SP Jawbone Branch (Part 17) - Upgrading Bracing, Mojave Structure & Foam

This post is a quick follow-up to SP Jawbone Branch (Part 16) which mostly covered the more complex Owenyo #1 structure and the brackets used to hold up the south side of the layout.  I realized that I haven't really posted photos of the upgraded basic structural system within the modules themselves.

Owenyo #2 with bracing removed

My first implementation of the bracing under the standard modules was with mitered and glued joints, which several of my friends who I consult with expressed concerns about.  After I've built the stronger version of this structure used on Mojave West and Middle panels with 2x2 corner blocks which were cut to accept the braces showed a much better strength, I planned to knock out any braces that were not firmly attached on Owenyo #2 panel and upgrade the installation.

New 2x2 corner blocks cut and slotted for installation.

I used the table saw with additional 3/4" ply shim to move the 2x2 blocks being cut to the proper location over the angled blade.  Definitely use the plastic push handle to guide the lower part of the block through the saw.  I was very carefully holding the upper corner of the block, but sure that I was not pushing into the blade if the block kicked out of the saw.  I want to keep all 8 fingers and 2 thumbs for many more years!

The other main change I made with this upgrade, which I planned to do before I actually glued them, was to thin the braces to only 1" from the edge thickness of 1.75".  

The new braces are all test fitted before glue is applied.  A small hammer is used with a scrap piece of MDF preventing damage to the edge of the MDF braces.  Clamps are used to hold the 2x2 blocks in place while the glue dries.

Cutout for the foam scenery insert in Owenyo #2.

The thinned diagonal braces are shown here.  I broke the edges of the MDF with a rasp.  Many future cuts will be prevented by doing this.

Here's the "tunnel view" of the Mojave Staging Yard with Owenyo #2 module above.

In the above photo, notice the reduced height of the bracing.  This is the upgrade which I planned so that my knuckles don't get killed reaching into the staging yard!  The stack distance at the front edge is only 4", but it's now 4.75" to 5.75" in the interior space above the staging yard.  I know the track will raise the equipment a few fractions of an inch, but the new space should more than make up for that.

Middle Mojave Staging

The last of the plain panels to build is the "Mid-Mojave" panel.

Diagonal EF and FG installed with new square braces at E and F on Mid-Mojave

The blocks are marked A, B, C, etc to show where on the panel they go.  The diagonal braces are also marked AB, BC, etc to show where they go, as each is cut to fit.

Mid Mojave panel with diagonal braces prepped.

I used some of the wider strips to make the bracing under Mojave, as it will not be needing the same type of tight access.

Large Clamps used on the five square cross braces at the west end of the Mid-Mojave panel

This one used Tight-Bond II wood glue and was quickly assembled with the large clamps spanning over the square braces and the smaller clamps holding the 2x2 blocks in place while the glue sets.

Middle of the panel clamped and glued.

At some of the corner blocks I have added pieces of 1/4" MDF to fill the slots or wedge the braces to exact length.

Eastern end of the Mid-Mojave panel

I may decide to add a couple of support blocks where the black marks are on the front and rear frame rails where they cross the wall bracket arms.  While the layout seems strong now, it may be better to bulk up these areas to help spread the vertical loading on an area wider than 1/4".

Underside of Mojave Middle Staging Yard panel looking east towards ladder.

This workbench area under the staging yard will be used as before.  The 13" clearance should be enough for my regular use of the space.  I have a light-table and other low profile items planned for this area.

Mojave Middle Staging Yard panel looking west towards West Mojave panel.

The panels are sitting pretty well with the wall brackets supporting them.

Owenyo #2 - Breaking Up the Plywood (MDF) Pacific

Many years ago layouts which were simply sheets of plywood with no dramatic scenic features were dubbed the "Plywood Pacific".  To break up the same syndrome settling in at Owenyo, a couple weeks ago I started making some changes to the western end of Owenyo #2 Module by cutting out a section to start the contouring terrain.  The land form change needs to start in #2 module because in the middle of the curve in #3 module, just west of here, there's a timber culvert under the main track that will need some place to drain.

Sketch of how the terrain falls away from the west switches in Owenyo.

This is also the first section of the layout that needs to start transitioning to 'cookie-cutter' benchwork and roadbed style to mate with the planned Owenyo #3 corner module  The construction of the Owenyo #3 module will be a full hybrid of MDF and Expanded Styrene Foam for the land forms and the 'High Line' NG trestle pit for the SG track buried down into the surrounding foam.  

The opening in the MDF cut for the foam insert.

I cut the top sheet of MDF with the table saw and then flipped the module on its edge to cut the corner.  These cuts allowed me to get the saber saw blade inside of the structural frame of the module to do the rest of the cutting.  I had some rough Sharpie marker paths to follow, but basically free-handed the actual cutting with the saw.  The edge was then finished a bit with a rasp to knock off any sharp edges.

