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Customizing & Kitbashing

Plymouth MDT Rebuild- Nov 2012

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siouxlake
Hudson

Status: offline

Posted - November 25 2012 : 11:42:21 AM

I had a pair of AHM Plymouth MDT's that I was planning to rehab and this month was the time to get started. I found inspiration from a photo of a real Plymouth MDT operated on an Iowa rail museum property.

One of the shells I had was used to experiment with my Sioux Lake railroad orange, so I started with that one. I had a problem cleaning the Badger Modelflex paint off it using standard 91 alcohol, so I turned to my second weapon- Super Clean, which I get in 1 gallon containers at (you guessed it!) Wal Mart. A 24 hr soak did the trick. This is the shell as I started on it:

The Iowa diesel in the photo has (among other features) a divided side window, a rear light and additional grabs located in front below each front cab window. This version has no front porch, as the HO model does, so a bit of artistic license was used. I used these elements in my rebuild.

I had scavenged some round can motors from a VCR and found that one of them, a Mabuchi, would fit in the same space as the old motor, with only minor modifications to the chassis. I tried researching the specs for this motor online using the printed model number on the motor, but was not successful. Again, this came from a VCR built in the early 90s, so it may be no longer manufactured as such. I did find references to similar model images, suggesting that it is a 9VDC motor. Since I have no intention of racing around the layout at 12V, this works for me.
Here is the original chassis configuration:

Here is the Mabuchi motor with a brass Atlas (?) worm gear that Nelson clued me into, which I bought several of online last spring.

I had to seat the motor, so a bit of styrene was fit into the original motor, as well as enlarging the gear hole (the gear runs vertically down to the geared wheel axle):

And how it seats on the chassis (I used Loctite gel CA glue to mount the motor to avoid height and fit issues with the worm meshing with the geared wheel):

The original wheel wipers barely cleared the chassis deck and made resoldering difficult, as well as being corroded from decades of use:

I bought a piece of brass sheet stock (yes, I could have used phosphor bronze, but that was unavailable locally and I didnt feel like spending more than the $3.00 that the brass sheet cost -plus it makes many more wipers in the future) and redesigned the wiper with a longer vertical "tang" so that I could connect wires to it more easily:

I replaced the front bulb with a round-top 3mm warm white LED, drilled a hole for the same LED in the rear of the hood back wall, and then connected things up. I replaced the front weight with some fishing weights, appropriately reshaped- this had the advantage of moving the balance center closer to the exact middle of the chassis, over the front wheel. The overall weight was not increased, for the reason that the lower speed of the motor might be compromised (my view) by any significant increase in overall weight). The wheels were cleaned with 1000 grit wet/dry and alcohol, then the gearing was oiled with ATF.

I placed a strip of electrical tape along the bottom front of the motor, to protect against shorts from the wheel wiper tangs and wires, painted the contacts with liquid electrical tape after soldering, and wired the rear LED to the motor tangs, to simplify wiring. The rear LED is a press fit into it's new hole, so removing the shell- if needed- will be easy. I painted the can motor black, to minimize it's visibility from outside. I also placed reflective foil (backed with doublestick tape) on the underside front of the shell near the front light tube ahead of the front LED, to increase the focus of the LED out thru the front lens. Both LEDs were separately wired with a 470 ohm resistor for each, off the positive lead.

The shell was cleaned, holes drilled for grabs, and the window side openings divided with styrene strip. I opened up and cleaned up the front cab window openings to match, as best I could, the Iowa MDT's appearance, as the AHM model has two front windows on each side of the center partition. I then primered the shell and masked it for final painting. I opted to tint and install new clear window "glass", as the original window part was pretty beat up and crazed- even with tinting, the damage would be visible. The original part covered the rear and sides of the cab, but not the front. I soon realized that a front window would be difficult to install, as the top opening edge was offset from the lower edges. The tinting would offer a sufficiently darkened interior to compensate. Kadee # 27 couplers, which have a lower arm with the coupler mounted higher, were recommeded by Kadee's website conversion chart and used (sure- I bought them at a discount at a swap meet previously, back when I was originally going to work on thi MDT!)

The real world inspiration for this model's paint comes from a taconite mining railroad in northern Minnesota. The rational for this being on my Sioux Lake railroad is that my engine repair facilities are always glad to accept contract work for engine repainting and rehab (a short line is always short of cash!):

I could not replicate the white lettering, so I opted for the same font in black, located a bit differently, as the MDT has smooth surfaces on the cab. I was able to use standard blue for the rear lettering, which closely matched the Rustoleum "Sail Blue" that is, itself, a close color match (visually) for the Northshore Mining blue. I clued my paint scheme to the photo, but only placed lettering on the rear, as the front has a grill hatch pattern that would not lend itself to easy decaling. I used four small white safety rectangles on the chassis side fore and aft, as -even in a Minnesota winter- that blue would be easily seen. The white used was a Rustoleum flat white. The chassis sides were painted flat black and dullcoated.

I finished the decal work, then Dull-Coated the entire shell, to tone down the gloss of the blue
I have some diesel horns coming for the cab roof, and will paint those the same blue (or black). The final result is seen in the following images:

But wait...there's more!

The OTHER MDT will be painted and lettered for the Minnesota, Sioux Lake & Western. Either in MOW livery (as my MOW project series was) or in the orange and red livery of my railroad.

I will just post a few images of the finished product, as this post explains the process.

Thanks for viewing.

Siouxlake/ Ron

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