LPR piston ejection

[SolarYellow]

I'm thinking about making an ejection piston from yellow tube for BT-50.

Will probably soak the OD of the piston with CA and sand it. Hoping I don't have to do that with the ID of the body tube.

Thinking I will set it up to fully eject the piston, so it vents when the piston uncorks the airframe and everything is guaranteed 100 percent out.

Expecting to have to brush out the ID of the tube between flights, but that's not a big deal.

Any advice?

 

[cbrarick]

bring sandpaper, you'll need it. The first couple of flights that brush might work but after that, all bets are off.

But on a 24 mm diameter rocket, why? seems unnecessarily complicated and heavy.

 

[rcktnut]

Pistons= PITA, took out of my PML 4" Patriot.

 

[Art Upton]

I removed all pistons on any rockets I bought from others built. The ones in the Gray tubes would lock up in winter

Edit: I would use other's built rockets I bought cheap for flights I did not want to worry about

 

[Azamiryou]

But on a 24 mm diameter rocket, why? seems unnecessarily complicated and heavy.

An interest in "advanced" (or at least different) rocketry techniques doesn't have to imply an interest in bigger motors or higher flights. Some of us want to do things because they're interesting rather than because they're necessary.

 

[Tractionengines]

I use pistons in a lot of rockets. They don't need to be too heavy, or complicat.... BUT they DO need to slide easily, and YOU DO need to clean the sliding surfaces every flight.

(Hardening the piston OD and the Body ID with CA, Epoxy, etc. will make cleaning and sliding easier.)

 

[Handeman]

I removed all pistons on any rockets I bought from others built. The ones in the Gray tubes would lock up in winter

Edit: I would use other's built rockets I bought cheap for flights I did not want to worry about

I have a "Gray tube" PML Callisto that has been using the piston for 20 years. When it was really cold at a January launch, I sanded the OD of the piston until if was loose in the tube. That was about 18 years ago and I've never had to sand it again. I usually clean the BT interior once a year, but I also never use more than 0.5g of BP. Hobbyline reloads come with more, and HPR with much more, but I only use the 0.5g with the piston.

 

[rharshberger]

I'm thinking about making an ejection piston from yellow tube for BT-50.

Will probably soak the OD of the piston with CA and sand it. Hoping I don't have to do that with the ID of the body tube.

Thinking I will set it up to fully eject the piston, so it vents when the piston uncorks the airframe and everything is guaranteed 100 percent out.

Expecting to have to brush out the ID of the tube between flights, but that's not a big deal.

Any advice?

I use pistons made from blue insulation foam that fit the tube, its flame resistant, and lightweight enough that the standard LPR kevlar shock cords dont need to be strengthened for additional weight. I have seen competition fliers use them as well in streamer and parachute duration models.

 

[aerostadt]

You know pistons are actually used frequently in LPR, if you talk about NAR competition. In fact Apogee sells 18 mm and 40 mm foam plugs that are used in NAR competition to guarantee streamer or parachute ejection.

 

[dpower]

You know pistons are actually used frequently in LPR, if you talk about NAR competition. In fact Apogee sells 18 mm and 40 mm foam plugs that are used in NAR competition to guarantee streamer or parachute ejection.

I've switched to using pistons (Ejection plugs from Apogee) whenver possible for streamer & parachute duration models.

 

[SolarYellow]

I have some of the Apogee parts in my bin just to mess around with at some point. I'm thinking about something a little more complicated, though.