it turn part of the way and lock up.  And then if you reverse, does it go around the other way and lock up?  Or will it not run at all?

[wm3798]

Thanks for all the feedback.
I've been otherwise engaged all day clearing out one of our storage units.
(All the train stuff is now in the basement, except my books and magazines. )

I will take a look at the specifics, and Max, I got your email and will follow up shortly.

Hopefully this evening I can monkey around with it.

Lee

[wm3798]

Here's what I've got so far...

Fireman's side with the OEM bolt.  Note the position of the eccentric hanger.  It appears to have two slots, and a round hole in the center.  It appears that the pin is in the upper slot, and the hanger and eccentric move freely.

Here's the engineer's side, which had the replacement screw and the solder blob.



Not that I touched up the solder, including adjusting the position of the eccentric a wee bit.  Also note that the hanger appears to be pinned through the center, at the round hole.
That seems to be the only difference in the valve gear one side to the other.  I don't know which mount is correct, but based on the apparent rework of the fireman's side, I would assume that side is not in its original configuration.



Here's the bottom side view for reference.

Functionally, with the motor disengaged, the drive rolled forward and back with no substantial hitch either way.
With the motor engaged, it worked in reverse, but not forward
Then after a couple nudges, seized up altogether.

So I'm at a loss.
The eccentric hangers appear to be riveted, so I don't know how to make them both the same, and that's the only visual that is mismatched.
Any thoughts?

Lee

[u18b]

Lee,
Where is it locking up.
What is hitting what?

[peteski]

I concur with Ron that removing the worm then pushing the free-rolling mechanism on the track is a good way to find the bind.
In many brass models (like this one), the gearbox has a bottom cover attached with 2 screws.  Removing those screws will allow the gearbox to be disconnected from the driver's axle allowing the drivers to roll freely.

EDIT: Never  mind. I replied to  Ron's post without reading newer posts in this thread. Looks like you already did that.

On the model, that curved part (called "expansion link")connected to the eccentric rod should pivot at the center hole (not one of the elongated holes).  Sometimes the pivot point is not a flared rivet but something that looks more like short length of a straight pin, bent over on the inside to prevent it from falling out.  In those models, it can be removed, so the pivot point for the expansion link could be moved to the proper hole.

1:1 nomenclature explained: https://en.wikipedia.org/wiki/Walschaerts_valve_gear.

[mmagliaro]

Okay, two questions...
When it locks up, are you sure it's a mechanical jam and not a short circuit?   If another engine is on the track when this engine locks up, does the other engine stop dead?

Did you try the wiggle test when it is locked?  See if the non-geared drivers and all the rods can move just a little back and forth?
See if you can tell exactly which little rod or linkage is jammed tight and won't move at all.

If you do confirm that it isn't a short, when you get it in its locked state, can you take some super-close, sharp photos of each side and from underneath again?

From the underside photo you just posted, it looks like the right-side front-driver crank bolt can easily be catching on the valve gear up front.