09-08-2010, 06:57 PM
Greg, I have a couple questions about your design choices for these engines.
First, why did you opt for linear saw-tooth ratchets? Since your base and most other features are Vitruvian, one would expect to see a circular ratchet attached to the winch drums. Marsden, Morgan, Feely, and Wilkins all seem to agree on that point. There is evidence of round ratchets as far back as Ephyra and, to my understanding, none that supports that type on stand-mounted engines after Biton of perhaps Philon. The Cupid Gem distinctly shows a round ratchet as well. Alan Wilkins did include them on his Cheiroballistra, but indicated that he did so because it was safer in case the rope breaks. The only evidence of a linear ratchet in a Roman context is the "C" channel one from Elginhaugh, but that is a totally different type.
Second, it appears that your center stanchion is aligned with the front of your hole carrier rather that with the curved portion that extends to the rear. This appears in Wilkin's writings and designs, but contradicts Marsden. Do you know of any source that suggests which is right? On my prototype, I made the center stanchion run the full depth of the hole carrier, but now after installing the arms I find myself having to cut out a lot of the "meat" of the front portions to gain clearance for the heels of the arms. Unless there is difinitive proof to the contrary, my next one will be recessed per Marsden's text.
Third, the centerline of your arms and the bowstring seem to be directly on a plane with the top of your slider. I know Wilkins says that this alignment is "axiomatic" but I'd like know to the source for this bit of wisdom. This has never been a requirement on crossbows where the bow is usually offset downwards with the string riding along the groove. Marsden's drawing of the gastraphetes (TT P.47) illustrates this point perfectly. Caminreal, Cremona, and the Cupid Gem all indicate that some degree of downwards offset or "underslinging" of the frame was normal. This is another deficiency that I plan to correct in my next version.
All of my nit-picking uber-geek questions aside, I really do admire the time and craftsmanship you've put into these machines. I hope you'll continue to share pics and data here on RAT.
Regards,
Randi/Clodius
First, why did you opt for linear saw-tooth ratchets? Since your base and most other features are Vitruvian, one would expect to see a circular ratchet attached to the winch drums. Marsden, Morgan, Feely, and Wilkins all seem to agree on that point. There is evidence of round ratchets as far back as Ephyra and, to my understanding, none that supports that type on stand-mounted engines after Biton of perhaps Philon. The Cupid Gem distinctly shows a round ratchet as well. Alan Wilkins did include them on his Cheiroballistra, but indicated that he did so because it was safer in case the rope breaks. The only evidence of a linear ratchet in a Roman context is the "C" channel one from Elginhaugh, but that is a totally different type.
Second, it appears that your center stanchion is aligned with the front of your hole carrier rather that with the curved portion that extends to the rear. This appears in Wilkin's writings and designs, but contradicts Marsden. Do you know of any source that suggests which is right? On my prototype, I made the center stanchion run the full depth of the hole carrier, but now after installing the arms I find myself having to cut out a lot of the "meat" of the front portions to gain clearance for the heels of the arms. Unless there is difinitive proof to the contrary, my next one will be recessed per Marsden's text.
Third, the centerline of your arms and the bowstring seem to be directly on a plane with the top of your slider. I know Wilkins says that this alignment is "axiomatic" but I'd like know to the source for this bit of wisdom. This has never been a requirement on crossbows where the bow is usually offset downwards with the string riding along the groove. Marsden's drawing of the gastraphetes (TT P.47) illustrates this point perfectly. Caminreal, Cremona, and the Cupid Gem all indicate that some degree of downwards offset or "underslinging" of the frame was normal. This is another deficiency that I plan to correct in my next version.
All of my nit-picking uber-geek questions aside, I really do admire the time and craftsmanship you've put into these machines. I hope you'll continue to share pics and data here on RAT.
Regards,
Randi/Clodius
P. Clodius Secundus (Randi Richert), Legio III Cyrenaica
"Caesar\'s Conquerors"
"Caesar\'s Conquerors"
