advanced chamber venting question

[singularity]

my current project (well one of two) is a fully automated (but not fully automatic) propane mortar. its primary ammo will be water bottles and every aspect of the firing process will be controlled by a pic micro controller. in fact there will be no conventional trigger, it will be fired when the wattle bottle slides down the barrel. as of right now the specs are as follows...

3"x12" chamber
3"x8" barrel (well the diameter is a little bit less than 3" maybe more like 2.75")
stun gun ignition
reed switch trigger
solenoid propane meter
green gas chamber (to hold liquid propane used to fire)
controlled via pic micro controller (eta one week program is already done though)

the only thing i am missing is some automated way to vent the chamber. the chamber is not a straight piece of it is a 3"x2"x3" "wye" fitting and i was hopping to mount the fan on the 2" section but i need some sort of actuated door to close off the 2" port of the wye when the mortar is firing other wise i get pretty much no compression. so any idea on how to actuate a small door the ghetto way? or is there a much better way to vent the chamber (keep in mind it must be completely motorized/electronic)?

if you need a diagram of it i can draw one

[Hubb]

Hooke up one of the mattress inflators some how. I have one that pushes and pulls the air and it runs off batteries.

To operate the door, why not hook it up to a solenoid valve as well, making sort of like a ram.

Or better yet, have a motor operate a check valve.

[jackssmirkingrevenge]

How a bout a separate air tank that feeds into the chamber through a solenoid valve, timed to give a blast of compressed air after firing?

[homedepotpro]

why not use a inflater like hubb said but put a big check valve between it and the chamber.

[singularity]

well having a tank of compressed air was my first idea but that would add weight and would limit the number of shots i could take becuase i would need compressed air for each one.


wow i completely forgot about check valves, o wait i though they wouldn't work with the low pressure that fans operate at (atmospheric pressure) but a mattress infalater would be perfect! thanks guys

[Hubb]

And then, to operate it, you can use one of these

[rna_duelers]

Have a schader valve,hook up tyo hand pump and pump air out n in like around the chamber will helkp it lots.