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

[u18b]

I’m hesitant to post this- but maybe it will help someone one day.  My point is that this project was tedious, time consuming, and required a bit of skill and patience. 

This thread should be seen as in the flavor of  @randgust  when he wrote about improving a Jamco junker.  It was partially about the challenge, not the wisdom of the project. 

https://www.therailwire.net/forum/index.php?topic=46241.msg602711#msg602711

The Model Power 4-6-2 Pacific is one of the best/worst locomotives made in N scale.   When you have a good one, it’s good.  Otherwise, it’s a disaster.   @spookshow  had educated me for years on this loco.  As each new release came out, he added details.

http://www.spookshow.net/loco/mp462.html

Years ago I bought a MP Pacific in Atlantic Coast Line while on sale.  I wisely test drove it at the hobby shop, and paid about $50.  That loco ran great, but as the reports got worse and worse over time, I decided to sell it.  I almost felt it was a ticking time bomb so I sold while it still ran.




Then, last year a guy gave me a Pacific which was dead from a poor sound installation (he was getting out of N scale).  I pulled the decoder (it worked!) and got the Pacific running in analog- but it had a bind.  It went into a drawer.




Fast forward to recently.   At a train show, I picked up 2 Pacifics.  One was listed as broken for $10.  Hard to go wrong for that price.   




The second was listed as running for $35.  I took a chance.

Unfortunately, the “running” one ran great in forward, but when running in reverse, I sometimes heard a ratcheting sound indicating gears were moving past one another.  Very disappointing.  Had I wasted almost 50 bucks?

Thus I embarked upon the daunting task of improving these awful locomotives.  Photos were taken with my phone and not top notch- but will suffice.

I decided to start with the worst locomotive.  If I learned anything and succeeded, then I would apply it to the better one.

The first step was to find out how to disassemble it- which is no small thing!!!

I had in my files a great document made by Jose Esguerra
Society of N Scalers  www.societynscalers.com. 
(that web address does not work, but there is a Facebook group with that name).

I placed the file unmodified on my website and will not repeat that information here.  I’m thankful for Jose’s work.  Read this helpful file here:

https://u18b.com/wp-content/uploads/2024/05/AHobbyistGuidetoMP462.pdf

So following that document gets you to this point.
What a mess!!!



Now there were multiple problems at this point.   The driveline was seized.  I determined that the main (center) driver was out of quarter- which I corrected (no photos).

[u18b]

But here also is a disaster.   I didn’t see it at first- but it is in this photo.




When I unsoldered the gray motor wire, the whole brush cap fell out of a cavernous hole!




I pulled off the back head (I think it’s called).  This exposed the motor retainer.




The motor retainer is held by two clips on the side.  Disengage them, and the whole motor slides out.




Here is a photo of the motor, retainer clip, back head, and end bearing that someone was selling.  My bearing did not come out when I removed the motor.




Oh my gosh.  This is bad.   I never saw Spookshow mention this problem of motor caps falling out.

But wait!   This Ajin motor is the same as used in the brass Little Joe.  Since I remotored one for a customer, I still had an old motor.  Great.  I’ll just swap them.

But I was shocked to see that it had the SAME problem.   There is a pattern here. 



So I have come to a conclusion.  Heat from soldering alters the composition of this plastic.   The plastic doesn’t just melt, it burns and CHANGES composition into a crumbling mess.

Now what?   This is a complete bust?

[u18b]

With nothing to loose at this point, I then embarked in a two hour detour.  I found a K&S brass tube which would just fit in the now-huge hole but the inside diameter was a bit small for the brush cap.




So I used a motor tool and reamers to thin the inner wall of the tube until the brush cap would fit inside.  I trimmed section, slide it on the brush cap body to make it fatter.






I then epoxied the modified cap into the motor.  How did I not ruin the motor?  By waiting until the epoxy was a bit thick, holding the motor in my hand with thumb nail holding the brush cap, applying the epoxy, and then holding the motor upside down (so the epoxy would not run down into the commutator) for about 10 minutes while the epoxy set.




For the future, this means I cannot now change the brushes when worn out, but I won’t be running this loco that much anyway, so it shouldn’t be a problem.

So the motor is repaired and runs!  Back to the chassis.

[u18b]

I did a search of Railwire and found a helpful thread (there’s a lot of good work on this board).

In it, the great Max @mmagliaro showed how he reduced the rats nest of frustrating wires by making spring contacts for the bottom plate.

