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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.

New Launcher Design Using Steel Balls to Secure Bottle

Discussion about Compressors, hose, pipes, fittings, launchers, release mechanisms, and launch tubes.
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RebelRockets
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New Launcher Design Using Steel Balls to Secure Bottle

Post by RebelRockets » Thu Jun 17, 2010 7:03 pm

Hi everybody,

I've spent the last few weeks redesigning my launcher and the result is a bottle locking mechanism similar to a Gardena quick connect, only it fits directly to a normal bottle neck instead of the smaller nozzle. This allows use of normal full bore launch tubes. It uses 1/4" steel balls to grip the bottle flange.
collar_off.JPG
collar_on.jpg
Full details for building, parts list, and more photos are on my web page.

http://rebelrockets.wordpress.com/launc ... -launcher/

I hope this is helpful to someone trying to build a launcher. I've only been able to test it a few times but so far it seems to work smoothly. Most of it should not be that difficult to build.

The problem is that the PVC parts needed are made in the USA, sold at Home Depot, and finding similar parts that work together so well elsewhere could be very difficult.

Good Luck!

Dennis
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U.S. Water Rockets1
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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by U.S. Water Rockets1 » Sat Jun 19, 2010 11:04 pm

Dennis,

That's a really great design. Did you come up with the idea to use a wire to retain the bearings? That's really a great way to solve the problem of retaining the bearings when the collar is retracted. It looks like something that could be adapted to other size fittings with a little work. The overall idea for how it works is something a lot of people should be able to make use of.

Thanks for sharing the design!


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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by RebelRockets » Sun Jun 20, 2010 12:31 am

Hi,

Thanks very much for your comments. In the photos above the black line is actually a piece of fishing line. I had not yet installed the elastic cord used along beside the line so that the detail cut in the PVC was more visible. There is no wire used because it would not be flexible enough for the action needed. The elastic cord must actually stretch a little bit toward the inside of the tube along beside the steel balls. That is why the little notches in each hole are cut there, to provide clearance.

I believe the method of retaining the steel balls was my idea, I am not aware of it being used any where else at this time. The elastic was used in experiments for a deployment device so it was handy on my work table. Because of the closeness of the bottle to the retaining tube there isn't much room for anything else. The bottle flange is a very close fit inside the tube. Even if you could keep the steel balls blocked by the locking collar on the outside, what would keep them from bouncing back inside and being blasted out by the water during a launch? Hopefully the elastic cord will hold up to that.

In case someone is trying to adapt this idea using other parts, this version works because the thickness of the tube wall is just a little more than half the diameter of the steel balls. They are always supported at their centers whether inside or outside the tube. 1/4" diameter seems to be the ideal size to fit up against the bottle neck at the flange.

Dennis



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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by RaZias » Sun Jun 20, 2010 6:11 am

I can´t see any O-ring there...

How you make it air tight ?


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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by RebelRockets » Mon Jun 21, 2010 10:20 am

Hi RaZias,

There is the usual launch tube with an O-ring installed in the completed launcher. It was just not installed for the photo in order to show the most detail of the new mechanism.

The web site should make it clear how everything fits together when finished.

Dennis



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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by Spaceman Spiff » Mon Jun 21, 2010 3:22 pm

That's a pretty neat idea. Does anyone know if ball bearings come with holes like those or do you need to drill them out? It would be a pain but worth the effort.

I was thinking if I wanted to use higher pressures that the same design could easily be made up from a could pieces of aluminum tube stock, right? I know there was an old timer that made a ball bearing release but he used it on a high pressure rocket and the PVC stretched and gave way where the bearings were seated.


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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by FredK » Mon Jun 21, 2010 5:03 pm

RebelRockets wrote:Hi RaZias,

There is the usual launch tube with an O-ring installed in the completed launcher. It was just not installed for the photo in order to show the most detail of the new mechanism.

The web site should make it clear how everything fits together when finished.

Dennis
Thanks for answering that. I was just gettin ready to ask that. One more question. How much pressure do you think your launcher can stand? I was thinkin of trying to build one and was wondein if it was stronger then a cable tie launcher.


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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by RebelRockets » Mon Jun 21, 2010 6:34 pm

Hi,

In response to Spaceman Spiff and FredK:

I used sling shot steel ammo to make the balls, it isn't as hardened as ball bearings so I assume it is easier to drill. Since I wanted to use my new lathe for something I chose to drill them myself. You may be able to use ready-made beads from a craft store if you can find the right shape & size of a hard material.

I see no reason that a metal tube couldn't be used if you can find the right size to fit the bottle flange. The tube's wall thickness would need to be just a little more than the ball's radius to work the same. Thanks for the warning about the PVC failure under high pressure, I had not heard that story. I'll watch for signs of stress and deforming.

As for holding up to high pressure, I have not really put it to a stress test as of yet. Most of my testing is done at home where it would NOT be a good idea to go for high pressure / high altitude launches. I have not built or used a cable tie launcher before so I can't say when they reach their limits. Since the steel balls act similar to the action of the cable tie heads in gripping the bottle flange, and the locking collar works the same, I guess the difference would be between the strength of the PVC (or metal) tube versus the strength of the cable ties themselves, how many are used, and how well they are mounted.

Dennis



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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by FredK » Mon Jun 21, 2010 10:38 pm

RebelRockets wrote:Hi,

In response to Spaceman Spiff and FredK:

I used sling shot steel ammo to make the balls, it isn't as hardened as ball bearings so I assume it is easier to drill. Since I wanted to use my new lathe for something I chose to drill them myself. You may be able to use ready-made beads from a craft store if you can find the right shape & size of a hard material.

