Propellant Type

would making lifting powder packing it in ur engine tube and then letting it dry produce more or less thrust than black powder? Also everyody says dont use pvc for engine tubes and this baffles me because ive always use it and ive never had a problem infact ive found it to work better i always seem to split cardboard could sombody explain to me why i shouldn't use pvc? And third what is a good way of getting two or more engines to fire at the same time as i have a 7.5 foot rocket that i don't feel like packing an engine the size of a bottle for again.

sort by: active | newest | oldest
1-10 of 16Next »
Nerdz7 years ago
Inside a rocket, there are intense pressures built up inside of it in a short period of time. These pressures can put stress on the casing of the engine and can rupture it. If it ruptures, it explodes. PVC when it explodes, can send shards in all directions. If one of these shards gets stuck in you, it cannot be picked up via xray. On the other hand if Metal explodes, It CAN be picked up on xray, hence why PVC can be more dangerous.

iirc PVC has a tensile strength of about 740 PSI. The max Pressure any given engine  can withstand is based on the type of material, its yield strength,  and the thickness of the material. So, If you used Aluminum (6061 alloy) You can use higher pressures since it has a higher yeild strength, but PVC is often favourable because of its cheap price, easy to manipulate and its readily accessible.

I would Recommend against Packing black powder when its dry, you may want to wet it, and let it dry overnight (or a few days for that matter). If your going to use BP, start with cardboard engines, since if your engine Fails, Nothing bad can happen and you wont get hurt.
521937 years ago
Does anybody know where to buy O type solid fuel rocket motors or 50% hydrogen peroxide?
you can distill your hydrogen peroxide,but its hard to tell when its 50% and can become quite dangerous at higher concentrations so if you go this route be careful that vapors dont start to form because these are combustible
covey128 years ago
i use pvc, but the problem is the plastic melts horribly, and i use sugar rockets with kitty litter nozzles
buildingteen (author) 10 years ago
i think jt's sounds most logical although if u make a good engine with black powder it usually burns a total of about 3 seconds and right after it fires its not even hot so i would assum that photo's reason is why most people say this as far as te shrapenal my engines never blow out like a grenade but they either burn out the top and light the rocket on fire or they blow the bentonite plug out the bottom and but all of them are logical
I know this is old but I just got here. I used zink dust and sulfur sifted through pantyhose in spent drilled co2 cartridges. Goes up very well, also goes sideways and explodes well. I would imagine a larger metal gas canister might work. A stun gun can create multiple spark to ignite.
sounds like your plugs aren't adhering to the pvc. bentonite shrinks when drying , pvc expands with heat and you don't mention any sort of glue so there may be a crack that develops and exhaust is burning out. hard to tell without a visual post-mortem.
Tombini jtobako9 years ago
Usualy the bentonite is pressed or rammed into the nozzle former, it acts like a fluid under that much pressure, making a nice and most importantly snug fitting nozzle. to buildingteen, If your plugs are blowing out; - Your nozzle is too small and is choking the exaust until it reaches critical pressure - You have not rammed the plug hard enough - or its too thin, maybe use twice the usual amount and ram it twice
photozz10 years ago
not to mention that when something goes wrong, PVC will easily create razor sharp shrapnel. Metal tubes are less prone to do so, and cardboard is safe.
Tombini photozz9 years ago
Can't agree with the less shrapnel comment but carboard tubes are safe, PVC tubes tend to melt and aluminium tubes (unless you had a real strong header grain) tend to blow out.
1-10 of 16Next »