Suggestions for dimensional scale lumber sizes.

[doctorwayne]

There's an article in the July 2009 issue of RMC on building a pile bent trestle. The support joists beneath the rails (below the ties, of course) consist of three 10"x16"s, on edge and bolted together, under each rail. The two outer members of each grouping start and end on the same bents at each end, while the centre member starts and ends atop an intermediate set of bents - in other words, except at the ends, each support member spans three bents spaced approximately 14' apart. The outer members start at the beginning of the bridge and extend 28' to the second bent. The centre member extends only to the first bent (14'). The next set of outer joists extends from the second bent to the fourth, while the centre member extends from the first bent to the third, a total of 28'. The joints are thereby lapped. (Three 10"x16"s bolted together are stronger than would be a single 30"x16" member (if you could find one) due to the dissimilarities in grain structure.)
The bent cap across the top of the driven piles which supports these joists is a single 14"x16", on edge, and the drawing shows six 14" diameter piles under each cap - four of them are more-or-less directly beneath the area of the 10"x16"s, while the other two are slightly outboard of the ends of the cap timber.

Wayne

[Puddlejumper]

Don't forget that the track on a wooden bridge is supported, beneath the ties, more-or-less directly under the rails, so those members need to be the heavy ones. For a wharf, their ends would most likely sit atop wooden pilings driven into the lake's bottom - cap timbers, as on a pile trestle, would usually sit atop the piles, with the rail support timbers atop them. As MountainMan points out, the depth of these members will be dependent on their span and on the load carried (which includes the surrounding deck area and the "live" loads of the train. I'd say that looking at a pile trestle should give you appropriate spans for your wharf - at least the part of it under the track, and then you'll be able to safely operate that steamer.

Wayne

Agreed. I don't think there is a need for lighter motive power... loaded freight cars don't weigh all that much less than the GP9... I would build a trestle for the support structure and use 3x8 lumber for the decking. I can't wait to see the finished structure!

[tetters]

This is exactly the type of discussion I was hoping to get going here.

One thing I think we all need to remember is that on the model, right below the decking there will be 1/8ths craft plywood. So I won't be modeling stringers under each rail. (Thank goodness!!! ...although that does sound like fun... hock: ). However it is good know what engineering would be required to build such a structure when tackling something like this.

That said, the input regarding the size and spacing of the trestles/piles I think is more critical here, considering that is what the casual viewer and fellow modeler is going to see plus the decking on top of the pier. Like I said, I can see some thing like 12 - 16 foot spans given what size of the lumber was used in construction.

I found three different sizes of hardwood dowels at the local Home Depot.

1/8" = 12 or 1 ft in HO scale. <---- good for utility poles.
1/4" = 24 or 2 ft in HO scale.
5/16" = 36 or 2 1/2 ft in HO scale.

I took a picture for comparison purposes next to the the 2-8-0 I have to show the size relative to the loco.



My eye tells me that the 2 1/2 foot dowel looks too big. However I think this might be the size that I am looking for if I want a bullet proof looking structure. At spans of 12' scale feet I think would be more then adequate in order to build a pier that looks believable and able to support the "weight" of the locos and freight. Once cross braced and combined with the overall look of the other trestles, this will look good.

Another thing I should also mention is the height of the pier...for all intents and purposes, the pier at 1:1 scale will sit about 2 1/2" high in order to meet up with the yard tracks which is about 18 scale feet (?). Also in the real world, the piles could drop another 10, 15 or even 20 feet below the water line. Especially as the pier moves further away from the shore. So I think the thicker and beefer the pile would be the way to go with out resorting to piles that look like fat stubby stumps.

Keep the comments coming. I am really enjoying where this is going.

[Puddlejumper]

I think the 1/4" dowels would be enough, and in my opinion would look better. Just my $.02

[tetters]

I think the 1/4" dowels would be enough, and in my opinion would look better. Just my $.02

Thanks. I think you might be right as well. I started off my day approaching a couple of problems with some "fresh eyes". It helps to get some new and different perspective.

[Sumpter250]

A pier, capable of supporting "rail traffic" would be first and foremost, built more like a pile trestle, wide enough for the rails, and rolling stock, and the attending machinery/vehicles, needed to move cargo from the train to awaiting ships.
The decking, would be heavy enough to support the "machinery/vehicles" + the weight of the cargo they carry, across its entire width. I would think a minimum 3" thick by up to 12" wide would suffice. The decking would have to be laid on stringers of the correct height to level the deck with the railhead.
The loco in Puddlejumper's avatar, was a B&O "dockside" 0-4-0.
Idler flats were more commonly used for loading freight cars on barges, to keep the weight of the loco off the barge, and or the movable apron, that was lowered, and secured to the car barge.
The pier could also be prestressed concrete, in more recent (late 40's on) years.

[nkp_174]

Yeah, I'm late to the game...

The issue for such a structure isn't total weight, but the weight distribution. For example, while their total weights are close...an Allegheny is far more of a nightmare on trestles than a Big Boy (slightly more weight distributed over few axles). The name of the game is Cooper Bridge ratings. I suspect that those lighter diesels would raise more havoc than 2-8-0 on spans approx the same length as the trucks.

Similarly, IIRC the axle loading issue was part of the reason why the CN used 4-8-4s while the CP used 4-6-4s (which had slightly higher axle loadings)...lower track/bridge standards.

My On3 trestle uses 8"x8" timbers set at 12" on center for ties. I'd run any decking perpendicular to them if I was turning it into a pier.

Many west coast narrow gauges ran their locomotives out on piers; the Pacific Coast Ry and North Pacific Coast were excellent examples.

[MountainMan]

The 1/4", if for no other reason that getting real trees the size of the largest dowel would be a problem and throw the scale way off as well. The following images may or may not help you:

Image # 1: a simple model of a wooden boat pier, showing basic construction:



Image # 2: a view of the top of a railroad pier:



Image # 3: old railfloat pier for the Hudson River Railroad:



Image # 4: pier pilings in production, prior to pressure treatment showing relative size:

[tetters]

...and just when I thought the thread had died. Thanks for all the interest and ideas gents.

I received the book I ordered from Amazon the other day. Interesting read to say the least. I had to remind myself when the book was published (1917) a few times. Especially when I came across a paragraph that indicated it would cost $20.00 to replace a pile on a wharf made with timber. No kidding.

Pile and trestles could be anywhere from 14, 12, 10 ft to as close as 6ft apart from each other. The 1/4" dowel will closely resemble the diameter of Pile I'll need to use in my build.

I also have a book (CPR Steam "in colour" Vol. 1) which shows CPR F1a Jubilee 2926 working the fishing pier at St. Andrews on the Bay of Fundy during the year 1960 pulling (or pushing?) five steel 40' box cars on the pier itself. It shows the pier at both high and low tide and the difference is quite dramatic. At low tide the pier looks to be as tall the loco while at high tide the pier is only a few feet about the water. Then there is the large structure which dominates most of the pier. I also get a kick out of the fact that that the piles and cross bracing appear to be quite chaotic. Piles are crooked, and the cross braces seem to point in every direction. It also looks like the rails sit right on top of the ties with no decking to fill in the "gaps". So good reference photos and makes me feel better that the idea is / could be reasonably close to some semblance of prototype operation.

I'm going to try and put together a mock up sometime in the weeks ahead to check my measurements to make sure I've got it all level and lined up.

Who knows I might get something built before the end of the year. ... but not likely...

[LynnB]

I'm thinking 12 x12 wood be about the right size.