Sunday, June 9, 2024

SP Jawbone Branch (Part 52) - Curved Front for Owenyo#3

In the last post, (SP Jawbone Branch (Part 51) - Cutting and Aligning the Trestle Spur), I was mostly doing evaluations and starting to chop up the roadbed top skin sheet.

This time, I decided to dive into attaching the front fascia strips before building the spline roadbed.  As I was debating doing this or the spline roadbed first...  I decided this is a better starting point as practice for my spline construction technique.  Also the addition of the pair of front curved strips will increase the structural stability of the whole module at this point.

Quick pin added to hold the curved fascia strip at the right end.

In preparation, I cut an angle on the front edge of the right end-plate.  I used a scrap of 1/2" MDF with slots cut at angles in it to form the right end block for the spline roadbed.  I also didn't get a picture of it, but this photo after the fact still shows the clamp holding the spline end block as it dries in place.

Adding pins to the pre-glued left end joint.

I put a couple areas of Elmer's wood glue at the left end and the right end plate.  Clamps were quickly placed and then I drilled some holes and wire finish-nail the strips in place so they couldn't move linearly against the frame.

Marking the second spline strip where it will dove-tail into the Y-shape joint.

After the basic curved strip was in place, I started working out a thinner strip to double the back side of the front curved strip.  The doubler strip was dampened with water and then Gorilla Glue was spread on the strip and placed on the inside of the curved fascia strip.

Preparing to cutoff second strip, which is still lapping past the top of the module.

A few more finish nails were added... and then clamped across to the far side of the roadbed spline.  I later also drilled a pin into the gusset at this corner joint as well.  This makes a total of four pins into this joint.

Time for All the Clamps!


Two pins finalize this joint, then second strip is camped in place.

The right end was finalized with two finish nails to secure the alignment of the front curved fascia.  This shot shows the doubler strip added and clamped behind the front strip.

Towards the left end of the doubled curved strip, with tail of my wedge strip to the left.

As soon as I got the doubler strip roughly in place, and started securing it with the clamp at the right end, I started securing it around the curve with all the clamps I could get my hands on!

Closer view of the Y-joint of the front frame and front fascia strips.

The inner joint blending the doublers together as the curve ends, I added two nails, one at each point where the 1/4" MDF strips touch.  At the top the wedge strip is visible which I'm using to keep the clamp where I want it and keep the force square to the strips.

Forest of clamps to hold the spline strips together while the expanding urethane Gorilla Glue bonds two strips.

The rest of the clamps being attached around the curve.  I placed a bit of MDF scrap and then a bottle of glue to keep the right end-plate from twisting under the force of the two curved strips.


Closeup of the right doubler strip clamped.  I cut the end of the doubler strip at a matching angle against the end plate.

Metal square in place to check cross square of the module.  The clamp is there to hold the shape of the front curve.

Part way through the construction, I notched the curved spline was pushing the right end plate and right wall frame "open".  So I lassoed the window bracket, which is pretty secure, and clamped against the right end plate.  This was somewhat expected, but I'm glad I caught it before everything was too far cured.  The metal square is there to double check the alignment against the right wall.

Roadbed slipped back in place to check distance and alignment to east end of the module.

Thankfully during this time, I had the door open, so I could sight along the right wall frame, and see that it was mostly straight.  I fed in the main track roadbed just to check overall geometry of the whole module.

Extra pins added to gusset and two at the Y-joint to secure the struture.

At this point I unclamped the whole curved fascia frame and wanted to see how the whole structure was in terms of stability and internal tension, seeing that it was actually holding shape.

Cross-Brace


I decided to add a crossbrace at this point to help secure the front curved fascia strips.  I will have to work the main track spline roadbed around this strip.  The foam scenery material will also need to be added above the bracing and around the up-coming spline roadbeds.

Front joint of new diagonal brace.

I installed a diagonal cross-brace between the front frame right corner to the middle of the front curved fascia frame.  Gorilla Glue was used to both the front and rear joint.  I also drilled out two pin holes and installed wire finish nails to keep the front secure.

Rear glued joint of diagonal brace, held vertically by the clamp.

The rear joint was just supported vertically with the clamp to keep the bottom edge even with the right wall frame beam.

Another forest of clamps to keep all frame member straight while diagonal brace dries.

I ended up placing a large clamp diagonally off the corner of the front square frame to the diagonal brace, with a slight compression, just to keep it straight.  I noticed that the right end-plate was not sitting square with the rest of the frame, because of the spring action of the doubled front curved fascia sheets.  So I also added a large clamp from the window bracket to the end plate, this squeezed the frame structure.

The shape of the module is really coming together now.

After finishing up the structure, the vertical keeper clamp on the rear corner of the diagonal brace was easy to pop loose from slightly over flowed Gorilla Glue.  The diagonal brace is starting to add some good racking and twisting prevention to the module's structure by dividing it into triangles.  The top edge is even with the cut down front frame, where the Trestle Spur roadbed will be placed.

Rough CAD plan for the future foam scenery and showing roughly the same alignment as the photo above.

I'll probably have to shim up the spur roadbed as the fine tuning of the vertical positioning of the trestle will be worked out against the main track curve roadbed, but I'll work that out later.

In Closing


Overview of the module at the end of mounting the front curve fascia strips.

For now that wraps up the construction blog.  I'm expecting the next major step will be cutting a bunch of strips for the roadbed spline, then bob them down to length, and start making modifications to cut notches for the spline to fit into the main framework.


SP Jawbone Branch (Part 51) - Cutting and Aligning the Trestle Spur
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