Saturday, April 10, 2021

SP Jawbone Branch (Part 23) - Switch Parts & LMRC Switch Standards

In previous posts on the SP Jawbone Branch, I've said that I'll be using the LMRC's standards for No.7 switches.  In this post, we'll be looking closer at the specifications and how to lay out a LMRC SP Standard No.7 Switch.  

No.7 SP Standard Switch in West Bakersfield - LMRC

Several switches will be of No.5 alignment or custom alignments with No.7 basic geometries and No.5 frogs because the switches are unique asymmetrical wye switches with both legs at different angles to the headblock.  There will also be a single No.5 symmetrical wye switch at Owenyo.

Details West Switch Kits

The frogs and points come from Details West.  I've been looking forward to getting into laying the track and switches for my new layout.

DTW SF-936 #7 and DTW SF-955 #5 switch parts with details and guard rails

Details West offers the frogs and points with additional detail parts, so I'll be using what I can.  I plan to insulate the frogs, so the provided white metal joint bars will not be used in the envisioned application.

DTW SF-936 No.7 switch points, frog and details.

The switch frogs have some casting sprue on the center of the back which must be ground or filled off.  I use rail-cutters to remove the sprues from the heel of the point rails.  I'll also be needing to drill out the point-tabs for the screws which will secure the points to the point bars.

DTW SF-936 No.5 switch points, frog and details.

The No.5 switch parts are almost identical.  15ft Points are included in both kits, along with the same guard rails.

My new "tool box" with ties and switch parts each in their own compartment.

I've assigned two of my tool boxes' compartments for the No.5 and 7 switch parts.  The points on the sprue barely fit in the compartments.  Mostly I'm opening the switch parts bags to get the frogs out at this point, so the tool box is for storing the other parts for later.

SP Track Standards

These are the basic set of specs I need to layout and construct the switches per LMRC standard.  Some variance will happen with the flow of the switches relation to the rest of the area.  I already know that several switches on my Jawbone Branch will be using 'funky' alignments, which will never work with 'R-T-R' prefabricated switches.  Non-symmetrical wye switches, 3/4 wyes, slightly curved or fully curved switches, etc.

Tie Spacing
Main Line 8'6" Tie Length
3 every 5'3"

8'0" Tie Length
3 every 6'0"

Switch Ties 3 every 5'0"

I'll be looking into which spacing I want to do on the HO Code 55 sections in terms of tie spacing.  Looking at some photos it seems that the tie spacing was still near Main Line standard.  That will be nice as I can then show the difference for the really ratty sidings and spurs at Little Lake and Owenyo.  I'll probably be trimming the flex track tie lengths to match the above specs.

SP Standard No.7 Switch

SP Standard No.7 Switch (closure rails omitted for clarity) - LMRC Pattern

63'2-5/8" HB to Frog Point
HB to PI 29'11-5/8"
PI to PF 33'3"
8'3" Guard Rails (11ft)

Switch Points 16'6"
18" Tab to Tip (this is for drilling the center mounting hole at the point bar)

Tie Schedule for No.7 Switch
15x 9'0"
8x 10'0"
5x 11'0"
5x 12'0"
4x 13'0"
5x 14'0"

SP Standard Headblock for non-power switches
8"x12" x 16'0" (some LMRC switches were built with 15ft HBs)
Power machine switches will use two standard tie dimensions, 16ft long, replacing one of the 9ft ties of the standard schedule.
Switch Stand on Turnout on Diverging Side Unless Otherwise Authorized

Several of the switches on my model of the Jawbone Branch will need to have the headblocks on the straight side.  Mostly at the east end of Owenyo.  The western end of the staging yard crossover needs to have the ground throws on the access side, where as normally crossovers have their headblocks facing the other track involved in the crossover.


No.7 switches may vary in HB-PF length from 63ft to as little as 57ft to suit situations of installation.  Also differences in switch point lengths from as long as 16.5ft to as short as 12.5ft.

