Why use caravans?

[pgw]

Why use caravans? I keep not understanding it.

When I try to establish a trade route, sometimes nothing happens at all. Does this mean that the two cities are not far away from each other?

And why would I use them to help building a wonder? Isn't it as simple to have other cities just produce coins and then buy the wonder?

Any help appreciated...

[CapTVK]

Well, if you make a succesful traderoute between two cities you should receive an amount of gold and tech bonus related to the number of trade arrows, size and the distance involved. Plus the two cities receive a few extra trade arrows every turn.
The other city should be at least 10-12 squares away to actually register, and bigger cities will also result in a higher gold bonus (of course).

And you should DEFINITELY use caravans for rushbuilding! It's far cheaper to build caravans an add them to a wonder than rushbuying the wonder instead.

[pgw]

Thanks . Can I find exact numbers somewhere? I.e. the formula for calculating the trade bonus from a trade route (calculated form city destination and city size). I played a bit with trade routes and found that you can have a maximum of 4 per city. So I would like to establish only the best ones . Is there also a difference between a trade route with foreign cities and my own cities?

[Messer Niccolò]

Should the formula be equal to the one of Civ II, you can easily find infos in the Great Library archive. Mr. Keegan has exploited very well the formula...
If it can help....

[pgw]

Found it out!

I browsed the freeciv source and found the following.

revenue from establishing a trade route equals:

(distance x + distance y + 10) * (trade city 1 + trade city 2) / 24

cities are on the same continent: * 1/2
cities are owned by the same player: * 1/2
for each technology that reduces trade revenue: * 2/3

So this answers my question!

[pgw]

In addition, I found the following:

* producing coins gives 1 coin for each shield

* buying a wonder costs 4 times the needed shields

* using a caravan to help building a wonder adds the shields the caravan costed to the shield stock

So it is indeed much cheaper to use caravans than coins to help building a wonder!

[CapTVK]

Guess my help isn't needed. You already found the formula yourself.