CAD plan for Owenyo #3 with the "High Line" Trestle over the SG pit.

The grade down towards Mojave as soon as I can, possibly just west of the end of the Owenyo #2 module, as soon as I can make the vertical easement to the 1.5% down grade.  One of my major gripes with trackwork in general is not having proper vertical curves transitioning between different grades.  This can lead to vertical uncoupling on longer cars and engines.  Starting the transition to the grade earlier will also help with the SG pit track "dive" under the NG transfer trestle by cutting the vertical distance the spur will need to drop. 

Here's the view of the foam block cut out.

I cut the foam 5.5" wide and 20.875" long.  One corner had to be cut off to mate against the diagonal brace inside the module.  This will cut the available "hand space" to only what is below the diagonal rib in this area, but that should still be sufficient for my needs.

Dry-fitting of the foam block.

Always be sure to test fit pieces before putting the sticky gooy stuff on the pieces!  The piece was actually a good snug fit against the diagonal brace and west end-plate of the structure.

Gorilla Glue applied and a couple of the clamps in place.

Gorilla Glue expands up to four times its starting volume... so be sure to clamp the pieces of material together.  Also expect drips from the bottom as it pushes out extra glue!

I clamped both ends, and eventually two places front-to-back.  Two wedges were pulled together from rem's to support the bottom of the foam, which pushed against the Mojave Staging level below.  Two gallon jugs were placed on top of the MDF roadbed to keep the glue from buckling the roadbed upwards.

View of the module after the glue has expanded and dried.

The glue dried and did stick one piece of foam that I put under the right edge vertical clamp... so a few bits of white pop-corn foam are now stuck to the underside of the purple foam, oh well.

Eventually I'll probably do some forming of the foam down towards the profile I randomly cut in the MDF frame and blend it up to the MDF roadbed.  I was sure to leave enough MDF roadbed to mount the headblocks of the switches.  I could probably also rasp down the edge of the MDF as well, reducing the amount of 'fill' material I'll need to use over the foam area.  I guess we'll find out in a future installment!

What's Next?...

This post pretty well catches the blog up on where the layout is as of the 18th of March, 2021.  I'm looking forward to getting some track soon.  The next sections of construction without the track needs to be pointed at the three following areas:

1. Decide on the alignment pins and bolt system to connect the modules, then actually build the jig and put the critical holes in the structurally finished sections of the layout. (Yikes!)
2. Continue construction of the secondary structure under Owenyo #1 and push the structural support for the "removable wye and keel".
3. Start construction of the Owenyo #3 module which will be a full hybrid of MDF and Expanded Styrene Foam plus a grade transition and the footings for the 200ft long transfer trestle!

In my CAD plan I start the grade as the track "rolls over" the edge of the grade just below the culvert.

This slight design change from how I quickly mocked the plan up in the computer should allow me to increase the length of the 1.5% grade and there by the vertical distance which I'll be able to get by the time the track reaches Mojave Staging below Owenyo.  

My rough 3D CAD model of the whole layout.

The CAD model shows about 5" and some change for a 1.5% grade, but that's with very conservative starting and ending points for the grade.  If I can extend the grade back nearly to the west switch at Owenyo and possibly even through the curved lead into the staging yard at Mojave, then I'll probably get at least another 3/4" of height (Edit: max of 1.2" assuming the following is true).  I've run the numbers again, a possible grade run of 480" and a climb of 6" results in an average grade of only 1.25%.  This gives me 0.25% to play with in terms of vertical easements and fudge-factor if I've made a mistake in my calculations.  I'd rather have a longer grade run and a slightly lower grade, just averaging the total climb over the whole path around the west, north, and east walls of the room.

I guess I've had enough 'simple' shown in these last two posts.  Nothing will be 'simple' from here on!  However, I'm not too worried about the next sets of challenge which await me.  The two small pits in Owenyo #1 module has let me see how the 1/4" MDF will respond to flexing.  Also the inserting of the foam and gluing to Owenyo #2 module has let me play with Luke Towan's MDF Frame and Foam Center construction method in practice.  I must say that it is very strong with the Gorilla Glue being used and properly clamped during drying.

3D CAD model of the structure I plan use building the Owenyo #3 module.

So I'm looking forward to changing from the simple 'box' construction of the first four panels and into the hybrid construction of the new section from a couple of road bed pieces, structural rails of MDF and precision cut foam sections glued in place filling up the sections in between.

In Closing

Stay tuned as I continue the construction of the SP's Jawbone Branch in HO scale.

Jason Hill

Related Articles:

SP Jawbone Branch (Part 16) - Brackets, Pits & Diagonal Joints - Construction of modules, supports, etc.

Jawbone Branch Index Page - List of all my SP Jawbone Branch modeling posts