SP Standard No.6 Switch

44ft       - 56'10" Overall length

12.5ft    - 15ft Points (DTW standard)

11x9ft   - 14x9ft
6x10ft   -  7x10ft
4x11ft   -  5x11ft
4x12ft   -  4x12ft
4x13ft   -  4x13ft
5x14ft   -  5x14ft

Details West offers No.5 switches points and frogs, so I'm using those in certain situations.  Notice that the same switch number changes length in the head block (HB) distance with the length of the points.  The DTW points are 15ft, so this will help the alignments being smooth.  I'll be working on an adjusted set of numbers for No.5 switches, which I will have several at Owenyo.

No.5 Switch PI-PF
23ft switch for the standard distance for that angle of switch and the gauge of the rails.

Laying Out Switch Geometry

The process of laying out a switch on my Jawbone Branch starts with marking the 'normal' route center line (CL) with a pencil.  Then a PI point is chosen.  The PI point can be derived from an already established second CL crossing the main track CL or it can be worked out in the following method.

Measure towards the frog end of the switch from the PI 7" and make a light (temporary) perpendicular mark (90 degrees) and 1" long, making a darker point at the end of this line.  Then make a track centerline from the PI to the derived point 7:1 towards the frog.  This becomes the switch angle, or switch "number".  The track will not need to follow the diverging CL all the way to 7", but basically just through the Frog before starting to curve as needed.

With the PI and frog angle set, measure ~30ft (4.13") towards the point-end of the switch, marking where the far end of the Headblock (HB) will be.  Note: Until I updated my list, I have started laying out the Jawbone Branch with ~4.0" HB-PI as my rough dimension.  I'll be going back through my marks on the layout top skin and remarking the HB/Frog points before I start construction of the switches.

I next measure the 33'3" back towards the frog to make the rough Point-Frog (PF) point.  This is the theoretical point where the two gauges of track will cross, and the ideal place for the tip of the frog point to be.  This point can also move up to 4 or 5 scale feet to get a smooth flow through the switch based on how the two stock rails will lay.

Switch schedule marked & ties stacked, East Owenyo

Now that the basic info has been physically layed down and marked on the layout roadbed, the next step is to glue down the Headblock (see dimensions above) and follow the switch tie schedule for the increasing length of ties.

Gluing Down the Ties

Ties glued down. Looking at locating frog.

Interlacing the standard length ties behind the frog is also done with individual ties, along with 4-5 ties past the HB on the point-end of the switch.  The glue is usually a white-glue variety.

Sand the Ties

3M 180-grit sanding block with foam core.

Once the ties are firmly glued to the roadbed, 120 or 220 grit sand block is used to clean the tops of the ties down to a consistent level, which should match the height of the bottom surface of the flex track rail which will be used.

Notching Ties for Rail Joiners

Rail joiners require notching of the wood ties with a chisels blade.  Flex track interlaced with wood crossover ties.

In my case, ME Code 55 flex track, which needs about 0.070" of tie material to match up.  When using Midwest or Northeastern scale lumber I found I don't need to sand the tops of the ties down.  However, when sing the Michael's craft toothpick building sticks, which are more like 0.085" do need to be sanded several times to get them down to 0.070".

Marking the locations with a pencil for the spike holes to be drilled.

Locate the frog early on and mark the location of the frog with a mechanical pencil.  I'm also marking the locations where I will need to spike the frog in place.

East Owenyo ties stained after the fact.  Stock rails and frogs in place.

The tops of the ties are then stained again and weathered as needed.  These switch ties are stained with acrylic black and some brown Apple Barrel paint in alcohol.  I happened to go ahead and glue down all the Mojave crossover and East Owenyo switch ties before I stained them.  So the stain was done after the rails were in place and most of the geometry marks had already been used, in case I wiped some of them out with the stain!

