There are likely huge advantages to a wedge machine* in expedient conditions.  Linear tensioning (the most preserving of the spring) can be accomplished by a couple of guys with sledge hammers.  Wedges could be available in different degrees of angularity.  The smaller the angle on the wedge, within reason, the more powerful will be it’s effect in leveraging the steel spreader bar away from the flat-topped crossbar (as in the Lyon artifact).

If the machine is brought into a shooting condition, and then tuned to make the bolt shoot nice and straight by using only the driven wedge method**, then after this it should be possible to rotate the washers with a powerful spanner an additional 180 degrees and turn a nicely balanced lazy ballista into a nicely balanced high velocity bolt shooter. Preservation of balance is the key. It is an axiom discovered during our work with Firefly that a balanced machine does not lose it’s balance if additional washer rotations are performed equally on both sides of the machine. This would help explain the unfathomably coarse 180 degree of washer adjustment on the Lyon machine.  The wedges do the balancing, after which a single pre-determined rotation of all the washers puts the machine into high power mode.  These higher power levels are determined by how much strain is put into the springs originally with the wedges.

Using wedges and sledge hammers for linear stretching and balancing, followed up by a single twist of 180 degrees in the all the washers equally, would provide maintenance crews with easy and repeatable service protocols that are built right into the basic design.  There seems to be some clear synergies between a wedge machine and the modular spring concept we worked out with Firefly.  They should work very well together.

Because our current plan for Phoenix utilizes Vernier plates that can easily lock down 180 degrees of twist, we can test the above scheme simply enough, while retaining our conventional approach to tuning if needed.


* The ancient author Philon describes the wedge machine.    See Marsden, Greek and Roman Artillery.

**There is no more nuanced a way of fine tuning a two armed ballista that by actually shooting it and carefully observing the flight of the bolt in the first few feet. Bolt flight is, after all, the final arbiter.  If the tail kicks left, then the left spring is acting a tad more powerfully than the right spring.  (Or vice versa, of course.)  A wedge machine would be brought into balance only by driving the wedges deeper and never backing them out as this would be an awkward and unpredictable endeavor.  Sneaking up on balance points ain’t that difficult once you get the knack for it.

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