» MAKE: NOISE — Discuss this article

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• O ring
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  My launcher has some severe problems. The O-ring seems fine, nice and tight. But, when I try to put the bottle on the launcher ,the O-ring stretches and folds itself down., allowing air to leak out. Is there any hope?
  thx
  

  Posted by Bobomlette on April 06, 2007 at 18:25:57 Pacific Time

• Seal
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  I'm having trouble getting the o-ring to seal at pressures above 40 psi. Any suggestions? I've tried using lots of vasiline, and even 2 o-rings.
  

  Posted by ilobsm on July 18, 2006 at 08:56:02 Pacific Time

• rocket vrs bottle
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  This launcher is a blast and I made a couple for friends. However, for me, a plain bottle (no nose cone, no paint, no fins) goes a lot higher than a "rocket" ie a painted bottle with fins. The weight of the fins and paint seem to really slow it down. Also the fins don't keep it from tumbling at all. So far it's great fun to just shoot the bottles and certainly the kids that gather 'round don't seem to care. But I suspect I'm missing something. Any suggestions?

  Posted by Slipmash on June 25, 2006 at 08:43:39 Pacific Time

• rocket vrs bottle
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  I'd say that if your fins aren't helping to stabilize your rocket, then you don't have a good fin design, or fin placement, or not enough weight in the nose. Try adding more weight to a nosecone, and extend the nose cone / payload bay length to move the center of gravity forward. Try moving the fins further back to move the center of pressure closer to the bottom of the rocket. The key to height is stability. You want all the work (thrust) to go into moving the rocket upwards, not side to side.
  
  Also, be sure the launcher is pointed straight upwards and not at an angle. The water sloshing around in the back of the rocket can set up waves during the thrust phase that deteriorate stability. You want the water to drain as evenly as possible out of the back of the rocket as it launches.
  
  I made the "Make 05" rocket and launched it to a height that the "launch team" all guessed at higher than 250'. If you're getting close to that with a bare bottle, I'd be shocked.
  
  Read about my rocket and find my fin design linked from there, or you can download the PDF directly.

  Posted by kwixson on September 05, 2006 at 01:25:44 Pacific Time

• Calling All Canucks!
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  This may sound nutty, but I'm having a heck of a time finding PVC piping and fittings here in Canada (SW Ontario). Are there any fellows Canucks (or anyone else for that matter) who can give me some clues as to where I can find this stuff? I'd love to be able to order some online, but the retail sites I found so far only ship within the US!
  
  Signed.... Frustrated!

  Posted by crazylegs on April 23, 2006 at 07:25:27 Pacific Time

• Calling All Canucks!
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  Hi. Go to Canadian Tire, Home Depot or any Plumbing supply and you will find what you're looking for. Pipefitter in Peterborough Ont.

  Posted by Tukto on April 09, 2007 at 15:13:10 Pacific Time

• Calling All Canucks!
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  Hi. Go to Canadian Tire, Home Depot or any Plumbing supply and you will find what you're looking for. Pipefitter in Peterborough Ont.

  Posted by Tukto on April 09, 2007 at 15:12:48 Pacific Time

• Calling All Canucks!
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  Hi. Go to Canadian Tire, Home Depot or any Plumbing supply and you will find what you're looking for. Pipefitter in Peterborough Ont.

  Posted by Tukto on April 09, 2007 at 15:12:37 Pacific Time

• Calling All Canucks!
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  Hi. Go to Canadian Tire, Home Depot or any Plumbing supply and you will find what you're looking for. Pipefitter in Peterborough Ont.

  Posted by Tukto on April 09, 2007 at 15:12:11 Pacific Time

• connecting parachute to base
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  one more clarification, please: your article says tie the parachute to the ring attached to the ..base... but from the video & pix, it looks like the parachute is attached to the eyering in the ...nose... which is it? does it matter?

  Posted by wetbehindears on April 13, 2006 at 22:14:29 Pacific Time

• launcher base?
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  I'm new at this. How do you get the rocket launcher to stand upright? Three stays can't be enough. Looks like it's stuck in the ground but that can't be stable when you've got the airhose on one end, right?

  Posted by wetbehindears on April 13, 2006 at 22:10:17 Pacific Time

• launcher base?
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  Pull the stays wicked tight. Also, I used old railroad spikes for stakes. Theyre more robust than tent stakes, and you can really put tension on the stays.

