I’ve been thinking about some discussions I had with Samuli Seppanen about trying to find out the relative power of sinew vs. nylon in a torsion spring.   As I recall, we were agreed that it should be possible to work out a ratio between the propulsive qualities of the two materials by using a pair of small, identical catapults — one powered by nylon, and the other by sinew.   This seems like an important enough question that it could stand to have a couple of different researchers probing it.  I have some fixturing and tests  in mind that should establish that ratio with adequate precision to make a reasonable prediction about how well Firefly’s torsion springs would perform if they were made out of sinew rather than nylon.

This is important because I have noticed a repeated criticism from some quarters, that if experimental archaeology can’t be counted on to demonstrate what a torsion machine can do when powered by sinew, then the whole exercise is “pointless”.  In a certain narrow way, I suppose this is true.   However, it has always seemed to me that any serious inquiry into the potential of a sinew based machine  would need to be predicated on some baselines established with a fully developed nylon powered machine of unquestionable power and performance.  Without that, there is no way to really know if all the other aspects of the machine (ie. the strength to weight ratio of the limbs, frame strength, rigidity, draw weight etc.)  have been taken to an optimum level.  It’s not like it is practical to do that kind of extensive research with something as rare and precious as a matched pair of full sized sinew torsion springs.  However, a small enough torsion spring made from sinew, maybe something the size of a 4″ blunt cigar, now that’s a happening thing! …

I have tried to be  careful in this blog to never openly state that Firefly’s ballistic performance is necessarily an accurate analog for a sinew powered machine.  It is perhaps the most obvious of objections to complain that because  modern reconstructions are powered by nylon,  they have no useful contributions to make.   In Firefly’s case, it might be helpful for any critics to remember that she is a work in progress.

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