Wheel Oddity

Meccano creations that can be driven around, travelling on just two side-by-side large wheels are neither new nor unusual (although I don’t recall seeing any recently, and I was in my teens when I last built one).

In contrast to the traditional arrangement of upright wheels (usually mounted on a common through-axle), I’ve wondered for quite some time, practicalities of wheels at a permanent tilt, wider on the ground (for stability) and closer at the top (for novelty). However, this arrangement brings awkward forces into play, so bearings, wheels and final drive all need to be extra sturdy, and it’s taken me years to think up a decent Meccano solution. However, recent inspiration to try Liverpool Junior Meccano Gears and Axles made the model buildable, at last.

I incorporated Infra-Red (IR) remote control from the outset, because pivot turns are so natural that a trailing lead would become a nightmare tangle.

I chose the earlier two channel Meccano IR because it has no problem running both motors simultaneously. (In contrast, the later Meccano IR, despite having potentially four channels, can’t operate more than a single motor at any given time, as far as I can figure.)

My first attempt took the simplest approach of giving each wheel its own motor. Although this ran, steering was far too rapid, rendering it impossible to control. This was exacerbated by Meccano IR’s lack of proportional speed control (i.e. capable of full ahead / stop / full astern only). More reduction gearing might have made it easier to steer, but would have reduced straight line speed to snail’s pace.

To tame steering while retaining forward and reverse speed needed a Gleasman-like transmission (i.e. the sort used on crawler vehicles) which was quite a challenge to fit into limited available space, especially working around the curse of perverse angles that I’d saddled myself with. I eventually got what I needed by reworking a train of Multipurpose Gears (part 187) I’d previously devised for a Chinese South Seeking Chariot (which itself was a solution to an ingenious contrates and pinions Chinese Chariot, designed decades ago by John Nuttall).

My creation is all Meccano (turning the usual blind eye to all those commercial washers), except that hard-line Purists may debate a space-saving trick (which I’m by no means first to use) visible in the drive train just before the black Contrates. The trick involves plastic Multipurpose Gears and plastic 19-tooth Pinions both with their brass centres pushed out, which are then pressed onto elongated brass centre extracted from a Plastic Worm, so the gears rotate together, but independently of the axle.

I apologise for picking my worst condition Large Flanged Rings, but I suspect the creation won’t treat them kindly, despite my adding a layer of insulating tape (colour co-ordinated) around their flanges.

The only thing still to do is devise a catchier name for it!

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