Model Power Pacific 4-6-2 Improvement: Fixing a Disaster and making a Pearl

[u18b]

Ron, you don't think that extra part was added to keep the flywheel from hitting the shell? I can't imagine what other purpose it might serve.

-Mark

Mark,  No.

Because the later version with the plastic cover is a loco that is Beardenized- meaning, it has no inner bearing.  The outboard bearing is fixed at the far end.   So this plastic piece cannot do anything to the flywheel (control-wise).  I think it's only purpose is a dust shield.  But.... without that curly part, if you pressed on the shield, it might break inward.  So I think the curvy part is just a structural support for the dust shield- but designed so that it does not touch the flyworm.

[u18b]

As a test, I took the broken/awful boiler and opened up that shaft hole that was rubbing.   The hole was too long for a motor tool bit, so I ended up using a regular drill bit and my drill.

My plan now is:

1.  Measure sound of my running early Pacific as a reference.

2.  Drill out the hole so the flyworm does not touch any more.

3.  Clean it all up, reassemble.

4.  Measure sound again to see if it it now quieter.

[spookshow]

I don't see how it's keeping dust out if it only covers half the opening...

-Mark

[u18b]

The gear tower fills the rest of opening.

[spookshow]

There was no opening in need of a dust cover before, and adding the extra parts only increases the cost. So, why add the opening at all?

-Mark

[u18b]

There was no opening in need of a dust cover before, and adding the extra parts only increases the cost. So, why add the opening at all?

-Mark

Mark,
Well, now that's a good question.   They also lost a little bit of weight.

We can only guess, but my experience with this loco suggests that the casting tolerances were too tight and possibly allowed something to rub on the flyworm.
There are three TWO possible places.  As shown here (there is no metal near 2).



I've already shown that I had a rub at point 3 on my junker. 
But notice also the tight clearance at point 1 at the outer circumference of the flywheel.   I have not noticed any rub marks on my flywheels but that is awfully tight.

[peteski]

This whole thing makes no sense to me.  If the original casting's tolerances around the worm/flywheel were too tight, why not modify (increase clearance) of the original boiler metal dies?  That way, only the metal boiler would have to be modified.

But they not only modified the boiler dies to create that large opening, but then they had to design brand new plastic cover, make expensive dies for molding it, and also add a screw.  That seem much more expensive than just increasing clearance in the original boiler.

[u18b]

This whole thing makes no sense to me.  If the original casting's tolerances around the worm/flywheel were too tight, why not modify (increase clearance) of the original boiler metal dies?  That way, only the metal boiler would have to be modified.

But they not only modified the boiler dies to create that large opening, but then they had to design brand new plastic cover, make expensive dies for molding it, and also add a screw.  That seem much more expensive than just increasing clearance in the original boiler.

I agree.  It is curious.

[u18b]

I’ve established that there appear to be rub marks in early Pacifics which might add to noise.




The part in question in the boiler is this ring.




The thickness of that ring seem to me to match this wear spot on the flyworm- as if MP is using this ring as a sort of inner bearing.






So I want to widen that ring and make it so there is nothing to touch on the driveline.

After disassembly, I used cotton swabs to clog up the holes for the light and the end bearing to keep metal shavings out.





I then went to my garage and found a 7/32” drill bit was the size I needed.     The 13/64 is too small and already passes through.  I had to use this bit because my motor tool bit were too short.







I then used a drill to open the ring.  It was a little tricky to hold, but I finally got the bit through the ring.




Of course this process left some burrs which I tried to clean up on both sides of the ring.




All finished.  Now the flyworm cannot touch this ring.




Upon reassembly, how did it run?
Better- but not as much as I had hoped.

More to come later

[peteski]

This design seems to bring up more and more questions than answers.
The worm/flywheel/motor shaft are one solid assembly.  The bearing block on the end of the worm shaft and the motor bearings on the opposite end should provide more than enough solid support for that part of the drive train.  I suspect that Model Power just didn't make that hole in the boiler large enough, so with whatever little play there is in the motor/worm/flywheel assembly it rubbed against the hole wall.

