Large Scale Central

Doc's Denver South Park & Pacific Cooke Mogul Build

A few years ago my narrow gauge interests turned from the D&RG to the DSP&P. This was accelerated with my purchase of an Accucraft Mason Bogie. Before that I had purchased a couple of Hartford kits for DSP&P equipment. Another engine that always impressed me was the Cooke Mogul. I did own an LGB Mogul that was modeled after the Cooke but sold it since it wasn’t a 1:20.3 scale model.
I started doing some research on the Mogul and found considerable help from David Fletcher and from Craine’s DSP&P website. I selected DSP&P engine number 71 to model.


I found several scale drawings of #71 which enabled me to construct my model pretty much to exact scale. Of course, I was confronted with the usual issue of finding or, heaven forbid, building a chassis. So, I turned to an old favorite, the Annie. The driver spacing wasn’t exact for the Cooke Mogul but it was close enough. So I purchased one of Bachmann’s updated chassis; however, it wasn’t the newest with all metal gears. I’ll have to live with it.

To get the Bachmann chassis to fit the Mogul design, I had to do some heavy cutting and trimming. Here’s what I started with,

And, here’s how it ended up. It was now a 2-6-0.

The next thing I did was to replace the pilot and boiler yolk. The wooden pilot is from a kit.


I then moved to the rear and chopped off a good portion of the chassis rear end including the original coupler pin.


I added some styrene details to mimic the rear frame and added support for the rear platform bracket. I also added some styrene to extend the frame. This was necessary since the Mogul had a slightly longer frame.


I was very lucky to find the right diameter PVC tubing for the boiler. When I added the boiler wrap, the diameter came out to be 50” at 1:20.3 scale which is the diameter of the actual Mogul boiler. Since I’m not a machinist and don’t have a lathe, I cheated and bought a brass sand and steam dome set from Accucraft. They are almost the correct ones but not exact. They look pretty good. In the following picture I show the engine with the Accucraft domes and a temporary Accucraft stack and headlamp. I thought of using this stack until I was corrected by David Fletcher. He said my model
required a Congdon stack and the Accucraft one was not correct. That eventually led to my involving my son. That story comes later.


The picture also shows the engine deck temporarily installed. I sorry I didn’t get any photos of that by itself. One of my many photographic regrets. Also shown is the pilot truck and cow catcher. The pilot truck is from a Bachmann C-19.

Here is a photo of the fabricated cylinders and yoke. The steam chests are from a Connie. As you see from the photo, I added two brass strips to reinforce the front of the chassis since I had removed so much of the original chassis. You can also see the temporary crosshead support bracket. This was styrene and I later replaced it with a fiberglass version for
extra strength.


I had to completely redesign the front section of the drive rods. Shortening them was necessary because the new cylinders were set back from the Annie position.


I was also able to salvage the piston rods from a Connie.


New cross heads were fabricated from styrene. The crosshead guide bar was also modified from a Connie.

Next I added some additional brake detail. The brake cylinder is from Trackside Details and the brake shoes are from the Annie. The clevis next to the cylinder is part of the reversing mechanism.

Here’s another view without the break shoes.


Continuing with the chassis/frame modifications, here’s where it stood so far.


To finish up with the chassis for now, here’s a photo of the pilot with the Ozark Miniatures Link & Pin coupler and tow bar installed. The tow bar was fabricated from a piece of thick solder. I also wrapped the bottom of the pilot with brass strip.


This photo shows the pilot attached to the pilot deck. The rock guards are made from heavy copper wire. It took quite a while to gets the bends just right. 0-80 and 00-90 bolts were used to attach the guards.


Enough for now. I’ll continue with work on the boiler.


Looking forward to watching this build progress, Doc. Very fine craftsmanship so far :grinning:

Beautiful work, Doc!

So glad you’re showing us how you did it, Doc. A true masterpiece.

Thanks guys - much appreciated.

Beautiful Build Doc. Moguls of this era are my thing. I think I am going to run for Dictator of our country and require all locomotives in the USA be wood burning Moguls.

Forgive me if I am wrong but I thought you abandon Large scale for On30 Micro layouts? Was that just a hiatus or did I miss something. I am not complaining. I can’ wait tp see what you start banging out in Large Scale. I loved the little On30 scenes and it is a big reason I decided to do On30 indoors, You were doing so much with so little.

