Instructables
Make a bottle rocket adapter just using recycled materials! All you need is a soda bottle, a cork, and bike inner tube (plus a drill and a bike pump for tools.)

What I love about this method is that it includes a way to take any cork and make it fit a bottle using the magic of microwaves!

This project was originally inspired by the howtoons about bottle rockets. My friend Will Macfarlane and I played with it a lot but found it tough to do with kids ages 6 - 8: the inner tube stopper would come unwrapped and kids had trouble putting it back together, let alone making it on their own. We got into microwaving everything in sight one week, including everything in Star's microwaving instructable, and realized that corks expand when microwaved.

This led to a new way to make bottle rockets! We've used this at Camp Kaleidoscope since '07.
 
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Step 1: Preparing the cork.

This is a really cool trick that Will and I discovered messing around with microwaves. When you microwave a cork (a real cork -- synthetics haven't worked), it expands and gets squishy. You can shove this into a soda bottle and the part shoved in will fit exactly to the mouth opening. As it cools it'll keep the shape and you've got a cork stopper!

We think this works because water in the air inside the cork gets hot and expands, causing the cork to expand. The whole thing cools really quickly -- I've never had to do anything more than put it in the bottle, leave it for a minute, and then take it out.

For soda bottle size, I like 20 oz. or 2 Liters: they have the same opening size, so an opening made for either one will work on both.

We've found that microwaving for 25 seconds worked well, and a lot more would burst our corks. The exact time will depend on the power of your microwave.

You don't always have to microwave the cork -- sometimes the cork will fit naturally into the bottle. What's a nice about this method is that it's not a problem if it doesn't. Rubber stoppers from chemical suppliers will work too, but this is a scarcer item. I think size #4 rubber stopper fits 20 oz/2-L bottles.
jianqiang5 years ago
Cool dude, an easier and lazier way we use to do it in HS was put dry ice or alkaselzer in full bottles, bottle em up, and throw them as fast as you can. Or else just get a 2 liter of barqs(damn, you know the rootbeer), shake it up, and throw it off a 2 story buidling
I assume that because you are an intelligent person, you would only throw anything off a 2 story building with no one in the area........imagine getting hit with the neck of the bottle after it explodes on the pavement.!!!

Cheers
NE patsrock3 years ago
finally i no how to stick a bike pump needle into a a bottle CORK! how dumb of me
Sandisk1duo5 years ago
fill 1/4 full of water for maximum hight
mythbusters did some tests and discovered that 1/3 is the best ratio for water bottle rockets =D
santigosopo4 years ago
 so ,  the  valve stay stuck with the inflator until bottle fly away 
Ben.land1014 years ago
 i think it's funner to leave out the water, hold the stopper, then pump it up and shoot people with it.
Mr E Man4 years ago
Looks good, but you should hot glue the strings of a parachute to the top, and drape the parachute over the bottle.
a better and more durable soloution would be to use a rubber bottle stopper!!!
LILhazY5 years ago
NICE & EZ
wee_man5 years ago
For maximum height attach to air commpresser hehe
ekulmeekul5 years ago
Yea thanks for the cork trick that will really help...
Wow, thanks for the Cork trick, didn't know they expand :D