These clips are from a PDE that used a motorized rotary valve fuel injection and a modified automotive ignition system and hand built tungsten electrode spark plugs. The tube i.d. is about 25 mm. The PDE is running on propane and oxygen mixtures. The runs were conducted at 10 Hz. The first video shows the wall material heating up as the engine runs, where some epoxy on the outside catches fire. Next, the force from the detonation waves cause a Shchelkin spiral mounted internally to be ejected out. The spiral was permanently magnetized from the heat during that run.