Sign in to follow this  
Hummingbird Aerospace

How to make a bottle rocket

Recommended Posts

So I am making bottle rockets and I have 2 questions:

1: Where can I get soda bottles from? I am on a trip to Australia and I don’t wanna have to drink 5 sodas in 5 weeks. And I dont want to spend too much money.

2: How can I build the launcher? I am not sure how many pumps I should put in with the bike pump, not sure how to stop water from flowing out of the bottle and in to the bike pump, not sure what diameter of pvc tube I should use, and not sure how to make a mechanism that will release it when it is primed.

 

I would appreciate it greatly if someone helped me with this. Thank you for your time.

I put this here instead of a bottle rocket forum because I am too lazy to create another account for another forum.

Share this post


Link to post
Share on other sites
3 hours ago, Hummingbird Aerospace said:

1: Where can I get soda bottles from? I am on a trip to Australia and I don’t wanna have to drink 5 sodas in 5 weeks. And I dont want to spend too much money.

I don't know how much a bittle of pop costs there, but it shouldn't be that much.  Buy what you need, drink some, and dump out the rest. 

Quote

2:

Did you try this site? There's even a NASA how to on this....

Share this post


Link to post
Share on other sites
21 hours ago, Hummingbird Aerospace said:

Where can I get soda bottles from? I am on a trip to Australia...

Couldn't you get, like, something from trash ? Just give it a good wash.

Or you could buy one and share it with friends.

21 hours ago, Hummingbird Aerospace said:

How can I build the launcher ?

Find a PVC with the closest diameter to the bottle's mouth - it doesn't really matter as you're trying to do pressurized gas here.

The simple 'n stupid way would be using a cork but I remembered in high school one of my friend used a contraption derrived from gas regulators or something. idk though.

EDIT : Thinking about it, that'd be bloody difficult. I think it's from bike pump receptacle instead.

Edited by YNM

Share this post


Link to post
Share on other sites
3 hours ago, Gargamel said:

Did you try this site?

My god, even "This Old House" (A home improvement-esque show) has a how to on the first page of results...

Share this post


Link to post
Share on other sites

But... if I were to do this off the top of my head....simplest form I can think of: (You'll need a cordless hand drill for this)

Make a nose cone of construction paper or what not.  Flexible, but light and stiff at the same time.  Cheap too, as it will probably take a beating.  You play KSP, so you understand what you have to do if it flips around after launch.  Someone should have some heavy coins laying around somewhere...

Cut fins out of cardboard or some other light but stiff material.    Attach these to the bottle to make fins, and legs that will stand the rocket upright when "fueling".   If you're going to use tape, I'd use packing tape, not duct tape, as it's stronger, lighter, and is 'smoother'.  But since we're on a budget, use what you can.  If you have CA glue (crazy glue), it would work well here to hold things on.  Just press and hold for 20 seconds till it sets up. 

Get a rubber stopper, slightly (like .5 mil or 1/32") big for the opening, so it just doesn't fit.  If you can find one that is the perfect fit already, great, but you might not be able to, so get oversized and a few sheets of sandpaper.

Get a Schrader valve (common bike tire valve) with threads so that it can screw into the stopper, and some metal tubing, maybe 3" long (~75mm) so it's about an inch or so longer than the stopper, both (valve and tube) of about the same size diameter.   The valve can be a slightly (1/32" ish, ~1mil) bigger diameter, as we're going to use it to cut threads in the stopper.  Get a drill bit the same diameter of these tubes.    A local hardware store should have all of this. 

Drill a hole in the center of the plug. 

If the plug was purchased a bit oversized, keep it on the drill bit when you are done drilling, and CAREFULLY sand away the surface to reduce it's diameter.  Do this by keeping the plug as far up the bit as you can, pulling the trigger of the drill, and lightly apply the sand paper on the side that is turning away from you.  This will keep your fingers from getting tangled up.  I do this technique all the time on my Lathe at home.   Do not close your fingers, do not have anything that can get caught in the works of the drill (no jewelry, sleeves, long hair, etc).  Rest the paper lightly on your fingers and push it gently onto the spinning stopper.  Sand just a little bit, and test the fit.   Take light passes, and keep going until the plug fits, but is very snug.   You'll probably launch the sandpaper across the room a few times, that's ok, pressing lighter is better than a heavy press.  You'll figure it out. 

