Build a Structure - Peter Bowen - RGS Timber Trestle

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PeterBowen
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Re: Build a Structure - Peter Bowen - RGS Timber Trestle

Post by PeterBowen » Mon Jan 05, 2015 9:23 pm

Adding NBWs to Stringers

The trestle desk stringers consist of scale 8" x 24" timbers that are assembled 3 wide with spacers and these are then bolted together every 16' -  a drilling jig helps to locate the position of the NBW (nut bolt washer) castings.

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Re: Build a Structure - Peter Bowen - RGS Timber Trestle

Post by PeterBowen » Tue Jan 06, 2015 7:17 pm

Adding Ties to Stringers

Finished splined stringers with temporary longitudinal spacer inserted to hold the stringers apart ready to accept the ties.

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Pre-stained in the shoe dye and alcohol solution and left to 'pickle' for different lengths of time produces (in my opinion) a good selection of aged and weathered timbers representing well aged wood ties a scale 8' x 8" x 10'

The ties are added to the splined stringers and spaced a scale 3" apart. Note the unstained temporary spacer holding the splines apart. The centreline of the middle spline on each side is a scale 30" apart.

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Every so often water barrel platforms were added as seen here with the extended ties.

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Peter Bowen
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Re: Build a Structure - Peter Bowen - RGS Timber Trestle

Post by PeterBowen » Thu Jan 08, 2015 7:43 pm

Ties and Trestle Deck

The splined trestle deck is completed with the placement of the 8" x 8" x 10' pre-stained ties.

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Clamps and more clamps - you can never have enough clamps to hold parts and assemblies together...!

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Prototype photos showing weathered wood and fittings . . .

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Peter Bowen
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Re: Build a Structure - Peter Bowen - RGS Timber Trestle

Post by PeterBowen » Fri Jan 16, 2015 8:11 pm

Applying Rail to the Splined Trestle Deck

The splined trestle deck is now complete with ties and before assembling this to the trestle bents it is time to spike the rail on to the ties. The RGS typically used rail length of 30 feet. I used weathered Micro Engineering code 70 rail cut to scale 30ft lengths and individual spikes.

The first challenge is to align the rail lengths into position ready for spiking. I used an aluminium straight edge clamped to the ties to align the rail.

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To avoid splitting the ties and to allow the spikes to be driven into the tie and splined stringer below I pre-drilled the spike locations using a pin vise to drill a 0.8mm hole through the tie and into the splined stringer. Then using needle nose pliers to drive the spike into the tie and holding the base of the rail firmly seated to the tie.

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Spikes are driven into the pre-drilled holes and have just about enough grip to firmly seat the base of the rail to the ties. Note that the spikes are placed every 6th tie. Pins show the location of the spikes in the photo. Sorry its not that sharp.

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Re: Build a Structure - Peter Bowen - RGS Timber Trestle

Post by PeterBowen » Mon Jan 26, 2015 7:10 pm

Problem with Rail Spikes

Construction progress was halted recently as the rail spikes refused to hold the rail securely to the ties. Pre-drilling an undersize hole for the spike to prevent splitting seemed to work but there was not enough grip to hold the rail.

In the past I have used Shinohara code 70 spikes which I had purchased some 30 years ago and had literally thousands of them. They are work very well when hand laying code 70 rail to ties on a fixed roadbed but spiking rail to a splined trestle bridge beam is another problem unto itself.

Several different sizes of spike were tested and used including Micro Engineering Micro Spikes measuring 4.5mm in length and .28mm in diameter, Micro Engineering Medium Spikes measuring 9.0mm in length and 0.8mm in diameter and Peco Rail Spikes measuring 14mm in length and 0.8mm in diameter.

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The photo above shows the 3 sizes of spikes plus a prototype spike...! (from the White Pass & Yukon Railway in Alaska) and a scale trestle tie for scale comparison.
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Re: Build a Structure - Peter Bowen - RGS Timber Trestle

Post by PeterBowen » Tue Feb 10, 2015 9:48 pm

Hand Laid Rail Spiking Update

Construction progress has been slow over the last several weeks due to my new role as Renewals Officer for the British Region NMRA. It is quite a daunting task but I have had great support from John Firth and I am beginning to get the hang of it...!

I revisited the "spiking of rail" problem and have concluded that the answer is to use the trusty Pliobond method. Pliobond is a thermally activated adhesive, that is applied to the base of a length of rail and allowed to dry. When heat is applied with a soldering iron the adhesive 'comes to life' and bonds almost instantly to the surface it is applied to.

