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

[peteski]

Max, in the example you found Tony *HAD* to mount the new coreless motor in the frame because he also scratchbuilt a whole new shell for it, so he could not depend on the original diecast shell to hold the  motor.

The 4-4-0, 4-6-0, and 4-6-2 all share similar design. While I have not done too many tuneups of these locos (I do own several, bought at fire sale prices), but I don't think there is inherently that much wrong with them working as-designed.  Just some judicial small tweaks. I think it's actually a pretty clever design. To me doing tweaks is still much easier than milling out the entire motor cavity and mounting a motor directly in the frame.  But then again, I'm not Max. 

[mmagliaro]

Max, in the example you found Tony *HAD* to mount the new coreless motor in the frame because he also scratchbuilt a whole new shell for it, so he could not depend on the original diecast shell to hold the  motor.

The 4-4-0, 4-6-0, and 4-6-2 all share similar design. While I have not done too many tuneups of these locos (I do own several, bought at fire sale prices), but I don't think there is inherently that much wrong with them working as-designed.  Just some judicial small tweaks. I think it's actually a pretty clever design. To me doing tweaks is still much easier than milling out the entire motor cavity and mounting a motor directly in the frame.  But then again, I'm not Max. 

Yes, I realized that it was out of necessity for a custom engine.  My point was just to show that it was possible to mount the motor to the frame, and also to show from Tony's fine handiwork with the bracket and worm carrier that it wasn't particularly easy.

... and thank you.   

[u18b]

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

Thanks Max.

I remember Tony scratch building his B&O P7d Pacific for the Cincinnatian.   That was an amazing project.

I did not remember his chassis.

[u18b]

Quick update teaser.

I solved the problem.    The noisier one is now corrected and runs as smooth and quietly as I could hope for.
I'll be posting more information and some videos once I process them.

[u18b]

I could not help but notice this line from Tony Hines post:

The Model Power loco design is going on 25 years old, is one of the hardest loco's to kit-bash, has no free standing grabs, very little detail whatsoever. They are very good running loco's when right, once you have a problem with one, you might as well throw it away, the driver centers are very soft and any hint of shorted driver will melt them in a heartbeat.

He was, of course correct at the time.   However, I hope that this thread has shown that corrections are possible.
His warning about the soft plastic driver centers is a good argument for me to make both of mine DCC only, and no analog except for testing purposes.  The auto instant shut-off of DCC is a protective advantage for this loco.

[peteski]

His warning about the soft plastic driver centers is a good argument for me to make both of mine DCC only, and no analog except for testing purposes.  The auto instant shut-off of DCC is a protective advantage for this loco.

Well, it's not that certain.  I have seen melted trucks on DCC powered track too.  Basically there can often be "almost shorts" occurring on DCC track.  They have enough resistance for the current passed through those "shorts" to be high, but just below the DCC breaker's trip point.  Since boosters can supply rather high current to the track, this can spell disaster.  Lets say the DCC booster breaker is set to trip at 3A and the current through the "short" is 2.5A, at 14V that is 35W or energy dissipated at the "shorted area!  That is way more than enough to heat up the conducting surfaces way past the melting point of plastic.

Actually running on DC would be safer than on DCC as most DC throttles only supply sub-amp current to the track, plus most of the time you run the model at less than 12V.  So a short at 6V with the throttle which supplies about 0.6A, that is only 3.6W of energy dissipated at the "short"area. It would take some time for things to heat up.

[craigolio1]

Well, it's not that certain.  I have seen melted trucks on DCC powered track too.  Basically there can often be "almost shorts" occurring on DCC track.  They have enough resistance for the current passed through those "shorts" to be high, but just below the DCC breaker's trip point.  Since boosters can supply rather high current to the track, this can spell disaster.  Lets say the DCC booster breaker is set to trip at 3A and the current through the "short" is 2.5A, at 14V that is 35W or energy dissipated at the "shorted area!  That is way more than enough to heat up the conducting surfaces way past the melting point of plastic.

