Water Rocket Launcher Construction Tutorial: Part 11

Welcome back! We hope that everyone has had an enjoyable and productive week and you are ready to roll up your sleeves and get back to work on the launcher construction. In this chapter of our epic saga, we are going to be adding a remote release mechanism to our launcher.

A remote release mechanism is necessary because we are working with pressurized air inside a plastic container which could burst and cause injury (possibly severe). You will need to be able to operate your launcher to fire the rocket from a safe distance. Whether you plan on holding your own friendly competition or choose to compete internationally with water rockets around the globe in the WRA2 record competitions, you will need to abide by a water rocket safety code which will specify the minimum safe distance you need to be from the rocket.

For our design, we are using a very simple and easy to fabricate release mechanism. The parts we need to obtain are some screw eyes and some strong string. We chose this fluorescent yellow string because of it's obvious high visibility. This is a safety feature to help prevent someone from accidentally tripping over the string and launching their rocket by mistake.

For our release to work easily, we want to be sure that the launching collar holding the cable ties against the nozzle of the rocket is pulled perfectly straight and parallel to the launch tube and cable ties. To make sure the collar is pulled perfectly straight and evenly we need to be sure the screw eyes we will be using to guide the release string are aligned well and are symmetrical on either side of the launcher.

To help align our screw eyes, we are using our square to draw a line along the center line of the launch tube. Fortunately for us, there is a mold line exactly bisecting the 90 degree elbow at the base of our launcher, so we just lined our square up with the mold line and drew our line at the center of the launch tube onto the base board. If you don't have a mold line you can use your eye to estimate where the line should be or measure to find the location of the center of the launch tube and draw your line there.

Now we mark some eye locations along the line we just drew. We wanted to make sure that the eyes were spaced farther apart than the width of the U-bolts so that the release string would not rub on them so we picked a measurement that was outside the U-bolt width and just made sure to use the same measurement from the edge on either side of the launcher.
Once we had our screw eye locations, we used a small drill to make some pilot holes in the wood to insure the screw eyes were in the right spot and could not go in crooked from hitting the grain of the wood. It's always a good idea to make a pilot hole when screwing material together like this.

Below you can see what the finished eyes look like. Be sure and twist them so they end up perpendicular to the launch tube as shown in the picture below. If you have them parallel to the launch tube the string will not feed through them from the proper direction and the mechanism will be difficult to operate due to friction.

The next steps we need to take are to measure out about three feet of the release string and fasten it to one side of the release collar. The other end of the string will feed through the eyelet on the side of the launcher which will face away from the operator and come out of the side facing him/her. If you put it through the wrong side you will realize the mistake in a few minutes and then you will have to take the string back off and start over.

The release string will now cross over to the screw eye on the opposite side of the launcher and you can feed it back into the other eyelet from the side facing the operator to the back side and up to the hole in the opposite side of the release collar. Tie the release string onto the collar at this spot.

The remaining roll of release string will tie onto the piece we just connected ot the launcher forming a "Y" shaped pull string. You will want to tie the main roll of string in a knot that can slide freely from side to side in such a way that it will center itself when pulled tight and will pull evenly on each side of the launcher.
If you're building this for a scout troop you can use this opportunity to demonstrate some of the more practical knots and use the example to illustrate how some specialized knots have practical uses in real world situations!
Everyone else can just make a loop around the release string with the rolled string and tie it back to itself!

When you are finished, you can now give the launcher a quick test. Push the collar up onto the nozzle of the bottle and see that a yank on the release string will pull if off the nozzle without any trouble.
If you sense a lot of resistance you can apply some cooking oil spray to the cable ties and this will lubricate them so they slide freely. You may wish to apply some lubricant now regardless because you may want to launch some high pressure rockets and the lubricant will help release them with higher pressure inside, as the pressure can increase the friction of the collar.

At this point you can take your launcher and start flying! Congratulations!!!
However, we have some suggestions coming up next week for how to improve the launcher and finish it off professionally. You may want to come back and see our ideas before you start launching.
We were able to spend most of the day today working on the launcher enhancements because the materials we ordered for Project 3000 did not arrive in time for construction as planned. We should have what we need within a day or two. We look forward to bringing you another updated on Project 3000 shortly. In the meantime we will put the finishing touches on the launcher enhancements.

Thanks for visiting, we will see you next week!