The electric winch installation is almost complete.  The side opposite to where that shackle ties off the end of the winch rope,  will soon be equipped with an extra pulley to allow an additional fall of rope so that our 4700 lb winch can easily handle the 5,000 lb load.   This orange beastie doesn’t have quite the same terrifying clickity-clack as the hand winch, but the couch-potato aspect it provides will make data collection a much more pleasant and prolific experience.

While it pains me to admit it, there is a structural issue with the diagonal struts that needs to be addressed.  For a while now I’ve been fighting to keep the starboard limb from rising up laterally at full draw.   It is clear that the diagonal struts need to be made from a heavier cross section material as the 5/8  inch stuff we are currently using has a tendency to bow out when under load.  This allows the field frame to tip back slightly, the effect of which is magnified by the long arc of movement out to the limb tip.  You can just make out the bow in the strut in this next photo taken from the at rest position.

When it is under load the bow becomes quite pronounced.   One can only imagine how damaging it would be to the entire machine if the kind of loads we are running were attempted with no diagonal struts at all, as some researchers have suggested.  If a winch powered,  iron frame ballista,  is going to perform above the level of a glorified garden toy,  it is essential to stabilize the field frames back to the stock by triangulation with a decent set of struts.

It is by this argument that we infer the existence of the vernier plates on the original Orsova machine, because without those plates there really is no good place to attach the struts to the field frames.    Possibly a strut could be connected to a projecting length of tang from the kamarion,  but this would be a profoundly inelegant solution and not nearly so strong as a lug projecting from a vernier plate.   Of course,  a vernier plate also provides the necessary hole pattern to create the fine rotational discrimination of 7 1/2 degrees in the washer that is essential to balance the two torsion springs.  Also it provides the opportunity to utilize the maximum amount of spring cord by providing a rebated rim for the washer to rotate in, and thus allow the full diameter of the 3.1″ hole in the end caps of the field frame to be available to receive an increased spring diameter.  And in the words of Philon, from his manual on artillery, “The man who wants to shoot far must try to put on as much spring cord as possible…”

Very rarely is there only one good way to do something.  However,  having wracked my brains for years on this matter,  and now with this bowed strut and lifting limb situation, I am all the more convinced that the original machine must have had a sturdy set of struts and vernier plates to attach them to.

For any newcomers to this blog, here is a snapshot of Firefly belting out a 415 gram bolt to a range of  892 yards.  If you scroll back several pages we have  some videos and write-ups of all the action.   The four diagonal struts we are talking about are clearly evident in this shot.

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