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GWR Posting Carriage – Part 3


MikeOxon

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In this post, I turn to the design of a chassis for my model Posting Coach. Fortunately, there is a detailed contemporary description and illustration, given in Whishaw’s book ‘The Railways of Great Britain and Ireland’, published in 1842.

 

According to Whishaw: “The under carriage is formed of two soles, 7 feet 8 inches apart, 9 inches deep, and 4 inches thick, and projects 10 inches at each end beyond the body ; and six cross pieces, one at each end without the line of the body, which are 15 inches deep and 4 inches wide; and the others arranged one before and the other behind each pair of wheels, and equidistant from the centres of axles. The two ends of each of these cross pieces are finished with ornamented scrolls, and project six inches beyond the outer side of each sole. The diagonal braces, which are of 1½-inch iron, run from each angle of the carriage towards the centre of frame-; the carriage is furnished with complete buffing and traction-apparatus (see Plate XI.), and is mounted on four of Losh's wheels, 4 feet in diameter, and 10 feet from centre to centre of axles. The bow-springs are each 5 feet 4 inches in extreme length, the bed of each being 6 inches below the centre line of wheels.”

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Perhaps someone can enlighten me regarding the curious circular structures forming part of the draw gear?  I assume it is a shock-absorbing system.

 

Rather than making my own drawing, I decided to import the Whishaw drawing into ‘Fusion 360’ as a ‘canvas’, on which I could build up the frames as shown below:

 

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Building the Frame over a ‘canvas’ in 'Fusion 360'

 

I built the chassis ‘upside’ down and provided a thin floor, to ensure overall rigidity and to provided a firm mounting plate onto which the body can be fixed.  I created the undergear, axleguards, springs, etc. by using exactly the same methods that I described in a previous post about my early cattle wagons.  I did not print the headstocks at the same time, since these rise above the level of the floor and would not have allowed me to print from a level base. Instead, I drew these as separate ‘bodies’ in ‘Fusion 360’, aligned with the solebars.

 

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3D model of Chassis in ‘Fusion 360’

 

I decided to take a risk by omitting any support structures in the openings above the springs, because I find it all too easy to damage fragile parts when trying to remove supports. In fact, the test print came out remarkably well and needed no significant cleaning-up before use. The following photo shows the model mounted on its wheels but, otherwise, exactly as it appeared immediately after removal from the printer bed, with no ‘cleaning-up’:

 

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Chassis with wheels fitted

 

Once I had printed all the component parts, I could assemble them into my complete model of the Posting Carriage. I printed the headstocks separately and slid these into position over the ends of the protruding solebars, as shown below:

 

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Model carriage as printed

 

This is my model exactly as it came off the printer. The remaining tasks are largely ‘painting and decorating’ :)

 

It is really surprising to see how small a ‘luxury carriage’ of 1838 actually was!  It is hardly surprising that Brunel’s idea of placing the wheels outside the body was swiftly abandoned. Unfortunately, this decision meant that very little space was left around the tracks, so Broad Gauge stock was never able to expand much beyond the confines of the British standard loading gauge.

 

Within a few years, railway vehicles started to outgrow their ‘road coach’ forbears and even the primitive 3rd-class carriage of 1844 was considerable larger than this small vehicle! I have placed my two models together to illustrate the comparison.

 

 

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Posting Carriage model compared with closed 3rd-class Carriage of 1844

 

Mike

Edited by MikeOxon
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Very interesting build. 

 

I am puzzled by the two sets of wishbone shaped structures too. The use of a a pair of lateral springs for buffers and drawbar I am familiar with, but those appear to be extra . Maybe the lateral springs were only used for the buffers and the wishbone device was just for the drawbars ? 

All a bit of a guess really . 

 

First prints look good. 

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Very impressed by how quickly this has come about. I like how you are applying 3D printing to a period that we normally associate with complex scratch-building efforts.

 

I know your interests lie in the design and printing challenge, but that coach would look superb with a lick of paint and some of Andrew's passengers.

 

But where did the luggage go? Next project?

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3 hours ago, Mikkel said:

But where did the luggage go? Next project?

I was wondering what to make next and now, Mikkel, you have provided the answer :) 

 

There were some curious luggage trucks with sloping sides that would present an interesting challenge.  One appears in the same Bourne lithograph of Bath Station, in which the Posting Carriage also appears.  Note also what seem to be (tall) Horse Boxes distributed along the train.

 

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Extract from lithograph by J.C. Bourne

 

You are correct that I enjoy 'the thrill of the chase' but am not so keen on the 'kill'.  I seem to be driven inexorably back in time, so perhaps I need a 'North Star' to pull these early vehicles. 

 

My trouble is that currently I have no idea what to do with all these strange vehicles I'm creating.

 

Mike

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2 hours ago, MikeOxon said:

 

My trouble is that currently I have no idea what to do with all these strange vehicles I'm creating.

 

We want a layout!  We want a layout! We need more broad gauge layouts!!!!

 

Seriously, it doesn’t have to be big or complex, it could be so thing more than a souped up scenic test track - what ever you fancy... 

 

Duncan

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2 hours ago, drduncan said:

We want a layout!  We want a layout! We need more broad gauge layouts!!!!

I started this whole BG blog with a plan to make a diorama of the site of the Bullo Pill accident.   All these developments in 3D printing distracted me from that idea and I'm now building models from an earlier period.  I have to wait for inspiration to strike :)

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That luggage truck is an extraordinary creature! It will be perfect with the carriage.

 

19 hours ago, MikeOxon said:

My trouble is that currently I have no idea what to do with all these strange vehicles I'm creating.

 

From a reader's perspective, you have already provided much of interest. Then there's a full finished train, which would be an achievement in itself. And surely such a train would be of interest for the BG society magazine, with or without 3D printing details?

 

As for layouts, if that is a possibility, perhaps some inspiration in BG John's thread:

 

 

But of course, it's always easy to have lots of ideas on other people's behalf :)

 

Edited by Mikkel
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Excellent work, and as others have said, quick too! Well done.

I fully appreciate what you mean about the process rather than the finishing. I have a number of items of rolling stock waiting patiently for me to paint them. I really enjoyed creating them but finishing the painting and getting them on the layout? Well, that’s where I struggle, it’s much more exciting to move on to the next build.

Very much looking forward to the luggage box. Am I right in thinking there were a couple of different sizes?

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What's all this? - no pressure then!

 

2 hours ago, 5&9Models said:

....... as others have said, quick too!

The speed has a lot to do with lockdown, plus the ease of correcting mistakes on a computer. 

 

It took me about a day of armchair modelling to create the main outlines of the carriage and then almost another day to add various details.  The actual printing takes place while I'm having tea.

 

Somehow, my first test print came out a bit short.  That would have been a major crisis in 'real' modelling but just a few moments with the push-pull tool on the computer!

 

I saved a lot of time with the chassis by simply erecting the joists over a copy of the Whishaw drawing and checking the overall dimensions.  None of that careful measuring and re-measuring ... and then finding it's still wrong :)

 

There were (at least) two sizes of luggage boxes - and they really were 'boxes' built onto the frames of open carriage trucks.  Lots of 'twiddly bits' that, thankfully, only need to be drawn once and replicated with cut and paste commands.  Compare that with hours of shaping with files, etc.

 

Mike

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