Monday, March 29, 2021

SP Jawbone Branch (Part 19) - Owenyo #1 Secondary Bracing & Wye

The last three (SP Jawbone Branch Part 16, Part 17, & Part 18) blog posts have been on the structural aspects of the modules.  Now I'm moving on to the next phase of construction as I wrap up the last of the secondary bracing.

Plan for the underside of Owenyo #1 module

One of the advantages of drawing the structural details on my CAD models is that for several months I've already been visualizing what the structure will look like.

Secondary Diagonal Bracing

Special cut corner 2x2 blocks to accept the secondary diagonal bracing.

Following the same style of diagonal bracing from the Owenyo #2 module and the two staging modules of Mojave Yard, the more complicated Owenyo #1 module mixes diagonal bracing into the heavier support structure for the removable wye.

West end of Owenyo #1 module with diagonal bracing and front edge fascia dry fitted.

The west end of the module is mostly just needing the diagonal bracing installed.  Corner supports for the two diagonals along the front edge are still needed.

East end of Owenyo #1 module with the two "Pits" cookie-cuttered and bent down.

The edges of the Narrow Gauge "Pit" are cut longer and also relieved back, which will have the foam glued in from the bottom to create the slopes.

Finishing the Primary Wye Supports

Wye Issues?

Wye structural support "Keel" or spar.

Without the diagonal truss bracing the module was able to twist when I put a little force down on the tail of the wye spar/keel.  However with the secondary bracing installed the module does not twist anymore.  When force is applied to the top of the wye now tries to lift the whole rear edge of the Owenyo #1 module.  I'll probably still make a bracket or clip to hold the back edge down near the center focal point of the wye bracing.

Sistering & Supporting Front Frame & Wye "Keel"

The last two major structural support elements need to be installed before I can start working on the wye or moving forward with the rest of the construction.

I sistered up the front frame with 2x2s to provide a good anchor point for the lower plate.

This is the rather nightmarish structure to support the removable wye module as a cantilever.

Intermediate 3/4" plywood shims for the support of the wye and front frame.

A layer of 3/4" Plywood is needed to build up the depth to match the oak wye 'keel'.  The two triangles were also thinned to make a shelf, matching the two heavy diagonal frames.

Here's the intermediate cover plate marked to be cut.

I cut the two triangular sections to anchor to the front plate of the wye.  My table saw makes short work of this joint work.  The 2x2 riser cutout is made with a saber saw.

I cut a slot in the intermediate cover plate.

I don't want to cut any more height off the wye's structural keel than I need to.  I cut away two plies of the 3/4" plate.  The right side I also cut away the profile of the 2x2 riser.

The wye tail thinned to match the intermediate cover plate slot.

The cover plate is also 3/4" plywood with the same 2x2 notch cut for the riser.  The intermediate plate layer is glued in place.  

Lower cover plate.

I marked out the four support areas under the plate where I will attach it with screws.  Before I screwed this cover plate in place, I decided that a couple of holes should be added to lighten the module and also to provide some good handles!

Here's the wye 'keel spar' in place along with the 2x2 riser.

The front edge of the layout is definitely heavier now with all this box structure assembled.  Time to test it and see if my balance issue is still a problem.

The cover plate screwed in place with the keel-spar in place as well.

Well, with the module in place it definitely takes very little down-force on the tail of the wye to lift the back edge of the module across the 2x2 riser.  Time to build a bracket to hold it down back there!

Wall Bracket Hold-Down

A couple of scraps thrown together to make a bracket.

I decided the quickest and easiest way to build a bracket for the back of the Owenyo #1 module was to take a chunk of 3/4" ply and a small scrap of 1/4" MDF frame material rem, glue them together.  Then glue and clamp to the back of the module's frame.  (Yes, I'll have to grind off the tips of those two screws, OUCH!)

Hold-down bracket installed.

The module is now secured to the wall and can't rock if an engine heads out onto the wye.  I'll just have to remember to remove these two screws in the wall-bracket when I want to take this module down to work on.  Not a big deal really.

In Closing

Jawbone Branch coming together.

The next step is getting the holes drilled for the alignment pins and bolts.  Then track?  Hope so!

Jason Hill

Related Articles:

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

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