Tuesday, 26 November 2013

A game of chance...

Games, gambling or fun, often use a pair of dice in order to supply a random number between 2 and 12. Simpler games may use one die returning a random number between 1 and 6. Simple little things but not if you want to make one in Meccano.

A thread on the Spanner II List, wandered off it's original subject and ended up discussing building a die using modern flanged plates. The plates being discussed are the 1½ x 1½ inch flanged plates shown below.

Flanged plate A551 (51b)
The plates are designed to be put together with other small flanged plates to make rigid boxes and hollow columns. The flanges are cut back so they fit nicely together with all the flanges hidden inside. Paul Dale had made a Die using some replica plates but these are not exactly the same as the Meccano plates. Six Meccano plates fit together nicely to make a perfect cube.  Using threaded bosses it is possible to build an enclosed box but Paul had said his box was made using only the six plates, 21 bolts and 21 nuts...

The flanges are cut back
Six plates make a perfect cube
That was it, nothing was going to get done until I had worked out how this was possible. Working it out in my thoughts, It seemed a relatively straightforward task to bolt five of the six plates together, but how was the sixth one going to be secured? nothing for it...

The parts and tools
... six plates and twenty one each of nuts bolts and, in my case, washers were gathered together. the cube was assembled as shown below.

Stage one
Stage two
Stage Three
Stage four
So far, so good. Now for the tricky bit. Place the five remaining nuts inside the open cube...

Loading the cube
...then slide the last flanged plate in position, sealing the cube.
The next bit will either really irritate you for hours or give a real feeling of accomplished in minutes. Turn the cube over and rattle and tap the cube until one of the nuts is over the bottom corner hole. The modern easy-start or finger-safe nuts are the best for this.

Engaging the nut with the bolt
Carefully insert the bolt so the nut is sitting on top of the bolt. This may take a few attempts. Best to close the door at this point. We don't want to offend anyone when the nut falls off for the twenty-seventh time.

Hold your breath...
Using a drift or the small hex-key, gently turn the nut while rotating the bolt by spinning the hex key between finger and thumb. You will find that some nuts will be locked by the adjacent corner nut and this will allow you to tighten it up fully with no intervention. The drift can be used to hold the nut still while the bold is tightened.

The finished die viewed from one side...
...and the other.
Now all I have to do is work out how to take it apart. All good fun now I will be up half the night catching up with all the stuff I should have been doing this afternoon.!



  1. I didn't have enough genuine flanged plates when I built my original, hence the slightly different replicas.

    - Pauli

  2. It is interesting how a small difference in the design of the part can make so much difference. I don't think Meccano have ever used these, and the other small flanged plates, to their full potential as the don't have the threaded boss (Part No.64) available any longer. Using it makes it very easy to build totally enclosed forms.

  3. Ralph wrote:
    "... Carefully insert the bolt so the nut is sitting on top of the bolt. This may take a few attempts. Best to close the door at this point. We don't want to offend anyone when the nut falls off for the twenty-seventh time..."

    All Meccano builders have their various techniques for fastening bolts to nuts in tight and occasionally (as here) completely enclosed spaces.

    The moistened extreme tip of a finger often suffices. Or there is the holding-the-nut-in-place-with-a-box spanner trick. Or employment of Selotape or Bluetack or surgical forceps. But obviously none of those will work here.

    For those lacking Ralph's patience (27 attempts to get the nut on the bolt would be pushing the limits of mine a bit too far, I think) it struck me a less trying way of solving this Meccano "locked box" mystery (shades of Sherlock Holmes?) would be to use that ever faithful old friend Araldite.

    A couple of minute dabs of Araldite of opposite edges of each of the nuts to be secured inside the "locked box" by bolts inserted from the outside will do the trick.

    1) Position the prepared nuts exactly in place over the selected holes of the unassembled flanged plates
    2) tighten the nuts in place with the bolts so that the nuts will adhere to the flanged plates under pressure
    3| set aside for a few hours to let the Araldite dry
    4) unscrew and remove the bolts
    5) assemble the flanged plates
    6) reinsert the bolts and screw firmly into the pre-Araldite-positioned nuts.

    Araldite is powerful stuff, so use only the tiniest pinpricks of it on the edges of the nuts in order to avoid any of it getting into the screwholes of the nuts.

    Michelle O'Brien

  4. After spending most of the day completing this infernal challenge, I realised not only had I paired the numbers wrongly, but one side had 9 bolts instead of 6!
    The bloomin' thing is staying that way as I have run out of patience and the air had a distinct blue tinge.

  5. Ralph, very tricky! And a better design as my old die, which I published under http://www.schraube-und-mutter.de/models/wuerfel/wuerfel_top.html

  6. Michelle,

    All very well in theory but the flanges will not allow the nuts to be positioned prior to assembly - see the picture captioned 'Closed!'

    Besides that cheating!


  7. John,

    All you have to do is make sure the opposite side has -2 bolts on it and you will be OK as it will then add up to 7 :-)


  8. Dieter,

    I like your dice - much easier to assemble than mine and you have tree of them. I don't think I have enough stamina to grind my teeth through building two more!


  9. I wonder if I could make one and mount it on a pair of gimbals. I could then use two stepper motors driven by a microprocessor. The micro could generate a random number between one and six and rtotate the dicebto show the correct side. Maybe at Christmas.

  10. Roger,

    That sounds like fun. Please let me know how you get on.