DEVELOPMENT OF THE WHEEL
(Most of this is just my imagination – could well be wrong somewhere ... i'd love to get extra info. from experts)
The first necessity for the development of wheels was hard flat ground, not rocky, not marsh, not sand.
Then because of the inevitable bumps in the tracks, they needed big wheels – (small wheels like skate boards only work on really flat ground).
The wheels had to be so big, that the middle point, the axle, was so high up – that the carts had to be broad – (thin carts would have fallen over) – so very early we get the 2 seater which you climb up onto.
Even elephant tracks weren't wide enough ... so, slowly tracks developed – and the bumps in the road meant going slowly – so its oxen pulling the load – not horses.
Sitting high up had 2 advantages: you could see over the ox's head, and, the facts of life are, when an ox farts, shit shoots out, so this landed underneath the cart instead of on top of it. It was altogether a successful design.
First came solid wheels, slices of tree trunks – which needed clamping in, otherwise they fell apart – so i imagine then someone came on the idea to replace the clamps with spokes – and thus the first spoked wheel developed around 2,000BC.
Around 1,500BC. steel was developed (from mixing carbon in with the iron – and appropriately, carbon was originally won from cow dung) ... so then a light cheap bendable metal was available to make metal rims outside the wheel ... and a vital factor for smooth rotation: a metal casing around the hub to contain the animal fat.
Originally animal skins were wettened and wrapped round the wheel, these tightened all the joints in the wheel as they dried. After the development of metal rims, a blacksmith heated the rim and as this cooled it tightened all the wooden joints in the wheel.
Life went on ...
The structure and weight of a spoked wheel made it far more efficient and meant it lasted far longer than a solid wheel, and so it was worth the extra effort and cost.
People could move with their belongings and family – this was a big step for mobility – markets opened up ... trade – money ... and also inevitably – transport of war supplies. Local rulers developed the quality of local roads to facilitate progress.
Chariots are reported quite early on – they were far narrower with smaller wheels, with the axle ca: 1 foot or 30 cm. from the ground. Chariots usually replaced the wooden spokes and rims with metal ones, the metal may explain why they are reported so early.
(I don't understand how small wheeled chariots could be used in warfare, they would surely get bogged down, or 'our hero' would get thrown off the chariot speeding over bumpy fields. I can well understand how impressive they were for parades in local areas with good roads.)
Even if you didn't have enough money to buy a cart and cow ... you realised how important they were – and you wanted one ... you dreamed of having wheels ... the wheel was as indispensable as a car, as internet ... Internet has tons of little problems ... the wheel had far simpler problems : bumpy roads and Dukkha, which meant the hub rooms needed continually topping up the with goo and fat. (A secondary problem was that after a few years the steel rims became loose as the wood shrunk).
(would love to learn more from a wheelwright sometime).
The first ball-bearing idea – a series of metal rods – could well have been made and used around 500 BC. but would have been very uncommon ... (I wonder what Buddha would have made of the "wheels within wheels" idea).
On the American continent, they had no horses donkeys or cows or any 'beast of burden' till they were 'imported' from Europe ... Buffalo could not be tamed to pull or carry heavy loads ... In Mexican archeology digs they found childrens toys with wheels ... so, they understood the concept, but never developed it, because no animal could pull the weight.
Unlike storytellers → books → town criers → radio → television → Internet and then a new invention every day – the spoked wooden wheel stayed pretty much the same for centuries – up until the 1800s when trains, rubber tires, bicycles and cars were invented, and with that modern heavy transport on land.
Please continue with Development of meanings of Dukkha and Sukkha