On18 Trestle – Pt VI

woodsiesAs usual with me I often have a hell of a time getting the bits and pieces I need for a project. This is no different. I had decided that 6″ x 6″ ties would work for the bridge ties for an On18 trestle. I went to Michaels (40 mi round trip) .. and they didn’t have any stripwood that size .. darn it. Well .. I had a pack of “Woodsies” (come to think of it they came from Michaels) .. that were the right size. Very rough compared to quality stripwood .. but ‘what the heck’ .. figured they would do for rough (read that narrow gauge) ties.
gluing_tiesHere, I’m about 2/3 the way through laying the ties. Once they are all applied I will use a sanding block to level the tops. I will have to replace a few – these are not exactly precision milled pieces of wood – but again that’s fine with me as they work to represent fairly rough cut ties.

The longer ties facing to the inside of the curve will support a walk. The four long ties on the back-side will support a water barrel platform. There will be another on the other end.

endingI have glued in scrap pieces of stripwood into the end of the trestle to completely fill in the stringers. Once this sets up I will drill out a place for a small 1/4″ tube. That will allow me to run a screw through into the abutment bridge seat. That should secure the trestle nicely and allow me to remove it to access the area behind the trestle.
Adding Rails
stackedGetting the rails attached. I am using a combination of Barge cement and spikes. Once I am happy with the gauge I will shorten the ties about half of what is sticking out pass the rail.

I need to find some stripwood for the walkways. Off the top of my head .. six inch wide stock possibly. I think 12″ wide boards would overwhelm the sucker.

Guard Timbers
guardtimbersGuard Timbers – They should always be employed, and where an outside stringer is used should be placed immediately above it. Heavy timbers .. 6 in. x 8 in., with the narrow face down, is a good size. The length may vary, using such timber as can be most conveniently obtained; still it is better to have them from 16 ft. to 20 ft. long. The joints should always come immediately over a tie and be broken; i.e., those on opposite sides would be different ties, not two joints coming over the same tie. A bolt should extend through the joint tie and outside stinger. The guard tie should always be notched down at least 1 in. over each tie.

The ends of the guard timbers at either end of the bridge ought to be rounded off or cut at an incline, as in Figs. 116 and 117. Every tie should be fastened to the guard timber in some way, especially when they are not fastened to the stringers. A bolt should be put thought the guard timber at every fourth or fifth tie, and should extend through he outside stinger (if used). The balance of the ties may be spiked or fastened by lag-screws. Spiking is much cheaper. If lag screws are used a wrought washer is to be placed under the head of each lag-screw and a 3-in. to 3½-in. cast washer under the head and nut of each bolt. [1]

Place the guard timber about 8½-in. from the outside of he head of the rail. [2]

[1] A Treatise on Wooden Trestle Bridges according to the present practice of American Railroads

[2] Engineers Report on Brooklyn Elevated (1924)

Guard Timber Placement
guardtimbers_positionI was thinking about ‘how long’ to make the guard timbers. Obviously I couldn’t go with the suggested 16-ft. to 20-ft. Heck .. the 12-ft. dictated by the curve would still result in the ends of the guard timber much closer then it would be to the rail at the center of the timber. I then thought about the long timbers I have sticking to support the walk. I have a long tie .. then five normal length ties .. then another long tie. This makes approximately 6-ft. between each long tie. Cutting my guard timbers to this length of course results in a length that is about 1/3 of the suggested .. but .. shrug. What the heck.

I at first thought .. ok .. run a guard timber from one long tie to the other (A). Then I thought .. visually .. if I ran the guard timber from the tie centered between the long ties (B) .. that SHOULD (I think) visually sub-divide that arc. You would have the arc formed by the guard timbers and the arch formed by the long ties .. and I am thinking that with the guard timber ends anchored on that central tie would blend the two arcs into one that is visually larger.

I can’t .. PROVE that .. but it seems it would be so.

From “A treatise on wooden trestle bridges according to the present practice on American railroads” pg 68

RefugebayOn all trestles of any length say two hundred feet or over, refuge-bays or small railed platforms to receive workman or track-walkers who may be caught on the bridge by a train should be placed every two or three hundred feet apart. These cost but very little, and are very efficient in insuring greater safety to employees, especially on single-track trestles. Fig.153 shows an excellent attachment for this purpose. Every fourth or fifth refuge-bay on trestles over one thousand feet long, especially when on or approached by a curve, should be made large enough to receive the handcar; and when the section-men or the repair-gang are at work on the bridge they should always be compelled to place the hand-car on the refuse-bay, together with all idle, tools, before they begin work.

I thought this worth posting. I was looking for information on the construction of the foot-walk – and figured that this was applicable for the posts and railing.

foot-walkContinuing. Used a scale (more or less) 3-in. x 6-in. Guard Timber and 2-in. x 6-in. lumber for the foot-walk. I have a little more walk to finish then need to put bolts into the guard timbers .. and finally the railings.
By accident this morning I found some info on foot-walks on a trestle. From “Proceedings of the American Society of Civil Engineers, Volume 43, Part 2” .. page 2221

The standard ties are 6 by 8 in. in cross-section, full dimensions, and are 8 ft. long. For the outside tracks, where a footwalk is required, every third tie is 12 ft. long and carries the footwalk

Ok. Whatever the length of the ties they added 4 ft. Mine extend three foot. It appears from the drawing that that extra foot was used for a kneebrace for the railing posts.

The outside footwalk, laid on the 12-ft. ties, consists of five pieces of slatting, 2 by 6 in. full dimensions.

The ‘slatting’ have a gap between them .. say ½-in. giving a total width of about 32-in.

That’s pretty much the width I ended up with. I didn’t extend the ties that extra foot though. Hindsight .. yeah I probably would. Instead I went with something similar to what was used for the.. where looking at it now I realize that at least in part the lack of a kneebrace is simply because the design with posts and railings on three sides doesn’t need that.

I’m not going to go back and re-do the design now. Each post is held with two bolts so it’s not exactly weak .. but .. like a lot of what I do I like to think .. “How would they have done it?” (meaning .. at this point the guys building the trestle go .. “ummmm…” .. and figure a way around it.

A way around ..
rb_postThe rendering to the left shows the refuge-bay construction as applied to my trestle. The post is heavily notched so it is supported by the tie. That ‘thin’ bit left is still 1½-in. thick but that is around 0.030-in. in O scale. Note that there would be a couple of bolts staggered through that ‘bit’ into the tie to hold the post in place .. but the post would be subject to levering since that would be the only place it was secured. My find through hindsight that I could have extended the ties a foot for a kneebrace doesn’t help now as the ties are already part of the trestle.
rb_post2I think if I extend the post down, bolt a short piece of blocking on the stringer then a 2×4 will act as a kneebrace. This should work fine and is what I will go with (probably) unless someone comes up with something better.

I tend to model by attempting to figure how someone would have solved a problem in ‘real life’ .. rather then tearing out what I had done before. To me .. that makes the scenes more ‘real’ .. since such fixes are often seen in that ‘real life’. Shrug. What works for me at least.

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