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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.

Joining bottes without splices

Members post instructions to construct water rockets, launchers, deployment systems, staging mechanisms, splicing bottles, and payloads.
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wormster
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Joining bottes without splices

Post by wormster » Thu Nov 07, 2013 8:33 pm

I have been working on a new method of joining bottles without the need for splicing. I realise that this won't be eligible in competitions as the joint contains metal components (but there again I will not be entering the FK1 into any competitions).

Method:

Take one of these bad boys http://www.ebay.co.uk/itm/Swagelok-SS-4 ... 0952933874 and remove the internal ferrules, they can be discarded as they are used to grip the pipe and form a seal.

Next add two M10 Dowty http://www.ebay.co.uk/itm/10-X-M10-DOWT ... 1021749376 washers ether side of the center section.

Then drill out the bottom of one bottle and secure one nut on the inside of the bottle.
(we're looking for German engineering here - Goodntight).

Next drill out the bottle cap to suit and and pop it on the exposed thread.

Add the remaining nut and tighten it up
(again we're looking for German engineering here).

Finally screw in your next bottle.

After doing all of this you end up with a good mechanical, pressure tight joint that can withstand a fair amount of punishment from rough landings. Another benefit is that you have a 1/4 inch internal reducer in the system which IMO gives a little more "bang for your buck". This allows you to stack bottles in line with each other (the only problem (as such) is that you need a fairly long shroud to cover the joint), I'm currently working on a similar joint, but instead of going base of bottle to bottle cap I'm trying to go base to base (which will remove the need for a long shroud), hopefully this will allow me to construct a top filling rocket!

Comments TH:



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U.S. Water Rockets1
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Re: Joining bottes without splices

Post by U.S. Water Rockets1 » Sun Nov 10, 2013 12:00 am

wormster wrote:I have been working on a new method of joining bottles without the need for splicing. I realise that this won't be eligible in competitions as the joint contains metal components (but there again I will not be entering the FK1 into any competitions).

Method:

Take one of these bad boys http://www.ebay.co.uk/itm/Swagelok-SS-4 ... 0952933874 and remove the internal ferrules, they can be discarded as they are used to grip the pipe and form a seal.

Next add two M10 Dowty http://www.ebay.co.uk/itm/10-X-M10-DOWT ... 1021749376 washers ether side of the center section.

Then drill out the bottom of one bottle and secure one nut on the inside of the bottle.
(we're looking for German engineering here - Goodntight).

Next drill out the bottle cap to suit and and pop it on the exposed thread.

Add the remaining nut and tighten it up
(again we're looking for German engineering here).

Finally screw in your next bottle.

After doing all of this you end up with a good mechanical, pressure tight joint that can withstand a fair amount of punishment from rough landings. Another benefit is that you have a 1/4 inch internal reducer in the system which IMO gives a little more "bang for your buck". This allows you to stack bottles in line with each other (the only problem (as such) is that you need a fairly long shroud to cover the joint), I'm currently working on a similar joint, but instead of going base of bottle to bottle cap I'm trying to go base to base (which will remove the need for a long shroud), hopefully this will allow me to construct a top filling rocket!

Comments TH:
An idea similar to this was used before splicing was invented. The joint was made using a brass hollow threaded tube called a "lamp rod" because that is what it was used for (making lamps). The idea applied to water rockets was called a "Robinson Coupling" after the inventor of the technique. The idea is pretty well respected and can even be applied to plastic components if you can find them or make them from hardware store bits.

The only real downside of this method is the smallish passages between bottles is a choke point that prevents the air pressure from moving quickly from compartment to compartment as the water drains out.

Another thing to watch out for is that the claw part of bottles is often a weak point that bursts at the lower pressure compared to the top and sides. If you keep the claw part of the bottle attached, it may cause the maximum pressure your rocket can hold to be reduced.

It is a lot quicker than splicing, so as long as you are not going for the maximum pressure you can make, it is a great alternative. Your design looks to be among the easiest the build, so it has a lot going for it. Nice work!


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Re: Joining bottes without splices

Post by bugwubber » Sun Nov 10, 2013 2:54 am

I gave up on using couplings in a bottom to bottom configuration because the upper bottle tends to trap water. It was fine as long as i didnt try to fill more than 1 bottle with water.

Many of my rockets now have a cap attached to the top of the pressure bottle. To make sure everything stays centered, I'll put the cap on an identical bottle and then glue the cap in place with plp or vhb tape. Then im free to drill the cap and bottle if i wish or just use it as an attachment point for the payload bay.

Bugwubber


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Re: Joining bottes without splices

Post by ptx » Sun Nov 10, 2013 6:23 am

bugwubber wrote:I gave up on using couplings in a bottom to bottom configuration because the upper bottle tends to trap water. It was fine as long as i didnt try to fill more than 1 bottle with water.

Many of my rockets now have a cap attached to the top of the pressure bottle. To make sure everything stays centered, I'll put the cap on an identical bottle and then glue the cap in place with plp or vhb tape. Then im free to drill the cap and bottle if i wish or just use it as an attachment point for the payload bay.

