Modeling a MoPac GP-12 1067

[mahcr450]

I was inspired enough by Charlie Duckworth’s earlier build of GP-12 1065 that I decided I had to have one too. His article in the Winter 2018 Eagle magazine has been a great reference.

For this locomotive I’m going with one of the MI rebuilds which became 1067 in the roster. It’s almost the same as 1065, so I didn’t have to look for a lot of detail reference. Here is one image I found.

[mahcr450]

I’m going with the same model as Charlie. It’s a Bachmann RS-3 and I actually found one cheaper with DCC and sound. I’ll have to replace the decoder, but I’ll take this one to the next swap meet.

Lots of images of the Bachmann model, so jumping right in to the disassembly and modifications. I’m going to start with the frame. The MoPac used a different fuel tank, so I needed to remove the old tank and some metal from the Bachmann frame.

I made cuts where the body shell mounting screws go through the frame to remove enough material for the new tank.

[mahcr450]

After some measurements, I drew a 3D model and printed the replacment tank in resin.

It’s difficult to see the detail in the clear resin but I was able to add the drain plugs to each side of the tank. I kept, and added the speaker holes but not sure if I’ll mount a speaker in the same spot.

[mahcr450]

I was able to add mounting holes for the Bachmann air tanks so I’ll be able to add them back after paint.

[mahcr450]

There is a company that makes the cooler frame that hangs under the walkway on the right side. I found them doing research but going to have to look into it again. If I remember correctly, it was a brass casting.

My paint booth is a little cold right now so moving from the frame to body shell. I had to strip Great Northern paint from the shell so still a little color left. I removed the exhaust stack and some of the smaller details not needed. I also made the cuts for the new radiator fan box.

[mahcr450]

I made the opening a little smaller than the fan box and used a needle file to get the fit correct. The resin prints are a little tall so I had to sand the base down to the numberboards until it fit like I wanted. I was happy to see the width was very close for the shell.

The pictures I’m posting could be better. I’ll try to get some clearer images as I go forward in the build. Probably last post for today. I have to wait for putty to dry on the old exhaust.

[Charles Duckworth]

Mike
Will be interesting to see how the Canon fans look on the fan box with there openings.

[mahcr450]

I was able to paint some blue today. Here is the finished fuel tank and the chassis back together. There is a small cooling coil that mounts under the walkway on the right side behind the air tank. Still working on that detail.

[mahcr450]

I also sprayed some primer on the body shell. I think the fan box looks good. I printed the MU hose storage pockets for the footboards. Still some finish sanding to do where I removed some of the detail.

[mahcr450]

Not to get off topic but I wanted to show some of the limitations of 3D printing. MoPac had a number of the Phase III locomotives and I would really like to have a couple without trying to find a Stewart shell or waiting on Bowser. I hoped to draw a replacement for the long hood on the Bachmann model. Here is a very early test print.

[mahcr450]

Here is the big issue so far. In this image you can see the layering in the curved surface. It would sand off easy enough but not with the rivets in the way. One bright spot are the filter inserts. These actually turned out really close to the prototypes. I haven’t given up yet. There are a number of measurements that are off now that I have the print. I might scrap the curved hood and just print the sides.

[Charles Duckworth]

Mike
I found trying to use the Stewart sides that they were too short compared to the Bachmann sides so I had to add some Evergreen to the top and bottom to get them the right height.

[mahcr450]

Slow progress this week. I spent too much time on this cooling coil assembly and finally got it how I wanted.

[mahcr450]

I also got the exhaust manifold mounted on the hood. This shell didn’t have the correct headlights so I’ll be modifying those to the correct type.

Charlie – In know you wanted to see Cannon fans but I went the cheap route here. I had picked up a Proto 2000 GP-9 shell at a swap meet for parts. These are the fans from that shell.

[Charles Duckworth]

Mike
These fans look great. Don’t forget to cut out the area on the shell where the cab sits so the speaker fits. Unless you’re going to add the speaker in the fuel tank. Who makes the fuel tank details you’re adding?

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