Cooke domes

[Mike McKenzie]

Doing some 3d Cooke mogul and connie domes in S for Jim Courtney.













Just thought I'd get some feedback from the crew. The rolled-over collar at the top of the steam dome needs it's walls thickened a touch to pass the pre-flight at Shapeways. These are the mogul domes (though I think they're the same size as the connie domes) and are an appropriate fit for an Overland boiler diameter. Jim wants the connie domes to fit a RailMaster boiler.

Thoughts?

Mike McKenzie

[Mike McKenzie]

Hmmm, formatting could have been better...

Mike

[Keith Hayes]

Nice.

Is the inside of the steam dome hollow?

[Mike McKenzie]

Hey Keith, the domes are solid. There's only about .08" from the top of the 'collar' to the top of the solid interior, hopefully enough of a platform for any appropriate fixtures. The bottom has a centered 'divot' for attaching with a screw to the boiler.

These are Sn3, not for sale yet as I still need to tweak the steam dome so it will pass Shapeways' print-ability QC. I'll probably not put a mark-up on them, Frosted Ultra Detail will cost about 18.00 (sand and steam pair, 9.00 a dome), Extreme Detail will run 27.00. I haven't ordered anything in the Extreme Detail material, so not sure how much finer the finish will be. Not sure if those prices are acceptable for essentially plastic domes, that's out of my control, and I wouldn't use a cheaper material.

Mike

[Mike Trent]

Looks interesting, Mike.

Are these going to be used on a Mogul or a Consolidation?

The domes on a Cooke Mogul are a much different height than the domes on a UP rebuilt Brooks Mogul. I can show pictures of two (On3) 1900 era 2-6-0's side by side which show the differences in the two locomotives. Over the years, much has been said about the old Balboa Cooke models having been way off, but I don't agree at all. I think both the Balboa Cooke models and the PFM Brooks models are quite accurate to the locomotives they represent. The Brooks rebuilds have noticeably higher domes and cabs, as though they were to more closely match the Cooke engines.

The Cooke Consolidations may not have been built with that higher boiler that the Moguls had.  

[Mike McKenzie]

Hey Mike,

These domes are for the Cooke mogul.

These 3d models were based on both Cooke mogul and consolidation drawings provided to me by Jim Courtney. I scaled the drawing images to 1:64 using known dimensions like axle to axle centers, imported them to CorelDraw and set the page scale to 1:64. That way I could 'trace' the drawing images (magenta lines in the image) and establish real world dimensions that made sense to me, rounding up or down to the nearest fraction (30" instead of 29.893" for example). Then I used those dimensions to build the 3d models at 1:1 size.



Comparing the mogul to the connie, it looks to my eye that the respective domes are the same size. Given that I don't have precise prototype dimensions and that the drawings were done years ago with pen and ink for a model magazine, I think they turned out pretty close. The 'collar' on the top of the steam dome did not pass the preflight at the 3d printer due to thin walls, but I can fudge that so you can't really tell.

Jim wanted the mogul domes to fit a Overland boiler and the connie domes to fit a RailMaster boiler. I'll use the bulk of the mogul domes to finish the consolidation domes with a few minor tweaks to account for the boiler diameter, etc.

Mike McKenzie

[Jim Courtney]

To be precise, the specifications that I forwarded to Mike for the original Cooke 2-6-0 domes included a bottom saddle diameter to fit the Overland first run C&S #21 (OMI-1654), boiler diameter of the model = 0.842 inches = 54.5 scale inches.

The rebuilt Brooks engines #21 and #22 had a rebuilt driver wheel base very close to the original Cooke 2-6-0s of 1884.  The driver wheel base of the first run Overland #22 was incorrect for the rebuilt Brooks engines, in that they were equally spaced (matching the equal driver spacing of rebuilt Cooke 2-6-0 #9, that was imported at the same time as the first run Overland  #22, in the early 1980s).

I have asked Mike to draw and print matching Cooke domes for the 2-8-0s, using a bottom saddle to represent the Cooke 2-8-0 as modeled on the Railmaster C-16 boiler = 0.802 inches = 52 scale inches.  I have been collecting and fabricating parts for these two conversion projects for years, and printed domes will come close to allowing actual construction. The wealth of new brass castings from The Leadville Shops, appropriate for these conversions, has also spurred on interest in completing these 2 projects.

The drawings I supplied Mike included Cooke 2-6-0 drawings from a past issue of Model Railroader, and an erection drawing of the Cooke 2-8-0 from Farrell's book.

I think the domes that Mike has come up with look perfect, exactly what I was looking for.  The use of 3-D printing opens incredible new possibilities to create parts that were never cast in brass, such as headlights, domes, stake pockets for coal cars and passenger car roofs (especially C&S baggage, RPO and combines).

[Mike Trent]

Good luck, it will be an interesting project. Keep us posted!

In the enclosed photo, On3 the still unfinished #22 sits beside #7. You can see that the unreboilered Cooke #7's boiler sits higher off the frame on that elevated Cooke saddle than the UP rebuilt #22. Folio sheets confirm this. The UP rebuilt #12, #13, #21 and #22 are all lowered and appear chunkier. with their new boilers and cabs.

I hope to have #22 ready for transport to Rob Smith next month. I'll post more photos then. #7 is an extensively reworked Balboa Cooke DSP&P Mogul, #22 began life as an old PFM #22. There are photos of #7 posted on this site, just search the topics if interested..

 

[Jim Courtney]

Mike,

Glad to see that you are not a brass purist!

For years I pondered how to find or fabricate brass castings/parts to complete these projects, perseverating on how I would develop the necessary soldering skills that Derrell Poole has mastered so beautifully.  It finally occurred to me that multimedia construction might be the only way to complete these projects in my lifetime.

Jim

[Mike Trent]

Thanks Jim.

I have nothing but admiration for those who have the skill and tools for all brass construction. But I possess neither, and have found a lot of satisfaction in building some pretty nice projects over the years using whatever worked at the time. This sort of thing is now quite common among our G Scale brethren including David Christian Fletcher.

They are more delicate than all brass, no doubt, but after over 30 years, they have held up astonishingly well, some under some fairly stressful situations along the way. A friend once noted, if adhesives can be used in aircraft construction, they ought to be able to handle a 1/4" model.  

[Jeff Ramsey]

Way cool models Mike! Could you imagine this time period in 1:1 scale replication?

[Robert Stears]

Nice work. Is that part of a coal ramp in the back ground?

Sent from my iPhone

On Aug 13, 2015, at 10:36 AM, Mike Trent [via C&Sn3 Discussion Forum] <[hidden email]> wrote:

Good luck, it will be an interesting project. Keep us posted!

In the enclosed photo, On3 the still unfinished #22 sits beside #7. You can see that the unreboilered Cooke #7's boiler sits higher off the frame on that elevated Cooke saddle than the UP rebuilt #22. Folio sheets confirm this. The UP rebuilt #12, #13, #21 and #22 are all lowered and appear chunkier. with their new boilers and cabs.

I hope to have #22 ready for transport to Rob Smith next month. I'll post more photos then. #7 is an extensively reworked Balboa Cooke DSP&P Mogul, #22 began life as an old PFM #22. There are photos of #7 posted on this site, just search the topics if interested..

 

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