An Edwardian car

Leafing through Constructor Quarterly for modeling ideas, I came across this beautiful old Edwardian car (apparently a 1908 Panhard et Levassor). It was originally described by the late Keith Cameron in Constructor Quarterly #1, and rebuilt by Graham Jost, who in a letter in CQ #112 said he "did not find the instructions particularly easy going".  No more did I...

Here is what I had after the first burst of building activity:



I came close to giving up at this point, because I could not for the life of me figure out how the steering column was meant to be supported.  And also because I knew that I had prose like this to look forward to:

"The rear side panels of the passenger compartment are made from two 3-1/2" Strips, formed in their lower 1-1/2", two 2-1/2" Narrow Strips, and a 2-1/2" x 1-1/2" Plastic Plate, all held in place by 3/8" Bolts and four Washers spacing them from Obtuse Angle Brackets (slightly flattened) secured to the first and fourth holes of the 3-1/2" x 2-1/2" Flanged Plate."

But I persevered, and reached a point where all was done but for the passenger seat and motor.  A good point for a photography break:
    

I made one improvement to the model as it came to me: the doors open!


Here is how I mounted the steering column. It passes through an elongated hole in the footboard and then through a 2-hole coupling bolted to a short axle rod, which is held in a 3-hole coupling to its right, which is bolted directly to the footboard.  By rotating and sliding this short rod in its coupling, the 15-tooth gear's orientation and pressure on the contrate gear can be adjusted at will (up to the limits imposed by the elongated hole's size):



The remaining problem with this arrangement is that the 15-tooth gear can "wander" and climb off the contrate if enough steering pressure is applied.  I don't know how to fix that without major changes.  Using a simple coupling where the orthogonal axles meet to hold them in place won't work because the small contrate doesn't allow enough room for one; but there's no room for a large contrate in this design.  I decided to let it be and rely on the driver not to apply superhuman force to the steering wheel.

The joys of eBay

Recently I won an eBay item entitled Antique Meccano Erector Set with Wood Box.  The parts are quite varied, some from the nickel era (pre-1926) and some from the dark green/red era ('26-'34), with a few Erector interlopers mixed in. The box is not marked in any way, but its compartments are well proportioned to take Meccano parts, and I have a feeling it is indeed a Meccano (perhaps Gilbert Meccano?) product.  I am putting these photos here in hopes that an expert may shed some light on the matter.

The box is quite beautiful, to my eye.  Front, back and side:
      

The first sight of the open box is quite spectacular.  The lid has a stiff board with the keyholes used in Meccano stringing cards, and a set of parts still wedged in some of the holes.

 

The box contains three removable trays, two of which have a cutout designed to make room for the Boiler part 162.

  
  

The set in all its glory:

The sprockets, eccentrics, gears and other brassware were a fairly good haul for the price:

And finally, here are the interloper parts, mostly Erector if I'm not much mistaken.

Thank you eBay for satisfying my acquisitive mania once again, and helping fill my poor house to the bursting point with heavy rusty metal of dubious resale value!

The Hoberman sphere

Recently I picked this up in a charity shop for a few dollars:
 
A very nice Hoberman sphere - or something like it, since the original Hoberman sphere was apparently an icosidodecahedron, whereas this one has 24 identical kite-shaped faces that meet at 18 4-way junctions and 8 3-way junctions.  If you know what such a thing is called, let me know.

The entire thing is made of just 6 types of part: the 4-way junction cap, the links that meet there (male and female versions), and similarly for the 3-way case, in which the links are slightly shorter.

When I got home I could hardly fail to start tinkering with Meccano and see what might be possible.  I did not find any prior art on Meccano Hoberman spheres (although I have found plenty since; after 100+ years there is little new under the Meccano sun).  I started with a basic expanding linkage:
   
Note that for the whole circle to collapse satisfactorily, the strips must be joined at points that are offset slightly from their center, here achieved using fish plates.  The next step was to use curved strips to achieve the same thing:
 
This was a very pleasing model in itself, fun to fiddle with, but I could not stop there so I made the obvious 3D version.  It came together easily enough, given the patience to attach 96 bolts and 96 nyloc nuts.
 
I found this one quite photogenic, so here are some more pictures:
          

In retrospect, this would have been a perfect time to stop, but I did not.  This model expands, but only by about 20% - nothing like the original, which also has far more vertices.  I had to go on!

To make a very long story shorter, I ended up with this:

  
  

It is 16" in diameter when closed and 35" when open.  It uses 288 curved strips part 89, which I had just enough of, thanks to the 2003 Ferris Wheel sets that keep turning up in said charity shop (hence the unfortunate colors; all zinc would be nicer).  It also uses 528 bolts and 1056 nuts, all lock-nutted in pairs (I did not have enough nyloc nuts for the job).  It took dozens of hours to make, of which 10% were fun design and tinkering and 90% were entirely menial.  I have never lock-nutted so much in my life, and I never will again.

So I honestly cannot recommend this as a Meccano project for any sane human being.  It was mind-numbingly repetitive and fiddly.  If however you still want to give it a shot, read on and perhaps you can benefit from my research and mistakes.

Detailed construction notes

What polyhedron is my plastic toy based on?  I did not find it described online.  Though the faces all have the same trapezoidal (kite) shape, there are two types of vertex, one where 4 edges meet and one where 3 do, and two types of edge, as the ones that meet at 3-way junctions are necessarily shorter than the ones that meet at 4-way junctions.

The vertices are not hard to model, except that the 3-way ones need angle brackets opened out to an angle of 120°.  Here is a close-up of both types of vertex:

  

The two types of edge are a little harder.  For the longer type, I used three "scissors" made from pairs of 11-hole curved strips lock-nutted at their central hole:

  

But the shorter edges need to be shorter by a very exact ratio, which I just about managed to calculate using spherical trigonometry as 0.78365.  Not easy to achieve in Meccano.  I found an ugly way to make an edge that is 0.73333 smaller by chopping down some of the curved strips like this:



This 7% inaccuracy is a hidden advantage.  The perfect ratio would allow the sphere to expand fully, making it extremely hard to collapse again without 3 people manipulating it at once.  This inexact ratio constrains the sphere to a maximum size that collapses again without effort.

Nothing else about the construction was especially interesting.  The main remaining question, as always, is what to do now with this big unwieldy hunk of metal.  Somehow I don't think my children will want it in their inheritance...

There is a ton of fascinating further reading about 3D expanding structures online.  I will link to just one: 3-dimensional Expanding Structures (pdf).  These MIT lecture notes cover a lot of the subtleties in a way I have not seen elsewhere.

Additional photos

Here are larger sets of photos for some of the Meccano projects documented here, as well as photos of some projects yet to be written up.

Meccano Madness
Meccano Display Cabinet, 2016
Meccano Braiding Machine
Meccano Braider II
Meccano Plate Rolling Machine
Meccano Walking Hat
Meccano Menorah
Meccano-Compatible Grub Screws

And some more photos in my gallery on the NZMeccano site.