Building a Mopac GP-12 1065 (ex M-I RS-3)

[peggyrothschild]

I gave the carbody a light coat of Dullcote to seal the decals and give some ‘tooth’ for later weathering pastels to be applied. I added the original windows back in with the exception of the engineer’s side and added an Athearn ‘all weather window’ using Canopy glue (Athearn part ATHG68223).
I rebuilt the original fuel tank and added Evergreen plastic and Tamiya putty to plug the area. This will be sanded smooth.

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[peggyrothschild]

Added the pilot MU hose stations (Detail Associates SY 2208 or 2209) that adds much needed detail to the Bachmann plain pilot and steps. I noticed the engineer window was not centered and the Canopy glue lets you pop it off without harming the paint. Ordered MU hoses which is Detail Associates part MU 1508.

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[peggyrothschild]

A little paint this morning on the new parts. New fuel tank and air tanks next.
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[peggyrothschild]

The modified fuel tank for the GP-12 wasn’t an easy change. If one is doing an original M-I RS-3 the Bachmann model fuel tank is perfect. However, if you’re doing a GP-12 the fuel tank was enlarged by the MP and the metal casting on the frame of the model needs to be reduced so it fits. I had an Exacto metal cutter I put in the Drill press and spend 45” cutting away metal so the rebuilt fuel tank would fit (fortunately I still had my fingers intact after this). There is probably safer ways if one had access to a milling machine. Be careful on this part or just ignore it completely if you don’t have the right tools.

Good news is the original air tanks are the correct length. Details Associates part FU 3102 gives the fuel filler pipes, and two different sight gauges to detail the tank.

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[peggyrothschild]

Weathering
I use a photograph of a piece of equipment to keep my weathering in check. It’s too easy to over do it. Here’s a photo from Jim Boyd’s book of how I’d like the HO GP-12 to turn out.
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Like painting an oil painting I start with an under painting to get the base colors down. Looking at Jim’s photo there was lots of light gray/brown particularly on the walkways. There’s also some of this same color, lightened with white around the fans. The carbody shows lots of oil leakage to that was replicated with black oil paint. The brown on top of the carbody is Brown Panpastels. The advantage to using oils is they are easily to remove if you need to start over. Panpastels and military dry pigments are almost impossible to remove and weathering with an airbrush is as well. The oils take a day or two to dry and must be sealed with a flat coat. Everything has its advantages and disadvantages but I’m sold on using the water based oils.
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Once the water based oils dry I’ll give the carbody a light coat of Dullcote to seal the oils and then add more Panpastels and paint in layers.

[peggyrothschild]

Added a second light coat of Dullcote and went back over the top of the carbody with the brown Panpastels and the fan area with light gray oils and highlighted the access hatches. Will Dullcote again and work on the walkways and sides next.
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[peggyrothschild]

Finished; air hoses and radio antenna added just need to replace the Alco decoder with the EMD 567 12 cylinder one and put the couplers back on. This has been a fun project and a locomotive that only the MP and M-I had on their rosters. Was lucky in the number of photos available and from several different angles.

Would be interested in hearing if anyone else is considering building a GP-12. If you are and need the Plastruct tube to make up the exhaust let me know and I’ll mail you a couple of pieces. I had to buy a package of five.

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[Joseph Berry]

Charlie,

Thanks for sharing…all the weathering looks fantastic!! Very nice project using a very affordable starting point.
With my hearing today, I couldn’t tell an ALCO from an EMD anyway…but I’m glad Soundtraxx is doing the correct
decoder for these MP/MI rebuilds. Many folks will appreciate that. I do remember seeing these units and the GP16’s.

That shot with the GP-12 coupled to the EMD Geep is great…

Thanks again!

[peggyrothschild]

Gary
Thanks for your comments. Will be fun running this locomotive on the Bagnell turn. Hopefully House of Trains will have the decoder in soon. Would like to add two of the sugar cube speakers to take advantage of the 12 cylinder sounds. I experimented with the oil paints quite a bit and happy with how they came out. They were much easier to control than adding weathering with an airbrush.

[peggyrothschild]

Final post; to quote Gene Wilder in ‘Young Frankenstein’ “Its alive”……

Added the Soundtraxx decoder (part number) 885024 yesterday with a sugar cube speaker and the sound is amazing. The original bulbs were replaced with LEDs. One could reuse the Bachmann speaker but I was told the sugar cube speaker would sound better and I put it in the cab.

Hope you enjoyed following this transformation from a RS-3 to a GP-12. Looking back the three modeling challenges on this model were 1) replacing the Alco fan with the two 36″ EMD ones, 2) building the exhaust unit and 3) rebuilding the model’s fuel tank and modifying the metal under the fuel tank to accept the new one. Looking at the Athearn RS-3 it already has the GP-12 type fuel tank so that would eliminate the last step, has the correct headlights and separate hand grabs on the ends. One could convert the Athearn carbody and eliminate those steps but I’ve also learned the Athearn shell is a tight fit for the 885024 decoder and the shell has some accuracy issues.

Here’s a thread on the various HO shells with two responses for the Bachmann the most accurate.
http://dieseldetailer.proboards.com/thread/11549/question-on-best-rs-availble

Any questions let me know.

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[peggyrothschild]

Better sound clip

[elsaanderson820]

Thank you Charlie.
I saw your models in Austin and they look fantastic.
I have a brace of Loks coming to do this conversion.
I have been wanting to do this for years. Thank you for showing the way.

[peggyrothschild]

Thomas
Glad you’re enjoying the GP-12 build. If you have any questions just let me know. I just posted a bunch of detail photos in the blog on 1078.

Charlie

[elsaanderson820]

I have almost all the parts on your list. However, there are several items you mentioned later, like plastruct parts you used for filler, and the filters, etc. Do you have a more comprehensive list?

Having trouble finding the 36″ fans.
Also, I have several extras of the spark arrestors (SA 124) and pilot steps (SY 2208).

[peggyrothschild]

Thomas
I had one package of the 36” fans from a purchase years ago. To get the second set I saved an eBay search and found a set within a week. You can also try using the Cannon set shown here. They look much better than the solid plastic ones but I was too far along in building the fan box to modify it. http://dieseldetailer.proboards.com/thread/11407/cannon-36-inch-radiator-fans

The filler patch I used for the top of the car body was .040 Evergreen styrene but .030 would work too. I plugged the headlight holes with .030. If there’s anything else let me know.

[Author]

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