The loops and tangs evident in the Orsova artifacts demonstrate the use of modular components in iron framed Roman ballistas.  In designing Firefly, I tried to extend this theme of modularity, figuring that if the artifacts themselves demonstrate this feature, then there is no telling where those sneaky old Romans left off with the strategy.   Firefly’s rope springs are modular, pre-wound bundles that are carefully stitched together to insure they maintain their shape as they are sucked into position in the field frames during the installation process.  Changing out the spring bundle in a field frame takes about an hour.

After proper pretension and tuning with the limb in place, this modular approach seems to work quite well.   The advantages of having spare, pre-made springs to swap out quickly would seem to be a huge advantage to anyone trying to maintain these machines.  It certainly was for this muggins who had to do all the work alone.   It is difficult to imagine that the innovative Romans who came up with as revolutionary a design as the Orsova machine, would not have tumbled to this approach also.

In this next photo we see the set up used to induce linear stretch into a pre-wound bundle that had just been installed into the port field frame.   If you blow the photo up to maximum size it is possible to see the steel spacers that are slipped under the crossbars to lock in the linear stretch.   One might call it an updated version of Philon’s “wedge-machine”.  (See Marsden’s,  Greek and Roman Artillery.)

 

feather 017

 

On the other hand, perhaps the iconoclastic Romans engineers that developed the Orsova machine had enough willing hands to run the spring cord around the crossbars and tension each strand as they went.  If that more traditional approach to pre-tensioning yielded a performance advantage, that would pretty well negate any argument for modular springs because they were merely more convenient for the maintenance department.

…….. And so, if we are to get to the bottom of this, it seems Phoenix will need springs installed the old fashioned way. Tediously and with a stretcher.  Strand by strand by strand…..

Maybe.

 

 

Leave a Reply