Thanks Devon. I was on a posting hiatus. Never stopped building and didn’t abandoned large scale for 0 scale. Too late to go small with my old man’s eyes.

I believe there is confusion between you Doc Watson and, Doc Tom who was doing the island sugar cane rr and then the shelf rr both in On3

Yep got my Docs cofused.confused.

Here all this time I thought it was the same guy. Both of you do great work. And this build is brilliant. Just my sort of thing.

Love the giant Ballon stack. I think even diesels should be required to have big balloon stacks

Before I leave the chassis discussion, I want to show a picture of the deck near completion. I covered the deck with 1/16" basswood strips and stained them.

Getting back to the boiler now. As I mentioned, the boiler is made from a single piece of PVC tubing. By adding a styrene wrap, I was able to achieve a scale diameter boiler of 50”. Since there was quite a number of rivets involved, and to make life easier, I decided to construct the wrap separately. After cutting the styrene to fit, I took a straight edge and marked the positions of two rows of rivets. Then I predrilled the holes for the rivets and inserted Tichy plastic rivets (0.040). I then ran a bead of thin CA along each row and when it dried, I turned the sheet over and trimmed the rivet stems. To attach the wrap I started on the bottom of the boiler and glued the wrap along the edge and after that dried, I
slowly worked my way around the boiler a couple inches at a time clamping as in went. The wrap is tapered at the rear because the bottom of the boiler was cut out at the back to allow it to slip over the rear of the chassis.

Here’s a view of the wrapper installed. Not sure what you call it but you can see that the boiler yoke/cradle has an added styrene strip with NBW castings. This strip was glued to the boiler instead of the yoke to ensure a snug fit to the boiler. The rivets around the front of the smokebox are 0.080 Tichy plastic rivets.


Since the Accucraft smokestack wasn’t correct, I had to make a new one. I managed to dig up the original Patent drawings for a Congdon stack. From that design, I made scale drawings in the actual size I needed for 1:20.3.

I didn’t feel like scratch building a stack so I contacted my son, who is a professional computer graphics person who just happens to be quite good at 3D printing. He took my drawings and printed a stack for me. How lucky can one be? Here’s the stack as it came off the printer.

The stack was printed in three pieces. Here’s the screen a very nice clean print. (He sure is talented)

The Screen with the cap and styrene strips added:

The completed and painted stack:


In addition, I had him print a new lamp and support bracket from my drawings. I designed the lamp opening so that it would accept a Bachmann lens assembly.


Beautiful work Doc. Thanks for taking the time to post it.


Doc, I am certainly enjoying following this journey. You are doing fine work. And yes, I agree, your son is very talented. I was wondering if 3D printing was going to play a roll in this build. Looking forward to the next episode :smiley:

Thanks Dan and Jon. My son has many talents. He’s self employed and his biggest client is the NFL. He does the graphics for all the teams’ helmets and Super Bowl Trophies. Wait till you see the tender coming up.


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Doc, Excellent as always. almost as good in these pics as it is when close up and personal with it. Fantastic stack :sunglasses:

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Wonderful work! I’m surprised that ANYONE has the patience to do rivets that way, but they sure look good! :yum:

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Now THAT’s a backhead!!

Amazing rivet work and other details, love it.

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Holy carp, that’s some great work! Really fascinating project too. Makes me want to do something like that “one of these days”. My “someday” project list just got a little longer!

Thanks Ray. Compliments coming from you mean a lot.


Hats off to your son. Now that I am getting deep into CAD and 3D printing, I can appreciate the work it took to design that stack. The rivet work looks great and he did something I have yet to try which is making an over lapping mesh (by that I mean each wire is weaved over then under the next). I have no clue how one does that. Then he bent it which is another thing I haven’t learned yet is to make more organic shape. So beautiful work on the designs and prints.

Aside for the print work the back head is a work of art. And the wood will be gorgeous. I still think nothing mimics wood better than wood. Yes the grain size is not prototypical or even present in stuff like Bass wood and Balsa wood but those woods (or veneers) still take stain and paint. Paint sits on top of plastic and it looks like it is sitting on top of plastic. But would also absorbs paint and especially stain and it looks so much better.

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My son’s talents aren’t limited to the computer or 3D printing. Here’s what he built a few years back.

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