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USWaterRockets.com - Research & Development Report - 3D Printed Water Rocket Gardena Nozzle
   

3D Printed Water Rocket Gardena Nozzle

Introduction:

This 3D Printed Nozzle is used for Water Rockets.

A type of Water Rocket launcher that has been popular for well over a decade uses a garden hose quick release connector for the launcher mechanism. These connectors are often called Gardena connectors because of a popular brand of connector that these launchers and nozzles were made from.

Constructing a launcher from a hose quick release mechanism is as simple as screwing the female section to a base and attaching a launch cord which will pull the connector latch open.

We wanted to produce a large quantity of these nozzles for a school event, so we began investigating the effort that would be involved. The research we conducted convinced us that we would have to come up with a new way of doing things.

History:

The major drawback of the Gardena launcher design is that making a Water Rocket Nozzle from a Gardena hone fitting is time consuming and labor intensive, due to the fact that soft drink bottles have a different size thread that does not match hose connector threads.

There are a number of excellent tutorials available on the internet for adapting the hose fittings to bottle threads, but these methods can be tedious and/or messy.

The Gardena or similar type of Garden Hose Quick Connect fitting is commonly used to make a Water Rocket Nozzle and Launcher.  Mating the Hose fittings to a bottle is difficult because the thread size and pitch do not match.  One way to adapt the threads is simply to load up the threads with adhesive and force the parts together, and hope the glue forms a seal.

If we chose to use one of the common methods for adapting the fittings, it would be very time consuming, as these methods are not well suited for volume production, and great care must be taken to insure proper fit and alignment, then each nozzle must be individually tested for leaks.

Another solution is cut the  bottle caps and fitting to make a combination of the two.  The trimmed hose connector flange can be attached using the modified cap.  Getting a good seal is always a problem with any of these hand made solutions.

We have been exploring a much easier way to make custom nozzles that makes mass production more feasible. The process, if you have not guessed already, uses a 3D printer to generate the nozzle from raw plastic. 3D printing is automatic, repeatable, and very inexpensive. We used a CAD program called Alibre to create the custom nozzle object, and then printed it on a Rostock Max V2 3D Printer.

We have shared the 3D file for this custom 3D nozzle, but because the nozzle is part of a system of mating components that also involves high pressure compressed air, there are some specific instructions and safety precautions which must be adhered to for using this nozzle for your own rockets.

We designed a totally new nozzle with the correct dimensions and correct threads for soft drink bottles.  The nozzle is designed to be 3D printed.  The nozzle is compatible with bottles that have two or 3 threads on the top.

SAFETY WARNINGS:

Before you can use this nozzle, you should carefully read these instructions for use. You will need to supply your own rubber seals, which we will provide the specifications for later in this article. Note: We have successfully printed and tested this nozzle using ABS filament, and with T-Glase filament. We do not recommend PLA plastic because it is somewhat biodegradable and may soften when used with water. We did not test any other filaments for this project.

CAUTION: Since 3D printing is a new technology, there are differences between each printer and each plastic filament, so we cannot guarantee that these nozzles will be dimensionally accurate when printed on your setup, and they may not withstand the pressures at which you will be using them.

You are using this design at your own risk. Please take the time to carefully and safely test your prints before using them, and as with any Water Rocket, always assume that the rocket can explode or fail at any point during use, taking the proper safety measures for this eventuality at all times.

The 3D Printed Nozzle looks like this when printed.  A #111 size O-ring is used  to form the seal with the female fitting on the Launcher.  The nozzle has two methods to seal against the bottle. Either a #213 O-ring on the base of the nozzle, or a 1 inch flat washer on the mouth of the bottle.

Instructions:

We printed these nozzles using the highest resolution settings of our printer (0.1mm Layer Height). The finely detailed threads and sealing surfaces may not work well with less precision. Depending on your printer, you may have to sand these areas or clean them up to get a good seal with the rubber washers and O-rings.

After you print out your nozzles, you will need to obtain the correct rubber seals that are necessary for use with the nozzles. In a pinch you can purchase some hose quick connect fittings and take the rubber pieces from there, but you may wish to buy the seals in bulk because they are more cost effective this way.

This nozzle is typically used with a 1.0 inch outside diameter flat rubber hose washer to seal against the top of the bottle. Some hose washers are smaller than 1 inch in diameter and may prove to be difficult to seal properly, so we suggest avoiding the smaller washers if possible.

Try and use a real 1 inch flat washer, as they are larger than the cheap hose connector washers that come with the fittings.  The cheap hose connector washers are barely larger enough to work, and may not seal well.  A true 1 inch flat rubber washer is large enough to form a perfect seal.

There is an O-ring that forms the seal between the nozzle and the launcher. This is a standard size #111 O-ring, which slips over the tip of the nozzle and into the groove in the nozzle. The 1 inch flat washer is inserted into the open end of the threaded area of the nozzle where the bottle screws in. Optionally, you can omit the flat washer and substitute a #213 O-ring seal. This seal is placed over the neck of the bottle and rests on the small flange at the base of the bottle threads. A mating groove at the edge of the nozzle will compress the O-ring against this flange. If you have bottles with only two thread revolutions on the top, you may optionally use both the flat washer and #213 O-ring for a redundant double seal. Bottles with three thread revolutions on the top typically do not fit with the double seal, sorry. For these bottles use one seal method or the other.

Slip the #111 o-ting into the groove at the tip of the nozzel.  The 1 inch rubber flat washer is placed  inside the nozzle.  The #213 O-ring rests on the small flange below the bottle threads.

When we designed these nozzles, we took the time to pressure test them very carefully, to prove the design was safe and strong. We were able to pressurize the nozzles to 200PSI with no failures and no leaks. We tried to get the nozzles to fail but the bottles we used were not able to hold enough pressure to destroy the nozzles, and so the bottles distorted and then exploded before the nozzles failed or leaked.

We do not know the ultimate pressure these will fail at. We do know that the exploding bottles did not damage the nozzles. We will probably go back and test the failure point with a reinforced bottle in the future.

The nozzle was tested to 200PSI, where the bottle began to severly deform.  At 200PSI, the bottle eventually exploded.  The bottle shattered, but the nozzle was completely unharmed by the explosion.

We made a video showing off the nozzle design and out 3D printer. Check out the video and leave any questions or comments you have about printing these nozzles in the comments section of the video. If you subscribe to our channel, you will not miss any of our other 3D printed projects.

3D Printed Water Rocket Gardena Nozzle Video:

3D Object Files:

The STL file for this nozzle design is available on Thingiverse. Please click the link below to go there and download the file.

http://www.thingiverse.com/thing:781367

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