Actually running on DC would be safer than on DCC as most DC throttles only supply sub-amp current to the track, plus most of the time you run the model at less than 12V.  So a short at 6V with the throttle which supplies about 0.6A, that is only 3.6W of energy dissipated at the "short"area. It would take some time for things to heat up.

I can vouch for this. Had some Kato passenger car axles melt on a multi club DCC Free-mo-N layout a couple of years ago. Thankfully I have lot of replacements. I would have been very sad if it were a steam loco.

Great thread by the way!!!  I have one of these locos and it runs quite nicely but I have dealt with the driver quartering issue. I’d love to see a fix for that.

Craig

[u18b]

Craig,
Quartering….

I just put some ACC on the axle tip.
We will see over time if it holds. 

Also, I have to take photos, but the reason axles slip is also because of cracks in plastic (common problem).

[mmagliaro]

Craig,
Quartering….

I just put some ACC on the axle tip.
We will see over time if it holds. 

Also, I have to take photos, but the reason axles slip is also because of cracks in plastic (common problem).

I have tried that.  It only kind-a sort-a works. I also tried various incarnations of LocTite.  Roughening the axle tip with some sandpaper, and gingerly cutting some slits into the inside face of the driver hole with a #11 Xacto blade helps, because the surfaces have some tooth,and the glue can seep into the slits in the plastic, so it becomes more of a mechanical fastening as well as a glue bond.  It's hit and miss whether it lasts.  I've had some hold, and I've had some not.  One I can definitely remember would just keep slipping out of quarter no matter what I tried with adhesives.

[CNscale]

Quick update teaser.

I solved the problem.    The noisier one is now corrected and runs as smooth and quietly as I could hope for.
I'll be posting more information and some videos once I process them.

This thread is better than a murder-mystery. It turns out that where N-scale steam locomotive performance is concerned, there may be *multiple* villains.

[u18b]

This thread is better than a murder-mystery. It turns out that where N-scale steam locomotive performance is concerned, there may be *multiple* villains.

That is EXACTLY what's going on here.
I've corrected a couple of problems which are entirely unrelated but which all together effect the total performance of the locomotive.

[u18b]

Ok, here is the simple thing I did to solve the problem.

The motor and flyworm are all one assembly- that’s a key info point.




When I slide it into the boiler section, the shaft at the tip of the worm does not line up perfectly with the bearing- causing a bind.




Here is what Model Power did.  Stock black tape.  IMPORTANT- notice it does not go ALL the way down the side of the motor slot.  It is closer to the outside edge.




Here is what we’ve got as a drawing.




There are only three points that hold this (red arrows).  The tip bearing and the shoulders of the motor which limit how deep the motor can go.   The blue is the spot that was rubbing and I opened it up with a drill bit,





While the motor assembly is all one piece, the PIVOT point is the center of the motor.  That’s key.  Small changes in the motor result in larger changes at the bearing tip.




This is what Model Power did.   The tape was twisting the motor and forcing the bearing tip to the right (when viewing under side).




When I removed the stock black tape, I saw improvement (tip moved to the left), but it was still not perfect.  There was still a slight bind.




So the solution was to pivot the motor in the opposite direction by adding a bit of Kapton tape at the FRONT edge of the motor.




I applied Kapton tape at the flywheel end of the motor.  On my first try, the motor would not insert into the boiler cavity without forcing, so I removed the tape on the top and bottom edge (purple) so the only tape was on the outer edge (I said “top” in the photo, red)






NOW we’re talking.  The bearing tip is lined up and slides into the bearing perfectly.   The bind is eliminated.

[Mark5]

wow Ron, this sure has been a "deep dive" 

Thanks for documenting all this!

Mark

[u18b]

Thanks Mark.

It's been a challenge, but fun.

Working on a video.  Will post when ready.

[u18b]

Video is up.

I'm about finished with this project.  Very pleased with how it turned out.

Here is a video.