  Posted by Bobomlette on April 06, 2007 at 18:23:14 Pacific Time

• bottleneck / o-ring issues
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  I am cutting a pretty deep groove into the launcher pipe for the o-ring, and it is still too wide for the bottle to fit. Indeed the 2-L bottle fits very snugly over the pvc pipe itself, so I cannot understand how it is possible to fit the bottle over the o-ring. The o-ring is always going to have a diameter larger than the 1/2" pipe. Are their different inside diameters for different 2-L bottles?
  

  Posted by _Buzz_ on April 07, 2006 at 18:49:17 Pacific Time

• bottleneck / o-ring issues
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  Sand or file the inside of the opening of the bottle. If you rounded or bevel the edge of the bottle and apply some vasaline to the ring and bottle the bottle will fit over the ring with little effort.
  
  Mike

  Posted by mikeguyver on May 03, 2006 at 11:22:33 Pacific Time

• bottleneck / o-ring issues
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  The Make prototype rocket was built out of 2-litre Pepsi bottles.
  
  If yoy are having trouble fitting the bottle over the 0-ring, there a few things that you might try
  
  1) Bevel the insde of the mouth of the bottle by carving or sanding. This will create a slight funnel that will allow the ring to go in.
  
  2) Use some Vasoline as a lubricant in the mouth of the bottle, this will help the bottle go over the ring, and help seal the bottle.
  
  3) With the 0-ring in place on the luanch tube, use a sharp razor to carefully slice around the outside of the 0-ring, reducing its diameter to suit your needs.
  
  Hopefully, using one or all of these tweaks, you will find the right fit.
  
  Good luck,
  
  steve

  Posted by finkbuilt on April 10, 2006 at 13:23:08 Pacific Time

• bottleneck / o-ring issues
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  This was helpful--thanks! A dremel was very handy.

  Posted by _Buzz_ on April 14, 2006 at 10:38:36 Pacific Time

• bottleneck / o-ring issues
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  Disclaimer: I'm the guy presenting/exhibiting/demonstrating water rockets at the Maker Faire. I went with a version of Paul Grosse's "copper tube launcher," but I thought for the Faire, it would be fun to build two hand-pump mounted launchers for kids- a "10 minute" one using a cork & a ball inflation needle and the other a "clark cable" original PVC version.
  
  I'm a bit miffed at the write-up in Make:5. I use and like Smart Water bottles as they're quite thick so seem to hold the pressure without exploding and my family doesn't drink soda, but the bottle on page 82 is labelled as a soda bottle. The clear cap suggests pretty strongly it's Smart Water.
  
  So I do use Smart Water, but I always mention that only soda bottles are really meant to take high pressure without bursting. I've used a single-layer Aquafina bottle at 140 psi, but the heat & pressure caused it to deform.
  
  Then, step 1 shows a simple schedule 40 1/2" PVC pipe as the "spine" of the launcher and the o-ring is specified as 22mm O.D., but an I.D. or thickness is not given.
  
  O-rings are specified using AS568 or if you're shopping at an Ace in the US, the Danco rings they carry have their own funky numbering system.
  
  22mm O.D. is about 0.866 inches.
  A Danco #12 is 13/16" (0.8125) O.D., 5/8" I.D. and 3/32" thick
  A #13 is 7/8" (0.875) O.D., 11/16" I.D. and 3/32" thick.
  
  So, one of these might work, but...
  
  Schedule 40 1/2" PVC pipe isn't thick enough to hold a 3/32" thick o-ring and not collapse.
  
  If you consult designs like http://www.geocities.com/wrgarage/launcher.htm, you'll see that they use an inner reinforcing pipe. This requires boring out the 1/2" PVC though, which I can't see doing without a drill press.
  
  I'm going to pick up some 1/16" thick o-rings and try to build a no-drill-press launcher (no internal support tube) with them, but I don't expect it will hold much pressure, which isn't a big concern for a hand launcher used by kids. I don't think I want more than about 40 psi anyway.
  
  I haven't carved by slot in the pipe yet, so it's possible that shallow slot in the pipe with one of these 3/32 rings stretched to fit might work and allow a bottle over it, but o-rings should be slack-- they aren't rubber bands.
  
  1/2" PVC is a close fit in a bottle neck, but that's OK-- you want the o-ring to be in compression. Get it wet before trying to slide the bottle over it. Smart Water necks are 0.850" I.D. and 1/2" PVC is 0.840" O.D. so, yes, it's tight, but it needs to be- as the pressure goes up, the bottle neck will stretch & form a worse seal. The copper tube launcher holds the neck from the outside so higher pressure gives a better seal.
  
