Well I never knew that about Roman Chariots.....

[Imperial Dave]

http://www.seeker.com/secret-of-roman-race-chariots-found-2187581176.html

interesting piece on Roman chariot design and specifically the wheels.....very clever lot the Romans 

[Jim Webster]

http://www.seeker.com/secret-of-roman-race-chariots-found-2187581176.html

interesting piece on Roman chariot design and specifically the wheels.....very clever lot the Romans 

trying to work out why two iron rims were worse than one. Cannot see weight being an issue given the thinness of the rims

[Imperial Dave]

rotational weight perhaps? The further from the axle or centrepoint of a wheel a weight is placed the more centripedal forces come into play and the more work/increased drag will occur?

[Patrick Waterson]

It may be more to do with how much they wanted the respective wheels to flex or not flex during turns.  The outer wheel, according to the article's thinking, needs toughening to avoid bursting when it sustains the weight of the chariot during a turn.  Meanwhile, what is the left wheel doing?  It is under very little load during a turn, possibly even parting company from the ground, but regains its usual load as the arena track straightens out again.

The question is: if the inner wheel had an iron tyre, would it reacquire its load without trouble - or would it be inclined to slip and lose traction when it contacts the ground again?

[Duncan Head]

The summary of the original JRA article does admit alternative explanations:

One possibility for having apparently only one tire on the Tiber model — which was probably a toy for a rich individual; the emperor Nero, an avid racer, was said to play with toy chariots — is that two different castings were used in the toy's production, and either one could have been used in the assembly, in random selection from a box.

[Patrick Waterson]

There may be something to Duncan's observation.  My impression from the pictures given is that the left wheel is retained by an axle which had been hammered at the end to spread the metal and hold the wheel, whereas the right wheel can slip freely off its axle, whose end is unspread.  Hence the present right wheel may be a replacement from a different toy.

[Imperial Dave]

so are we saying this is a mash up and in fact chariots for racing had either wheels lacking a metal rim or they were present in entirety?

[Erpingham]

so are we saying this is a mash up and in fact chariots for racing had either wheels lacking a metal rim or they were present in entirety?

We could get a bit techy and ask how was the model made?  Mass production using moulds or a one-off lost wax original?  Swapping parts would work if you had piles of components which could be put on willy-nilly but if everything was bespoke then you would have an original for each wheel and the difference is more likely to be intentional.

[Imperial Dave]

so are we saying this is a mash up and in fact chariots for racing had either wheels lacking a metal rim or they were present in entirety?

We could get a bit techy and ask how was the model made?  Mass production using moulds or a one-off lost wax original?  Swapping parts would work if you had piles of components which could be put on willy-nilly but if everything was bespoke then you would have an original for each wheel and the difference is more likely to be intentional.

without knowing much in the way of Roman toy making....I would tend to agree with you Anthony. It feels like an intentional act which the fact of anticlockwise/left turning racing appears to support and also would there be lots of these things knocking about and if a rich individual needed a repair....surely it would be a 'better job'?

[Patrick Waterson]

A local toymaker for the offspring of the discerning nobility would not necessarily make every example unique: once he had done his first lost wax impression, he would have a mould which would then serve for everyone who wanted to keep up with the Roman equivalent of the Joneses.  He may well have more than one.  Wheels would be moulded separately, quite possibly by more than one toymaker.  Hence, if a wheel cracked or went missing, the parent (or more likely the slave) would take the disabled chariot to the nearest such toymaker and desire that a new wheel be fitted forthwith.  Such a wheel would probably be one cast for an upcoming chariot, as it would be available immediately while the chariot under order would not be due for collection for another day or few and hence there would be time to make a new wheel for it.

And if the replacement wheel did not 100% match the lost one, would it matter provided the youthful recipient was happy with the result?  Considerations of possible implications of tyre types matter a lot less when one is ten or so.

[Erpingham]

The question really is one-off bespoke v. mass produced.  My understanding of lost wax processes (and its a while since I studied this) is that the mould is a one shot thing - you destroy it to extract the cast.  The other thing is you should be able to tell the method used to cast the object from the object itself. 

[Imperial Dave]

what we need is a specialist engineer to examine the 'evidence' and say whether use of two different wheels would in fact make sense from a driving/control/speed perspective. That would then tend to support (or not) whether the 2 different wheels was deliberate (or not)

[Patrick Waterson]

The question really is one-off bespoke v. mass produced.  My understanding of lost wax processes (and its a while since I studied this) is that the mould is a one shot thing - you destroy it to extract the cast.

Yes, true, but that is not the whole story.   If you want a mould that will last, you use the lost wax stage to make the metal template or prototype.  Around this template you make a two-piece or even three-piece mould for producing the actual items.  Once the mould is baked, let it cool, take it apart, extract the template, reassemble the mould and pour in your bronze.  Cool, disassemble the mould, extract the casting.  Henceforth you can reassemble, cast the item and disassemble the mould any number of times.  The mould will gradually start to wear with continuing use, but even then for a while cleaning up the finished casting will be easier and quicker than making a new mould.

  The other thing is you should be able to tell the method used to cast the object from the object itself.

Provided you know how, but yes, it should be possible.

what we need is a specialist engineer to examine the 'evidence' and say whether use of two different wheels would in fact make sense from a driving/control/speed perspective. That would then tend to support (or not) whether the 2 different wheels was deliberate (or not)

Indeed.

Lacking such an individual, we are left with the perhaps dubious analogy of more modern racing craft: I refer to the 'sulkies' used for harness racing.  What caught my attention is that there are two basic types: symmetrical and offset.  Looking further into what constituted an 'offset sulky', this disappointingly appears to be one not with differently-configured wheels but rather with the seat set nearer one side than the other.  'Offset sulkies' have incidentally been associated with a high number of 'locked wheel incidents', indicating that centralised balance may be more significant than wheel or tyre considerations.

Flipping through a few chariots and chariot representations in the hope of gleaning something, the chariots from Tutankhamun's tomb, which are admittedly from a few centuries earlier, have identical wheel types on each side (with leather tyres).  This at least tells us that wheel uniformity was the norm for non-racing chariots.

Regarding racing chariots, this relief of a Roman chariot race has right wheels aplenty on view, but even at maximum magnification none of them look tyred.  Conversely, this plaque gives the impression of a tyre.  This funerary relief appears tyreless.  Regrettably none of these shots give us a glimpse of what the wheel on the other side of the chariot looked like, but it does at least appear that tyred right wheels were not universal.

[Dangun]

It seems relevant to ask: were chariot races always held in the same direction (clockwise or anticlockwise)?

[Duncan Head]

It seems relevant to ask: were chariot races always held in the same direction (clockwise or anticlockwise)?

See the original link:

Since it was easier to guide the horses into left-turning bends, most races ran anti-clockwise.
"Indeed, the right side tire works best in oval-shaped arenas if the turning is always leftward," Sandor said.