Bugwubber
Hi Bugwubber
Nice method to align bottles.
Do you use it for the Robinson Coupling?


ptx

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Re: Joining bottes without splices

Post by bugwubber » Sun Nov 10, 2013 9:38 pm

nunopt wrote:
bugwubber wrote:I gave up on using couplings in a bottom to bottom configuration because the upper bottle tends to trap water. It was fine as long as i didnt try to fill more than 1 bottle with water.

Many of my rockets now have a cap attached to the top of the pressure bottle. To make sure everything stays centered, I'll put the cap on an identical bottle and then glue the cap in place with plp or vhb tape. Then im free to drill the cap and bottle if i wish or just use it as an attachment point for the payload bay.

Bugwubber
Hi Bugwubber
Nice method to align bottles.
Do you use it for the Robinson Coupling?
Right, after the glue has set, I can drill and tap the cap and bottle together for a hollow threaded rod. I had set aside all my complex and spliced rocket projects this year so I could focus on the single bottle Scout rockets. Hope to pick those back up this winter.

When I don't want to couple bottles, I'll just melt a few holes in the top of the cap with my poor abused soldering iron prior to the glue up. This allows the PLP to squeeze through and get a mechanical lock on the cap. Without the holes, PLP will eventually let go of the cap. I've used this method for Charlie Laser Pears and CALGON.

Bugwubber


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Re: Joining bottes without splices

Post by bugwubber » Mon Nov 11, 2013 3:16 pm

wormster wrote:I have been working on a new method of joining bottles without the need for splicing. I realise that this won't be eligible in competitions as the joint contains metal components (but there again I will not be entering the FK1 into any competitions).

Method:

Take one of these bad boys http://www.ebay.co.uk/itm/Swagelok-SS-4 ... 0952933874 and remove the internal ferrules, they can be discarded as they are used to grip the pipe and form a seal.

Next add two M10 Dowty http://www.ebay.co.uk/itm/10-X-M10-DOWT ... 1021749376 washers ether side of the center section.

Then drill out the bottom of one bottle and secure one nut on the inside of the bottle.
(we're looking for German engineering here - Goodntight).

Next drill out the bottle cap to suit and and pop it on the exposed thread.

Add the remaining nut and tighten it up
(again we're looking for German engineering here).

Finally screw in your next bottle.

After doing all of this you end up with a good mechanical, pressure tight joint that can withstand a fair amount of punishment from rough landings. Another benefit is that you have a 1/4 inch internal reducer in the system which IMO gives a little more "bang for your buck". This allows you to stack bottles in line with each other (the only problem (as such) is that you need a fairly long shroud to cover the joint), I'm currently working on a similar joint, but instead of going base of bottle to bottle cap I'm trying to go base to base (which will remove the need for a long shroud), hopefully this will allow me to construct a top filling rocket!

Comments TH:
Wormster, is that price per piece? I see 10x for the washers.

Bugwubber


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Re: Joining bottes without splices

Post by ptx » Mon Nov 11, 2013 3:57 pm

bugwubber wrote:Right, after the glue has set, I can drill and tap the cap and bottle together for a hollow threaded rod. I had set aside all my complex and spliced rocket projects this year so I could focus on the single bottle Scout rockets. Hope to pick those back up this winter.

When I don't want to couple bottles, I'll just melt a few holes in the top of the cap with my poor abused soldering iron prior to the glue up. This allows the PLP to squeeze through and get a mechanical lock on the cap. Without the holes, PLP will eventually let go of the cap. I've used this method for Charlie Laser Pears and CALGON.

Bugwubber

Inventive way to join bottles, I suppose you are talking about this ..
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Re: Joining bottes without splices

Post by bugwubber » Mon Nov 11, 2013 6:13 pm

nunopt wrote:
bugwubber wrote:Right, after the glue has set, I can drill and tap the cap and bottle together for a hollow threaded rod. I had set aside all my complex and spliced rocket projects this year so I could focus on the single bottle Scout rockets. Hope to pick those back up this winter.

When I don't want to couple bottles, I'll just melt a few holes in the top of the cap with my poor abused soldering iron prior to the glue up. This allows the PLP to squeeze through and get a mechanical lock on the cap. Without the holes, PLP will eventually let go of the cap. I've used this method for Charlie Laser Pears and CALGON.

Bugwubber

Inventive way to join bottles, I suppose you are talking about this ..
Right. that rocket lawn darted on one flight but that joint survived.

Wormster- here's another way to do this join without metal. I was saving this for this winter's water rocket ski so haven't got any flight tests on it yet. It is simply 2 small pieces of 1/2" pvc, glued on to a 1" piece of 1/2" cpvc. I drilled a 5/8" hole through the cap and bottle that the cpvc fits through. Used "all purpose" cement.
CAM00130.jpg
CAM00136.jpg
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Re: Joining bottes without splices

Post by wormster » Tue Nov 12, 2013 1:49 pm

bugwubber wrote:
Wormster, is that price per piece? I see 10x for the washers.

Bugwubber
Could be, I get mine F.O.C. from work along with the swage connectors (it all comes out of the scrap bin!)

I only used the fleabay links as examples, they're cheaper from other suppliers!



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