first hybrid

[McFear]

hey all,

attached is a diagram (very basic) of a hybrid spud gun that im going to try make.

i have talked to DYI a little bit about it already and he said that i am wasting material by using so much as a burst disk (green) and then choking it down with a smaller diameter barrel.

there arent any dimentions yet and as DYI pointed out to me there isnt much point in doing this without having the diagram to scale but i figured i would still just post, get some ideas and take them back to the drawing board.

basically the chamber will be bolted onto the barrel as the only seperation between the pieces. the chamber will be milled out of a solid piece for strength. the only parts of the chamber that will be breached will be a drilled and tapped hole for a spark plug for the ignition, and two smaller diameter holes at the rear of the chamber for the fuel and air input valves. i am thinking of making it a 35mm ID chamber with a depth of maybe 80mm. OD depends on what i can get hold of. material mild steel most likely. i prob wouldnt make the wall thickness any thinner then 4mm.

fuel would be propane and air. burst disk, al foil.



basically with the diagram, the two parts of the picture is the chamber view from the top and the completed peice from the side in a cross sectional view.

on the cross sectional view, you have the fuel and air inputs at the left, moving along the chamber wall there is the spark plug and then coming up to the end is the end of the chamber, the burst disk pile and then the barrel. ifyou zoom in on the start of the barrel there are two lugs of sorts behind the projectile. these are just an idea, dont know if i would put them in or not. would be so that if its loaded through the end of the barrel it wouldnt fall against the burst disk cause if fired could cause hell of a lotta damage.

umm think thats all.

Fear

[Gippeto]

So, (basically) you ignore sound advice, then ask for more?

[McFear]

i never said i was ignoring it. i said i was seeing what everyone else thought. i did mention that i had talked to him, i did mention that it was only an idea.

all of the things that he said were in need of changing, i am doing, i posted up here for more ideas. im sorry if i didnt make that clear.

[starman]

You need to make your burst disk the same size as your barrel. A larger disk will need to be unnecessarily thicker to hold back the equivalent psi of a smaller disk and thus making it more difficult to fashion and mount.

Also, your design does not allow for very fast burst disk exchange.

[McFear]

yeh i know it doesnt allow for fast disk exchange, but i wasnt sure how best to go about putting the disk in there so that wsa how i thought it would best work for simplicity.

i didnt think about the size of the burst disk. that will completely change the design though.

eh, back to the drawing boad, Gippeto, this is what i posted up here for. because starman just gave me some ideas that DYI never mentioned.

i am taking all your ideas and will hopefully merge them all into a good cannon. i am only looking to at most doing a 10x shot. and that will be after extensive use at a lower power.

thanks,

fear

[SpudFarm]

hey, talk to me on msn and i can help you there and give you some diagrams