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Author Topic: GWR 4-4-2 North Star and subsequent 4-6-0 Star Class design and build  (Read 583 times)

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Offline Snowwolflair

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Following on from my Nelson Bear and U1 models I have decided to turn my attention back to the GWR.

The predecessor of the Castles and Kings were the Star Class which in itself themselves were developed from the North Star the Churchward interpretation of similar French "Atlantic" class locomotives.

Approaching the models from the CAD point of view the Star Class were 85% of the design of the North Star, the main differences being the front of the running plate and below.  The Farish Castle chassis also looks to be suitable and in 1:1 scale they were basically identical.









Offline Railwaygun

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the elliptical wheels will make it a great runner!
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Offline Doc Pye

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An interesting project! If you do go ahead please don't put it up on Shapeways, as they have priced themselves out of the game, at least for me, especially when you tag on their overpriced shipping.

Offline Snowwolflair

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I list on Shapeways for "strangers" or where there are parts that I cannot print, like brass or when the shape is too complicated for my resin printer.

The models do sell well and the process is completely hassle free.

For friends and my club members I print the parts I can on my own printer at cost.  @Hailsone has already reserved a Star  :D
« Last Edit: June 26, 2020, 09:31:03 AM by Snowwolflair »

Offline longbow

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Are you making the 4-6-0, the 4-4-2 version, or both?

As I'm sure you know, the backstory is that North Star was initially built as a 4-4-2 to allow evaluation against the De Glehn compound Atlantics. Churchward decided that 4-cylinder simple engines were the way to go, and the rest is history. And only a few years earlier the GWR's were still building outside framed 4-4-0s for express duties.

Offline Snowwolflair

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Are you making the 4-6-0, the 4-4-2 version, or both?

As I'm sure you know, the backstory is that North Star was initially built as a 4-4-2 to allow evaluation against the De Glehn compound Atlantics. Churchward decided that 4-cylinder simple engines were the way to go, and the rest is history. And only a few years earlier the GWR's were still building outside framed 4-4-0s for express duties.

I am going to do the CAD for both in one file.  The parts that are different I can create as two component sets and switch them on and off in the CAD.  I also plan to build both as final models.

Offline Doc Pye

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Quote
@Hailsone has already reserved a Saint 

I must have missed that....more info please :)

Offline Snowwolflair

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First steps for the CAD

The basic shape of the boiler and firebox.



The modified shape of the Farish Castle chassis is in blue



And this is what needs cut off the Farish Castle chassis to fit and not require the firebox shape to be compromised.  I will need to dismantle the chassis and mill this metal off.




Offline Snowwolflair

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Once I took the chassis apart I was able to judge the final cut which has involved the removal of the top parts of the casting that secure the motor.  This actually gives me some needed extra space with the downside that the motor will be glued in place.




The test print fits perfectly which means that I can proceed with the rest of the design without having to compromise the shape of the firebox.



The chassis will now get a thorough clean and a coat of paint.

NB the firebox is deeper than it will end up as the running plates for the Star class and the North Star were at different heights, and this will be trimmed when they are drafted.

Offline Snowwolflair

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The CAD is progressing with split versions for North Star and the Star class.  I am waiting the arrival of the second Castle mechanism which I will modify for North Star before I go much further.






Offline Snowwolflair

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Re: GWR 4-4-2 North Star and subsequent 4-6-0 Star Class design and build
« Reply #10 on: July 07, 2020, 01:53:08 PM »
I am looking for some help on what colour to paint North Star.  The photo at the top of this post above appears to show her in green and black, and the following photo and hand coloured drawing appear to show her in green and bauxite.  I believe both are probably correct but I have no idea when the change happened.

I need to decide soon what colour to paint the chassis before I assemble it.





Online chrism

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Re: GWR 4-4-2 North Star and subsequent 4-6-0 Star Class design and build
« Reply #11 on: July 07, 2020, 02:37:48 PM »
I am looking for some help on what colour to paint North Star.  The photo at the top of this post above appears to show her in green and black, and the following photo and hand coloured drawing appear to show her in green and bauxite.  I believe both are probably correct but I have no idea when the change happened.

According to a plate in Jim Russell's "A Pictorial Record of Great Western Engines", which he describes as being reduced from a diagram at Swindon Paint Shop in 1954, they changed the livery from Indian Red to Black for the outside of the frames and for the wheels in 1906, the same year as North Star was built.

I would guess, therefore, that it is perfectly feasible that she was in green/red when first built and changed to green/black next time she was deemed in need of repainting - whether that would have been because she actually needed a repaint or because it was decided to bring her up to the latest livery I wouldn't like to guess.

The green in both periods was the standard GWR Middle Chrome Green.
« Last Edit: July 07, 2020, 02:42:27 PM by chrism »

Offline Snowwolflair

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Re: GWR 4-4-2 North Star and subsequent 4-6-0 Star Class design and build
« Reply #12 on: July 07, 2020, 02:48:15 PM »
That's great, it explains why all the Indian Red photos are posed where as all the running photos are green/black.  I can safely paint her green and black.

Offline Snowwolflair

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Re: GWR 4-4-2 North Star and subsequent 4-6-0 Star Class design and build
« Reply #13 on: July 07, 2020, 08:23:35 PM »
Here are the two versions of the chassis. 

The North Star has an 8mm rear wheel mounted in a 3D printed part that fits snugly into the bearing box opening on the chassis.  The result is a simple but effective conversion and you can see the required part in the picture. 

This was the last technical hurdle and I can now get on with the CAD.




Online Andy-S

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Re: GWR 4-4-2 North Star and subsequent 4-6-0 Star Class design and build
« Reply #14 on: July 07, 2020, 08:32:45 PM »
Following this one with real interest and admiring your work, wish I could do the same, they both would fit in really well with my fleet.

 

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