Remotoring a Minitrix K4, any advice?

[VonRyan]

I have before me a Minitrix K4 with a DCC decoder installed.
The current Minitrix motor doesn't seem to like DCC very much and I'm wondering what is the best DCC-friendly replacement.
The K4 is not mine, it actually belongs to a fellow member of my local N-Trak club, who also happens to be 93.
I'm simply inspecting it and replacing the motor for him.
I was wondering what experience others have had in replacing the motors in these engines, especially in instances where a DCC decoder has been installed as well.
I'm definitely looking to replace the existing motor with something more modern.

Any information and advice is much appreciated.

-Cody F.

[Lemosteam]

This can be done but there is no real "drop-in" replacement.  This locomotive does not have DCC but I did the exact conversion when I made my E6 from a K4 chassis and that one does have DCC.  It uses a Life Like motor from the old plastic frame E, F and GP locomtives.  It is fairly inexpensive if harvested from find at a train show:
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Performance results comparing a stock K4 and my modified version:
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[mmagliaro]

John's upgrade is excellent, and the motor is pretty easy to find and inexpensive.
My experiences with this beast are with pricier motors: You can use a Mashima 10x15 or 10x20,
or a Maxon 13x20 from micro-loco-motion.   These are all $40 - $50 motors.  They run magnificently, but
they ain't cheap.

I've never put DCC in one of these either, but I have done conversions for customers where I isolated the motor
and the LED I put in the for the headlight so they COULD add DCC if they want.  It is not hard.  Just a layer
of tape or styrene to make sure the motor doesn't contact the metal frame. 

Here's a YouTube of one I did this way.  Info on the motor, gears is in the video.

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Oh, and I also have a booklet with step-by-step instructions on the conversion that you can download from my
website here:  http://www.maxcowonline.com/maxspage/downloads/minitrixK4Overhaul-revision_2.pdf

Oh, and if when you are doing this, you get in a bind trying to get the worm gear off the motor, give us a shout here.
That's a tough one.  (gear.... "in a bind"... heh heh... get it?)

OH!  And if you do this, you MUST put Spectrum or Kato trucks in the tender and rewire.  If you don't do that,
the sputtery pickup of the K4 will ruin all your best efforts to improve it with a new motor.

[peteski]

I am not familiar with that particular loco but most European-made locomotive models have RFI suppressing circuit wired to the motor. Usually it consists of 2 small coils and a capacitor across the motor leads. Those components can "confuse" the decoder (especially if the BEMF motor control is enabled).

[mmagliaro]

I am not familiar with that particular loco but most European-made locomotive models have RFI suppressing circuit wired to the motor. Usually it consists of 2 small coils and a capacitor across the motor leads. Those components can "confuse" the decoder (especially if the BEMF motor control is enabled).

Cool!  But not a problem on the K4.  There ain't no coils, no caps, no nothing.  Just wires from the motor right to the loco and tender wipers.

[CodyO]

Slap it on a Kato C55/57 mech use the minitrix pilot wheels and a Bachmann or Kato mikado tender with minitrix shell on that
Quick one hour good running K4 works for me at leastx

[VonRyan]

Right, So i think i'll be going with the more expensive motor since it is on his dime not mine and he wants the best out there.
Only thing I can seem to understand is the whole process John went through... Is there really that much of a need to disassemble the entire locomotive... I figured it'd just be a matter of taking the worm off the old motor (however hard it may prove to be) and putting it on a new motor.
Surprisingly, the tender trucks haven't been a problem for the engine.
The only sputtering issue is getting the engine to get moving, even on clean, straight and level track-age with clean wheels... Which is how I determined that the existing motor doesn't like DCC all that much.
What makes new tender trucks necessary, is that where the only pick up is, or is it just that the tender has given other a bit of trouble?

-Cody F.

[Lemosteam]

Cody,

There is no drop in motor that will fit this chassis without some form of rework.  Most people dissaemble the chassis to keep debris out of the mechanism, but covering it with tape and vacuuming frequently with a brushed mini nozzle helps alot. 

The work I did on the chassis was to make the motor fit.  You could easily stop there if you are not going to superdetail the chassis and boiler.  I added a brand new pilot, and cast a huge lead weight.

Electrical contact is everything in DCC, no?  I would definitely do as Max suggests.  In so many threads that has been identified as the number one assist to better running quality.

[VonRyan]

I just read through Max's entire write-up on remotoring a K4 and it seems like something I could do, although with much less precision... so all his excellent measurements are already out the window for me.
(A Chinese caliper is as good as not owning one, especially when it thinks a .22 caliber shell casing measures .26" in diameter... and thinks a quarter inch drill bit is only two tenths of an inch...)

I might go as far as to have the engine balanced to improve its traction, that way when combined with the new motor, the engine will hopefully be able to pull a complete, brass, 1938 Broadway Limited set, which I am currently looking after so as to hand it off to have its decals put on.

As is, this is certainly shaping up to be more than just getting a set of brass MP-54's to run, which went from initially sounding like needing a new chassis, to finding out that only a wire had frayed and disconnected.

-Cody F.

[mmagliaro]

(spelling edits)

John already alluded to some of this, but...

1. The motors I use won't "drop in".  You need to take the old motor out and file the frame to make it fit.
You may also need to ream out some of the inside of the shell to get it to fit over the new motor if you use
a 12mm or 13mm round like the Maxon I use.   If you try to do this without taking at least some of the engine apart,
you are probably asking for trouble.

