Strange piston deployment behaviour when testing

I have tested twice with placing a charge in the rocket, at the top of the fin can, below the PML piston. The first test the charge was small and it push the payload/nose cone off without moving the piston. The second test, I used a bigger charge. The payload/nose cone went flying off and pulled the piston out. The piston wasn't blown out.

The expanding gas behind the piston is moving past the piston. How can this be?

The piston slides easily. I even use baby powder to help it slide and it slides easily. It is tight enough that it doesn't rattle/wobble in the tube. When blowing with my mouth I can blow the piston out. With a charge, the piston doesn't move. How is this possible?

Thanks

Mike

Reply to
Mike
Loading thread data ...

I wasn't expecting such a quick response from PML. They explained to me that this is not atypical of ground testing and that probably what is happening is that the piston moving forward is ejecting the payload/nose cone but the air cooling behind the piston is drawing it back in. As long as my parachute comes out when it is time, I will be happy.

Thx

Mike

Reply to
Mike

How big a charge are you using? If you are using a much smaller charge than the typical motor charge, that could cause the behavior also.

Reply to
David

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.