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I've been working on a marble dispenser for the little ones. The box in the center is meant to be pushed. When pushed, it aligns three slots and allows the marbles to drop. (See figures). The problem that I'm having is the marbles aren't even making it through the first slot--if two or more try to enter at once, there's not enough room and they get stuck.

I tried using a funnel to feed marbles into the hole, but they still get stuck. Any ideas on how to prevent that?

Marble dispenser in closed position

Button in closed position

Button in open position

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  • If all the holes are aligned, do marbles also get stuck? Is it only when they hit the top of the moving block that they get stuck? Commented Oct 13, 2014 at 21:32
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    I think Matthias Wandel covered this sort of issue in one of his videos. In one I watched, his stored marbles are lined up in single-row channels. He also carves the entry hole so it is slightly conical. Commented Oct 14, 2014 at 15:32
  • @MaximeMorin, Yes, if marbles are aligned, they still get stuck. They are getting stuck at the very top hole as two are fighting to get inside the same hole at once.
    – dfife
    Commented Oct 14, 2014 at 16:35
  • @RedGrittyBrick, yeah...I did look into Matthias Wandel a little bit (though probably not enough). I'll scour through those. I think you may be right, though. A single channel (e.g., PVC pipe) that feeds into the hold may be the best way to do it. I wish I'd thought of that before I built a box!
    – dfife
    Commented Oct 14, 2014 at 16:37
  • After perusing Matthias Wandel's stuff, I saw that he has one element of his marble machine where there's three holes. I think that may be the solution--drill three holes so they can't get stuck (kinda like the fingers for a bowling ball). I'll keep you posted.
    – dfife
    Commented Oct 15, 2014 at 15:00

2 Answers 2

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It occurred to me that this problem has already been solved... Gumball machines and/or coin-op toy dispensers at the grocery store are capable of selecting just one of something. A quick search reveals a solution like this:

enter image description here

Seem to me you may be able to adapt your design to work something like that. Even if not, I'd look at gumball machine designs...

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  • Nice graphic. I do think having a longer shaft will help, but at the same time, I still think the marbles will get stuck as they try to enter the shaft.
    – dfife
    Commented Oct 15, 2014 at 14:59
  • It seems you have a predilection for second sight, @bobfandango. I ended up finding a gumball machine at the dollar store and bought that. (Now what am I going to do with what I built!). I did find that enlarging the hole worked too. I finally got around to taking pictures so you can see the problem (and the sorta solution): dustinfife.net/blog/1-diy-marble-dispenser-kinda
    – dfife
    Commented Oct 24, 2014 at 0:41
  • @dfife Very nice carpentry there! Sorry it didn't work out. But you'll always have the joy of all the work that went into such a nice looking final product. Commented Oct 24, 2014 at 0:53
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The size of the hole should not be more than 1.2 to 1.5 times the size of the marble size, if its too large the balls will begin to come in pairs and get stuck, However I think your problem is the lack of funnelling in the ball receptacle, A good idea would be to buy a paintball dispenser from a paintball gun.

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  • Thanks for the response. I hadn't thought that it's too big. (I actually thought it might not be big enough). A paintball dispenser's a good idea, but I don't think it would be much different than the funnel I tried. I'll do a quick try with the smaller hole.
    – dfife
    Commented Oct 13, 2014 at 20:14
  • I would also ensure the reservoir of marbles is not too deep. If part of a second marble is in the hole in addition to the marble to be dispensed, the entire stack of marbles above the hole must be lifted to select just one marble. If the column inches of marbles is too high, overcoming that pressure may make it tougher. Commented Oct 13, 2014 at 21:33
  • alas, that didn't work. They're getting stuck before they get to the hole.
    – dfife
    Commented Oct 14, 2014 at 16:25

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