Ballasting can then be done before the rails are installed.  This is somewhat easier now as the rails are not in place and the ballast shouldn't cause trouble sitting on the ties or getting stuck around the completed rails.  On the Jawbone Branch, many areas with switches will have minimal ballast, with the track down 'in the dirt'.  I've decided to hold off on ballasting the switch work, as I'm using a number of marks on the roadbed and ties to align the frog with the stock rails.

Frog resting at the marked offsets from the two centerlines.  Wye tail flextrack in place.

It is possible to have the flex track already in place, following the marked centerlines at this point.  The stock rails (rails that are continuous through the switch) are now layed down.  Usually the main route stock rail is installed first by roughly spiking it to follow gauge through the switch.

Stock rails joined with the flex track.  Frog marked with pencil around the edges.

The Frog is now located roughly based on the PF point off of the stock rail, then the frog should be spiked to gauge at that point.  The straight route is spiked first.  This is easier to do as you can sight down the straight rail and determine that it is straight.  Ideally, flex track can be spiked on center to both sides of the switch and the straight stock rail can be sighted between the two pieces of flex track.

Checking gauge after spiking the frog in place on the stock rail. - This is the house track switch west of the switch shown above.

The diverging route stock rail is slipped with a standard rail joiner onto the flex track at the point end of the switch.  The diverging stock rail may have a slight kink bent near where it will lay at the Headblock, about 1/8-1/4" away from the frog.  This kink is to kick the stock rail outward from the gauge and allow the width of the point rails to fit at the Headblock.  Note that this kink also defines the 'normal' and 'reverse' routes through the switch. 
Drill points marked around the No.7 Frog.  These marks are drilled with my Dremal

A minor point about my installation of these switches onto MDF roadbed.  Yes, I am pre-drilling every spike hole with a No.72 or 73 drill bit in my Dremal tool.  I found that 8-9k RPM seems to be very good at clearing the MDF chips/powder from the holes.  Pine spline roadbed or upsom board used at LMRC don't need the holes pre-drilled in 95% of the locations.  Although some of the splines seem to have extra hard pine, so it wouldn't be a bad idea from time to time.

Basic stock rails and frog placed and secured with a few spikes.  Note, keeping the guard rail areas clear.

Next spike a few places between the flex track at the HB end of the switch.  This should allow the natural flow of the diverging stock rail to flow from the HB past the Frog and out the heel-end of the switch.  The diverging stock rail is lightly spiked to gauge at both ends of the frog.  Generally the first rounds of these spikes are placed just outside of where the guard rails will be fitted.  The spike heads are long enough that I can do slight adjustments to the position of the rails by rotating the spike heads themselves.

Check the two stock rails at this point to get a good flow through the switch.  If either stock rail is not in a good alignment, having kinks or reversals in direction of curve then adjust the stock rails to get a good alignment.  If this doesn't help, then consider moving the frog to create a better alignment through the switch.  I generally visualize the flow of the rails before they are installed or spiked.  During this project, I've been using the mechanical pencil to helping to see how well aligned the frog and rails are.  Note: Moving the frog may very well also move the track center of the route coming out of the switch!

Heel Rails

On crossovers, the stock rails become the heel rail for the opposite switch.

The "Heel Rails" from the frog to the flex track on each route exiting the switch.  These should again be set to gauge off of the respective stock rails and spiked in place.  An electrical gap will also be left between the frog casting and the heel rails.  Flex track or continuing hand-layed track will then extend out from the switch.

Stock-Heel rails of Mojave Crossover gauged and installed.

Crossovers are somewhat of a catch 22 situation relating to the stock and heel rails alignment.  Just trust that you've marked your frogs half-gauge offset from the calculated centerline is correct.  Everything should work out.

I'm planning to use some thin styrene to keep the heel and closure rails from working their way over and contacting the frog electrically, which would cause a short circuit depending on which way the switch is thrown.

