Churchward era underframe details

[HowardGWR]

I thought I would open this thread as I find the material on this subject (chiefly Harris and Russell) rather difficult to use.  I would hope that if enlightenment ensues, then perhaps Miss_Prism may consider expanding on that very helpful website GWR Modelling.

 

First Bars 1 and Bars 2.  I have tried to discover what is the difference regarding trussing (the bars thus) between them.  Harris describes the subject on page 72.  He merely says the 'positioning' of the trussing differs but does not explain how.   I have scoured the photo material in Russell and elsewhere, as well as used the search facility on this valued RMweb site, etc, but have not managed to turn up anything.

 

Thus the first question is 'what is (are) the difference(s) between the two trussing methods'? 

 

The second error, that also prompted me to open a thread, is on page 250 Fig 435, which Jim describes as 'cantilevered' and 'Bars 2'.  According to my understanding it is Multibar.  I don't think the word 'cantilevered' is appropriate either, but I am no engineer.   Am I right?

 

More where this comes from but that can wait a moment.  Hope someone knows and can kindly respond.  Thanks.

Edited January 13, 2017 by HowardGWR

[K14]

The second error, that also prompted me to open a thread, is on page 250 Fig 435, which Jim describes as 'cantilevered' and 'Bars 2'. According to my understanding it is Multibar. I don't think the word 'cantilevered' is appropriate either, but I am no engineer. Am I right?

I think the correct term is 'Queen Post Truss', with the early versions being adjustable & the later 'Multibar' fixed.

 

First Bars 1 and Bars 2.  I have tried to discover what is the difference regarding trussing (the bars thus) between them.  Harris describes the subject on page 72.  He merely says the 'positioning' of the trussing differs but does not explain how.   I have scoured the photo material in Russell and elsewhere, as well as used the search facility on this valued RMweb site, etc, but have not managed to turn up anything.

 

Thus the first question is 'what is (are) the difference(s) between the two trussing methods'?

We have three Toplights at Didcot (four if you include the Dreadnought), but two of them are ex-WW1 Ambulance rebuilds & that muddies the waters somewhat.

 

Exhibit 'A' - 1159. The published literature will tell you that it's a K.36 from Feb 1925, but little else. As built it was a D.47 on Lot 1195, Oct 1912 & numbered 3556 (stamped in some of the doors, but struck out & re-stamped 1159).  According to Harris that lot was 'Bars 2'; It has two trusses constructed of flat bar that run over two queen posts & held to each by a pair of sizeable nuts - thus it's adjustable to some extent. The queen posts are forged, approx 6' apart & the truss bar is approx 21" below the solebar.

 

Exhibit 'B' - 3655 (chassis only, under H.7 9520). The original 3655 was a C.28 built on Lot 1136 in March 1908, so a 'Bars 1', however it was converted for ambulance use & then "unconverted" in the 20s. Harris lists a 'new' 3655 to C.31 on Lot 1292 (9/21), also stating 'Bars 1'. The trussing is exactly the same pattern as that under 1159/3556, with 6' queen posts & a 1/2" difference in depth to 1159.

 

Ambulance conversions are a minefield, & without seeing the registers I have no idea if original numbers were restored or just reallocated ad-hoc to each rebuild off the line. It's also of note that, according to Harris, Diagram C.28 was built in both Bars 1 and Bars 2 versions. The VCT claim its origin was in a 1912 C.31, which, if correct, would explain a lot.

 

Exhibit 'C' - 3963. Nice & easy this one... built Nov 1919 on Lot 1256 to Diag. C31 & listed as a 'Multibar'. It has conventional fixed angle trussing (inverted, so the flat is on the top) with two angle-iron queen posts & a pair of angle-iron cross braces tying both trusses together.

 

Exhibit 'D' - HMS Dreadful, 3299, built Sept. 1905. Four queen post truss sets. The flat bar is vertical for much of the diagonal section but then has a twist to take it horizontally over the queen posts with another twist  to send it vertical again so that it can be riveted behind the solebar.

 

Swindon & Cricklade have E.83 No. 7545, built Dec. 1907 that should be a Bars 1, but looking at this photo I can't see any difference. Other preserved Bars 1 examples are:—

 

7538 - E.83, L.1138, 12/07 - WSR

2434 - C.30, L.1167, 02/10 - Bodmin & Wenford

2447 - C.31, L.1172, 02/11 - Llynclys

2370 - D..47, L.1180, 08/11 - Bridport

 

If anyone can get a tape measure near any of those, it might clarify matters.

