Wednesday, 19 April 2017

BRODIE BRIDGE MILEAGE 65.2 / 65.0 - Part 2


We continue our study of the One Hundred Foot Through Plate Girder Span that is still in place at the former Kettle Valley Station of Brodie.  In the last post we looked at the standard plans for this type of bridge when built new and on tangent track.  We will examine the specifics of the very similar Brodie bridge which was built to replace an existing wooden Howe Truss Span and was located on a 12 degree curve.  In HO, that is a curve of about 65 1/2" radius and in N scale it would amount to 36".  We hope that this post will be a help to modelers trying to erect their miniature versions of these interesting engineering marvels of the early 20th century.

A photo of the underside of Brodie bridge provides a perspective on how the various members were fitted together.

And herewith is seen the aforementioned divergence from the
standard plan, namely; the floor beams sit on triangular corbels the
effect of which is to lift the bridge deck higher with respect to the main girders than the standard plan shows.  Normally, the floor beams would intersect the main girders at their bottom flange instead of sitting on the triangular corbels.  Looking at the end/section views reproduced here and comparing them to the photo one can see that the top-mounted triangular gussets connecting the main girders to the floor beams are missing from the Brodie bridge being replaced by these underside triangular corbels. The standard plan would give a dimension 6'-0" from the top of the ties to the top of the main girder. At Brodie that dimension is 2'-10" according to our field measurement.  Thus the height of the corbel would be the difference: 3'-2". 

Two other items to note in this and a second photograph are:
  • The position of the struts which are angled rather than square to the stringers.
  • The offset of the Stringers in each section 
These two features are also seen in the plan view below taken from the drawing published in the previous post on Brodie junction.  Note also how the centreline of the curved track is located on the bridge and how it intersects the straight centreline of the bridge.
To summarize the differences between the CPR standard plan and the Brodie plan (and to suggest an explanation), they are:
  1. The height of the rail is higher with respect to the main girders by 3'-2" necessitating triangular corbels to support the Floor Beams.  One could guess that the raise in height is a result of the CPR making use of the existing concrete abutments that fitted the former wooden Howe Truss Span.  These abutments are irregular and show several additions to what would seem the original pour.  They differ significantly from each other as well.
  2. The Stringers are offset and the Struts are angled to the Stringers.  It seems obvious that this is done to more directly support the ties and rails of the 12 degree curve that transits the bridge.
We will briefly note some details.
  • Ties were 10" high x 12" wide x 13'-6" long according to the tie bill in the 1950's.  Field measurements of the current ties revealed they were taller at 10" x 16"!  Current tie ends are square cut.  Ties are "dapped" or notched about three quarters of an inch(?) to fit over the stringers.  Referring to the opening photograph and the first drawing, one can see that there is no gap in the ties where the flood beams are placed.  This is effected by the placement of a shallow 5" x 12" tie over the beam to carry the rail.
  • Rivets are specified as 7/8" in diameter which refers to the shank.  Industrial specs state the head of the rivet would then be about 1 1/2".  Field measurements confirm that they are 1 1/2".  Spacing in general is about 3" to 6" o.c. depending on location.  Towards the middle of the bridge the rivet spacing is generally wider.   Patterns can be seen in the photos.
  • Splice plates joining the web sections of the main girders together are 14" wide filled with rivets spaced at 3" to 4 1/2".  See photo below.
  • Stiffners or L's applied to the Main Girder Web are 3 1/2" x 6" , the smaller leg riveted to the web with rivets spaced at 3" to 4 1/2".  See photo below.  They are oriented with the short leg toward the centre of the bridge.  One is overlaid on each of the splice plates.
  • Gussets atop the floor beams on the inside which join those beams to the girders are riveted to the web of the girder accounting for the short horizontal strip of 12 rivets seen in the photo below.

  •  5 Cover Plates (top & bottom) Lengths are specified on the Elevation Drawing.  Four rows of rivets are spaced unequally, there being a space of 6 3/8" between the inner two rows.  See the photos of the underside for pattern.
  • Bridge Shoes or pedestals.
                                                                 


Merritt or west end.     

Roller pedestals are about 29" x 43" x 13" high









 
 


Brookmere or east end

Fixed Pedestals are about 28" x 36" x 12" high













In the previous post on Brodie, we erred in the date of the issue where a drawing that Patrick Lawson had made of this standard bridge was published in the Mainline Modeler magazine.  A correction has been made there and we repeat here that the issue is that of October 2003.
 
One final thing to note is that there is a noticeable tilt when viewing the bridge and abutments from several angles.  It would make sense that curve elevation would be designed into the Brodie loop at least since the abandonment of the Coquihalla subdivision and possibly before that.

