Old School Minitrix repower job

[Lemosteam]

Repowering a Minitrix K4 for a Railwire WM patron.  His old school ways get an old school treatment.

I use an old LifeLike 5 pole motor, high torque, strong motor, you can see it in the background.  First I cut a tight slot in the back wall of the chassis and clean out anything that might interfere with the motor:


0.5mm must be removed from the front mortor mount to allow the back of the motor to sit flush with the back wall:


The motor fits very snugly in the slot to prevent the housing from twisting under torque:


Here is the motor located temporarily.  Instead of trying to ream out the front motor mount, I used some pliers with serrated jaws to grab the pilot lightly and grind down the plastic front motor bearing pilot housing until the housing fits perfectly in the front mount:


Motor closeup:


Rear wall:


I ream out the Minitrix worm till it fits on the motor shaft and secure it in place with red Loctite:


An oversize brass plate traps the motor in the chassis, it is only double stick taped in place for now:


The plate is trimmed and screwed in place:


A side view prior to wiring:


Wired up on the Brakeman's side!  I drill down angle holes through the bottom frame toward the ender for the tender wire exits.


Rear view, just have to cut off the extra shaft:


Engineers side wiring:


Worm and worm gear (reduction) closeup:


And lastly running with original axle wiper tender trucks on uncleaned filthy track:

@wm3798

[peteski]

Nice job John: clean and very clever install.
I also really like the fact that no adhesives or caulking goop is used (like in many other motor retrofits).  This means that the chassis can be easily disassembled for servicing and reassembled in perfect alignment.

[narrowminded]

Nice, John.

[Mark5]

Looks great! How does it run? (I mean at slow speed - I saw the racetrack vid  )

[randgust]

Wow, I pulled this up not quite knowing what it would be, and when I looked at what you did.... wow, that sure looks familiar.  At least for the motor that works here.

This kind of applies to the other thread too where we were talking about awful original Trix motors and what to do about it.   The 'surviving' Trix F-unit from my earliest start in the scale was repowered with what I 'think' was a Sagami motor which looks a lot like a Con-Cor PA1 motor which looks just like the Life-Like motor you've got in there.   No matter what you call it, that five-pole skewed motor was a honey, I still have them in my Alco RSD15's.

So, fitting nicely in the same thread here.... this actually is a press-fit in the original chassis.  No screws, original universals.



I just got so disgusted with having to clean the original motor commutator and the fire-ring problem I decided to massacre one to see if it would work and just be a more reliable mechanism.  Now, the other four of its sisters are gone, it's the survivor, much like the Alco PA's that got an EMD 567 as an experiment.

Now, its still a 'fast unit' but it MU's rather nicely with other units, the treads are worn to brass so it pulls like crazy.  It's just as reliable as any other unit I have, it just doesn't look as sharp as an Intermountain.   I have to admit I've NEVER had to pull the motor back out for maintenance, and it's been maybe 30+ years since I did that.

[Lemosteam]

Looks great! How does it run? (I mean at slow speed - I saw the racetrack vid  )

I won't know until the unit gets to its new owner. They plan on installing a Bachmann tender. The throttle in the video was about 2/3. At 1/2 it would stall from the dirty track. I have put this motor in other units with nice slow speed performance. The track in the vid is literally filthy. I was glad the pickups on the Trix tender even worked.

It's a poor man's substitute for what Max does.

[Mark5]

I have put this motor in other units with nice slow speed performance.

Thanks, that is good info! I have a few oldies cued on my ponderous list of projects.

[Lemosteam]

Thanks, that is good info! I have a few oldies cued on my ponderous list of projects.

@Mark5 , here is another example from 8 years ago:

[rodsup9000]

here is another example from 8 years ago:

 WOW, John, That is what I call creeping slow.

 Where do you buy your reamers from and how did you keep the hole concentric in the worm??  I really need to get a small diameter metric set. I think most of the imperial one I have are made by F & D Tool. (I guess I need to see if they make metric ones)

Thanks for posting this great tutorial. 

[Lemosteam]

@rodsup9000 , I use these:

https://www.micromark.com/Micro-Size-Precision-Reamers-Set-of-6?gclid=EAIaIQobChMIwdrt8cPm4AIVjLjACh1N0Ad6EAQYAiABEgJwwvD_BwE

The pentagonal shape and long taper keeps them centered just fine. Despite what some think, the accuracy is not as critical as you would think. This is not a transmission.  There is so much clearance in the mesh it simply won't matter.

One thing I did not mention is the armature had a lot of end play, about the same as the thickness of an MT washer. I reamed that out to 3mm to fit the shouler at the end of the shaft before the bearing. I snipped out a section of the ring and snapped it in there.

[mmagliaro]

Really nice work, John.  I really like the thin brass plate on the back, so you can screw it to the frame and screw the plate to the motor, so the whole thing can be disassembled with screws.

I was going to ask about those reamers you used too!  I followed the link you sent, but the linked ones don't look like the ones you showed in the photo.  I agree that a reamer or drill bit will follow the hole down the worm by hand just fine.  These mechanisms are not that high-precision.  There's a lot of slop in an M0.4 worm (or even the M0.3 gears used in modern N scale stuff). 

That's a great application for the old Life-Like motors.  As you know, I'm a big fan of them too.  They are cheap, reliable, and very very powerful with excellent low-speed performance.

[Lemosteam]

In this case I started with a 117 Dremel engraving bit and took the pic. It is too small for the motor shaft anyway. After a while got tired of that bit and I used the reamers in the link. I have used both in the past.

If you noticed ,there are no screws into the motor, intentionally this time ( I know you are familiar with the first time I did this). There is really not much axial force against the plate and the motor is fully constrained, so I opted not to drill into the motor this time. It's really easy to damage the magnet or armature, so I decided not to.

[peteski]

John, aren't those reamers tapered? So the hole will also be tapered?

[mmagliaro]

I don't know about John's, but the jeweler's reamer set I have, which looks very similar, is definitely tapered.
I have reamed out worms with them because the taper is slight enough that the worm would spin straight enough on the shaft anyway without visibly wobbling.  Remember, with gears like this, anything that's "eye accurate" is good enough.
(With mod 0.2 gears, I wouldn't try it).

Having said that, I do own a 1.5mm "chucking" reamer, which has no taper.  And that's what I use now.

I think I bought mine off eBay, but they look something like this:
http://www.atlascuttingtools.com/products/1.5mm-HSS-Chucking-Reamer-Straight-Flute.html?gclid=EAIaIQobChMIn5Of5Jnn4AIVzFuGCh2rLwcrEAQYASABEgL8I_D_BwE

[Lemosteam]

John, aren't those reamers tapered? So the hole will also be tapered?

Yes the taper is so slight that it yields a nice slight press fit, depending on how far you go, but I ream equally from both ends to mitigate that.