2. Don't be afraid of the precision of the measurements in my guide.  If you get it "close" on a styrene pad to support
it, you should hook up an ammeter and experiment, gently holding the motor in place and running it, looking for
minimum current draw.   I use a little pressure clamp to hold the motor in place while I test it, so I am not
subjected to the whims of my clumsy fingers.

When you get the perfect "spot", lightly tack the motor in place with a few drops of
ACC, let it harden, recheck the running, and then back it up with epoxy.  If you are industrious, you can make
some sort of nice screw-in bracket for it, but I never seem to have the room with the Maxon.

3. Sooner or later, you will regret not fixing the tender pickups if you don't do it.  The K4 is a very finicky,
stall-prone beast in everyday use if those tender pickups aren't replaced.

4. As for increased pulling power...
The larger motor I use, I suspect (although I don't know), seems to rebalance the engine just buy accident, so
that it pulls a ton more after this motor replacement.  I never set out to do that, but everyone of them
I've done with the Maxon can pull a lot more than before.  And remember, motor power has nothing to do with this.
If the wheels slip, you're done, no matter how powerful the motor is.  The key is weight and balance.

If you want to see how much one of these can pull (after I redo it), here's a YouTube by
a kind and gracious soul who got one of mine:  (this is not my video, just my reworked engine):

http://www.youtube.com/watch?v=tvuABS6WWWM


.... and remember... the Kato C55 is a nicer chassis with nicer wheels.  It may make more economic and practical
sense to change the shell, cylinders, pilot, trucks, etc, on one of those than to rebuild a Trix.

[VonRyan]

Well, since the engine is not mine I cannot make the call on replacing the chassis with one from a Kato C55, thus I will stick to the original plan of just replacing the motor, but in line with your guide, which leads me to the question of does Micro-loco-motion still sell their K4 conversion kits, let alone the motor you used... I looked through his site, but didn't find much listed about much of anything.
As for hooking the engine up to an ammeter, that's out of the question since I don't own one of those either.
I'm aware that the motor isn't exactly a drop-in job, but the process does seem something I can muddle through with a couple files and a razor saw.

I'm sure I'll be changing the tender pickups, but most likely scavenging parks off of another K4 since the loco's owner doesn't want to spend very much. I will try to convince him otherwise as to the benefits of replacing the trucks with something with more pick-up.

-Cody F.

[mmagliaro]

Micro-Loco-Motion is Eldon Shirey.  He hasn't updated his website in years.
You should just email him at    micro-loco-motion@sbcglobal.net

He sells a "kit" consisting of the Maxon motor, and a new worm + brass double gear that will
increase the gear ratio.  This greatly improves the low-speed running and reduces the Trix's
meteoric top speed.    I think the kit is $50 or so, including the gear.  Prepare to wait.  He is a very busy
guy, so it may take weeks for him to get you the new gearset, but it's worth it.
Another problem that this kit indirectly solves is the issue of pressing the worm off the Trix motor and
getting it mounted on a new motor.  The original worm is hard to press off, and even if you do,
it is only bored out for 1.2mm, so it will not fit on virtually any replacement motor you try because they
will all have 1.5mm shafts, so you would need to bore out the worm, or turn down the shaft on the new
motor (I've done it both ways).   Replacing the motor+worm+doublegear avoids all that.

Oh, sorry for the confusion.  I know you are fixing this for someone else, so using a Kato C55 is not an option.
If you try to improve the tender by just using another K4's trucks, that won't help.  The fundamental problem
is that the original tender uses wipers on the axles, which are notoriously unreliable, and also only
give you pickup on half the wheels in the tender.

[strummer]

4. As for increased pulling power...

If you want to see how much one of these can pull (after I redo it), here's a YouTube buy
a kind and gracious soul who got one of mine:  (this is not my video, just my reworked engine):

http://www.youtube.com/watch?v=tvuABS6WWWM

Wow...that is unbelievable.

Mark in Oregon

[VonRyan]

Micro-Loco-Motion is Eldon Shirey.  He hasn't updated his website in years.
You should just email him at    micro-loco-motion@sbcglobal.net

He sells a "kit" consisting of the Maxon motor, and a new worm + brass double gear that will
increase the gear ratio.  This greatly improves the low-speed running and reduces the Trix's
meteoric top speed.    I think the kit is $50 or so, including the gear.  Prepare to wait.  He is a very busy
guy, so it may take weeks for him to get you the new gearset, but it's worth it.
Another problem that this kit indirectly solves is the issue of pressing the worm off the Trix motor and
getting it mounted on a new motor.  The original worm is hard to press off, and even if you do,
it is only bored out for 1.2mm, so it will not fit on virtually any replacement motor you try because they
will all have 1.5mm shafts, so you would need to bore out the worm, or turn down the shaft on the new
motor (I've done it both ways).   Replacing the motor+worm+doublegear avoids all that.

Oh, sorry for the confusion.  I know you are fixing this for someone else, so using a Kato C55 is not an option.
If you try to improve the tender by just using another K4's trucks, that won't help.  The fundamental problem
is that the original tender uses wipers on the axles, which are notoriously unreliable, and also only
give you pickup on half the wheels in the tender.

I probably could rig up something with beryllium copper or phosphor bronze to pick up from the wheels (rather than axles) if the owner doesn't like the idea of the tender being cut up for kato trucks, which he probably won't...

-Cody F.

[mmagliaro]

I honestly don't understand this statement (about cutting up the tender).
You don't have to "cut up" the tender.  You only have to cut slots in the bottom of the tender so that the
Kato or Sprectrum truck tangs can protrude up inside.   Unless the engine is on its back, this modification is invisible.
And another plus is that you put a body-mount MT coupler on the tail which look and works far better than
the truck-mounted variety.