The net effect of the research and organization of the material in this presentation is that Coquihalla Man cannot long postpone the building of a miniature version of this important bridge for the benefit of the trains and crews that work the Kettle Valley Model Railway.  Sigh...

Q

Sunday, 9 April 2017

BRODIE BRIDGE MILEAGE 65.2 / 65.0 - Part 1


On March 19 our post provided a comprehensive look at the junction station of Brodie on the Kettle Valley Division.  A reader has asked about the girder bridge and it happens to be on our list of projects to build for our miniature Brodie junction.  So the following provides additional information, drawings and photographs on this Merritt Subdivision bridge at Brodie, identified as Bridge Mileage 65.2 for our favoured era and later on as Mileage 112.9 of the Princeton Sub.  Our field notes state it was erected by Dominion Bridge Co. and Joe Smuin in Kettle Valley Mileboards states that this happened in 1931/1932 to replace the original wooden Howe Truss Span.  We will deal with the bridge itself in this and the next post but the concrete abutments are complicated and irregular and will not be given much attention here.  In the photo above, note that the abutments are open whereas later views such as the next photo, reveal that concrete has been added to enclose the ends of the bridge.

As must be obvious, this action shot was taken from the running board of one of the last Princeton way freights in March of 1989 on which the author was privileged to ride from Merritt to Princeton and return thanks to Helmut, a now retired CPR dispatcher.  We have here a good view of the ties, the alignment of which is staggered due to the bridge being situated on a 12 degree curve.  That is about 65 1/2" radius in HO and 36" in N scale.







  This view is unavailable today as the rail has been lifted and the ties are covered with two layers of lumber to more safely accommodate the many hikers and cyclists who travel the Cross-Canada Trail much of which traverses the abandoned right-of-way of the late Kettle Valley and Kootenay Divisions of the CPR.  The author has made numerous field trips to the site of the bridge recording various details in photograph and measurement.  Fortunately, we acquired from the CPR engineering department some drawings to supplement the field information and find that the two sources largely corroborate each other.  It is hoped that our study will enable some enterprising modelers to reproduce this interesting piece of engineering or variations thereof.
 
This close-up crop reveals the method in which the CPR painted the designated mileage numbers on the end of steel girder bridges.  It must be noted that this number conflicts a little with other documents that denote the bridge as Mileage 65.0.  After abandonment of the Coquihalla Subdivision in 1961 the Brodie bridge became Mileage112.9 of the Princeton Subdivision but those digits are nowhere evident in any of our photos or entered in our field notes.

From our files we present details from a drawing of a standard CPR One Hundred Foot Through Plate Girder Span.  It differs from our subject bridge in one major particular but that will be easily explained so that the construction details should be useful to modelers in this and other bridge projects.  The drawing will be presented in sections so that the measurements and notes will be legible.  It bears a date of December 26, 1929!  No boxing day holiday for the drafting department that year.  Here is the Title Block with some basic specifications.
The  Elevation and Plan Views with major components labelled in red.


From these two portions of the drawing and others, the specifications of the main structural members are deciphered as follows:
  
2 Main Girders measuring 10'-1 1/4" high x 18" wide x 102"-9" long overall, each built up of 6 sections and 2 short end plates. Each girder composed of:
  • 6 webs 10'-0" high x 3/8" thick x 16'-7 3/4" long
  • 5 Splice plates 14" wide
  • 19+ L's or angles 6" x 3 1/2" (stiffeners)
  • 5 cover plates 5/8" to 1/2" thick top and bottom
  • 2 end plates with web of 1'-4 1/2" wide and L's (stiffeners)
7 Floor Beams @ 44" high x 12 1/2" wide x  17'-11" (approx.) overall built up of
  • web 44" high x 7/16" thick x 12'-11" long connected to the Main Girders by L's
  • splice plates
  • extension plates
  • L's or angles 8" x 6 1/2" & cover plate 13"
12 Stringers @ 33" high x  12" x 16'-7" (approx.)
  • "Carnegie Beam" i e,  a solid "I" beam (not built up)
  • Connected with L's 8" x 8" to Floor Beam
  • Ties rest on these members
12 Struts which were Solid Channels 18" high x 4" wide x 7'-10 1/2" long
  • connected to the Stringers by L's
Lateral Bracing or diagonals were L's 6" x 4" x 3/8"
  • connected to the main girders and floor beams by various shaped Gussets (see plan for shape and size).
We conclude this study of the standard bridge plans with the End and Cross-Section views from the CPR drawings.


The next post will deal with the particulars and details of the actual bridge at Brodie.  For now, the modeler can examine the components with a view to acquiring the necessary materials for constructing a model of this 100 Foot Through Plate Girder Span.  Styrene will be the medium when the project is undertaken by Coquihalla Man.