26: Mechanical updates

As you have likely seen, the Globe prototype was a mechanical monstrosity, comprised of a hefty steel frame, top, bottom and rear panels, and corner protectors, a 3 phase squirrel cage motor and a 70cm 38.1mm diameter aluminium shaft. Aside from being obscenely heavy, it was also rather expensive, so my focus at the moment is bringing the weight down wherever possible, simplifying the whole design and reducing the cost.

  • The rear panel will be replaced with veneered MDF (so it looks nice from all sides).
  • The top and bottom panel will change from 3mm to 1mm (or maybe even 0.5mm) mild steel
  • The box section frame will go entirely. Instead the top, bottom and side panels will be held together with brackets.
  • The bottom section will switch from being 400mm high to 150 or 200mm (it was only that large to accommodate the motor and provide ample room to play with).
  • The 3 phase squirrel cage motor will change to a BLDC motor, which will now drive the shaft directly rather than using a pulley.
  • The shaft in general will significantly reduce in length, now only running up the first 10cm or so of the PCB and down through the significantly shorter box. It will also be dropping from 38.1mm diameter to either 30mm or 25.4mm depending on what that does to the price of the sliprings.
  • The anodised aluminium U channel in which the acrylic housing sits will probably be going. I will see how well this works with the next prototype, but the anodised aluminium was fairly pricey and was difficult to machine neatly.
  • The veneered MDF side panels will now be finger joined at their corners. I’m fairly sure this is going to look quite good, if some projects like https://www.pinterest.co.uk/pin/231302130840725312/ are any indication. This means that I can get rid of the metal corners which were proving a massive pain to implement.
  • We will be dropping down to smaller slip rings with less channels (since I now only need power through them).
  • The total width may shrink a little, I have yet to decide on this. The new PCB comes in at about 335mm (with LEDs protruding). With a wall thickness of 5mm this leaves 27.5mm between the PCBs edge and the acrylic housing. Theoretically this could be dropped down to about 5mm, therefore shaving about 45mm off the total width. While this doesn’t sound like a huge amount since the display cubes will be made to order, it will save money in making them smaller and smaller devices will be cheaper to ship. The only question is, will reducing this clearance result in more noise/structural issues as the PCB sweeps from an area of relatively low pressure near the corners of the cube, to higher pressure as it comes closer to the edges…damn I really need a mechanical engineer. In lei of a mechanical engineer we have…get a small cube and see what happens!

That’s most of the exciting stuff that’s going on. Obviously there are a whole host of smaller things that go along with this sort of stuff, if any of them become a bigger thing I will let everyone know.

The wood for the next prototype units has arrived already. The 4 veneer options I have gone for are: Walnut, Oak, Cherry and Sapele. These I feel provide a range of appearances to suit most people. If there are any additional types you would like, let me know and I will see what I can do.

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