Crumlin Viaduct

[corneliuslundie]

I have just been rereading the book about the Pontypool Road to Neath line and have for the first time noticed the parapet of the viaduct.

See for example: https://www.google.co.uk/url?sa=i&url=https%3A%2F%2Fwww.flickr.com%2Fphotos%2Ftaffytank%2F32727997865&psig=AOvVaw3WbI5zIpOu0i0_iIGCrYoq&ust=1595439713886000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCLiFkqLy3uoCFQAAAAAdAAAAABAJ

Any idea how it was constructed? Wrought iron I suspect with Kennard's expertise. And why such a complicated design? It looks as though the parapet was assembled from sections of about three "bays" which were produced off-site.

And how would one go about modelling it? It is just as well I have no intention of trying!

Jonathan

[philip-griffiths]

Hello Jonathan. 
 

I am very slowly putting together a model of the Kendon section. Though I wish I had decided to do it flat as working out the geometry of the chords in the curve and the interaction with the abutments has been part of the delay. The other has been how to build it. The first attempt using plastikard failed, so looking at brass section. The pillars are also complicated see https://coflein.gov.uk/en/archive/6295610/details/504. I’m now trying to learn a cad package to produce 3D printed parts for the fixings. 
 

in terms of the parapet.  We’ve discussed those on this forum before.  They are similar to the parapets of Crom Estate bridge in Northern Ireland. The NT has no record Of where they originated. A better view of crumlin’s parapet is here. https://coflein.gov.uk/en/archive/6257418/details/504  To me they look like they are cast. 
 

ive thought about having them etched though I’m told that they could be 3D printed. 
 

regards. 

[andrewnummelin]

Gents,

   I'd also guess at the parapet being cast: if it were built later I'd have guessed at welded wrought iron for the attractive supports with the top rail being cast but welding was not common at the time and there was a foundry on site. I suspect Alistair Warrington might be the person to approach for further details.

 

  For modelling I suspect any approach is going to be quite a challenge. Etching would have to be multi-layer to give the right profile of the supports, 3D resin printing would give a product that would not be as satisfying as a metal unit (and also probable very fragile), and lost wax casting (possibly from a 3D print wax) would be expensive!

 

   Just as much of a challenge would be the railings of the walkway under the main deck - simple tube but very complex posts!

Detail from "A26/B" from the old OPC photo collection.

 

 

I'd not looked closely at the curved part of the viaduct before, but my impression from a bit of the ".../6257418/details/504" image (below)

is that the main support structures are straight (cyan) but that the top is curved (orange). More modelling fun!

 

Must get on and build a new chassis for my NA&HR loco...

 

[philip-griffiths]

Hello Andrew

 

good to hear from you. Yes the trusses are straight. The issues on the Kendon section section is that it is curved, so

 

1. the outer trusses in each span are longer than the inner trusses,

2. The trusses are perpendicular to the stone parapets, but the pillars are angled

 

this means that nearly every Truss is unique...  there are four trusses per span.

 

i was not considering modelling the walkway.... I get the impression it came later but cannot confirm that. 

 

regards.