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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.

Home made high pressure pump

Discussion about Compressors, hose, pipes, fittings, launchers, release mechanisms, and launch tubes.
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SaskAlex
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Home made high pressure pump

Post by SaskAlex » Fri Mar 05, 2010 3:08 pm

Well, in another thread of mine I mentioned my home made hand pump, and a few people expressed some interest. I'm at school so I can't upload any pictures or anything, but I'll do my best to describe it.

The barrel of the pump is made of 1/2" drawn copper tubing. Check out http://www.copper.org/Applications/plum ... ble3a.html for working pressure ratings. The tubing actually has an inner diameter of around 9/16", which is almost exactly a half of the inner diameter of my bike pump. I can get about 200 psi out of my bike pump, so I should be able to get 800 with this home made one. I don't ever plan to go that high, though.

I made the plunger out of pvc turned on the lathe. I use some 1/2" O.D. steel pipe to connect the plunger to the handle. If you've ever taken a bike pump apart, you'll know that the seal on the plunger also acts as a one-way valve. It's quite simple, but hard to explain without a picture.

The bottom of the pump is made with brass fittings. The bottom one-way valve is made with a valve stem. I'll definitely need some pictures to describe this part.

The pump works, but it takes a long time to pump anything up. One of the problems is that you need an o-ring of the perfect diameter if want it to act as a one-way valve. If you take apart the top of a bike pump you will under stand this. My o-ring is a little small, and I have to occasionally stretch it out. Sometimes it seems like it doesn't seal until I've completed a significant portion of the stroke. So far, I've used it for pressure testing, but I haven't actually launched a rocket with it yet.

Anyways, it's worth a try to make one if you can't afford those ~$200 3000psi hand pumps on the internet, or if you're like me and just like to make things on your own. If you do make one, be safe! Make sure you stay well within the ratings of your components. There is never a whole lot of energy in the pump, since it's volume is so small, but it is right between your legs.

I'll try and get some pictures up this weekend.



Randino
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Re: Home made high pressure pump

Post by Randino » Fri Mar 05, 2010 4:09 pm

Yes, please do put pictures up when you can. A pump like that could be a great help to a lot of us. I usually use a compressor, but a pump would be a lot easier to bring with me to parties and such. It would also give me chance to show off my ripped muscles and further impress the ladies 8)

Randy


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SaskAlex
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Re: Home made high pressure pump

Post by SaskAlex » Fri Mar 05, 2010 11:30 pm

Well here are the pictures. I'm not sure if I'll be doing any more high pressure work soon, but if I do I'll make a small modification to the pump. I'm going to make a new plunger piece with a regular, full groove for the o-ring. This way the o-ring will always seal with the tube. Near the top of the copper tube, I will drill a hole. When the o-ring comes above this hole, air will fill the copper tube. This will solve the problem I mentioned in my first post where the plunger only seems to seal well into the stroke. You will be creating a vacuum on the up stroke, so you are wasting some energy, but it is very little.

Alex
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U.S. Water Rockets1
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Re: Home made high pressure pump

Post by U.S. Water Rockets1 » Sat Mar 06, 2010 11:27 pm

This is a really good illustration of how to make a homemade pump. The only things to consider is that you should make a diagram showing how the plunger and o-ring work together. Some people have never taken apart a pump so it may mot be clear how the o-ring allows air in only on the upstroke. Another thing that is important is to make sure if you solder any of the pipes together to be sure and use silver solder, because it makes a much stronger joint than other types of solder.

Nice work!


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SaskAlex
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Re: Home made high pressure pump

Post by SaskAlex » Sun Mar 07, 2010 6:57 pm

U.S. Water Rockets1 wrote:This is a really good illustration of how to make a homemade pump. The only things to consider is that you should make a diagram showing how the plunger and o-ring work together. Some people have never taken apart a pump so it may mot be clear how the o-ring allows air in only on the upstroke. Another thing that is important is to make sure if you solder any of the pipes together to be sure and use silver solder, because it makes a much stronger joint than other types of solder.

Nice work!

Well, if anyone is going to try something similar, I would not recommend the plunger that acts as a one-way valve. It's too hard to get right, especially with a small diameter pump. And you need to luck out and get an o-ring of the perfect size to even have a chance. I would recommend the solution I talked about in my previous post. The first sketch below illustrates that solution. The o-ring on the plunger makes a permanent seal with the sides of the barrel. On the up stroke you create a vacuum. When the plunger gets to the top of the pump (the position in the drawing) the o-ring goes above this hole and air fills the barrel for your next down stroke. I haven't tried this method yet, but I'm confident it will be far simpler and more effective than the "one way valve plunger".

The bottom sketch is supposed to demonstrate how the one way valve plungers work, for those who are really interested.
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andicirk
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Re: Home made high pressure pump

Post by andicirk » Thu Mar 11, 2010 10:44 am

excellent thread any chance that this could get bumped or linked to the how too section



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RaZias
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Re: Home made high pressure pump

Post by RaZias » Sun May 23, 2010 3:04 pm

Have ever tough in selling one of these pumps ?

I am interested in buying a 300 psi air pump. I hope it´s safe.


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