[u18b]

Pete.  I agree.   And this may answer Mark’s question.  Maybe they realized the tolerances were too tight and just opened up the whole area for n the revised version with the plastic cover plate.

I’ll post more tonight.   I’ve not finished documenting issues.

[u18b]

When I reassembled, I began noticing a new problem-  yes another.

The motor and flyworm are all one assembly that slides into the boiler.   At the end, (toward the nose) there is a square hole where a Delryn bearing sits.  The worm shaft slides into this.

On the later Pacific, sliding in the motor was perfect.   But not with this earlier one.

The motor was canted to the right when viewed from below.  So the tip of the shaft did NOT simply slide into the bearing hole.   There was misalignment.

You can see it here.




Here is a closer view.   What will now happen is that when you push the motor in anyway, the bearing will now place  a sideways force on the motor shaft (to the left).  This will leave a bind on the drive train and cause extra friction and noise.




I saw another potential problem.   I remember that in the good (later) Pacific, when I removed the motor, the bearing stayed in the boiler.   But in this locomotive, the bearing came out along with the motor.

Now I see why- the bearing will not be seated all the way in it tightly.  With black on black colors, it is hard to see, but that bearing lip is not tight with the boiler wall.




I used tweezers, pressing on the outside lips, to press the bearing firmly into its slot.

When I inserted the motor, the tip was still skewed to the right.  More investigation revealed why.

Inside the cab on the left side (upside-down), there is nothing on the side walls.




But that is not the case on the right wall.   There were two pieces of tape which provided a bit of a tight friction fit for the motor- no doubt to reduce any possible motor rattle.




However, with the tape positioned in the BACK of the right side, that will push the tip on the other end to the right.

So I removed the tape.



This removal allowed the worm shaft tip to move a bit left, but still not perfectly centered with the hole.

I have more experimenting to do.

Here is a photo of the bearing seated in the boiler. The lip is tight (yellow).   I pressed on the bearing at the sides (blue).




So I’ll see if I can make this smoother and quieter.   More tinkering to go.

[u18b]

By the way, I know some have said (and more probably thought)- “just get a BLI Pacific” …. And that is still a possibility.

However, remember that I only paid 10 bucks for one of these.  Thus that makes it worth it to me if I can make it better.

And for those who don’t know me very well…. This is who I am.   I’m a performance nut.   Much of my modeling for decades has been in how to improve performance.  I’m a bit obsessive about it- and I love it.  Especially when rewarded for long hours of work.

So I fully realize that most of you will not make these changes to your MP Pacific, but I enjoy this kind of work.  And I answered some questions … and have come to a better understanding of these locomotives as a result.

We learned things we didn’t know before.

Well worth it to me.

[peteski]

By the way, I know some have said (and more probably thought)- “just get a BLI Pacific” …. And that is still a possibility.

Neah! Keep on doing what you are doing.
I'm with you!. Tinkering with model trains is the best part of this hobby.

I also like the finely molded see-through spokes in the drivers, and the delicate photoetched side rods.  Other models often have clunky looking siderods. The rest of the model is  not too shabby either.

Plus, I  enjoy following  your excellent writeups.

[mmagliaro]

Ron,
I think it's GREAT what you are doing.  (But then, I classify myself as that same kind of nut, so....)

I own one of these from the old first run, and if I were to ever use it in a kitbash, I don't think I would
go this route, especially now seeing what you are finding.  Given the painful disassembly design and the
wire routing, it might be better to just scrap the whole motor mount in the boiler and instead mount it to the frame, and
machine out the bottom of the boiler so it can just be placed on top, like a more conventional loco design.
I am sure it wouldn't be easy, requiring some sort of custom bracket on the frame to hold the motor in place.
In my vague distant memory, however, I remembered seeing a project by Tony Hines where he mounted
the motor to the frame on one of these.  I found it!   
https://www.therailwire.net/forum/index.php?topic=51660.msg703259#msg703259