Pneumatic air pump questions

[razor1000]

I'm working on a case mod that involves pneumatics (I'll not go into it until I've got something to show everybody.)

I want to be able to fit the pump into my case, but most proper pneumatic pumps are HUGE! Plus, I want it to be affordable, and I really only need like 20-30PSI.

So I was looking at air pumps for fish tanks, and they seem to be able to push out the PSI I'm looking for, and they are small.

But I'm curious to know if the thing will burn out if I don't put some kind of release valve in it. Once the piston is extended all the way there is nowhere for all the air to go, so it seems like the pump will just keep building up the pressure until something gives out.

I guess I could put a pressure sensor in there somewhere and have it turn off the power to the pump when a certain PSI is reached, but that's kinda more complicated that I want it to get.

Anybody out there know anything about pneumatics?

 

[itx]

Just about any pump that will deliver that kind of pressure will be large, and more importantly loud. You could, perhaps, use one of those pumps for inflating car tires. They run off 12 volts and are usually fairly small.... But they are still very loud. Do you really need a cylider or could you get by with a linear motor?

 

[theNoid]

In advance, any pump of that size, or putting out that much power will be loud as all hell. Be scared.... be veeeerrrryyyyy scared.

 

[Leatherface]

it's more than you need, but check this out. as for your pressure question, if you put in an air tank, you can install a pressure switch to shut the compressor off when it hits a certain PSI. you can then get a couple cheap selenoid valves, hook them up to a momentary toggle and hit it one way the piston opens, hit it the other way the piston closes.

 

[Adisharr]

One option is to use a two port cylinder with a five way (five port) valve with a closed to pressure center. Both of which are very inexpensive.

 

[razor1000]

*itx:
I thought about tire pumps, they would be nice because most run on DC, but I decided against using one because of cost, and power. I think >50PSI is overkill. Plus I don't want to be picking pieces of PVC pipe out of my face.

*Leatherface:
ooooooo, chrome! I like it, but it is waaaay over my desired cost. Plus I would need all those other bits and pieces, and that would cost money too. Plus all the added complexity.

*Adisharr:
Are you speaking English? A five-finger discount with a chocolatey center?


So I figured I should tell you guys more about my design. I don't want to give it all away, but I intend on making it "open-source" once I finish, anyway, so I guess it wouldn't hurt.

Priorities here are cost and simplicity.

I thought I would build a cylinder with brass or copper pipe pieces, but then I realized that PVC would be much cheaper and easier to work with. Since my design doesn't really need high pressure, I think PVC will do fine. Plus you should be able to paint it with vinyl dye, I think.

So here's my design:

The inlet is a hose barb, and the piston is a small piece of PVC pipe inside a larger piece. I cut a notch near the end of the piston for a rubber O-ring that will make the air-tight seal. I still need to think of a solid way to cap the hole in the pipe. I just need to make another trip to the hardware store.

I took an end-cap and cut a hole in it just big enough to fit the piston through, and then added another, larger O-ring there so that the piston will stop there.

I don't think I need to be able to reverse the airflow, since I believe there will be enough pressure on the piston to push it back down when the pump is turned off.

As for the pressure relief, I think a small hole near the end-cap will be sufficient. That way when the piston-seal passes the hole the air-pressure drops, allowing the pump to be left on, while keeping the piston in the extended position.

Comments?