(the people at Ajin were crazy to design such a nightmare loco where wheels cannot even be removed!).

I decided I would go for this change at some point.

https://www.therailwire.net/forum/index.php?topic=44647.msg575085#msg575085

I removed the screw on the bottom cover plate.




I then removed the small screw on top that holds the engines in place. 
Where upon I discovered a new problem- a bent piston shaft (which was easily corrected).



OK.  Now I’m down to the bare gear assembly.




And yes, I had a bent pick-up as is common with these locos (Spookshow warned me)




Since I was committed, I pulled the bottom plate off and snipped the wires at the plastic.  Now I could work.

[u18b]

Now, it was somewhere around here that I discovered a design flaw.

Remember, my other Pacific made a ratcheting sound indicating gears passing each other and out of mesh.  My natural assumption was that the main double worm gear was out of mesh with the worm.  But the worm is in the boiler.   Holding the wheel assembly in my hand, I discovered that  the double worm gear could un-mesh from the center wheel!

Thus making the boiler tight to the wheel assembly would NOT solve this.

Look at this.   The worm is purple, the worm gear is red, and the main driver is yellow.  The problem is the driver is too far away from the worm gear (blue arrow)  As designed, the mesh just barely touches.  But if any distance is introduced (the bottom plate not perfectly tight) the the gear pass each other.



The only solution is to move the wheels UP.

EDIT:  After I completed this project, I looked at the second L&N Pacific and saw that it had wheels out of quarter as well.
Holding a fully assembled loco, since the wheels are pressed onto the axles without splines, I found I could hold one wheel on a wheelset and gently turn its opposite wheel (thus getting it into quarter without removing the wheelset).

Well, this is too loose.  So I’m guessing it’s possible to have a loco in quarter at one time, which goes out of quarter over time (because a wheel slipped on its axle).

Thus I predict the following sequence of events happens.   The wheel slips out of quarter, which causes a bind, which then places pressure on the wheel gears.  The bottom plate gives slightly to this pressure and the gear comes out of mesh and ratchets.

This is confirmed by the fact that once I placed the wheels in quarter, the ratcheting stopped




So I drove out the transition gear pins to driver 1 and 3- leaving the worm gear (photo not shown).   I then used a small round file to cut the channel for the wheel bearings higher.   I kept doing this, and testing the insertion of the center axle until I could feel I had a good mesh that would not easily fail.  I can’t say how much I removed.  (~5 mil?)

(If I do this project on the second Pacific, I will measure before and after with a caliper)

NOTE:  Is this imprecise?  Yes (but it worked).  I really wish I had a lathe.  My son encouraged me to buy one.



Then, when I had a good mesh on the middle driver- I left that alone and never worked on it again.   I drove out the pin for the worm gear and removed the gear (which was now covered in metal filings).

I then filed on the slot for drivers 1 and 3.  The chassis had to be balanced and all wheels touch the rails evenly.  Since I started with the center driver, when all is placed on the rails, I could still wiggle and move the center driver.  So I would cut on 1 or 3 some more.   The goal was to have all wheels tight to the rails.

When finished, all these parts were washed.  Ready to proceed to the next step.

[u18b]

I was ready to apply Max’s technique, but this would still mean the boiler was wired to the chassis.  Max’s solution only allows you to remove the bottom cover plate and work on the pick-ups.

And then I had an idea.  Why not do the SAME thing on top of the chassis frame and place springs between the chassis and the boiler?

I proceeded, convinced I could do it.

I pulled the inner insulator plate off of the pick-ups.




Actually, my little inner plate broke.  No problem since I am going to trim it anyway.




I used a soldering iron to carefully remove the wire remnant from the holes.    I then soldered springs as Max describes.

Here I’m reposting Max’s two photos from the thread mentioned above.
Max spring idea:



Max’s pads.

[u18b]

So my idea was to duplicate Max’s pad on BOTH sides of the chassis frame.

So here are my springs installed.  Max bent the outer plate upward, but I installed a spring.




The top of the frame has casting flash which I removed.




I made a tiny circuit board for that flat spot where the wire holes are located.




I took a Atlas VO-1000 pick-up strip, drilled a hole, soldered a wire to it and then trimmed it.




I then used clear acetate window stock to make insulators, as Max described.  ACC in place.




Top view.




Drilled holes for the circuit board and put in place with ACC.




