Round spinning dice set. 8:58 video:
Previously:
https://www.homemadetools.net/forum/...458#post122549
1920s Demley mechanical dice - GIF
Dice dotting machine - GIF
Round spinning dice set. 8:58 video:
Previously:
https://www.homemadetools.net/forum/...458#post122549
1920s Demley mechanical dice - GIF
Dice dotting machine - GIF
New plans added on 11/22: Click here for 2,593 plans for homemade tools.
bruce.desertrat (May 23, 2021), Christophe Mineau (May 23, 2021), johncg (May 23, 2021), mklotz (May 23, 2021), rlm98253 (May 22, 2021)
rdarrylb (May 23, 2021), Toolmaker51 (May 24, 2021)
First, barring 'Vegas-level scrutiny', I think these are more than random enough for , say, Monopoly use. Certainly more random than the real dice in the video. (they have divots for the spots, which subtly biases the cubes weight distribution; real casino dice have spots that are screen printed for that reason. Casino dice also have sharp edges and corners, not rounded. although I don't know if that's to shorten the rolling time or just tradition. A LOT of engineering goes into making them.)
Since they're turned on the lathe they're perfectly concentric to the axle, so there's no bias in weight distribution there, and I'd be surprised if there was a microgram total of material removed by the laser etching. that leaves only variations in the placement and strength of the magnets, and that's governed by the care in drilling the holes precisely and the magnets themselves (which are all produced on automated production lines to exact specifications these days).
Testing this would be an interesting project in itself. You would need to devise some mechanism to repeatedly apply the same rotational force to the rollers.
Toolmaker51 (May 24, 2021)
bruce.desertrat (May 24, 2021)
I don't think that would actually change anything, because I'm going to presume that the magnetic 'brake' is the primary source of bias, adding more numbers (like the D20 I mentioned) won't change it except for offering more places to bias the roll.
I thought about adding a spring-loaded ball fitting into evenly spaced detents (which would provide a clicking noise as it spun) but that could stop from plain friction between numbers; the magnet solution actively brakes it at the right point to make it work to display the number.
It's going to be hard, if not impossible, to eliminate bias in the design; only minimize it with careful machining and construction. Probably why this approach hasn't taken the Casinos by storm :-)
It's a really cool object, and exercise in machining though!
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