last updated: 7th January 2017 - Day 180 Light Shadow and Polaron G2 flights

Safety First

Search

Site Index

Tutorials

Articles

Rocket Gallery

Labs

Where To Buy

10 Challenges

Links

Blog

Glossary

Contact Us

About


Construction - Basic

Body

Ring Fins

Flat Fins

Nozzle

Nosecone

Construction - Advanced

Robinson Coupling

Splicing Bottles #1

Splicing Bottles AS#5

Reinforcing Bottles

Side Deploy #1

Side Deploy #2

Mk3 Staging Mechanism

Multi-stage Parachutes

Fairings

Construction - Launchers

Gardena Launcher

Clark Cable-tie

Medium Launcher

Cluster Launcher

Launch Abort Valve

Quick Launcher

How It Works

Drop Away Boosters

Katz Stager Mk2.

Katz Stager Mk3.

DetMech

Dark Shadow Deployment

Articles

Recovery Guide

Parachutes

How Much Water?

Flying Higher

Flying Straight

Building a Launcher

Using Scuba Tanks

Nozzles

Video Taping Tips

MD-80 clone

Making Panoramas

Procedures

Burst Testing

Filling

Launching

Recovery

Flight Computer

Servo Timer II

V1.6

V1.5

V1.4

V1.3, V1.3.1, V1.3.2

V1.2

Deploy Timer 1.1

Project Builds

The Shadow

Shadow II

Inverter

Polaron G2

Dark Shadow

L1ght Shadow

Flight Log Updates

#180 - Light Shadow

#179 - Stratologger

#178 - Coming Soon

#177 - Reefing Chutes

#176 - 10 Years

#175 - NSWRA Events

#174 - Mullaley Launch

#173 - Oobleck Rocket

#172 - Coming Soon

#171 - Measuring Altitude

#170 - How Much Water?

#169 - Windy

#168 - Casual Flights 2

#167 - Casual Flights

#166 - Dark Shadow II

#165 - Liquid Density 2

#164 - Liquid Density 1

#163 - Channel 7 News

#162 - Axion and Polaron

#161 - Fog and Boom

#160 - Chasing Rockets

#159 - Measurement

#158 - Dark Shadow

#157 - Polaron G2

#156 - Foam Flights

#155 - Down The Barrel

#154 - Revisits

#153 - ClearCam

#152 - Mullaley, Axion G2

#151 - Competition Day

#150 - Rocket Salvos

#149 - Glide Fins

#148 - Too Windy

#147 - Descent Rates

#146 - G2 Launcher

#145 - Harness

#144 - Water vs Foam

#143 - Whalan Reserve

#142 - Doonside

#141 - Windy

#1 to #140 (Updates)

 

WATER ROCKET CONSTRUCTION - LAUNCHERS

These tutorials show you how to build some of the components we use on our rockets. While it may not always be possible to reproduce these components exactly, many of the designs can be customized based on the materials you have available.

For a full list of all construction tutorials go to the Construction Index.

Gardena Launcher
Release mechanism detail. with attached string.
Rocket guides in place.
Release string pulley at the bottom of the release mechanism.
A rocket sitting on the launcher in launch position.
A quick release hose connection for the air supply.
The release string is neatly stored for transport.
A typical launch setup with air supply and release string.
Launcher and rocket.
The launcher consists of a stable base with a vertically mounted release mechanism. The launcher also provides a guide for the rocket during take off. This helps to steer it in the right direction before the fins can take effect.

Procedure

Base

  1. First we start with the base. Cut a square or rectangular piece of wood as shown in the photo. Don't worry about exact dimensions as it does not matter. If it is too small the launch pad will tip over, but if it is too big it becomes cumbersome to carry and transport. Make sure the wood is not chipboard or MDF as it will get soaked quite a bit. Marine plywood is usually the best choice. The wood should be fairly thick to provide enough support for the guides.
  2. Attach an aluminium frame to the base. This helps keep the launcher from tipping over. Again exact dimensions are not important.
  3. Find the center of the board and draw two concentric circles, one at 95mm and one at 115mm. These will represent the two most common bottle diameters 1.25L and 2L respectively. If you are using different size bottles measure the diameter and add ~5mm for clearance.
  4. Divide each circle into thirds and mark the locations on the board. This is where the vertical guides will be placed.
  5. Find wooden dowel or aluminium tube of around 10-12mm in diameter and cut into 3 equal lengths. These will become the rocket guides. The length of these will depend on the release mechanism height. The guides need to be long enough to guide the rocket during the first part of the launch. Exact length is again up to you.
  6. Drill vertical holes at the markings on the board such that the guides do not overlap the circle. Make sure that these holes are a snug fit when you insert the guide. This is best done with a drill press rather than a hand drill.
  7. Repeat the drilling for the other circle(s) spacing the holes around the circumference.