Take whats left of the sandpaper and rough up the tube, marring the outer face of it, but only for the length or so that will be inside the stopper.   This will help the epoxy bond the stopper to the tube. 

Once you have a good fit in the bottle, confirm that the tube will just slide into the hole.  It should be close to snug.   Do the same with the bike valve, but scew it into the stopper.  The threads on the valve should cut a new set of threads into the stopper.  You'll have to screw it a little bit, then back it out, then repeat.  Keep doing this till it will screw in fully into the stopper.

  Now put a thin dab of epoxy on the threads of the valve, but only on the half away from the end/opening.  Screw it into the stopper.  Put some of the remaining epoxy around the edge of the seal between the valve and the stopper. 

Put some more epoxy on the tube, staying about 1/8" (~4mm) from the end.  Push it into the stopper, spinning as you go, this will spread the epoxy around.  Do not use CA glue (Crazy glue)for either of these steps, the setup time is too quick, and might harden before you are fully in.  Also, heat from friction has a bothersome habit of causing the CA to trigger early too. 

Once the epoxy has fully cured per the instructions (READ THE INSTRUCTIONS ON THE EPOXY!), you should be ready to go. 

Fill the bottle with water to whatever level you think will work.   Put the stopper in.  Attach the pump.  Set on the ground.  Pump.  Whooosh!   Realize you put way to much/little water in, adjust your levels, and repeat!

The bike valve should be a one way valve on it's own, so you shouldn't get any water coming back into the pump. 

But if you can't find a threaded schrader valve, you could get a tube that the clamp of the pump will clamp firmly too.  Might need a little Silicone grease to firm up the seal (like $1 for a tiny tub from the hardware store).  If you can clamp the pump to the tube, put your finger over the end of the tube, and pump and air has to fight it's way out from under your finger, this might be a cheaper option.   BUT, you'll need the end of the tube to sit way above the top of the water level so you don't suck some back into the system.   So like 10-12" (~30cm) worth might be needed, or more.   The downside to this design is that the tube will have to pull out of the bottle without catching on the sides, which if you can't avoid this, will pretty much ruin the project IMO.  So if the local hardware store has threaded schrader (bike tire) valves, and they don't break your budget, get some.

 

estimated budget (US$): (assuming you already have a bike pump and hand drill, and cone/fin material laying around.):

2L pop bottle - $2

4" of tube - $2 (12" $6)

threaded schrader valve - $3

Stopper - $2

Sandpaper - $1 (for a sheet of 100-120 grit, that should cover all the bases, one sheet is plenty.  Lower grit will tear up the stopper too much, higher grit won't mar the tube enough)

Drill bit - $2

Epoxy - $5

CA glue - $1

So....

$18 bucks US, call it $20 Cause I guessed on half of these. 

And if you ask nicely, they might have some scrap 3-4mm polystyrene sheets lying around, or some other material that will serve as both the nose cone and fins, they might give it to you cheap/free, depending on the type of store you're in. 

 

 

 

Edited by Gargamel
  • Like 1

Share this post


Link to post
Share on other sites

I have heard that they key component in a bottle rocket is the rubber bung you use.

This part decides on how well it will hold pressure and at what pressure the bung will release, launching your rocket.

Get you one which looks like this:

demijohn-rubber-bung-holed-1466-700x700.

Should be available from many places (laboratory supplies [eg: Fisher], but also model shops and shops/sites that sell stuff for brewery). It is the key component, so spending a buck or two is warranted here.

Share this post


Link to post
Share on other sites

Any rocket building info in this thread is use at your own risk

Squad is not responsible for any badness resulting from this discussion. Neither is Take Two. And most especially, I am not. No one will reimburse you for the loss of any appendages or sensory organs resulting from following advice or "facts" in this thread. 

Do not try this at home. 

  • Like 2

Share this post


Link to post
Share on other sites
6 minutes ago, Vanamonde said:

Any rocket building info in this thread is use at your own risk.

Duh.

But I'll acknowledge it's probably a bike pump receptacle and not a gas regulator.

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this