This is my design for a 2 Liter Bottle Water Rocket and Launcher Pad.

First, I know this is not the first 2 Liter Bottle Water Rocket launching system ever designed.  This design actually took inspiration from several of the designs that NASA had posted.
Second, depending on where you buy your parts and what stuff you have on hand, this may not be the cheapest design either.  You will need to decide if this design provides you the characteristics that warrant the potential additional costs over alternative designs.  I had some very distinctive goals with this Water Rocket Launcher system that I personally felt the other designs did not fulfill.  For example:
  • The design needed to survive rapid repeated use in a very short amount of time.  Scaling to 100+ repeated launches in a day with the ability to turn around and do it again the next day.  Not only did this mean it needed to be rugged enough to last, but it had to have a system that allowed for quick resets.
  • The design needed to allow children 6-17 and adults of all ages to pressurize and launch the system from a safe distance (~20 feet). Although staging / clamping and safety check would be done by an experience adult / young adult prior to pressurizing, it was important to me that each participant had the opportunity to be involved in the act of pressuring and releasing the Water Rocket.

Third, I know the design is not perfect.  I am hoping, like I did with other designs I found, someone will see this design, identify refinement opportunities, and be inspired to improve on it.

Disclaimer:  This “Instructable” is provided “As Is” without any express or implied warranty of any kind including warranties of merchantability, noninfringement, or fitness for a particular purpose.  The Author of this “Instructable” does not warrant or assume responsibility for the accuracy or completeness of any information, text, graphics, links or other items contained within this “Instructable” post.  In no event shall the Author of this “Instructable” be liable for any damages whatsoever (including, without limitation, lost profits, business interruption, lost information, damaged electronic equipment and circuits, damage to property) or be liable for any personal harm / pleasure / death whatsoever (including intentional or unintentional, without limitation, cuts, scratches, lacerations, punctures, bruises, inhalation, swallowing, or insertions) arising out of the use of or inability to use this “Instructable”, even if the Author of this “Instructable” has been advised of the possibility of such damages or personal risks.

In short... Do your own engineering work and analysis of the approach for your specific implementation to determine validity, safety, and assume accountability for the outcome of your engineering assessment; assess and mitigate the risks specific to your scenario and skill level. Use good sense on how, where, and if to use this approach; if you are unsure, do not use it... I would have said common sense, but common sense is definitely not common.

This Bottle Water Rocket Launcher Design has 3 major system components:
  1. 2 Liter Bottle Water Rocket & Pressurization Plug: This system stores the pressurized water and air and, on Launch Pad Clamp release, allows the 2 Liter Bottle to generate thrust projecting the 2 Liter Bottle housing into the air.
  2. Launch Pad: Holds the 2 Liter Bottle Water Rocket while the system is being pressurized and provides a mechanism to quickly release the pressurized water / air.
  3. Modified Bicycle Pump / Pressurization System: Although any bicycle pump can be used to pressurize the system, this modified version provided additional hose length and pressurized water back flow protection.  Whether you use this modified bicycle pump or any off the shelf bicycle pump design, a bicycle pump or air compressor is required.

Summary of Procedure:

Launch System Component Assemble
  1. Getting your Materials (Parts & Tools)
  2. Assemble Pressurization Plug
  3. Assemble Launch Pad Clamp Bracket and Hinge
  4. Launch Pad Base preparation
  5. Launch Pad Base Pressurization Plug Housing rough-in
  6. Launch Pad Base Pressurization Plug Housing tuning
  7. Fastening Launch Pad Clamps to Launch Pad Base
  8. Place the Launch Pad Clamps under return spring tension
  9. Secure Stabilization Feet to Launch Pad Assemble Base
  10. Affix Velcro Launch Pad Clamp release strap
Bicycle Pump Optional Step:
  1. Disassemble Bicycle Pump
  2. Assemble Bicycle Pump Hose Extension
  3. Reattach Bicycle Pump Hose & Head
Operation, Safety & Additional Notes
  1. 2 Liter Bottle Water Rocket and Launcher Pad Operation
  2. Safety and Additional Notes

Step 1: Getting Your Materials (Parts & Tools)

Get your Parts...

2 Liter Bottle Water Rocket: 
Item: 2 Liter Bottle - Quantity 1
  • Use: This is the rocket body housing which stores the pressured water.
  • Price: Hopefully you dig this out of recycling or save it after finishing a refreshing beverage.  If you need to buy one, they are ~$0.50 - ~$1.50 containing a beverage.  (I have used Pepsi and Coke product 2 Liter Bottles without issue.)
Items: Rubber Stopper, #3, 1-hole – Quantity 1
Items: 2” Long .453 inch wheel diameter (TR Valve Number 418) Tire Value – Quantity 1

