optimal fan placemeant in specialized cannon

[singularity]

for quite some time now i have been working on my newest cannon the mortar mk 2. its basically an automated combustion cannon meant for airsoft skirmishes. the primary ammo is meant to be "airsoft grenades" made from water bottles. all i can say about these "grenades" is they will be used as mortar rounds and they literally exploded (but they have undergone intense testing and cannot harm anyone unless they were actually holding them with bare hands)

but onto the question, were would be the best place to mount a small 40mm chamber fan meant only mix the the fuel and air? i was thinking right at the propane meter inlet but was not completely sure.

secondary side question: i need to go from 3in pipe to the diameter of a water bottle (approx. 65mm) but putting a second piece of 3in pipe within it would make the barrel about 3mm to small. any ideas on how to make the barrel the correct diameter?

<img src="http://i78.photobucket.com/albums/j85/i ... CN3214.jpg">

here is a picture of the entire cannon its basically a piece of 3 in pipe with a clean out attached. on the pipe there is a solenoid propane meter and a stungun in a custom housing with a key ignition. connected to the propane meter you can see the green gas chamber i removed from an airsoft pistol and modified to fit in a standard ball valve. behind the cannon you can see the metal brackets which will become the mortar's support. i have already programmed the micro controller which will work this thing so basically the only thing i need is a barrel and a couple switches.

[hi]

i put the fans in the rear of the cannon and have it blow out of the cannon. this saves the fan (it lives longer for some reason) and it helps exhaust the gas after its been fired..


as for the barrel, cut a strip out of the barrel (literally a strip down the entire length of the barrel), then remove the strip and use hose clamps to close the gap in the barrel. crude, but it works.you just have to be careful when you do it.

another solution is to wad it with paper or foam, but that is very obvious.

edited to a that- if you look up my "advanced" combustion in the showcase, it too has a 40mm fan in a 3'' pipe. its at the rear and work great.

[Maniac]

ohh finnaly we get to see the long awited auto mortar. I have been long awaiting this as you can tell. I cant wait to see the results from this thing. Im glad you didnt waist those AEG motors on the venting.Onto the question... i would mount it toward the inlet but not right next to it so it would be circulating all of the air equally.( It probably doesnt matter to much where you put it.)

[singularity]

hi - the "cut strip then shove inside method" (as ill call it) wont work thats what i was talking about when i said 3mm to thick

maniac - im glad to see someone other than myself is excited about this project

[ALIHISGREAT]

hmm a sabot is probably the best option or you could find different bottles?

[Novacastrian]

My suggestion is toward the rear of the chamber. I think that this works best because the gases are traveling towards the front of the chamber- hence fan at back would escape most of the hottest gases. Just my 2 cents.

[rna_duelers]

Like Nova Said-Towards the rear of them chamber,and what ever you do don't put it in front of the spark gap or good by fan.

The injection nozzle looks like it is towards the rear of the chamber as well so it would make sense to mix the fuel from the point of entry.Have it venting out towards the barrel because heat rises and so do hot gasses,so it's better to be helping them vent out the barrel with the fan and it can also draw in fresh air easily.

[psycix]

When putting a fan near the barrel, all air from the chamber has to pass the fan to enter the barrel.
This is not good since the insane airflow on that point will cause the fan to break quickly and also block flow a little.
Near the back of the chamber is better and also like RNA said: place is somewhere near the fuel-injection point.