|Pier and Dock|
The Deep River RR Pier and Dock – in this case it’s both. From my understanding (minimal) .. the pier is the structure supported on piles and the dock is the area of water alongside where the ship loads/unloads.
I’m going to basically follow the design of a railroad trestle and modify it as needed for a pier (that’s mainly due to an excellent resource “A Treatise on Wooden Trestle Bridges” by Wolcott Cronk Foster published 1897 .) Up to about 10 ft. in height. Wooden trestle bents generally consisted of vertical piles .. above 10 ft. in height they would drive the outside piles at a batter of from 1 in. to 3 in. per foot. I will be following the trestle design for bent caps, stringers and so on.
|Narrow-Gauge Engine Weight|
This next bit is ‘pesudo-engineering’ .. or .. ‘imagineering’ .. please .. engineers don’t freak on me! I’m having fun playing with numbers here.)
EBT Mikados weighed between 112,00 and 163,000 lbs. A RGW Mike (K36) around 185,000 lbs. Light Mikados built for the Walbash in 1912 weighed 266,000 to 290,000 tons. Later heavier Mikados at the Walbash weighed around 338,000 tons.
At the extremes that 112,000 lb EBT Mikado weighed 33% of the heavy Walbash Mike. The RGW K36 at 185,000 lbs weighed 70% of the lightest Walbash model. A little math tells me that to weigh 33% of another it would have been 69% the width, height and length. That RGW K36 at 70% of the weight of the lightest Walbash would have been 89% of the width, height and length.
I’m playing with numbers here but the book the D&RG trestle was published in 1897. With that in mind I am going to compare that 112,000 EBT Mikado with the light Walbash Mikado which weighed 266,000 lbs. .. which comes to 42%. A locomotive that is 42% the weight of another .. and for the purposes of this fantasy, reduced proportionally .. would be 75% of it’s full-sized sister in width, length and height.
|Size of Stringers Needed|
In “Railroad construction: theory and practice” pub 1922 it has the following concerning stringers.
“Disregarding all refinements as to actual dimensions, the ordinary maximum loading for standard gauge railroads may be taken as that due to four driving-axles, spaced 5’0″ apart and giving a pressure of 40000 pounds per axle. This should be increased to 54000 pounds per axle (same spacing) for the heaviest traffic.“
Using the calculations that the Narrow-Gauge locomotive weighs 43% of the Standard-Gauge locomotive (and keeping the 5’0″ wheel spacing) we get a pressure of 16800 pounds per axle.
We then get a chart for ‘Stresses on various spans …’ for spans of 10 to 18 ft. Just below the chart it refers back to the earlier 54000 pounds per axle for heavier traffic .. where it states ..
“ … there will be no appreciable error in assuming the corresponding values, for a load of 54000 lbs. per axle, to be 54/40 of those given in the above tabulation.“
Ok. Then for my 16800 lbs. per axle load for my narrow-gauge then the corresponding value would be 17/40 or 42.5% .. of course.
From the chart, with a span of 10-ft. the load on one cap will be 41200 lbs. For our narrow-gauge locomotive that will convert to 17304 lbs. If the stringers and cap are made of long-leave yellow pine (why not), the allowable value, according to Table XXI, for “compression across the grain” is 260 pounds per square inch; this will require 67 square inches of surface. If the cap is 12″ wide (it is), this will require a width of 5.6 inches.
From the chart showing ‘Stresses on various spans …” we find that (for Standard-Gauge) and a Span of 10 feet, the Max. movement, ft. lbs is 51500. Multiplying that times 42% for Narrow-Gauge we get 21630.
For rectangular beams. Moment = 1/6*R’bh2
21630 X 12 = 1/6 X 1300 X 5.6 X h2
My strip-wood stock I have is 1/8-in x 1/4-in .. or .. 6-in x 12-in full size. Let’s try replacing that 5.6-in width with the 6-in and see how that changes the stringer height.
21630 X 12 = 1/6 X 1300 X 6 X h2
If we double the stringers so we have 12-in. and run the formula again …
21630 X 12 = 1/6 X 1300 X 12 X h2
So. We need a pair of stringers, each measuring 6-in. x 10-in. The stock I have that measures (scale) at 6-in. x 12-in. will do fine! Yea.
Ok Ed. You like playing with numbers .. but .. so?
The D&RG trestle lists the stringers as “8 in. x 16 in. x 32 ft.“. In the book it states that “Bents should be spaced at such a distance between centers as will use the length of timber easiest to obtain for stringers inthe most economical manner. The distance varies from 12 ft. to 16 ft.; spans of 14 ft. and 15 ft. being the most general.“. Looking back at the D&RG trestle having stringers of 32 ft. that pretty much tells me they spaced their bents at 16 ft. OK?
From “Wood Structural Design Data” pub 1986 in the Safe Load Tables for 16 ft. spans we can get some more numbers to play with. Hooray.
For “Allowable unit stress in extreme fiber in bending, psi. let’s go with the 1300 psi. from the earlier Chart XXI. From the chart (using the 1,300 psi. column) we find that a 8 in. x 16 in. beam will safely support 16,266 lbs Total uniformly distributed load .. and 1,016 lbs. load per linear foot of beam. Cool.
With the Narrow-Gauge load at 42% of Standard-Gauge as calculated earlier we can modify those numbers. 42% of 16,266 is 6,832 lbs and 42% of 1,016 is 427 lbs. Again .. much coolness.
Now. I went back to the chart for 16 ft. spans and went backwards looking for these numbers.
A 6 in. x 12 in. beam spanning 10-ft. and using 1300 Fb will give us 10,506 lbs and 1050 lbs. respectively.
Looking back we see that each rail is supported by two stringers. So the total load needed to support is 20,204 lbs. Two 6-in. x 12 in. stringers, each supporting 10,506 lbs is 21,012 lbs. Shazam. Hooray and all that.
|So. From two different directions I calculate that two 6-in. x 12-in. stringers under each On30 rail will be fine. There you go. Pseudo-Engineering at it’s best!|
Length: 17 inches .. that will be enough to run the length of the ‘water’ section stopping just short of the far bank. That will represent a 68 foot long pier/dock.
Width: I ended up with a 5-1/4″ width. this is room for the narrow gauge track with a 9-ft traveling crane straddling the narrow gauge .. with room for a truck to drive onto the pier for loading/offloading and finally an outrigger rail on the dock side. That should provide plenty of interest.
Edit: Found some information in a book titled ‘Wharves and piers: their design, construction and equipment‘ – by Carleton Gren pub. 1917. That would be a “fender Timber” that I was looking for. I found several drawings of them – 8×8 in.; 8×12 in.; 6×10 in. In the drawing to the left from Depot Harbor, Ont. there are several items of interest. The fenders are 10×12″ in two rows about six feet apart. They are bolted on with 1 in. screws spaced 5 ft. apart. The Bollard is also shown, which I had forgotten about.
Looking at various drawings I think the best bet for the dock side of the pier is to double up on the pilings there so you get a vertical surface to which I can mount the fender timbers.
Note: I was at Lowe’s yesterday and knowing they had large timbers for sale I wandered over there. The 6 in. x 6 in. timbers are BIG. My little docking area isn’t for giant ships but small boats as the pier is only 10 ft off the water. 6 in. timbers would be quite large enough .. thank you very much!