In a magic setting I am working on they have what are called Steam Rails. Big enchanted Engines that run on rails set into the ground. When you add water to the engine, it heats up the the water and turns the water into steam and the steam is then used to push the tires along tracks. Hence my version of trains. The water made for the steam rains on the road are made by Clerics who cast create water for the engine.

Enchanting in my world is long and costly. It is pulling magic out of a parallel universe and putting into objects. The more powerful the object the longer the enchantment. The steal rail engines can take YEARS to make. The only way to speed up the process of enchanting is ti have MORE people working on the enchantment but then the more people workinv in the enchantment the more people who must be payed.

My problem is a have been doing study on cars and once steam trains are made someone will eventually stick them to onto a carriage and then there are cars.

I do not want cars in my fantasy setting. The steam rails are supposed to be rare and have an magic sense to them. I need a REASON as to why people who not just make smaller steam run carriages.

My ideas was the size of the magic steam producing engine cannot be made smaller than a curtain size or other wise they explode under the presure of the steam. But if so why would they not make it out of a thicker or stronger or resistant steel for the engine...

Maybe the weight of the Engines are simply too much for the carriages but then why wouldnt they make stronger carriages to hold the engines...