Question

The big bellows groaned and the burning coal cracked.

Answer 1

I am assuming that this is your question :

What was going at the Ramsjo Ironworks when the peddler reached there ?

Answer: The Ramsjo Ironworks was a big plant consisting of a smelter, rolling mill, and a forge. Master smith and the helper were doing work  with the mass of a pig iron. The bellows which were big  groaned and the burning coal cracked. There was a thumping on the anvil and the fire - boy put the charcoal into the mouth of the furnace. In the midst of the sounds, the blacksmiths could not notice the peddler.