This guide design was chosen because it allows for both ring fins, and the more conventional flat fins.

Release mechanism

  1. The release mechanism is consists of a garden hose fitting attached to an air hose. We have used a brass fitting because it was of reasonable quality and had a smooth pullback action. Be careful when using cheaper plastic fittings as these may not seal as well and may prematurely release the rocket at higher pressures.
  2. Attach an angle bracket vertically to the center of the base. This should be long enough to enable a rocket to sit on top and still have enough clearance for the fins.
  3. Attach a length of garden hose to the garden hose fitting, and then attach the air hose directly to the garden hose. Use of hose clamps and adapters is encouraged. The air hose attachment method will depend on what you have available and what your air supply has as its output. Try to keep the number of transitions to a minium in order to minimise potential sources of air leaks. We used a quick release adapter at the base to make it easier to pack up and transport.
  4. It is a good idea to put a non-return valve in line with the air hose to prevent water from going back into the air supply. We built a custom non-return valve into the hose fitting, but others have used bicycle tyre valves or other forms of valves. If you cannot get your hands on a valve, it should be possible to just create a loop in the air hose whose apex is above the the rocket's fill waterline. Kind of the S-bend principle of a toilet (where the air is pumped in from the sewer end). I highly suggest you don't use a toilet as your non-return valve.
  5. Attach the hose and/or the base of the hose fitting securely to the vertical angle bracket using hose clamps, or cable ties. Ensure that the centerline of the hose fitting is inline with the centerline of the concentric circles on the base.
  6. Using another hose clamp attach either side of a piece of string to the movable part of the hose fitting. To this string attach a long piece of string that will be your launch string. Create a hole in the bottom of the vertical angle bracket to feed the release string through. If the edges are too rough you could set up a pulley system as we have done, to stop the string being cut. The idea is to turn the horizontal pulling action into a vertical one to pull down the hose fitting.
  7. You can hammer in a couple of nails in the base board that will allow you to wrap the string around for tangle free transportation.
  8. We painted the board with water proof paint to help stop the wood from absorbing too much ... you guessed it ...water.

Air supply

Your choice of air supply will depend on what you have available and are comfortable using. A bicycle pump is cheap and easy to use, but requires a lot of work. A car foot pump is easier but still requires a bit of work.

We prefer to use a small 12V compressor intended for filling car tyres. Ours goes up to around 120psi. We use a small 12V 7.5Ah sealed lead-acid (SLA) battery to power the compressor. Both are easy to transport and a battery charge will last you all day. The typical fill time for a small 2L rocket is around 40seconds - 1 min.

For higher pressures you can use more expensive compressors, but for really high pressures you can use a SCUBA tank with an adjustable regulator. We prefer to use a SCUBA tank on the larger rockets, but it is a little cumbersome to carry around.

Many different designs for launchers are available on the internet so make use of your favourite search engine.

Back to Top

Remotely Operated Launch Abort Valve

Launch Abort Valve

The purpose of this tutorial is to build a simple remotely operated pressure release valve out of common materials requiring no special tools.

Background

An abort valve is a very important safety feature of a launcher. On occasions you will encounter a situation where an already pressurised rocket needs to be prevented from leaving the pad and pressure in the rocket needs to be released. Some reasons for aborting a launch include:

  • The recovery system malfunctions or accidentally deploys while the rocket is still on the pad.
  • The range may become unsafe such as when people, vehicles or animals enter the range.
  • A slow leak may develop that might lead to a catastrophic failure if pressure is not released quickly.

While a pressure release valve could be located close to the air source, a problem exists if the launcher needs to use a non-return valve (check valve) to keep the water from flowing back into the air line. In this case the non-return valve should be located as close to the rocket as possible. In order to release pressure from the rocket the pressure release valve needs to be located on the rocket side of the non-return valve. Having a manual pressure release valve next to the rocket means a person would need to operate it while standing next to the pressurised rocket. A remotely operated valve is required for safety.

