- Feb 12, 2010
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I am looking at some PML kits and I see ejection piston.So my question is what is a ejection piston.Alex
Amen to that. In fact, the first time they flew a piston the parachute did not open because the force of the ejection charge blew the piston out so hard that it yanked the 1/8" tubular kevlar cord between the motor mount and the piston right out of the 1/8" light ply piston bulkhead, sending the piston up the shock cord and parachute shroud lines to reef the chute. No damage on landing and replacing the 1/8" light ply with 1/4" aircraft plywood has eliminated that particular failure mode.Larry
You can't do this quick fix for the TARC problem, so there's a real advantage using a piston cup instead of a Nomex chute protector. You can put anything in piston cup and it will get pushed clear of the rocket when the ejection charge fires.
That's exactly correct. I've had several flights with a 4" Thug and Hobbyline motors where the charge pushed the nose cone off, but not hard enough to stretch out the shock cord. The chute never left the BT. Makes for some hard landings. I also had one flight where the rocket never arched over, it stopped in a vertical position, blew the nose cone, chute deployed and it landed with all the dog barf still in the BT.I had always assumed the ejection charge was blowing the parachute out and the nose cone was only going along for the ride. It appears that it is really the opposite that is happening, the nose cone is getting blown off and its inertial yanks out the chute.
Thanks for the response. I found some over at https://www.commonwealth.net/rocketstore/rocketryframes.html as well.Performance Hobbies has 3/8 and 1/2 tubular kevlar. I've also seen it on Wildmans site.