  I found it easier to get my hands on a Dremel and a pipe soldering torch than a drill press, but YMMV. Also, in California where code doesn't allow PEX, sweating pipe is useful if you're a homeowner.
  

  Posted by morganw on April 09, 2006 at 23:14:44 Pacific Time

• bottleneck / o-ring issues
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  I picked up a 7/8" o-ring which is a little bigger than the 22mm.
  
  I don't know what smart water is, and where I'd get it. Is it in a 2-L bottle?

  Posted by _Buzz_ on April 10, 2006 at 13:09:53 Pacific Time

• bottleneck / o-ring issues
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  > I don't know what smart water is, and where I'd get it. Is it in a 2-L bottle?
  
  Sorry- I shouldn't have mentioned the different bottles issue when o-rings are the real problem. Smart Water is just a bottled water brand, but the bottles are multi-layer laminated, thick and strong so seem to hold pressure which single-layer PET water bottles won't (they stretch and will probably burst).
  
  If you have a supply of 2L bottles, they should work fine, and as they're actually designed to hold pressure, could be safer.
  
  On to the o-rings:
  
  Here are pictures of my mini-launcher
  
  This fits on the head of a bicycle frame pump for hand-held (low pressure!) launches. The page has close-ups of the groove I made (with the corner rather than face of a rectangular file) and o-rings with 1/16" and 3/32" wall thicknesses in O.D. of 12 through 16 16ths (3/4 to 1 inch).
  
  The Cupertino Home Depot was out of Danco #76 which is a 13/16" O.D. 1/16" wall thickness o-ring. I think this one would be perfect. I'm using a #40 with 3/4" O.D. and it's in tension while in my groove which is not what you want for a great seal, but it's fine for my little launcher.
  
  Other pieces in the picture are a 1/2" schedule 40 PVC SxT (sleeve to Female Pipe Thread) coupler, a 1/2" to 1/4" brass bushing and a 1/4" MPT (Male Pipe Thread) to 1/4" barbed fitting which fits OK, but not great in the schrader-valve side of the pump head.
  
  I'm going to cut the barbed fitting shorter so the shoulder fits right on the pump head, get a short pump and give this one to my 6-year old. I got into water rockets because his version of the same toy one I had as a kid broke (the pumps have plastic shafts now), so I thought rather than buy him another junky one, I'd build one. The 120psi monster with 4 foot tall rockets is kind of fun for him to watch, but this'll let him do his own pumping & launching.
  

  Posted by morganw on April 10, 2006 at 22:23:29 Pacific Time

• Simple launch mechanism
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  I have made a simple version of this using a garden hose click on connector.
  
  Use the male part of the click on connector to screw onto the PET bottle.
  
  Attach the pull down click female part of the connector onto some plate attached to a simple tripod. Get a small ring the fits over the pull down click component. Then get a hand brake from a bicycle and feed the wire throught the ring so when you depress the break it pulls down on the hose connector and releases the male connector. Now simple insert a bicycle tyre value throught the middle of the connector (Where the water would normally flow) so the pump connection part stick out the bottom. Fill the bottle with water click it into position on the connector then attach a pump. Pump away then pull the hand brake to launch.

  Posted by Leja1965 on April 03, 2006 at 21:34:41 Pacific Time

• Simple launch mechanism
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  I'm new to all of this and have to build a simple, cheap rocket as a science project, I figured out how to build all the connections and releases, exept for the connection between the pump and the hose, If you have any suggestions, please reply!

  Posted by rocketeernoob on January 19, 2007 at 18:39:59 Pacific Time

• Fin Template?
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  Does anyone have a template for the fins? If so, put one up on the web somewhere, if you don't mind. If not, I will post one when I make my fins.

  Posted by drbolt on March 14, 2006 at 10:27:10 Pacific Time

• Fin Template?
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  http://www.perkins-observatory.org/educational%20files/rocket.pdf
  It's a 2 pg pdf on a 2-liter rocket. I haven't used it, but it has a template for fins.

  Posted by VinnyF on March 15, 2006 at 06:49:44 Pacific Time

• Fin Template?
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  can you show me some fin templates

  Posted by children on March 22, 2006 at 11:39:23 Pacific Time

• rocket platform type?
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  Does anyone know which is better - the launch tube as in the article, or the traditional launch pad for competition? I'm interested in making this my new hobby, and just looking for info.
  
