Round spinning dice set - video

[Jon]

Round spinning dice set. 8:58 video:

Previously:

https://www.homemadetools.net/forum/...458#post122549
1920s Demley mechanical dice - GIF
Dice dotting machine - GIF

[bruce.desertrat]

now do D-20's :-)

[meyer77]

Nice job, Nice shop!

[Toolmaker51]

So, how does one go about assuring that 'rolling' the dice is just as random compared to dice cubes? I do like set of processes involved, action seen in results also satisfying as they 'park'.

[bruce.desertrat]

So, how does one go about assuring that 'rolling' the dice is just as random compared to dice cubes? I do like set of processes involved, action seen in results also satisfying as they 'park'.

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]

Yup, same impediments I imagined, a lot of ''if's'' center around the magnet arrangement depth, concentricity and squareness. What about larger diameter and double or triple up sets of 1 through 6's?

[bruce.desertrat]

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!

[Unkle Fuzzy]

If the spin is initiated by hand that will be fairly random and some sort of randomization could be incorporated into a brake to stop the wheels.

[meyer77]

I noticed the 1 and 6 were next to each other shouldn't they be opposite each of each other, does that affect the out come of the roll?

[bruce.desertrat]

I noticed the 1 and 6 were next to each other shouldn't they be opposite each of each other, does that affect the out come of the roll?

No, because the traditional dice layout doesn't affect the outcome, either. It appears to only be an old (VERY old) custom "Because we've always done it like that" is a powerful design motif.