Ammonium perchlorate composite propellant produces undesireable subtances during combustion, such as hydrochloric acid (HCl). Motors need to be cleaned after use to remove acids and other “crud” because a dirty case and closures can contribute to motor failure during flight. For example, grime on a case can prevent the o-rings from containing the hot gases and flame, and cause early ejection when motor ejection is used to deploy the parachute.
Motors can be cleaned and reused in the field. To do this, you will need:
- Trash bag
- Wet towelettes (“baby wipes” from any grocery or pharmacy)
- White vinegar
- Bottle cleaning brush
- Dish detergent
The wet towelletes serve to remove grease and gunk from the motor, as well as your hands. (You should clean your hands before handling the delay grain when assembling a motor to prevent contaminating it with grease, which can cause it to not work correctly.)
White vinegar will quickly remove burned propellant from the aluminum motor components. It is a safe substance to use in the field and at home, unlike some commercial solvents, and does not harm aluminum. (You may observe some coloring being removed from a motor case or closure during cleaning. That does not affect the motor.) The use of rubber gloves is recommended to avoid “stinky hands.”
Smaller motors, like most Aerotech 38mm motors and smaller, can be soaked in white vinegar in the field by using a long, wide mouth plastic bottle or a tray. Only a short soak, 5-15 minutes, should be needed to removed hard, burned propellant.
Dish detergent can be used to thoroughly remove grease from motor components.
Submitted by: Dean A. Roth