Launch Pad Assemble:
Item: Pressure Treated Lumber 2X4X16 inches – Quantity 1
  • Use: Launch Pad Assemble Base.
  • Price:  Hopefully you have some scrape lumber laying around; if not, price for a 8 foot 2x4 at Home Depot is ~$6.00 - http://www.homedepot.com/p/202061034
Item: Pressure Treated Lumber 4X4X16 inches – Quantity 2
  • Use: To provide stabilization feet for the Launch Pad Assemble Base.
  • Price: Hopefully you have some scrape lumber laying around; if not, price for a 6 foot 4x4 at Home Depot is ~$7.00 - http://www.homedepot.com/p/100043272
  • Note: You will need ~3 inches of ground clearance to easily affix the Bicycle Pump Hose Head to the Rubber Stopper Schrader Valve.  Doubling up with 2X4 should work fine.
Item: 1-1/4 inch x 8 inch Punched Angle – Quantity 2
  • Use: Clamps and holds 2 Liter Bottle to Launch Pad Base while system is being pressurized.
  • Price: Pretty common item at any home improvement store; Home Depot has it for ~$9.50 for a 4 foot length. - http://www.homedepot.com/p/202183466
Item: 4 Inch Adjustable Spring Hinge – Quantity 2
  • Use: Retracts clamps holding pressurized 2 Liter Bottle to Launch Pad Base.
  • Price: Theses are ~$16 a piece from Home Depot.  I have seen them a couple dollars cheaper online, but with shipping it is usually a wash. - http://www.homedepot.com/p/202033836
Item: 1/4 inch - 20 X 3/4 inch Machine Screw with Nuts – Quantity 4
Item: 1/4 inch - 20 X 2 inch Machine Screw with Nuts – Quantity 4
Item: 1/4 inch Flat Washer – Quantity 8
Item: 1/4 inch Split Washer – Quantity 8
Item: 2-1/2 inch Deck Screws – Quantity 4
Item: Velcro 23 inch X 7/8 in with Hook and Loop – Quantity 1
Item: #18 Twisted Mason Line (~25 feet) – Quantity 1
  • Use: To pull apart Velcro from itself from a distance allowing the Launch Pad Clamp havles to snap open releasing the 2 Liter Bottle from Launch Pad Base.
  • Price: Home Depot has a 225 foot roll for ~$3.00 - http://www.homedepot.com/p/202079597
Item: 3/8 inch Vinyl Bumpers – Quantity 6

Modified Bicycle Pump / Rocket Pressurization System (Note: Optional modification)
Clarification: Any factory bicycle pump will work for this project; however, since I wanted to extend the distance between the bicycle pump and launcher for added safety, I decided to modify one.  Here is the configuration I used to extend the hose distance of the bicycle pump.

Item: Bell Air Attack 300 Air Pump - Quantity 1
  • Use: To pressurize system with air.
  • Price: Walmart has them for ~$10.00 - http://www.walmart.com/ip/24311975
  • Note: I choose the Bell Air Attack 300 Air Pump because it was inexpensive and easy to modify.  Although I did not try other similar style bicycle pumps, it is my assumption that as long as the inner diameter of the pump hole is a 1/4 inch, another bicycle pump should work just fine.
Item: 1/4 inch PP Standard Check Valve - Quantity 1
  • Use: To prevent water from draining into the pump and extended pump hose line.
  • Price: U.S Plastics Corporate has them for $0.70 - http://www.usplastic.com/catalog/item.aspx?itemid=23369
  • Note: Normally the existing check value in the pump is sufficient to prevent pressurized water and air from leaking from the system; however, since I extended the hose length, I wanted to ensure pressure remained more consistent at the 2 Liter Bottle.
Item: 3/8 inch X 1/4 inch X 20 feet Clear Vinyl Tube (rated 55psi @ 70F /20C) - Quantity 1
  • Use: To extend the hose length of the bicycle pump.
  • Price: This is a pretty common item at any home improvement store.  For a 20 foot length, it will be ~$5.00 - http://www.homedepot.com/p/202257573
Item: 3/4 inch Electrical Tape - Quantity ~3 inches
  • Use: To provide additional thickness at the end of the Clear Vinyl tube being inserted into the Bicycle Pump to ensure secure fitting when screwing down bicycle pump hose clamp.
  • Price: This is a pretty common item at any home improvement store.  ~$1.00 per roll. - http://www.homedepot.com/p/100130843

Get your Tools...
  • Circular Saw, Electric Drill, Hack Saw, Pencil, Philip Screw Drive, Ratchet Set, Rubber Malt, Vice, Metal file, Needle Nose Pliers, Pliers
  • Drill Bits: 1/4 inch, 3/8 inch, 3/32 inch, 1/2 inch Spade or Forstner bit, 1 inch Spade or Forstner bit, 1-5/8 inch Spade or Forstner bit
<p>Hi, what a great, high-quality instructable! The *one* part I'm not clear about is how the velcro release works. I don't understand how to route it in such a way that it will hold closed yet release both hinges easily with just a tug of the mason line, which also seems like it might tip the system when pulled. Can you provide any additional images / explanation for this?</p>
<p>Looking at the Velcro product picture, you can see there is a slot in which the other Velcro end can be pulled through. By doing so, this creates a loops that can be<br>wrapped around one of the Launch Pad Clamp Halves securing the Velcro to the<br>pad. The routing of the Velcro strap to secure the Clamp Halves in the closed position is illustrated<br>in the attached picture.</p>
<p>Hi, This is a very comprehensive set of build instructions with very good safety notes included. A definate must build for when the grandchildren are next round to stay. I see hours of endless fun for me oops! I mean the grandchildren. As an addition to the projectile construction may I suggest listed in Instructables:-</p><p>Water Rocket<br>by JoeGadget on April 26, 2014</p><p> Well done keep the space faring going.</p><p>Regards,</p><p>Harold</p>

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