Today I will be finishing up a special bracket arrangement that attaches to the rear of the klimakion. This is the ladder like structure than connects in to the bottom of the field frames. The bracket will allow the trunnions that form the pivot point for elevating and depressing the machine to be movable fore and aft, thus creating an adjustable center of gravity. This is an instance where we temporarily diverge from the likely Roman solution to forming this pivot point. From the Cupid Gem, it appears they simply ran an iron rod through the wooden stock at the appropriate location, and called it good. Eventually Firefly will also receive that same solution, in the meantime I want to be able to fool around with the center of gravity to find out what is most desirable for some of the fluid, offhand style shooting I have in mind. It’s kind of an over-design and then work backwards approach.
A similar strategy will be employed to figure out the meaning of those holes apparent on the tangs of the original kamarion. Our current reconstruction has used a simple lug and wedge system for mating the tangs to the loops on the field frames. This approach was chosen because it offered high confidence that the joint would be as strong and reliable as it could possibly be. On the firing line this will allow us to conduct tests that will demonstrate the maximum levels of power and accuracy that can reasonably be considered achievable with this type of machine. Once that is established, we can modify Firefly to explore how an approach that is more strictly interpretive of the artifacts affects performance (e.g. Aitor Iriarte’s suggestion seen in his diagram below).
So again, short of changing the spring size, in certain key areas we have deliberately over-engineered the solutions to insure that the final performance on the firing line is as good as it possibly can be. Once that is achieved we can modify Firefly to hair split designs that may be more consistent with the strictest interpretations of the archaeological evidence. Why go to these lengths? Because every serious attempt to reconstruct an ancient two armed ballista that we have ever seen has fallen way short of the performance levels indicated by the Ancients. (No offense fellow reconstructors.) Our mission is to first secure the performance and then work backwards towards more detailed explanations similar to Aitor’s shown above. Overshoot and then regress. This is a very, very long game we are playing here.
A final note: it seems some researchers have given up trying to duplicate authentic levels of power in torsion engines by claiming that the modern synthetic spring materials today’s researchers are forced to use cannot compete with the sinew used by the Ancients. My experience with three strand nylon shows this is not true if sufficient pre-load is put into the bundles. Naturally a sinew based spring would perform differently than a nylon based one, but probably not so much in the accuracy department, which, once the springs are normalized to the torsional load they must bear, is largely dependent on other factors such as the machine’s rigidity and ability to repeat it’s mechanical positioning back to the at rest state. Anyone following this blog knows that Firefly has the performance aspect well in hand. No brag, just fact. The rest of the master plan is just work.
As I said, this is an excruciatingly long game, and beneath all the scribbles and bluster that I use to stay motivated, there is method to the madness. Back to grinding now……….
