I want to make a replica of a Roman dodecahedron, in order to experiment and speculate on its purpose (which is not known, although various competing hypotheses exist - some of them quite absurd).
It seems as though the dimensions and markings might be somewhat critical (the holes are different sizes and the faces are scored or marked in different ways), but I can’t seem to find much in the way of empirical, complete descriptions of any of them.
There’s a site herethat looked promising, but doesn’t seem to have the exact figures.
Is there anywhere on line or in print that I can obtain this information?
Sure. The critical bit I need is the sizes/proportions and relative positions of the holes in the faces - they’re all different, and that’s going to be an important feature, I suspect.
Seriously, though, to make a replica, your best recourse would be to obtain good photographs, with a scaling object (e.g. a ruler) in the photo. You could communicate with the curators at museums that have these things in their collections.
Frankly, I think you could make a darn good replica, simply from the photos you supplied! Get some modeling compound (clay, sculpey, whatever) and muck around with it until it looks right. Proceed to metal casting…
Getting really advanced here: how good are those new “3-D Printers” that can duplicate objects by building up microlayers of plastic? The last time I saw one used in industrial prototyping, the layers were about 2mm thick, giving the object a kind of “jaggy” look. If you could arrange for a museum to allow the object to be scanned – absolutely non-harmful! – you might be able to get a 3-D facsimile.
I agree that the hole sizes might be important. I spent a little time trying to pin down the relative hole size from a couple pictures, but never had anything close to a complete set of hole diameters. ETA: not just the hole diameters, but also the circles around them. Basically, I fit ellipses to the holes and circles in PowerPoint, then assumed the different distances to them was negligible so I could use the major diameters of the ellipses as their sizes. I have the data on another computer.
I can model it in wax, then use that to make a plaster cast for pewter - I’ve done that before and it works well - in fact, looking at some examples of these artifacts, I’d say they were probably lost wax cast (although some of the finer ones appear soldered from individual pentagonal plates).
But there’s no point starting until I can get the exact spec. I can make something that resembles these items, but I’m never going to know if I’ve discovered the true usage unless I’m using one that has the same physical properties.
BTW, my pet hypothesis at the moment is that these were devices for gauging a taper on the end of a shaft (if the shaft jams in two opposite holes simultaneously, it’s the right shape to fit a standard cast spearhead or something)
So my take is: What makes you think they only had one use?
A device like that with different size holes on each face (so 6 different size combinations) and that will always have two holes upright and free stand no matter how it’s placed down is useful in many many ways in Roman times.
Scroll holder (insert into larger holes)
Paper weight (or scroll weight)
Flag / standard holder
candle holder
game (flip coins into the holes as a betting game)
plus other uses in the thread above.
IMHO is that they were just a standard household item for middle / upper class romans, and the exact hole sizes don’t matter as long as you have different combinations of larger/smaller to fit different size objects you want to shove in there to stand up.
After all, most of the dodecahedra (and other platonic solids, apart from cubes) that were made in recent times were probably made for that purpose (and an otherwise similar Roman icosahedron has also been found).
From what I’ve read, there is no standard sizing for those things i.e. the hole sizes vary from example to example. There may be some constant proportion/ratio thing going on, but nothing online points to a study. Maybe that pay journal coremelt linked to goes into it, but I doubt it - the wide size disparities point to a standard design for whatever purpose, but a kind of home-brew manufacturing system. ETA: this page says some examples have equal-sized holes, which also complicates things.
I don’t think that - at least, not yet, and my opinion on their purpose has already changed many times.
However, if I build in an assumption that the hole sizes (or at least their relative sizes and positions) don’t matter much, any conclusions I arrive at (no matter how tentative) may be undermined by it - or worse, the inaccuracy of my replica may drive me to the wrong conclusion, or completely prevent me from approaching the right one(s).
I feel the need to start off with an example that represents, as accurately as possible, one of the extant devices. It’s the least risky approach.
http://www.romandodecahedron.com/en/hypothese
This guy claims on his page that: “The data necessary, like diameter, measurements, holes and the location where it was found, all come from the publication of Nouwen”.
Nouwen,R.1993. De Romeinse Pentagon-dodecaëder: mythe en enigma. Publicaties van het Gallo-Romeins Museum, Tongeren, Nr 45, Hasselt.
Only available as a physical book in Dutch.
I’m going to contact the museum by email to see if the book contains a table of dimensions. If not, maybe I can persuade them to measure the artifact for me (assuming they have one in their collection, which is not clear). Their website seems to suggest they’re quite meticulous about documentation.
Marcus: You’re using your gladius? That’s the wrong die, a gladius only does 1d8 of damage. Maximus: I said I called upon the blessing of Mars. Marcus: OK so that gives you a +2 to hit if Mars so grants it, but it doesn’t change the size of your sword. Maximus: Hey, I swing a sharp sword and better than most. Marcus: You can work the edge and polish the hilt but in the end, it is as it came from the forge. Maximus: … this is about my character, right? Marcus: I guess so. Maximus: You GUESS so? Marcus: Well, I’ve always thought it was pretty funny that you call yourself “Maximus”.
And this is why we find the occasional die left discarded in the wake of a scuffle…
Starting from photos like the ones you showed, use Photoshop to compensate for perspective and show each side as a proper regular pentagon. Scale the images and print them out. Use a bit of contact adhesive to attach them to your metal, and cut the 12 sides using your printouts as guides. Attach (solder, weld, braze, depending on what type of metal you use) the sides to each other, and then attach the balls at the corners.