What did Daniel and his band do with a Roman catapult in Bronze Bow?
Daniel and his band dismantle the Roman catapult, board by board, so that the Romans would not be able to employ it against Rosh, and Rosh could use the reuse the material for supplies.
The Romans had left the huge machine on the road overnight. A wheel on the catapult had broken, and they would not be able to fix it until morning. Reasoning that Rosh would have no use for such a cumbersome weapon, the boys in Daniel's band want to have some fun with it by stuffing it with oiled rags and setting it afire. Thinking practically, however, Daniel says that it would be "no use to burn good wood...we're in need of supplies, not bonfires". The boys then agree to take the contraption apart, so, having gathered together their weapons, "files from the shop, chisels, and mallets", they make their way surreptitiously under cover of night to the "monster that crouche(s) there like an unearthly beast", overcome the guards, and get to work.
"One by one, shadowy figures (creep) from the rocks and (surround) the monster. They (work) silently, muffling under their cloaks the rasp of the file and the chipping of the chisel. Bit by bit, plank by plank, the monster (shrinks) and (crumples). Over and over, during the long night, the boys (retrace) the devious path to the watchtower, staggering under heavy planks and crossbeams. When the sun (rises) next morning the catapult (has) disappeared without a trace" (Chapter 17).