 

There are two other survivors of the Bars 1 era  - 2360 & 7447. The latter has acquired angle trussing at some point & 2360 is the old Whitewash Coach, so quite possibly modified out of all recognition.

 

Pete.

[HowardGWR]

K14

To say I am grateful is an understatement.  There is a lot to assimilate.  Because there were many score 'views' of my posting without reply, until last night and your reply, I put out a duplicate request on the private GWSG Yahoo online discussion group and received  two replies.

 

I will study and then attempt to produce a summary of what I have received.  If I say one of the replies was from John Lewis and the other from Robert Ferris, then I am sure members here will find the results interesting.  

 

Of course let that not prevent or discourage colleagues from making any further comment; indeed they will be welcomed by me.

 

Once again, thank you Pete.

[Coach bogie]

Truss / queen posts on ex 2360 taken in York yard. The balance of the underframe has changed many times.

 

 

Mike Wiltshire

[Coach bogie]

The 4 bar truss/queen posts and the twist as described in k14's post.

Mike Wiltshire

[HowardGWR]

This is what I got from GWSG members John Lewis and Robert Ferris.  Many thanks to them.

 

JL wrote

"The underframes were:

 

1.    Bars truss: Flat steel bar truss rods with round section queen posts, having a screw thread at the bottom of each queen post. Large nuts on the bottom of the queen posts trapped the truss rods and provided a degree of adjustment. See the close up at RC2 Fig 434.

 

2.    Multibar truss. Round section truss roads, duplicated between the queen posts. The queen posts were angle with a casting on the bottom through which the truss rods passed. There was also a rod from each of these castings which passed across the coach. Adjustment was by means of nuts on the ends of the truss roads bearing on the castings. See the close up at RC2 Fig 435.

 

3. Angle truss.The truss rods and the queen posts were made of steel "L" section angle. This truss was non adjustable.

 

Bars 1 coaches were built with bars underframe trusses.e.g. RCA2  Fig 10.

 

Bars 2 coaches  could have either bar truss underframes (eg RCA2 Figs 177 and 182) or multibar underframes (eg RCA2. Fig 312).

 

Steel panelled coaches could have either multibar underframes (See eg RCA2 Figs 323-325) or angle truss (see eg RCA2 Fig329 and later).

 

Note: 70ft coaches had 4 sets of trusses, 57ft ones had two.

 

Quite a lot of the 57ft toplights were sold to the War Department for use in Ambulance trains. When repurchased c.1921 they had to be repaired. This could even include a replacement underframe of the "wrong" type! See RCA2 Fig 58 - originally a Bars 1 type coach."

 

Robert Ferris wrote

"Regarding your second question (whether RC2 Fig 435 is in error, notes Howard) I agree. Fig 435 is the Multibar arrangement - In this case the queen posts were of angle section with castings attached to their lower ends. The horizontal part of the truss comprised two parallel rods, while each sloping part was a single rod. At the queen post the two horizontal rods and a single sloping rod past through the casting. Each rod being threaded at the end and secured with a nut which could be adjusted to change the truss tension. This multibar arrangement also had transverse rods between queen posts to prevent lateral movement of the post."

 

BTW note that John uses the abbreviation RC2 for Russell second book 1903 -1948, and RCA2 for Russell Appendix 2 Vol1, if you wish to examine your own copy, this may help.. 

 

Back with me now.  It seems to me the sobriquets given, AIUI,  by the late Mike Longridge, are insufficiently comprehensive, given that a Bars 2 vehicle could have multibar trussing and other variations.  Oddly enough, one would imagine that the terms "bars" applied to the trussing, whereas it seems they better apply to the panelling, albeit with a meaningless sobriquet for that feature!.  That's before we get into the id problems associated with the restored ambulance vehicles.  I begin to see that an RTR manufacturer could better stay away from the toplights unless he chooses a 1930s era state of a known photographed vehicle (say).

 

Good old GWSG, came up with the trumps.

Edited January 19, 2017 by HowardGWR

[The Great Bear]

The 4 bar truss/queen posts and the twist as described in k14's post.

4 bar truss.jpg

4 bar truss twist.jpg

Mike Wiltshire

 

Was the same detail, the transverse I beam the same for the other truss types as per the post below? I have been playing making some toplights using 3d printing and am now contemplating 70 footers.

 

This information in this thread is very useful in making sense of the underframe details in the photos in Russell.

 

Kind regards

 

Jon