Early c20 coach underframes

[The Fatadder]

I am in the process of finishing off a kit build of a Concertina brake third, however I need a bit of advice on the underframe trusses.

 

Looking at photos of Concertina coaches from what I can make out there  appear to be two designs of truss in use, on which has a flat bar truss which rotates through 90degrees part way along the angled section of the truss.  (I think I am right in saying this is the type of underframe on the Dreadnought at Didcot.

 

However looking at the 3 D43 brake thirds shown in Russell the underframe trusses look to be of a consistent profile, in particular is the profile round or rectangular.  I think i am right in saying that some of the toplights had a round profile bar for the trusses, so I am assuming that the concertina would be the same.  However before I start soldering metal onto my chassis, I would like to confirm

 

Thanks 

R

[The Great Bear]

Does this topic help in any way, Rich?

 

I think the underframes with round bars were a later development. The one with flat bars horizontal between the queen posts, twisting to vertical as you mention (and as per phtoto in this topic) are appropriate for the early toplights and I think also Dreadnoughts and Concertinas? But I am no gwr coach expert!

[The Fatadder]

Very interesting, I had never quite understood what the Bars 1 / Bars 2 / Multi bar was referring to with toplights, now I do...   Its a shame most of K14s photos seem to have vanished

 

However I am still a little unsure when it comes to the concertinas, certainly they were built with the 4 bar truss / queen post with twist in the truss.  but of the 3 photos of the D43 I have looked at in Russell I would say none of them have that distinct twist in the truss rod.  So by that logic it would have to be a bar truss, so model with 0.45mm wire?

 

I have attached a cropped image from Russell Vo2 

Edited January 21, 2022 by The Fatadder

[Siberian Snooper]

They look like flat bar, as there appears to be nuts on the bottom of the queen posts, but how they are attached to the underframe is a mystery, without the twist.

 

 

 

[Penrhos1920]

Here's a picture of a D43 with flat bar truss.  The twists must be right tight to the solebars and not in the middle.

 

 

Part of REAL photo 334.

 

I have another photo of a D43 with a E80/81 next to it.  Both have flat bars and invisible twists.

[The Fatadder]

Thanks for the responses, really helpful on the most confusing of coach underframes.  I think I have some suitable scrap fret to use to make the new trusses, so will have a crack at it this evening and see how I get on.  (Followed by a first trial fit of my 3d printed underframe details)