To convert pounds per hour to ounces per hour, you can use the conversion factor that 1 pound is equal to 16 ounces.
So, to convert 81 pounds per hour to ounces per hour:
\[ 81 \text{ pounds/hour} \times 16 \text{ ounces/pound} = 1296 \text{ ounces/hour} \]
Therefore, 81 pounds per hour is equal to 1296 ounces per hour.