Project
309 static test with new end cap and nozzle assembly.

Construction

• This 24" modified Incendio engine used a pour in place nozzle held in the engine casing by four 1/4-20 x 1/2" bolts. The end cap was held in place by four 1/4-20 x 1" bolts and two 1/4-20 x 7/8" coupling nuts. See drawing. The bolts in the end cap assembly were put through four 1/4" holes in the PVC engine body leaving the bolt caps outside the engine for strength. One of the two static tests had a 0.6" throat instead of the usual 0.7" throat. This is the engine in the picture above that failed catastrophically.

Pros

• New nozzle assembly is very easy to build.
• A complete engine can be built in one day.
• There is less throat erosion in this design due to more material around the throat. See drawing.
• There is no convergent section in this design but one is created as the fuel burns.

Cons

• End cap design still needs work.
• 1/4-20 bolts and coupling nuts caused the end cap to fracture more easily.
• Smaller throat area does not work. Chamber pressure was too high.

Pictures

• Debris from engine with 0.6" throat failure.

Video

• Exterior tank view of two tests.

CAD Drawings

• 309 Static design.

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