Trimmed and stripped wire ends, and soldered.




I then needed three or four hands to solder the springs in place on top.  Without burning and damaging a gear!




I think these are springs I saved from removing Rapido couplers years ago from freight cars.    These are a bit long- they will be trimmed.

[u18b]

On the bottom of the boiler, there is a plastic plate which serves to keep out dust and also hold the inner motor bearing.  My receiving pads can go there.    I think that wear mark is from the rear driver gear hitting this plastic (another design flaw?)




I used an alcohol prep pad to clean the oil and grease off of the cover.




I wanted something better than brass pads because of oxidation.  So I adapted the pads from an old RS-3/U30C/SD40 era light board.  They were the exact size I needed.




(reverse angle)

I used pliers to curve them slightly and then used ACC to lock them in place.  Notice the board on the left (nearest cab) fits up to the ridge on dust plate.  The right board was estimated by seeing where the spring came when test assembled.




I then installed the motor and wiring harness, being careful to NOT apply too much heat to the motor tabs!




The red and black wires were routed in their channels under the cab….




... trimmed, and soldered to the pads.



With the chassis all assembled, I applied some power to make sure it all worked.

[u18b]

Now, I still have a problem.  I have solved the electrical routing issue.  The chassis is now modular and can be easily taken apart.

But the ratcheting problem is still present!




And that’s because the play is even GREATER in the wheels because I filed upward on the frame (yellow).   I needed a way to FORCE the wheels upward (pink) so that the gears will stay meshed.




So I mixed some epoxy and used a toothpick to very carefully apply a small drop to the plastic frame at the elevated spot that presses on the wheel bearings.

The hard part was doing nothing and letting it cure for a few hours.




Much to my relief, it worked.   No loss of gear mesh.




I soldered the tender back up and took it for a test ride.  It ran wonderfully.  Smooth and quiet.



There is hope after all.
 

[u18b]

Well, in for a penny, in for a pound.  I made the boiler area modular for ease of disassembly.  I now don’t want the tender to be a tethered ball and chain!

So I set out to make the tender unpluggable and DCC (almost) ready (no more soldering and unsoldering!)

So I took a thin section of double copper clad board and cut traces for TCS 4-pin micro plugs.   It had to fit easily on top of the lead weight.    The socket on the right is the plug for the tender.   The socket on the left is for the analog plug or the decoder.





Now, these sockets are very delicate.   I learned from the EP-2 project that sometimes it’s good to lock them down.  So I soldered a band across the top and to the bottom of the board.   A multimeter checked for no shorts.

This board will sit on top of the tender lead weight.




I then took the TCS micro plug and jumpered the pairs of pins.   This is the analog plug.   The outer pins are the black and red track wires.  The inner pair are the orange and gray motor wires.   So this plug bridges the red with orange and the black with gray.  Heat shrink tubing and ACC to hold it all down completed it.




The board is fixed to the weight with ACC.  And the tender pickup wires are soldered in place.   The analog plug is installed.




The locomotive wires are trimmed.




And a TCS micro plug installed to the loco wires.   Then plugged into the tender socket.




Another test run to make sure all was working properly.

[u18b]

I added epoxy to hold down the board to the weight.   When dry, I began final assembly.    I bent the wires a bit so that the drawbar would go on its pin.




I installed the headlight (pretty pitiful) and all the valve gear.  Full reassembly.



Another run and the loco was fabulous- except for the stupid headlight.   In analog mode, it is too dim except for wide open running.




I may craft an LED replacement one day, but for now, a decoder will solve this since track power is always on at maximum in DCC.

[u18b]

So I took a decoder, removed the blue, white, and yellow wires, trimmed the rest and installed a TCS micro plug.  Here is the decoder with the analog plug.




And here is the decoder installed.




That’s all for now.  I’ll make a video of it running at some point.

[wm3798]

I have two of the MP Mikados, and a 4-4-0, and they have zero issues.  I'm now glad I've avoided their Pacific!
That seems like A LOT!
Lee

[u18b]

As a comparison, here is a shot of the Pacific in DCC.
Obviously the light looks better because it is at full illumination at all times.

The down side is that this incandescent bulb will not last as long.  You would not want this loco to sit non-running on the layout for long periods of time over weeks and months.  Sooner or later the bub will burn out.

[Ed Kapuscinski]

This makes me miss doing the N Scale Steam Annual.