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A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

Launch Rail

Discussion about Compressors, hose, pipes, fittings, launchers, release mechanisms, and launch tubes.
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thampson
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Launch Rail

Post by thampson » Sun Nov 09, 2008 11:12 am

I have added a launch rail to our launcher to improve safety in windy or gusty conditions with larger wrockets. We had one blow clean off the launcher and fly horizontally at our last launch day when a gust of wind knocked the wrocket over while pressured.

The launch rail in made form a curtain rail which .. and this is the best part .. cost me zip .. $0. I found 2 of them a neighbor was throwing out in a yearly council throw out day. Saved me about $30. Its about 1.8m high and the curtain holders act as perfect lugs when glued using PL Premium to the wrocket body

Initial testing works great. I have a detailed write up on the website for those interested along with some pics

http://wrocket.hampson.net.au/?p=584

will post some video of the rail in action from our next launch day

-todd-
HHWRSA


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Hornsby Heights Water Rocket Space Agency
http://wrocket.hampson.net.au

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Andromeda
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Re: Launch Rail

Post by Andromeda » Sun Nov 09, 2008 11:28 am

thampson wrote:I have added a launch rail to our launcher to improve safety in windy or gusty conditions with larger wrockets. We had one blow clean off the launcher and fly horizontally at our last launch day when a gust of wind knocked the wrocket over while pressured.

The launch rail in made form a curtain rail which .. and this is the best part .. cost me zip .. $0. I found 2 of them a neighbor was throwing out in a yearly council throw out day. Saved me about $30. Its about 1.8m high and the curtain holders act as perfect lugs when glued using PL Premium to the wrocket body

Initial testing works great. I have a detailed write up on the website for those interested along with some pics

http://wrocket.hampson.net.au/?p=584

will post some video of the rail in action from our next launch day

-todd-
HHWRSA
Nothing beats a free part for a water rocket. We must have found the most effective use for discarded items ever. That's a nice idea for a launch rail too. I hope you can get a chance to test it out soon.


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Bonami
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Re: Launch Rail

Post by Bonami » Mon Nov 10, 2008 5:42 pm

Hi everybody. Is there a advantage to using a C channel for a launch rail on a water rocket instead of a rod or a tube with launch lugs on the rocket body? Thank you.



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Re: Launch Rail

Post by Cloud Dancers » Mon Nov 10, 2008 8:00 pm

Bonami wrote:Hi everybody. Is there a advantage to using a C channel for a launch rail on a water rocket instead of a rod or a tube with launch lugs on the rocket body? Thank you.
I think that the advantage would be that you eliminate the drag of the "lugs" if you use "c channel". I use vinyl gutter which can be purchased at the local home improvement store. I have to cut some off but it works and it also eliminates metal touching the outside of the rocket. I once had a fin fly off and land about 30 feet away when my rocket exploded. The fins were made out of stiff plastic and were kind of heavy. Now I don't want anything near the rocket that could become a projectile. I have seen some launchers that look like fragmentation grenedes.


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Mark Chen
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Re: Launch Rail

Post by Mark Chen » Tue Nov 11, 2008 9:39 am

I designed a launcher system that used a loop of stainless steel cable and pulleys. The cable looped around small pulleys and formed two parallel runs of cable that an "I" channel would slip between. The "I" channel served as the launch rail only it was glued to the rocket. A turnbuckle on the launcher could make the cable very tight and this would insure it was 100% perfectly straight. It's one of those projects we want to build someday.

The same idea could be used to make a launcher which guided the rocket without a lug. You could connect 3 cables in a triangular pattern to the base of the launcher and then run them up to the top and pull them tight and have the cables themselves surround the rocket and guide it.

The advantage is you can make the launcher out of scrap lumber or some recycled materials and not worry about the parts being perfectly straight. The straightness of the guides is assured by the tension of the cables which act as the guides.


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thampson
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Re: Launch Rail

Post by thampson » Tue Nov 11, 2008 9:44 am

There is an advantage if you can use 3 rods for example to guide the wrocket as you then dont have to stick lugs to the wrocket. The lugs will cause drag on one side of the wrocket, in practice how much drag we will see when we launch at our next launch day. My guess is you may loose a couple of meters in height in drag and that it may tip over a few degrees

With the 3 rod design you need to secure the rods at the top as well as at the bottom otherwise the wrocket will still fly off at a bit of an angle as it pushes between the rods at the top, there are a few videos around showing this. There are also some good solutions to this problem by securing the tops of the rods together while still allowing the fins to get through, aircommand has a good one as well as at least 1 other I have seen.

For me, I wanted to make sure the wrocket would sit on the launcher vertically when it gets gusty. Around where I live is quite hilly and the ovals are on the tops of the ridges so its easy to get a gust come up the valley and sweep across the ground without much warning. The rail and lugs work very well to ensure the wrockets sits still on the launcher when its gusty. Im also happier that it provides a safer launch environment, I dont want another case of a wrocket blowing off the launcher and becoming a horizontal missile

hope this helps

-todd-
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http://wrocket.hampson.net.au

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Re: Launch Rail

Post by Tim Chen » Tue Nov 11, 2008 3:28 pm

Todd,

The idea Mark is working on with the cables has some nice potential because you can make the pulleys adjustable for different size rockets and if you pull them tight then there's absolutely no chance of bending. An enhancement to his idea I suggested would be to make the spacing between the pulleys slightly larger on the top of the launcher so the top of the "rails" had a larger opening and less friction. I think they also make teflon coated cable so if we use that it would make almost no friction.


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thampson
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Re: Launch Rail

Post by thampson » Wed Nov 12, 2008 9:53 am

Hi Tim and Mark,

Im having a little trouble visualizing what you are talking about .. do the cables act like a launch rod ie: to guide the wrocket. Is the benefit over using a guide rod that there is less friction ?

cya
-todd-


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http://wrocket.hampson.net.au

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Tim Chen
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Re: Launch Rail

Post by Tim Chen » Wed Nov 12, 2008 1:11 pm

thampson wrote:Hi Tim and Mark,

Im having a little trouble visualizing what you are talking about .. do the cables act like a launch rod ie: to guide the wrocket. Is the benefit over using a guide rod that there is less friction ?

cya
-todd-
The cables when pulled taught replace the rails in your launcher. You could make a launcher out of any cheap materials you have laying around and string a bunch of cables to contain the rocket. A benefit is that the cables use tension to keep them straight so there is never a chance of bending them if a rocket explodes or the launcher tips over or someone steps on the parts while you're assembling it. The tightly strung cables will always be straight! Come to think of it, they are a safety device if the rocket blows up they will hold the launcher pieces from becoming projectiles.


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Mark Chen
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Re: Launch Rail

Post by Mark Chen » Wed Nov 12, 2008 4:38 pm

You don't have to use pulleys either. I was just thinking of ways to make it "high tech". I think you could just as easily loop the cables through a screw eye or something. As long as the piece you wrap the cable over doesn't stick out in the path of the rocket then you're good to go!


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Re: Launch Rail

Post by Cloud Dancers » Wed Nov 12, 2008 11:01 pm

Mark Chen wrote:You don't have to use pulleys either. I was just thinking of ways to make it "high tech". I think you could just as easily loop the cables through a screw eye or something. As long as the piece you wrap the cable over doesn't stick out in the path of the rocket then you're good to go!
What size cable do you use. I was looking at Home Depot and they sell the stuff by the foot but it comes in all different sizes. What do you do to keep it from unraveling. Would bicycle brake cables work. I can get my hands on those easily.


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