hi guys i am new here...i am 16 and i am making a mini cannon that fires small wooden balls(made myself) for my school project....i hope to achieve the most "cannon-like" gun thus i have chosen to use combustion instead of pneumatic....my english isnt very good hope u guys dont mind.
i have made a very rough diagram about the dimensions..i will be using a sparker and bolts as electrodes..i want to ask if it is possible to thread bolts into pvc?
with my setup will it be possible to propel a wooden ball about the weight of a marble over 50meters? what fuel do you guys suggest? i read starting fluid is good..i kinda like it too as its widely availible in my country. if not i will stick to aerosols. can you guys also help me look at the dimensions of my cannon and see if it would work in theory?
also to seal the barrel to the chamber i would have to use reducer bushings and what kind of glue?
need help for school project and first combustion gun.
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MrCrowley
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Your English is better then half the members on here who speak it as their first language 
Now the cannon...I would say a 300mm long 80mm diameter chamber with a 20mm barrel 800mm long should work. Since this is only a combustion using DWV(reducer) should be fine but you can use a bushing which does that samething but reduces the size immediatly instead of a gentle slope like a reducer if you get what I mean.
Since your using metric I doubt you will find sch40 ratings. What country do you live in? Every country uses a different rating system.
Buy the 20mm barrel first before you make the wooden projectiles as the I.D of 20mm PVC isn't exactly 20mm.
Now the cannon...I would say a 300mm long 80mm diameter chamber with a 20mm barrel 800mm long should work. Since this is only a combustion using DWV(reducer) should be fine but you can use a bushing which does that samething but reduces the size immediatly instead of a gentle slope like a reducer if you get what I mean.
Since your using metric I doubt you will find sch40 ratings. What country do you live in? Every country uses a different rating system.
Buy the 20mm barrel first before you make the wooden projectiles as the I.D of 20mm PVC isn't exactly 20mm.
thanks i live in singapore....i think i will go down the the plumbing shop tonight and take a look at the pipes and ratings and ask a bunch load of questions...and i think i will use the reducer u mentioned instead of a bushing... 
but about the dimensions u mentioned 300mm long 80mm diameter...thats too big! i can only go smaller but not bigger length wise as theres a restriction to the size.
but about the dimensions u mentioned 300mm long 80mm diameter...thats too big! i can only go smaller but not bigger length wise as theres a restriction to the size.
That is really mini!