You may want to prevent water from going back down the air line for two main reasons:

  • Keep as much of the water in the rocket as possible.
  • The water may damage your pump if it is designed only for air.

If your launcher uses a launch tube that only allows air into the rocket above the water line you may not need the non-return valve, however, it is still a good idea to have one in order to prevent water escaping down the launch tube and into the air hose while loading the rocket onto the pad. And when the rocket takes off water is forced down the tube.

It should be possible to attach this mechanism to the air line of most existing launchers if they're not already fitted with non-return valves. In the procedure below we integrate a simple non-return valve into the pressure release valve.

Materials Needed

  • 2 x Gardena quick connectors
  • Gardena extension adaptor
  • Hose clamp
  • Epoxy glue
  • Sewing pin with a round head
  • Nylon String

Tools needed

  • Scissors
  • Drill
  • Screwdriver
  • Sandpaper
  • Pliers
  • Bluetac / plasticine / modelling clay

Procedure

If you are going to fit this mechanism to a launcher that does not require a non-return valve then you can skip steps 1 - 7.

    Non Return Valve
1. Sand the internal hole of the Gardena quick connector.
2. Put a piece of Blu-Tack, plasticine or modelling clay on the workbench and stand the Gardena connector on it's end (orange collar pointing up) so that the Blu-Tack blocks the central hole. You may want to make a protective cylinder from a piece of paper so that you don't get glue on the inside walls near the top of the coupling.

3. Mix up some epoxy and carefully pour it through the open end. Pour enough epoxy in so that it is about 1cm deep.
4. Let the epoxy fully cure for at least 24 hours. It is better to use the longer cure but stronger epoxy than the 5 minute stuff.
5. When the epoxy has cured, drill a small hole through the center of the epoxy. The hole should be smaller than the head of the pin. Usually about 1.5 - 2mm is good.
6. Insert the pin so that the head is on the inside of the coupling. With the sharp end pointing out of the hole.
7. Cut the sharp point off and bend the end of the pin 90 degrees. The bent section should be about 3 mm and there needs to be about 5mm movement of the pin. This is the non-return valve.
    Pressure Release Valve
8. For illustration we show the launch abort valve fitted to a simple Gardena launcher.
9. Here we cut the garden hose air line where we want to fit the abort valve.
10. Insert the two hoses into the respective couplings making sure that the one with the non-return valve is closer to the air source. Tighten the coupling nuts to secure the hoses. Snap the extension adaptor into the hoses to check to make sure everything fits. 

11. Put a hose clamp around the coupling with the non-return valve and pinch two ends of loop made from a short length of string under it.

Tie a string around the hose near the base of the coupling and run it to the other hose near the base of the other coupling and tie it off. Do this three or four times around the couplings. Make sure that there is enough slack in the lines to allow about 2 cm of movement.

12. The pressure release valve is now complete. You will want to attach the hose near the rocket to the launcher so that it does not move when you pull on the abort string.

Connect a long string to the short loop on the valve. Make the string as long as your launch string. It is a good idea to make it a different colour so that you don't accidentally pull the wrong one.

NOTES:

  1. If you use an air hose that is a different diameter to the garden hose used in this example, you can use a short lengths of garden hose connected to the couplings, and make hose adapters for your specific air hose. There are many adaptors available on-line or from your local hardware store. Here some examples:

    http://www.fittingsandadapters.com/brasshosebarbs.html
    http://www.justoffbase.co.uk/Tool-Shop/Air-Hose-Connectors

    You can also easily insert a inner tube (Schrader) valve into the end of the hose and use a small hose clamp to secure it in place. Be aware that these don't work as non-return valves when the air hose is connected to them.
  2. You should be able to use brass Gardena couplings or similar quick connect fittings if you wish to use higher pressures, but make sure that any connected hoses are also rated for the appropriate pressures.
  3. To reset the valve simply click the couplings back together.
  4. The simple 'pin' non-return valve is less than ideal, but for the most part it should seal well.
  5. You may find a Gardena quick connector that already has a non-return valve built in. These are unsuitable as the valve only operates when nothing is snapped into the connector.

References

Back to Top     Construction Index



Copyright © 2006-2016 Air Command Water Rockets

Total page hits since 1 Aug 2006:

George Katz - Google Plus