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« Sweet Railroad Music | Main | Pulling loaded gons from Sims »
Wednesday
Mar112009

Spacing for Railroad Ties

Railroad tracks are not all equal in appearance. Variation in track appearance comes from a handful of distinctive track characteristics that identify it as main, branch or siding track.  Modelers can exploit this fact to drive realism on model tracks.

Model railroads are inevitably crammed into less than adequate layout spaces that are often a lot smaller than the scaled down size of the original, so we cannot simply rely on long stretches of tangent to clearly differentiate between main and secondary tracks.

Fortunately, we don’t need to. The most noticeable differences in the appearance of the different types of track come from the ballast quality, the size of the rail and the spacing of the ties. To a lesser degree, the type of tie matters on main track - either wood or concrete.  This post will focus on tie spacing and how secondary track differs from main in appearance.

BNSF Mojave Desert main tracks at Fenner CA, September 2007

Differences in ballast, rail and tie spacing on main, branch and siding track reflect the differing physical demands on each of these track types.  Main track typically carries the most traffic and usually at higher speeds. Branch lines, or leads as they are also known, are generally rated at lower speeds and usually carry less traffic than a main line depending on the industries served by the lead. Sidings and spurs are usually rated at lowest speeds, particularly spurs which are usually rated at 10mph or lower.

Railroads match investment in the different types of track to the value they bring to the company. Limited spending makes sense on lighter, less travelled tracks where extra spending on engineering is unlikely to deliver additional return to the bottom line. Railroads save money through less roadbed grading, cheaper drainage solutions, cheaper ballast and less of it, lighter rail and less frequent maintenance.

Siding Hercules CA June 2007

As main track typically supports higher traffic volume than secondary track, main track is usually constructed to higher and heavier standards. Grading is more precise, ballast is deeper and well groomed, ties are newer and more evenly spaced and have the closest spacing of all track types. Typical tie spacing for main track is usually around 20 inches. Tie spacing is the distance from one edge to the same edge on the next tie.

Slower tracks and those seeing less traffic experience less stress and strain on the rail, ties and roadbed. These tracks can have more ups and downs in the roadbed profile and are usually constructed using lighter rail. Slow speed track generally has fewer ties in a given distance than main track and tie spacings is typically on the order of 21-24” though exceptions exist. 

Oakland Terminal lead, February 2009

Spurs are the lowliest of tracks from a construction standpoint, just a means of getting a railcar from the lead to the loading or unloading point. It is common for tie spacing to be the same or higher than the adjacent main or lead.  Leads and spurs can have short grades of over 3%, with occasional examples of 5-6% in tight quarters to reach a shipper or customer.

Richmond Pacific Tie Spacing

I thought it would be interesting to find out what the actual tie spacing is for the Richmond Pacific.  Here is the data I gathered from representative locations in the local area. (All tracks measured were adjacent to road crossings to ensure measurements were taken safely near the sidewalk or edge of the road. Always take care around railroad tracks and stay alert.)

All spacing measurements are from the edge of one tie to the same edge on the next tie.

Not unexpectedly, most of the average readings are around 21-22”. The exceptions are track 704, a siding track at Safeway Yard, and the new lead track on the east end of Seaver Yard where the track crosses Marina Way South. Both were close to 19 inches which is a little surprising as that is more ties per mile than main track. This goes to emphasize that the “rules” of tie spacing are not always rigidly applied.

New RPRC track 800 near Seaver Yard January 2008The other thing that is interesting, is that in many places, ties spacing was not highly uniform. Some were measured as close as 16 inches spacing and others were wide as 25 inches. Some ties were visibly skewed a few inches from perpendicular to the rail but most are reasonably square with the line of the track.

Modeling Options for the Different Tie Spacings

Atlas code 55 has eight ties per inch which translates to 20 inch tie spacing. So Atlas is good for modeling main tracks. To model siding or lead tracks with Atlas c55, the spaces between the ties can be cut to move ties a little further apart and to introduce a little variation in position.

Peco code 55 comes in at a dismal 5.5 ties per inch which corresponds to 29 inch tie spacing! Peco code 55 has shorter ties than seen on US railroads so out of the box, it produces a reasonable representation of 19th century logging tracks. It is hard to make Peco track look like modern US mainlines as a result.

Hand laying offers the greatest flexibility in achieving a particular tie spacing. For lazy and/or time-challenged handlayers (that’s me!), Fast Tracks offers tie jigs in several tie spacings for $15 each:

  • Main = 20”
  • Branchline = 22”
  • Siding = 24”

The Branchline jig looks like it will be the best match for recreating the local RPRC tracks in N scale.  Spacing variations are introduced after the strip of ties is placed on the roadbed.

So there are a couple of good options for varying the tie spacing of the different types of track in N scale to emphasize the type of track and the kind of use each track supports.

- Coxy

 

 

Reader Comments (4)

Interesting analysis, Steve.

BNSF also uses different type of ballast for mainline, branchline and siding. BNSF mainline ballast is more pinkish (feldspar I was told) compared to the light gray used by UP.

March 11, 2009 | Unregistered CommenterJimmy Low

I am surprised you did not even mention tie spacing on bridges.

That was what I was looking for. Alas, woe is me.

Good article, though.

Serge, There's only one tiny bridge locally. It's on the Siberia lead near Sims Metals. For the most part though, it's all regular track around here.

Sorry, Coxy

August 3, 2009 | Registered CommenterSteve Cox

We have three timber bridges we are rehabing and the existing tie spacing is approximately 12.25" on the railroad bridges.

May 28, 2010 | Unregistered CommenterBeau

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