|Excerpt from Railroad and Engineering Journal, Vol LXIII, No 10.|
Further research into early turntable designs revealed that gallows style turntables did not have rail stringers. In looking at the Manassas turntable, I concluded that it was very similar to a gallows style where the ties form a suspended deck. However, the Manassas turntable uses a wrought iron rod tension truss instead of a gallows. I was concerned about racking and twisting forces on such a design without a rail stringer, but a passage from an engineering book on early turntables explained that due to the low speed involved, those forces are minimal.
So I am rebuilding the Falmouth turntable be be a closer match to the Manassas prototype. I did not use the laser to cut these parts as I intentionally wanted some subtle variation in dimensions that comes with hand cut parts. I sanded the sharp corners and distrressed the wood slightly to make the parts look more "homemade." These parts form the main chords. I find it hard to believe that they mortised the main chords to accept the vertical truss supports, but the photographic evidence clearly shows this.
I am going easier on the black stain this time around as the wood should not be overly weathered. I'll have to make a new shaft and pedestal to make sure the height is correct.
Each tie has 4 visible bolts that hold it against the main chord. The bolts are in a distinctive pattern (see the prototype photo on the previous post). Adding these will be tomorrow's project. You really have to like adding NBWs to be an O Scale modeler in this period.