The manufacturers description of Pliobond states: Pliobond® contact cement is ideally suited for bonding steel, wood, rubber, leather, canvas, aluminum, fiberglass and glass. This adhesive actually gets stronger as it ages and is highly resistant to vibration and expansion/contraction.

I have used this method in the past for handlaying code 70 rail to individual ties, albeit on a solid roadbed or splined roadbed in HO scale and it works very well for laying rail very quickly. Small spikes are then used to secure and align rail at switches.

Strengthening the Trestle Structure with Cross Bracing

The photos below show the current progress with respect to strengthening the structure with cross bracing to support the weight of the bridge deck and ultimately heavy locomotives.

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As the substructure starts coming together there is a distinct lack of rigidity in the overall structure and since this trestle bridge will eventually span a small valley the trestle bents will be attached to the ground surface but until that happens the structure needs reinforcing to allow it to be transported without its eventual base for display at shows and entering for competition and the achievement programme.

The following photos show the addition of cross bracing to "stiffen" up the structure.

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Re: Build a Structure - Peter Bowen - RGS Timber Trestle

Post by PeterBowen » Fri Feb 13, 2015 10:25 am

Trestle Abutment Detail

At the ends of the trestle there would have been abutments to hold back roadbed fill. These abutments consist of a trestle bent with scale 3" x 18" timber boards which would have been nailed through the back before being backfilled. The iregular shape is due to existing profile of the roadbed embankment behind.

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Closeup detail showing reinforced boarding applied and cross bracing.

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This photo show the level of detail that can be achieved by distressing the wood timbers, staining using the shoe dye and alcohol method and the application of Tamiya weathering chalks which I tend to use a lot of to touchup and add additional staining and watermarks.

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Closeup of a typical reinforced trestle bent showing the effects of weather on wood.

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Re: Build a Structure - Peter Bowen - RGS Timber Trestle

Post by PeterBowen » Sat Feb 14, 2015 6:36 pm

Attaching Trestle Bents to the Splined Bridge Deck

I have been struggling with attaching the Trestle Bents to the Splined Bridge Deck trying to keep them square to the deck and upright at the same time. I created a styrene jig to hold them in place but this failed as I tried to apply sufficient weight to aid in the glue drying process.

I also struggled with clamps and pegs of all sizes and just could not apply enough pressure to hold the glued joints.

. . . and then I had a eureka moment...! let me explain:

Recently I attended the Bristol O Gauge show and got talking to a modeller who couldn't say enough about the merits of a SUPER thin penetrating cyano glue that bonds in ONE to FIVE seconds... so I purchased some and put it in the modelling toolbox with the other tools and bits that I had picked up that day.

Could it be that this stuff really works?

I did a test and stuck two strips of uneven wood  together along with my left thumb, a few stray metal spikes and the green cutting mat that features in most of my pictures into one totally bonded mass...!

I then did a more controlled test and blimey this stuff called ROCKET HOT really works.

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Needless to say construction literally zoomed ahead at Rocket Speed...!
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Re: Build a Structure - Peter Bowen - RGS Timber Trestle

Post by PeterBowen » Sun Feb 15, 2015 8:34 pm

Adding Horizontal Bracing "Girts"

Construction is nearing completion as the horizontal bracing "girts" are added to the structure to provide strength to the vertical bents as this forms amazing rigidity to the overall structure.

Threading the 32 ft long 8" x 8" long timbers through the openings in the trestle bents was challenging.

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Peter Bowen
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Re: Build a Structure - Peter Bowen - RGS Timber Trestle

Post by PeterBowen » Mon Feb 16, 2015 9:25 pm

Completing the Bracing

As the trestle nears completion the final cross bracing is added to ensure the structure is strong and stable.

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Re: Build a Structure - Peter Bowen - RGS Timber Trestle

Post by PeterBowen » Fri Feb 20, 2015 11:43 am

The code 70 rail has now been attached as previously described using the Pliobond adhesive method:

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The guard rail timbers have also been attached:

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Re: Build a Structure - Peter Bowen - RGS Timber Trestle

Post by PeterBowen » Fri Feb 20, 2015 9:41 pm

F I N I S H E D

The Rio Grande Southern style Trestle is complete...!!!

Rio Grande Southern Goose No. 4 a Precision Scale ON30 model with sound creeps across the finished Trestle after the Track Gang have ensured the gauge is perfectly aligned and ready to receive traffic.

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