DRRR Pier – Part VI

Stringer Blocking
When the stringers are not fastened directly to the caps they should be notched over them I in. A method for holding the stringers in place, and which is becoming quite general, is shown in Fig. 99. It consists of a piece of 3 in. X 12 in. plank, fastened, outside of each stringer, to the cap by four log-screws or by spikes. The stringers in their turn are kept at the proper distance apart either by a spreader made of the same material or by fastening the ties to them.

I highlighted the blocking they are talking about. Instead of notching the stringers which would weaken them where notched they added this blocking which in effect creates a ‘reverse notching’. A 3 in. x 12 in. plank is 1/16 in. x 1/4 in. in O scale so that’s easy.

Note that to attach this blocking they use log-screws or spikes – I am pretty sure they meant lag-screw. Elsewhere they talk about fastening the guard-rail to the ties. There, if used, they specify a 5/8″ x 8″ screw with a wrought washer under the head. It doesn’t specify the washer size but in the same section talking about using bolts they specify a 3-in. to 3-1/2-in. washer.

The spikes I used for the landscape timbers in my garden measure 1/2-in. across the head. I think it would be reasonable to suggest that the spikes used to hold the blocking to the caps would be easily 1-in. across the head. This would be ~0.20-in. in O scale. This is one of those ‘wow’ items I think .. taking the time to simulate the spike heads .. which should be visible between the ties.

Keystone Spikes Corp shows dimensions for their spikes. Listed as ‘Boat Spikes/Dock Spikes : .. used for heavy duty timber construction such as docks, trestles, highway crossings, etc.

Spikes with a head dia of 1-1/4 is a 1/2 in. body .. and 6 to 20 inches in length. Using .020-in dia Styrene then would represent that size spike.

Carpenter – US Army TM 5-551B 11-11 Decking: Standard decking consists of 4- by 8-inch planks which are spiked to each stringer with two 5/16- by 7-inch spikes, and set with 1/4-inch spacing. Openings between planks greater then 1/4-inch may be used in areas which are subject to heavy rainfall.

Keystone shows that a spike like the Army uses above – 5/16- by 7-inch spike – has a 3/4-in dia head. The slightly larger 3/8-in spike has a head just over 1-inch so .. yea .. .010-in Styrene would be just about right.

.. also .. using ‘pseudo-engineering’ – they Army was spiking down 4- by 8-inch planks. I will be using 4- by 12-in planks. Seems reasonable they would opt for the slightly larger 3/8-inch spike in that case anyway.

Stringer Blocking on the DRRR Pier
This pier supports a On30 track with two stringer pairs separated by Stringer Blocking A. Straddling that is a Crane Track, again supported by two pairs of stringers. Stringer Blocking B separates the On30 and Crane track stringers. On the far left, Stringer Blocking E is the outside blocking for the Crane Stringer pair. Stringer Blocking C separates the other Crane Stringer pair and a Vehicular Deck Stringer. Stringer Blocking D then acts as separators for the remaining Vehicular Stringers. The 12-in. sq. Crane Outrigger stringer has a dual role of also forming the blocking for the out-most Vehicular Stringer.
Stringer Block A
I’m going to start with Stringer Block A. Since the On30 track is the ‘main player’ .. everything else – the crane track and vehicular deck are just ‘supporting players’. I’m going to use a straight-edge and lay out the blocking in between the On30 Stringer groups – Stringer Block A. It’s important that they all be the same exact length since they will align the On30 Stringers. The important dimension here is the 0.381-in. .. the rest are nominal.
Dapping Ties
A little searching on Google and you find posts where people ask about bridge ties. The answers will often be more for modern practices. I am using sources, many from the turn of last century. They show a range of practices .. tie size, spacing and so on. In general, bridge ties were 8-in x 8-in. Spacing varied quite widely .. everything from 6-in to 16-in. In part that depended on the design of the bridge. When for instance the rail was carried directly above the stringers then there could be a wider spacing then the stringers were otherwise. Even the dapping/notching varied from 1/2-in to 2-in depending on the railroad. I decided on a 1-in dapp/notch over my stringers. This by the way .. was why the bridge ties are thicker. They are notched over the stringer and thereby reducing the tie thickness at that notch.
Dapping Guard Timbers
In a similar fashion, Guard Timbers were also dapped/notched over the ties .. and again .. a one-inch notch. There is more about securing the Guard Timber to the ties and/or the stringers but I’ll expand that when get there.
Green Foam Work Board
High Tech Clamping : Hey .. if it works .. all is good.
* RATS *
Well. The clamp worked .. and .. using the Green Foam worked .. somewhat.

It worked with the U-shaped pins to hold stuff down pretty well. It worked ok .. until I was test fitting the first stringer assembly and I noticed there was a gap over the center bent caps.


My first thought was that the strip-wood was warped .. but checking it .. wasn’t THAT bad. So I put a metal yardstick across the caps.

*R*A*T*S* # 1 .. the foam isn’t flat. Dang it. Ok. Going to pull out my 18-in. floor tile which IS flat. Just have to use tape to hold ‘stuff’ down.

*R*A*T*S* # 2 .. my 18-in. floor tile .. wasn’t. More like 15-1/2-in. (which translates to a 16-in. tile) .. Arrrgghhh. Off to Lowes.

Found a 18’in. tile. I KNOW it is because I took my tape-measure with me .. and the adventure continues!

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