  Thanks
  

  Posted by VinnyF on March 09, 2006 at 09:20:43 Pacific Time

• rocket platform type?
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  try the H frame its litterly a H out of pvc pipe with a T joint for the bit that sticks up. the H seems to give it more stability when you launch.

  Posted by merseyless on August 29, 2006 at 14:42:21 Pacific Time

• 2 Liter Bottles
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  Be careful when you are buying 2 liter bottles. The first couple I bought had flanges that were too big to fit into the 1" pvc sleeve. I went back to the store and found Dr. Pepper 2 liter bottles with the (older style I guess) small flanges that fit perfectly inside the pvc.
  
  For the music wire I found some round steel 1/8" wire at Home Depot - the kind in the verticle bins with all sorts of rods etc. I'm not sure what "music wire" is but this worked perfectly for me.

  Posted by savmac on February 23, 2006 at 23:42:31 Pacific Time

• Question about glue
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  What glue are you supposed to use for the nose cone? In the mag, it just says "cement it in place atop the nose section."

  Posted by Dwj300 on February 21, 2006 at 14:27:28 Pacific Time

• Question about glue
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  you can use crazy glue or cement glue, either or, what usually makes it work better is if you mold the cone to the shape of the bottle.

  Posted by rocketeernoob on January 19, 2007 at 18:44:02 Pacific Time

• Question about glue
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  It says epoxy. I am using epoxy that sticks to plastic very well.

  Posted by _Buzz_ on April 07, 2006 at 18:50:28 Pacific Time

• Water Pressure Bottle Rocket
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  In high school, I participated in an extracurricular competition called science olympiad. One of the events in SO, called "Bottle Rocket", is a flight-time competition based around the same kind of 2-liter bottle rocket design. There are a ton of great resources on the official SO website for all of you whom are interested.
  
  However, the main reason I'm writing is to share one of the secrets of my team's design: a ping-pong ball air deflector. With this design, a ping pong ball on the tip of a 16-24 inch pole is extended from the nose of the rocket, and functions to theoretically form an air cavity around the majority of the rocket's body, reducing drag. We certainly experienced much higher maximum altitudes, although we never actually calculated any physics behind the presumed reductions in drag. This design does not preclude the use of a parachute. We typically used the bottom 1/4 of another 2 liter bottle as a nose cone (or cap, as it may be), packing the parachute and its rigging underneath it and extending the ping-pong ball air deflector pole upwards from its center.
  
  Note: the spherical ping-pong ball may not be the ideal deflector shape, but it was an excellent substitute for practical reasons, namely, their strength, low weight, and economical cost.
  
  If you are somewhat skeptical, I encourage you to examine photos of the saturn rockets - you may notice a similar nose cone structure.
  
  Happy making!

  Posted by cxmac2 on February 13, 2006 at 15:02:43 Pacific Time

• Music wire
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  How in the world are you supposed to bend the wire?

  Posted by Dwj300 on February 12, 2006 at 09:48:48 Pacific Time

• Music wire
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  I followed the instructions to build 4 of these for a local science fair. I changed the wire piece, though. Instead of music wire, I used a coat hanger. It was much easier to bend, and free to get.
  
  And instead of cutting the notches in the release mechanism, I drilled two small holes in the coupling. The wire is basically a straight piece, sliding in along one side of the bottle neck (instead of both sides). On all 4 of my launchers, this works fine, and it was easier to build.
  
  

  Posted by RainyBrain on February 25, 2006 at 10:53:36 Pacific Time

• Music wire
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  I cut a length of wire around 12" and wrapped it around a piece of 1/2" pvc tube in a vise. On my first try, the wire was around 8" long which was nearly impossible to wrap with my bare hands. The 12" length of wire posed no problem to make the perfect spring.

  Posted by savmac on February 23, 2006 at 23:49:10 Pacific Time

• Music wire
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  I made a few water rockets a while back. The best thing I got out of this article is the idea of filing down the PVC pipe and putting the O-ring in there. But for the music wire just wrap it around a piece of medium sized pipe 1.5 times, then vice grip it around the pipe until you get the desired shape. Then take it off the pipe and it should be V shaped. If you don't get the music wire figured out, google the Clark cable launcher.

  Posted by evil_zman on February 15, 2006 at 14:32:13 Pacific Time