Before we get to the lab work, and videos of speeding nasty things, a little background is needed to place our efforts in some kind of socially redeeming context.  Kinetic prurience aside, we do have standards after all.

Professor Tracey Rihll from the University of Swansea has written a book about the history of the catapult, titled logically enough,  The Catapult.  This isn’t just any book.  It is a mind bending trip into the world of ancient technology.  I was left exhausted after every chapter,  my simple mechanic’s brain overloading as it  riffed on all the possibilities for future experiments here in the little catapult factory.  By any measure,  this is “THE” book to get if you have any interest in this deliciously arcane subject matter.  Hats off to the good doctor.  To all catapult noddies and genetically deranged  toxophilites:  go  get a copy!, you won’t regret it.

It is from Tracey’s book that we copy the following photo.

These are impact craters that appear to have been made by heavy fast moving objects.  They are located on the walls of Pompeii and are almost certainly the work of ancient ballistas.   In general there are three types of missiles thrown by ballistas:    iron headed bolts similar to the ones we have been using in our testing ,  lead and sometimes stone bullets known as glandes (glandes is plural, glans singular),  and finally stone balls of a suitable diameter.    Glandes are found through out the ancient world and Dr. Rihll has made a compelling argument that they were very likely used as catapult ammunition.  It had long been thought that these artifacts were used solely by hand slingers.   The ballistic coefficient of a lump of lead is naturally higher than that of a stone projectile, and so, Goliath’s forehead notwithstanding,  the lead glandes were considered by most scholars to be part of the natural evolution of the sling.  Here is a photo of some of them, also taken from Tracey’s book.

“Let them eat eggs” would be a suitable motto for these little lead pills.   Most of them will sit in the palm of your hand like an extra large AA chicken egg, on steroids.   Many were actually inscribed with taunts and jeers.  “One in the eye from Biggus Dickuss ”  etc. etc.   The current state of development of Firefly does not allow for the firing of glandes and stones.  That will probably require a special string with an integral pouch of some kind.  However, that does not necessarily stop us from smashing glans shaped lumps of lead and stone into a block of concrete to see if we can duplicate some of the impact craters seen on that wall from Pompeii.

And so finally, to the fun stuff.   We start with a rerun of that test done the other day shooting one of my standard bamwood bolts with a hardened steel quadrobate tip into a building pier.  This time however, the pier grew a bit.  We wouldn’t want to skew the results by using a puny target medium.  The block in the following video weighs about 500 lbs and has been sitting in the dry Okanogan topsoil for the last thirty years.  It seems a plausible substitute for that wall from Pompeii.   At least, it is the best we have right now.

Video is in 4X slow motion.    20100317133432(1)

Stats for the above shot are:  Bolt weight 7160 grains;  bolt head 4140 steel, quadrobate shape hardened to 40 Rc.;  velocity 298 fps;  energy 1411 fpe (1914 J).  The bolt head penetrated into the block to a depth of 2  3/4 inches and left a surface crater 4″ in diameter by 3/4″ deep.  The photo below shows the state of affairs before I attempted to remove the bolt head from the block.

———————————————————————————————————————————————— Moving on to the next shot,  we tried our tarted up version of a stone glans.   The photo below shows what we came up with for a delivery system.   The shaft of this special bolt  is made from  a  1  1/8″  bamwood broom handle.

Because it is highly unlikely that the concrete block would know there was a wooden shaft attached to the rear of our ovoid shaped piece of granite, it seems reasonable to assume that this test is a pretty good indication of what the crater would look like from a speeding stone glans.  How likely it would be for a free wheeling egg shaped projectile to strike end on is unknown, however, this angle of attack would seem to give the best chance of leaving some kind of mark on the block.

Here is the video of this shot with a stone “glans”,  also shot in 4X slow motion.   20100317141953

Stats from this shot are:  Bolt weight 7561 grains, velocity 291 fps, energy 1421 fpe (1927 J).   From the video it appears that the bolt is moving tail down.  This is probably the result of the larger than usual head diameter.  The bolt sits on the machine at an angle,  after that all bets are off for transferring a purely linear force vector into the projectile as it trundles down the bolt groove.  It is clear that at these velocities the stone glans simply disintegtates on the surface of the block.   The previous photo shows a small crater made by this shot.    It is outlined by the chalk circle and  measures 2 inches in diameter and just under 1/2 inch deep.  Not at all the thing if you want to leave your mark for posterity.  Although there do seem to be some pretty shallow craters on that wall from Pompeii, so maybe…..

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