Will the piston drop down at lift off?

Yes, possibly. It depends on the obvious factors, how tight the piston is, the acceleration of the rocket, etc.

Do I need to put a stop..To eliminate this?

No, the only thing to consider would be if it affect stability by moving back the cg possibly.

But if possible load it up with the piston all the way down and test the ejection charge to make sure the laundry gets hung out on the line...

Doug

Thanks. I will put a plastic rivit in the side just to be safe.

Hey Mike,

You might want to reconsider the plastic rivet... Suppose your piston does push down, what if it jams against the rivet and fails to function by virtue of being jammed against the rivet? I'd be satisfied with making sure I'd pushed it down as far as it could go prior to launch.

Ken Reilly

For my part, I'd say that I have used pistons in 99% of my rockets. I've never had an issue. Basically, there is nothing that I'm worried about it "dropping down on to" in the first place. I've used pistons in several rockets that have exceeded 50 gees, i.e. 38mm birds with a J570. Never had a problem.

Sidebar... I love pistons, as long as you check the slide and use a piston that is at least 1 caliber in length. I also use filament wound or convolute wound glass nearly exclusively; if I were using phenolic, I'd be less enthusiatic. If I were using cardboard or Quantum, I'd avoid pistons, for different reasons -- cardboard "dings", and can cause a jam. Quantum is highly temperature sensitive, and I've seen pistons jam there.

8) Mike, here is a great resourse...www.rocketreviews.com go to resourses then rocket glossary, piston ejection. This should help. There is a PDF file on Public Missle's site. Pistons are one of those things in rocketry you should give a try. I like them, but I don't use them on everything. 8)

These days I use pistons on everything I build under 4" and over 29mm IF it is made of FWFG or Convolute FG. I have used them on phenolic birds, but don't recommend it. I use it on all my PML kits built with Quantum tubing and have never had a problem - so long as you make sure you clean the inside of the bird out occasionally to keep the piston from sticking.

Warren

Pistons are good...added one to a scratch built Aura replica. worked great, no need to worry about Nomex, wadding, or any possibility of burning up your chute.

No stop. I sometimes overthink stuff.

Thanks for all the help