Thursday, 12 July 2018

Lineside Poles (2)

My initial effort was to try out ideas before settling on a design.   It also had an unexpected bonus, being some NSW prototype information.  Thanks to Bob Stack (SCR Blog), who not only provided me with a number of documents, he also mentioned that Ray Pilgrim (Bylong Blog) has already authored a number of Blog posts on lineside poles a few years ago.    My method differs from Ray’s, but it is good to see alternate approaches to the same topic

Down Block Signal near Shepherds Siding. 
Closeup of the lineside poles.  I am not sure how many of the wires are in use (if any)

Comparing the RIX crossarms with NSW prototype
In short, the RIX crossarms are a scale 10 feet long, vs the NSW cross-arm of 8 feet 3 inches.  Modification to get the right length is easy – take off almost 3.5 mm from both ends.  However, there are some other dimension differences that are harder to fix.  The cross-section of the timber of the RIX crossarm is about 3” x 5”, where the NSWGR cross section is 3” square.  And the spacing between  the 4 insulators on each side of the RIX cross-arm is a constant  10”, 10”, 10”;  where NSWGR has pairs staggered,  9”, 18”, and 9”.

I was then contemplating  repositioning 6 out of the 8 insulators on each crossarm to make space for the combiner strap, but the thought of this on 700 crossarms is not that pleasant, particularly as my one attempt to do this was fiddly, frustrating, and the insulators didn’t dry “square”.  But will the combiner  look OK fitted between the current RIX insulator spacing? 

There is also another measurement to consider, and that is the spacing between crossarms down the pole.  NSWGR prototype is 14”, and 28”, (scale measurement approx 4mm and 8mm), but because the RIX crossarms are beefier than scale, 4mm was visually too close.  So I chose 5 mm

The final piece of the puzzle was to find a picture of a pole with 5 crossarms.  The 1970 era Bomen had widely spaced crossarms on each post, although I haven’t a good closup to see how the bracing was done.  However  Shepherds Siding, which is just in the area being modelled still has poles with 5 cross arms, and a closer crossarm spacing.  So this is the style for the next experiment.

Construction is similar to the earlier method, although the combiner between the crossarms is finer,  now 0.010 x 0.020 thou styrene strip, and the brace at the bottom is physically not attached to the pole.

The thickness of the RIX crossarms is very obvious when one compares it with the fine lines of the prototype's 3" square arms.  And the extra 1mm spacing between arms throws out the proportions even more.   The finer 0.010 x 0.020 thou styrene combiner, and bracing is not too far off scale, although the insulator spacing makes this awkward, and prevents using a "stepped" approach.  The rail is code 70 microscale engineering:  8 posts can be cut out of each 910mm length of rail. 

Summary.  Looks OK, but doesn’t quite capture the feel of the prototype.   But short of fully scratch building each pole, I don’t think that level of effort is justified, particularly as I anticipate needing around 100 poles each with 5 crossarms for the mainline track, and the same number with only 2 crossarms for the branchline

So, it will be a compromise between prototype fidelity, and practicality.  One of the suggestions made is to glue a styrene block into the rail web, similar to the adapter NSWGR used, and so avoid having to drill holes for the crossarm bolts.  This would save a lot of construction time.  Or I could just glue the cross arms to the flatbottom of the rail, as Ray has done.    I am sure that I could continue with the experiment, but for now,  time is better spent elsewhere.  In the end, whilst not perfect, I have a reasonable representation of the NSWGR lineside poles in use around 1970

Lineside post opposite the signal picture at the front of this blog post.   There is much detail here, and wiring from the poles combined and brought down the post to a junction box.  But are any of these wires in use now?  The upper crossarm wires have been simply cut, with no upper wires seen going to the junction box below.  The other things to observe, is the way the wire bracing is attached to the post, and the arrangement of the double insulators in use for some of the wires   


I’ll get back to a real building for my next blog post.  Stay warm.

1 comment:

  1. Nicely done Rob, yes I took the easy way out, life is too short.

    Ray P