Project
323 Static - IE24D engine test.

Construction

• This was revision D of the IE24 engine. It became apparent after looking at some old static tests and flights that the majority of failures have been end cap failures. Pourstone, while a good material to make the end cap out of, has it's disadvantages. On one hand it's flame retardant and seals well, but on the other, it's brittle and fractures under stress. What was needed was a material that had the flame proof and sealing qualities of Pourstone as well as the ability not to fracture under the compressive forces of the combustion chamber pressure. In the end, a mixture of two materials was chosen. Pourstone would still be used next to the fuel but a much smaller amount, only 1/2". On top of that would be a 1 1/4" PVC cap inverted and put end down on the Pourstone. The PVC cap would then be bolted to the engine casing. This arrangement would allow pressure to be applied against the Pourstone which would push equally on the PVC cap which, being bolted in, would not go anywhere. The 1 1/4" PVC cap has an outside diameter almost exactly the same as the inside diameter of the 2" PVC pipe used in the engine casing. Four 1/4-20 steel bolts were used to hold in the PVC cap. Four holes were drilled and tapped while the Pourstone was still wet and the PVC cap was resting against it. This allowed the Pourstone to create a tight fit between the two. See IE24D drawing.
• The only drawback to this arrangement was a pressure seal was being made with two hard surfaces. This was the reason for the leak around the end cap when the fuel reached the outer edge of the engine casing. In the future a ring of caulk will be put between the Pourstone and the fuel to create a gasket which will stop the hot exhaust gasses from leaking long enough until the engine has burnt out. This will be revision E of the IE24 engine and will be tested during the 412 flights.

Pros

• Once the end cap issues have been resolved the IE24 engine will be a low cost, easy to construct, powerful engine.
• The PVC cap for the end cap reduces the weight of the engine.
• In this test the end cap leaked towards the end of the test but this is a great improvement over the past few tests where the engine casing has ruptured and the end cap was expelled.

Cons

• End cap leaked near the end of the burn.

Pictures

• Me next to the test stand in the desert.
• Test stand and mirror.
• Pressure switch and battery for ignition.
• Nozzle view.
• Two finished engines. (one engine was unable to be fired due to a igniter problem)
• Looking down into the new end cap.
• Divergent section of the nozzle after firing.
• Convergent section of the nozzle after firing.
• View of the end cap after firing.
• Holes in the engine casing where the end cap leaked.
• Gaps around the PVC cap where the end cap leaked.
• Another view of the gaps between the Pourstone and the engine casing caused by the flow of hot gasses.
• Erosion of the engine casing by hot exhaust gas.
• End cap assembly out of the engine casing. Notice the erosion on the PVC cap.
• Another view of the end cap out of the engine.
• Another view of the end cap out of the engine.
• The seal between the PVC cap and the Pourstone was very tight as indicated by the lack of burning on the two surfaces.
• Sequence of pictures showing the static test. (large file 462k)

Video

• Video of scale during test firing. Unfortunately, the video quality was not good enough to get a pressure reading.

CAD Drawings

• IE24D design.

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