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invention

Littlebits Powered Water Rocket Launching and Parachute System final entry #shapebits

by Leo Rolph

Published on June 1, 2015

In this kit is everything you need to make, launch and relaunch water rockets, using 3D printing, household items and powered by Littlebits. This is a great project; the kit makes what is normally a time consuming and difficult task, fun and easy, allowing more time to be spent enjoying launches.

The Littlebits powered water rocket is great for all ages it teaches physics, mechanical knowledge, electrical understanding and aerodynamics; safely and in a fun way.

I wanted to keep this project simple, focusing on an easily made and fun project. We used only the parts we needed and really showed the power and potential of simple mechanics, imagination and some well-designed, hardy, seemingly indestructible and versatile Littlebits.

The launchpad is powered by one DC motor and uses standard garden hose attachments as the coupling to the rocket, I was pleasantly surprised to find the motor is easily strong enough to pull the lever to uncouple the rocket. The launchpad works first time every time, looks lovely and transports easily.

The parachute system works perfectly on all ground based tests, using an elastic band as tension to pull the door open and a servo to unlock the door. The servo is activated by a 9v battery sliding forward as the rocket tips over at apogee and making contact with Littlebits power module (after some testing this seemed like the simplest fail safe method). On our first test flight (which is often all you get with rockets) out of caution we didn’t pressurise the rocket enough and the parachute didn’t have time to eject properly, and it came crashing back to earth(though the door did open). Amazingly all the Littlebits survived! With a little more time and another launch I’m sure the parachute system will be successful.

The whole rocket is in a modular design for easy modification. We were very limited by our time and amount of Littlebits, but with Wi-Fi you could remote launch, use a countdown timer, have second stage ejection and much more. This project for me was finished right at the last possible moment.

The Rockets components are live on Shapeways

https://www.shapeways.com/product/EVS96ZUSN/water-rocket-parachute-module-shapebits

https://www.shapeways.com/product/JD7QXE56F/littlebits-water-rocket-launchpad-shapebits?key=1fad86ec...

https://www.shapeways.com/product/YYURQFL98/water-rocket-coupling-shapebits

Also this site has some great info and getting the best results with your rockets. My rocket was really just simplified version to demonstrate the system.

http://www.aircommandrockets.com/flying_higher.htm







Credits: Thanks Warren Tarboton for helping with the modeling. Thanks to Kav for assisting with the launch and thanks to my wife for giving me the time:)

How To Make It

STEP 1

First print all the sections, launcher, parachute and PET bottle coupling.

STEP 2

To join two PET bottles end to end, first cut the end of two bottles, heat about two inches of water in a pot and just as it starts to look hot (little bubbles) dip one of the bottles into the water for a second. This will shrink one bottle slightly and allow one bottle to slide into the other. Scuff the joining bottle surfaces with sandpaper and glue them together with a flexible glue like Sikaflex. Cover the joins in a wide tape for extra strength. That should be a pretty good seel and should hold a lot of pressure.

STEP 3

Next cut 3 lengths of 30mm PVC pipe, 40cm long and install as legs in the Launchpad. Then use hot glue to fix the lego compatible mounting boards in desired places (we used this system for a more modular design with more freedom). Use standard garden hose couplings as shown in the pictures. To make the male couple use a threaded male connector (brought from a hardware store if you don’t have one) and glue it into a hole made in a PET bottle lid.

STEP 4

Wrap all the Littlebits on the Launchpad in clingwrap and tape the ends (I used Kapton tape because it looks cool) to keep everything dry, then mount them to the launchpad. Use tooth floss as string to tie the DC motor to the lever on the launchpad.

STEP 5

Make a parachute using a plastic bin bag cut into a circle, at 5 points on the edge fold over a small strip of stickytape, use a hole punch to make holes in the center of the tape (this will make a strong area to tie lengths of toothfloss at parachute cord). Attach it to a stronger lenght of string and tie to the top PET bottle nozzle below the parachute module. Then put the rocket together, install the Littlebits in the parachute module, make sure the battery is orientated properly and install the module on the rocket.

STEP 6

Using a butterfly metal tie attach a bicycle inner tube at one end of the hose (this is what the bike pump will attach to).

STEP 7

Make some fins by cutting the shapes out of foam board or balsa wood

STEP 8

Fill one third of one section of the rocket with water, place the rocket on the launchpad (assuming you’re in a nice big park), pump the rocket up to about 80 – 100 psi, flick the Littlebits switch and watch the rocked zoom at breakneck speed towards the clouds and then watch as the parachute opens, it lands safely… and you get to go again 

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