Where can you find more caravans? I found Carla at the beginning of the game and no one else since then. She goes to Sanctuary Hills and that's it. Do they go to other settlements?

Yes, I saw Carla at least one other settlement and that Armor merchant guy (forgot his name) with his caravan at one of my 2 people settlements that I befriended early in the game.

Carla is permanently in Sanctuary Hills for me. I have seen a fat armour trader around tenpines and Cricket in boston

She should be wandering off sometimes, recently found her stuck ontop of my main gate trying to escape the Sanctuary

They regularly travel to Bunker Hill and you can build caravan things in your settlement and they'll go there.

Uh, interesting, the bathtubs will attract caravans you mean?

No it's a separate building...

Oh okay thank you, ill take a look at that. All I saw so far was the tub thingy with the small description.

Tubs bring random, non-trader Brahmin to your settlement ( two headed cows ). There is a weapons trader at a small pond , right between Fairlane Hills Estates, and Boston Police Rationing Site. Sells very good weapons.. There is also a doctor trader that mainly wanders around County Crossing. Just wait there every hour until he shows up if you need meds, or to unload . Fat Armor trader ( very good armor for sale ), passes by Tenpines Bluff to eat all the settlers food at the camp fire. Just wait for him there. Trashcan Carla can't be missed in Sanctuary. Wait around for her. There are two others I know of, but can't remember their patrols. When I run into them again, I will edit for you.