SP Jawbone Branch (Part 35) - Cutting Out Owenyo #3 Module

SP "Loading Ramp" showing SP GS gondola for size - PacificNG collection

The main centerpiece of the west end of Owenyo is the Narrow Gauge dump-trestle to transload bulk loads from the NG cars into SG cars.  Finishing up the west end of Owenyo and building a section of the main line to the west will allow me to start operating Owenyo the way it should be done, using the long west end mainline as the lead with all switches in town facing west.

Along the wall, station of Owenyo rendered in CAD.

The Jawbone Branch's far east end has made good progress on the over the last couple months, including: ground throws on the switches, good lighting over the area now, and the first two Owenyo modules wired at least for DC operations.  I still need to find the guts to put everything away again and pull it all down to wire the third and last module of Owenyo to lift out the Mojave staging yard underneath and get it wired and the switches on the two ends spiked down.

However, lacking the motivation to do all of that, I'm instead getting sucked into the idea of attacking the next Owenyo module, which is much more complicated than the last five sections I've built.  This module will get away from the simple sheet and frame, with the whole module making the transition from level right-of-way at Owenyo station to the 1.0-1.25% grade down to the staging yard.  

Closer view of the 'trestle' at the west end of Owenyo, on the third module.

There are also track elements going below grade for the Standard Gauge under the Narrow Gauge "Highline" transloading dump trestle and also a small bridge over a wash to deal with.  These additional elements will mean that I'll eventually have to cut the top sheet of MDF and splice in foam under and around it to form the ground shapes.

Laying Out the Module

The main challenge for building this module is doing the best job of selective compression to fit the big straight trestle into the scene.  Thankfully, I'm not trying to make the NG side functional.  The trick will still be to create a suspension of disbelief about the grade down off the trestle to the left in my scene, while not breaking the scene with the NG track running along the back side of the stock transfer platform just to the left.

Closeup of "SG end" of Owenyo Transfer Trestle - owensvalleyhistory,com - sp_narrow_g37a_sml

From this and the other photos I've been able to find of the trestle, I should be able to work out the height, scaling, etc... but more on that later.  Note, this is the "NG side" of the trestle, which will be on the back-side of my model.  The material from pit that is dug for the SG track is piled to the right between the trestle and the NG mainline.  This will be nice to add something in the back of the scene as the view transitions to the curved backdrop.  I've planned as much as a 30" radius for the curved backdrop.

Red Caboose steel GS gondola posed for the mock-up trestle

For now, I'm just mocking up the rough height and size of the trestle with a pair of 1-2-3 machinist blocks and my yardstick.  I broke out the MicroEngineering Code 55 NG flex track to have on the top of the mock-up.

Looking north from Owenyo From Transfer Trestle - Brandon Collection WM

So this is a great overall shot from the trestle looking into the rest of Owenyo.  This really sets the scene as to how the trestle will fit into the scene.  Note the small 12ft single-span culvert-trestle, this will be a benchmark to tie the trestle into the mainline of the scene.

Mocking up the location of the main track curve and the trestle.

The switches will have to start with the headblock in the sprial easement of the curve transitioning into the tangent.  I've marked in pencil about where the culvert-trestle will be.

Reverse angle... so, question is what angle will work best for the trestle?

My main challenge with working with such a large structure this close to the main line is the selective compression.  The prototype has maybe 30-35 degrees of angle in the mainline splitting off from the original NG tangent.  The trestle should be only slightly off alignment from the rest of Owenyo, as there is a several hundred foot trestle ramp on the prototype, which will be truncated into the wall.

Cutting the Material

Top view of the sketches on the material.

In this view, there are several possible angles for the trestle to be built on.  The main track is only roughly marked.  I didn't have room while material was still in the full sheet to swing the track center for the main track on the 48" radius curve.  As it has already been worked out in the computer, I'm not worried to cut out the module from the sheet and then swing the main track arc from a tripod set up in the room once the module's structure is a bit more stable.

The cutting was quick with a saber saw.  The joint with the rest of Owenyo will also have the top sheet notched back to match for the "washes" going down both sides of the main track and back-filled with pink foam.  This should extend at least as far as the culvert, and possibly all along the front edge of the layout.

Module cut out and clamped into rough position.

At this point, the module's supported by some blocks on the Mojave staging yard and a C-clamped 2x2 post next to the door, there's a lot of sagging happening across the window.

View of the 'trestle' at the west end of Owenyo.

This CAD rendering shows my original "closest" position for the trestle with four 45ft long cars able to fit under the trestle.  However there's basically no room for the approach ramp trestle, especially with the NG track curving into the window between the platform and the trestle.  It feels like too much in too small of an area.

Trestle footprint and rough flextrack mocking up positions.

I'll probably settle on some version with a little more space between the main and the trestle.  This will need to balance against the proximity of the little 12ft culvert trestle and how close it should stay to the west switches for the siding and house track.  It's all a game to find a happy balance of the compression and elements of the scene.

Another view of the mockup.

The other challenge in here is to create the structure to support the module and build in a vertical curve transitioning to a 1.0-1.25% grade.  I'll also have to keep the twist out of the mainline section of roadbed so that when the module transitions to the door-spanning section the track is still cross-level.

Looking north from Owenyo From Transfer Trestle - Brandon Collection WM

Here's the prototype that I'm trying to replicate, notice that the little culvert trestle is actually lining up with the NG's ramp track.  Unfortunately, the model will have to be full height deck at this point because of the main line curve size and the size of the module.

Mocked up same photo as above.

The NG trestle track will actually be about 1/2" lower at this end once the track is set down into the pit, but it gets the idea across.

NG stock spot at left and NG trestle at right.

I removed my 1/2" shim from the east end of the trestle mockup, which brings it to about the height it will be in the completed module.  Note how close the NG track at left goes off the module is to the end of the trestle track where it meets the wall.  

Another higher angle view showing the issues of distance compression.

I don't think I can enlarge this distance very much, so I'll probably have to hide the height problem on the trestle with a well placed tree or two.

Rough joint of Owenyo #2 and #3 modules.

The Owenyo #3 module will need to be cut and slotted for the washes on each side of the mainline, which adds to the challenge of the #3 module's structure.

In Closing

That I think wraps up the mockup Owenyo #3 module for the night, glue bottle is for ballast!

It will be quite the challenge to finish this module and get it working as part of the existing layout. Plus, cutting the SG strip of roadbed out from the sheet and sinking it into the module, forming the pit of the prototype.  All this without compromising the structure of the module.  I think you can see why I've put off starting this section of the layout!  I expect the fully "cookie-cutter" construction of Little Lake will be the only modules that will surpass this one in general complexity, but this one has the additional complexity of the trestle and SG diving under it to consider.

Jason Hill

Related Articles:

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