Closure Rails

Straight Closure Rail at single point installed at Mojave Crossover in my Staging Yard.

The last two rails to install are the "Closure rails" from the frog to the point rails can now be measured and cut.  Rail joiners will be slightly flared at one end to hold the points and allow some movement as a hinge.  The frog end of the closure rails will be left without rail joiners, to provide an electrical gap.  The closure rails can now be spiked in place to match the gauge of their respective stock rails.

The closure rails will each have an "Omega" wire soldered to it, connecting the closure rail to the adjacent stock rail of the same electrical polarity.  The frogs will be powered separately or left dead-rail.  Small plastic shim pieces will be glued between the frog and adjacent rails as insulators, then filed to match the rail shape.

Point Rails

I'm not going to get into a lot of depth on this post about the DTW points, other than to touch on them lightly here. 

An end-view of a DTW point showing the step cast into the point for a good fit against the stock rail.

The switch points are designed to be fitted via rail joiner to the closure rail and have a 0-80 clearance drilled hole in the point-bar tab drilled.  The points are in generally good condition from the package.

Another view of the step cast into the stock-rail side of the DTW point.

Some points need slight adjustments to straighten a few shallow kinks and a couple of them have a slight twist down the point - I.E. the point tab is not square to the closure rail vertical.

Multiple Switch Alignments

East Owenyo complex of interconnected switches with continuous stock rails.

If another switch is immediately adjacent, or within a rail length (36" for HO), then it is probably best to build the whole switch structure with continuous stock rails as much as possible before moving on to the closure and heel rail steps.

Once the two stock rails are in good alignment, spike the stock rails more firmly at the frog to hold tension of the curve to the points and gauge at both ends of the frog casting.  The frog can be secured into place with several more pairs of spikes.  Spiking can now be completed between the frog and towards the point area of the switch, but leave the area where the points will be free of spikes, about 17ft long.

Notes for Jawbone Staging Switches

Note the headblocks of this crossover switch are to the outside of the crossover for access to a ground throw if I decide to use one.

I've changed the HB side for my staging yard, so that I can physically reach the switch stands.  Most other switches on the Jawbone will comply with the SP Standard.  The main exceptions maybe the 'curved' turnout at the west end of Owenyo which will still have the HB on the diverging side, but the main route's curve will make them look like the diverging route is the normal route.  On some switches an angle is  bent into the diverging stock rail next to the tip of the point will still show which is the normal route.

Up Next

Custom alignment using No.5 frog.

A No.5 three-quarter wye switch is needed for the switch leading to the SG-NG transfer pit, which is almost forming a crossover at the east end of house track.  There's still a number of switches to build. 

Owenyo Stub Sput (cropped) during scrapping- Rich McCutchan - - c_n_c43_decom_owenyo_862_sml

Next will come the flex track and the No.5 switch to the stub on Owenyo #2 module.

SP 2758 sitting on-spot next to the fuel tanks on the east leg of the Owenyo Wye. - Eddie Sims Collection

The construction of the Owenyo Wye Tail module, which will have a symmetrical No.5 Wye on it.

In Closing

Last night I ran the first engine under analog power at Owenyo!

Jason Hill

Related Articles:

SP "Jawbone" Branch Index Page - Links to all my blog posts on my new Jawbone Branch layout.

SP Jawbone Branch (Part 21) - Bolting and Aligning Modules - Wrapping up construction of the first 4 modules.

Freight Symbols Over Tehachapi - Part 4 - SP Locals - Tehachapi Pass's SP Local Freights, several of which work out of Mojave.


  1. What are your thoughts on Scaletrains producing the (MTH) daylight cars? Will they get the lettering correct? Have they reached out to some SP guys like you or SPHTS?

  2. I've had no contact with Scaletrains regarding any of their plans.


Please identify yourself at the end of your message. Please keep comments relevant to the post or questions to me directly. No random solicitation in comments. Spamming and phishing comments will be deleted.