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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.

O Rings vs swell sealing

Discussion about Compressors, hose, pipes, fittings, launchers, release mechanisms, and launch tubes.
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bugwubber
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Re: O Rings vs swell sealing

Post by bugwubber » Mon Jun 10, 2013 11:30 am

It does sound interesting. Do you have a picture of it?


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Re: O Rings vs swell sealing

Post by Nick B » Mon Jun 10, 2013 11:47 pm

bugwubber wrote:It does sound interesting. Do you have a picture of it?

The tapered swell? No.



It's just a pvc tube that is tapped and swelled with a steel pipe nipple and then threaded into the launcher. It is tapered since the nipple is npt tapered and gradually expands the tube. Then you just adjust your retention method/system to your best nominal bottle openings. If you experience any wear in the area of the taper you most often use (we haven't yet..) then you can re-adjust your retention system. It has been working very well for us. we even have a grasp for launching without retention, by knowing what pressures each tube typically lets go at. Most of our older o-ring tubes were the same way. The o rings were dialed in to launch at determined pressure ranges, if we wanted to skip the block n tackle to let one rip.


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Re: O Rings vs swell sealing

Post by andy_R » Mon Sep 15, 2014 2:57 pm

What are the exact specs on the 3/8 and 1/2 inch pipe - here in the UK we use metric, so I want to order the right stuff from the states. The materiels will be cheap, but shipping won't, so I want to order the right stuff first time! Are there particular suppliers that you recommend?



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Re: O Rings vs swell sealing

Post by bugwubber » Mon Sep 15, 2014 11:35 pm

andy_R wrote:What are the exact specs on the 3/8 and 1/2 inch pipe - here in the UK we use metric, so I want to order the right stuff from the states. The materiels will be cheap, but shipping won't, so I want to order the right stuff first time! Are there particular suppliers that you recommend?
US pvc pipe is nominally sized. 1/2" pvc is actually .60
" (15.26mm) inside diameter. What counts is outside diameter which is .84" or 21.4 mm. Carbonated beverage Bottles usually have an inside diameter of .85" or 21.5mm.

Best thing to do is to visit your local hardware store with a bottle or at least a bottle nozzle in hand and try to fit it over the various pipes.


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Re: O Rings vs swell sealing

Post by andy_R » Tue Sep 16, 2014 3:47 am

bugwubber wrote:
andy_R wrote:What are the exact specs on the 3/8 and 1/2 inch pipe - here in the UK we use metric, so I want to order the right stuff from the states. The materiels will be cheap, but shipping won't, so I want to order the right stuff first time! Are there particular suppliers that you recommend?
US pvc pipe is nominally sized. 1/2" pvc is actually .60
" (15.26mm) inside diameter. What counts is outside diameter which is .84" or 21.4 mm. Carbonated beverage Bottles usually have an inside diameter of .85" or 21.5mm.

Best thing to do is to visit your local hardware store with a bottle or at least a bottle nozzle in hand and try to fit it over the various pipes.
I know the OD required for the outer pipe, its the ID of the outer pipe and the OD of the inner pipe in the "o-ring" design that I need as these parts aren't readily available in the UK



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Re: O Rings vs swell sealing

Post by bugwubber » Tue Sep 16, 2014 1:54 pm

andy_R wrote:
bugwubber wrote:
andy_R wrote:What are the exact specs on the 3/8 and 1/2 inch pipe - here in the UK we use metric, so I want to order the right stuff from the states. The materiels will be cheap, but shipping won't, so I want to order the right stuff first time! Are there particular suppliers that you recommend?
US pvc pipe is nominally sized. 1/2" pvc is actually .60
" (15.26mm) inside diameter. What counts is outside diameter which is .84" or 21.4 mm. Carbonated beverage Bottles usually have an inside diameter of .85" or 21.5mm.

Best thing to do is to visit your local hardware store with a bottle or at least a bottle nozzle in hand and try to fit it over the various pipes.
I know the OD required for the outer pipe, its the ID of the outer pipe and the OD of the inner pipe in the "o-ring" design that I need as these parts aren't readily available in the UK
Oh ok got it. The funny thing is both pipes are called 1/2" here. The larger is Schedule 40, the smaller is Copper Tube Size.

1/2" "Schedule 40" PVC has an OD of .840" and avg ID of .602"

1/2" SDR-11 CTS (Copper Tube Size) CPVC has an OD of .625", ID of .469"

Now if you look at those numbers, you'll see the OD of CPVC is slightly larger than the ID of PVC. This is the problem I ran into. To solve this, I use a drill bit to ream out the inside of PVC to 5/8" (.625")

Others say they have no trouble sliding the CPVC into the PVC so it might be a regional thing. You can get CPVC in schedule 40 size, but its not common.


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Re: O Rings vs swell sealing

Post by U.S. Water Rockets1 » Sat Sep 20, 2014 10:47 pm

It's likely that a liberal coating of solvent based cement causes the surfaces of the pipes coated with the cement to soften a great deal and you can easily slide them together. The extra plastic material is dissolved into the liquid cement and is displaced with the excess cement when the pipes are pushed together. That's probably why some people don't have so much trouble getting the pipes together.


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Re: O Rings vs swell sealing

Post by andy_R » Sat Sep 27, 2014 9:24 am

Sooo....an idea occured to me. As we can't get the same size pipes over here in the uk very readily, I decided to do some "fettling". A length of 1/2" class E PVC pipe from a specialist hot tub/garden aquatics supplier that has an O.D. of 21.5mm and an I.D. of 17.2mm. Take a length of 21.5mm floplast waste pipe and make an axial cut about 13mm wide. This will now fit snugly inside the 1/2pvc pipe. Inset a lenght of 15mm copper tube into sleeve and pipe. Perfect fit. Remove one of the the o-rings from a 15mm pvc pushfit coupling and slide it onto the copper pipe. Test fit in the neck of a 2ltr pop bottle. Perfect fit. More to follow, hopefully with pics....



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Re: O Rings vs swell sealing

Post by U.S. Water Rockets1 » Sat Sep 27, 2014 10:04 pm

andy_R wrote:Sooo....an idea occured to me. As we can't get the same size pipes over here in the uk very readily, I decided to do some "fettling". A length of 1/2" class E PVC pipe from a specialist hot tub/garden aquatics supplier that has an O.D. of 21.5mm and an I.D. of 17.2mm. Take a length of 21.5mm floplast waste pipe and make an axial cut about 13mm wide. This will now fit snugly inside the 1/2pvc pipe. Inset a lenght of 15mm copper tube into sleeve and pipe. Perfect fit. Remove one of the the o-rings from a 15mm pvc pushfit coupling and slide it onto the copper pipe. Test fit in the neck of a 2ltr pop bottle. Perfect fit. More to follow, hopefully with pics....
We have made launchers using 1/2" Copper pipe as the inside tube of our o-ring design. It does not quite fit because the OD of the copper is a tiny bit bigger than the ID of the PVC, but some coarse sandpaper is all that was needed to make the ID of the PVC large enough to fit the copper pipe. We had to use PL premium to glue them together, since the PVC cement will not work on the copper pipe.


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