Of Scorpions & Sliders

[P. Clodius Secundus]

How does it ... slide?! :? ... but can you explain again?

I've got some CAD drawings and a 1/2 scale working model, but for now...
I see it working just like a monorail tram. The canalis fundus is the rail and the chelonium is the shuttle. If the rail is "T" or "I" shaped in cross section, the block could be "C" shaped so that it clamps down over the lips into the lateral grooves (the "C" channel was known ie. Elginhaugh ratchet) The original idea was John Anstee's, but I believe that following Ammianus, he included some guide rollers. IIRC There were some bronze rollers found with the Hatra frame that could perfom a similar function. They are often cited as part of a pulling-forward system but as I found out, there's no mention of such systems after the earliest Greeks. I believe Nick Watts uses a fixed-slider moving block on his Orsova ballista. To my way of thinking he has it almost right except he uses an up-scaled version of Heron's cheiroballistra case. That's like putting a rifle's wooden forestock or forehand on a cannon. With a winch to draw the weapon and a fixed rail the whole case forward of the ladder is superfluous and can be lopped off. Again that explains why the "sliders" on Trajan's are shown in the forward position and also why they appear too small to be part of the case. Back to the woodframers, John Anstee may just not have been enough of a heretic. Alan Wilkins' critique of his theory got me questioning exactly why everone knows that all Roman weapons had sliders. Throw in the contradiction apparent in the Cupid Gem and it all makes more sense.