I’ve been thinking for some time about building up a damaged and unfinished Kemtron GP-7, with the idea being that I letter it for the ATSF in the blue “bookend” scheme – one that I grew up with in Kansas.

What a kit looks like

The engine I’m working on was completed to about 75%. Preparing to write this article I pulled out the complete kit in my collection, seen below. This kit really took some skills to build, and working on this present project engine now I have an added level of respect for those model builders of years past that tackled and completed this kit. As I’ve said elsewhere, it is what people did in those days before the Internet. Everything is there, it was a well designed kit, but this is no easy build.

Adding dynamic brakes

In this first overall photo of the current project engine, you can see on the body a set of dynamic brakes. The ATSF ordered GP-7 units with and without dynamic brakes, but this is a detail I’d like to add. These parts are from an Athearn HO model, and will be a good stand-in for this OO model.

In the photo you can also see the big problem, one end of the frame is all detached. I tried to use my new resistance soldering unit to solder it, but it did not have enough “oomph.” No regular soldering iron would be big enough either. it was time for bigger equipment.

Busting out the torch

Here is where I should digress slightly. I’ve mentioned this before, among my hobbies is working on brass instruments, specifically French horns. Here is some recent work, using a special brace made from O scale rail.

The GP-7 frame repair I set up like when I work on brass instruments. The parts were first cleaned up completely.

Then the end was wired into place prior to soldering with 19 gauge annealed steel wire. Then I applied liquid flux and placed chips of solid core 50/50 solder. And got my torch!

I had difficulty wiring the ends exactly in place, and I liked doing this so much that I did it twice! The first time they were not at 90 degrees, the second time I got it right. There is no easy way to do all of this to be honest, although I could have set up a jig to position the parts. If I were to build up a complete kit I would have to plan it all out more. The original builder did really a very nice job.

I also noticed that one side of the fuel tank end casting was only glued on, having previously been soldered (the glue is visible in an earlier photo). I cleaned that up (must remove all old glue!) and soldered it back in place as well. The photos below show the setup with the flux and chip of solder, and how it looked after using the torch.

Cleaning up a classic American OO model

After each step I cleaned up the flux with water, and then decided to try to clean up the body overall a bit too, soaking in vinegar for roughly 10 minutes. Not enough to take off a lot of metal, but enough to take off some of the tarnish. Hopefully better prepped for paint, although it will get cleaned again before priming.

I will be looking at prototype ATSF models and seeing what I reasonably can do to match the details, and I’m hoping to set up the original drive as well as I can for good operation. A story I’ll continue in future posts. A number of challenges await, but all problems that can be solved.