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 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 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.|