I see no reason that a metal tube couldn't be used if you can find the right size to fit the bottle flange. The tube's wall thickness would need to be just a little more than the ball's radius to work the same. Thanks for the warning about the PVC failure under high pressure, I had not heard that story. I'll watch for signs of stress and deforming.

As for holding up to high pressure, I have not really put it to a stress test as of yet. Most of my testing is done at home where it would NOT be a good idea to go for high pressure / high altitude launches. I have not built or used a cable tie launcher before so I can't say when they reach their limits. Since the steel balls act similar to the action of the cable tie heads in gripping the bottle flange, and the locking collar works the same, I guess the difference would be between the strength of the PVC (or metal) tube versus the strength of the cable ties themselves, how many are used, and how well they are mounted.

Dennis
Thanks for the quick reply man.

I think I might try the PVC version first until I get the hang of it. I found some ball bearings from an old bicycle that look like they might work.

Thanks again man!


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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by Spaceman Spiff » Mon Jun 21, 2010 11:00 pm

RebelRockets wrote:Hi,

In response to Spaceman Spiff and FredK:

I used sling shot steel ammo to make the balls, it isn't as hardened as ball bearings so I assume it is easier to drill. Since I wanted to use my new lathe for something I chose to drill them myself. You may be able to use ready-made beads from a craft store if you can find the right shape & size of a hard material.

I see no reason that a metal tube couldn't be used if you can find the right size to fit the bottle flange. The tube's wall thickness would need to be just a little more than the ball's radius to work the same. Thanks for the warning about the PVC failure under high pressure, I had not heard that story. I'll watch for signs of stress and deforming.

As for holding up to high pressure, I have not really put it to a stress test as of yet. Most of my testing is done at home where it would NOT be a good idea to go for high pressure / high altitude launches. I have not built or used a cable tie launcher before so I can't say when they reach their limits. Since the steel balls act similar to the action of the cable tie heads in gripping the bottle flange, and the locking collar works the same, I guess the difference would be between the strength of the PVC (or metal) tube versus the strength of the cable ties themselves, how many are used, and how well they are mounted.

Dennis
Dennis:

I think the best advantage of the design you made is the way the bearings will roll off the collar when you pull it. I have noticed that cable ties create a lot of friction at high pressure. I had to switch to a thick rope to pull my collar on my spiderwire reinforced rocket.

Do you think the flange on the bottle necks would snap off under stress?


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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by RebelRockets » Tue Jun 22, 2010 12:06 am

Hey Spaceman,

I think if the flange begins to break off the bottle, you must be using a little too much pressure! :shock:
If the flange starts to get wavy at the edge from the 6 points of contact it has probably reached its limit.

I suppose the reason your collar is getting so tight to pull is that the cable tie heads are being deformed by the extreme force and smashed against the collar. Before going with the elastic necklace idea, I considered attaching each steel ball to a separate wire that attached to the launcher below it, much like a metal version of the cable tie idea. I dropped that idea for being much more difficult to make and probably too unreliable. Maybe someone else could make it work.

Thats brings up a few questions about cable tie launchers for people who use them.
Do the heads ever break off from the rest of the ties when you launch?
Do all of the ties usually release simultaneously or can a few hang on a little longer? Is that when they stretch and break?
How much pressure can a well made cable tie launcher usually work at?

Dennis



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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by RaZias » Tue Jun 22, 2010 5:38 am

I never used a cable tie launcher but I once had a made a connection to the my quick releases by zip-tie instead of a rope...I tought maybe it was more stronger...

The plastic quick-release had 2 zip-tie to pull it down, each one entered in the quick-release trigger by a hole made in the plastic.

After 20 launches at 115 psi the quick-release escaped from the garden hose and both zip-tie connected to it just got cutted, they were almost the widest ones avaiable.

Needless to say that the rocket flew away with the gardena quick-release and turned horizontal after 5 meters in vertical flight.


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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by WRA2 » Tue Jun 22, 2010 8:30 pm

RebelRockets wrote:
Thats brings up a few questions about cable tie launchers for people who use them.
Do the heads ever break off from the rest of the ties when you launch?
Do all of the ties usually release simultaneously or can a few hang on a little longer? Is that when they stretch and break?
How much pressure can a well made cable tie launcher usually work at?

Dennis
Hi Dennis,

The heads usually do not break off the ties. The bigger problem is UV. If you leave your launcher outside, use UV resistant ties.
The ties usually will release simultaneously. Stretching will depend on the number of ties used (the more the better).
If you are using w well made cable tie launcher then it will hold more pressure then the bottle will and the bottle will burst before the ties fail. If you are launching reinforced rockets using high pressure then metal cable ties are available but they are expensive but will not stretch or break.

A few good tutorials for building cable tie launchers can be found at :

http://www.wra2.org/forum/viewtopic.php?f=46&t=797


http://www.uswaterrockets.com/journa ... ial_Part_1


http://www.wra2.org/forum/viewtopic.php?f=46&t=270


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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by Tim Chen » Fri Jun 25, 2010 12:39 pm

Dennis,

I've been testing some cable ties by hanging weights from them and I've found that the ones I tested (a multi-colored assortment I got from Home Depot) they hold about 80 pounds of force without breaking. I think you could get by with just a handful of them but most people use a whole array of them and that would divide the max weight by the strength, so if you had 20 of them in a circle that would be 4 pounds force on each one.

This topic reminds me of the old "Duke Nukem" videogame. He used to have this one liner about steel balls:

[youtube][/youtube]


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Re: New Launcher Design Using Steel Balls to Secure Bottle

Post by U.S. Water Rockets1 » Sat Jun 26, 2010 10:20 pm

Cable ties are supposed to be rated for the strength of the latch mechanism. If they are rated for 100 pounds, then the ratchet will hold 100 pounds of force. The strap itself should be much stronger than that.


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